Bgas-cswip Grade 2 (2017)-slides And Screen Tests.pdf
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Course Objectives
To recognise and identify the benefits/disadvantages of paint systems. To understand the importance of surface preparation. To understand methods of application and testing. To understand paint system inspections. To interpret requirements of standards. To meet the syllabus requirements for the BGASCSWIP Painting Inspector Examination.
ATC 88 BGAS Painting Grade 2/3
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A cascade system of two grades:
Course Times Break Times/Prayer Times
Smoking/Mobile Phones
Grade one, offshore grade. Grade two, painting inspector.
Homework (every evening) Course material Practical equipment
You must have grade 2 to obtain grade 1.
Queries
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Copyright © TWI Ltd
Examination Details Grade 2 Theory: 50 Multi Choice one and a half hours allowed.
Practical Examination Abrasives: identification and uses. Rust grade – identification. Blast cleaning grade – identification.
Practical (Includes use of gauges etc) 50 multichoice, In two parts 25 questions Practical Theory and 25 Practical). One and a half hours allowed.
Hand and power tool grade – identification.
This is a closed book exam.
Use of whirling hygrometer and scales.
Profile measurement: testex and needle gauge. Dry film thickness measurements. Identification of equipment. Paint fault identification.
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Copyright © TWI Ltd
1
Candidate Requirements Prior to Course Event enrolment form PLEASE SEND A PHOTOCOPY WITH YOUR PAYMENT AND THE NECESSARY ENCLOSURES TO:
Pages to note: course text
TWI Training & Examination Services
2 x passport photographs: (print name, and sign on the back)
Customer Services Granta Park Great Abington Cambridge CBI 6AL Tel.: +44 (0)1223 891162 Fax. +44 (0)1223 891630 E-mail: [email protected]
OR
TWI North Aurora Court, Barton Road Riverside Middlesbrough TS2 1RY Tel.: +44 (0)1642 210512 Fax: +44 (0)1642 252218 E-mail: [email protected]
Page 23.1 to 23.13 (131-143) revision questions.
Course bookings – please complete page 1 Course and Exam packages – please complete pages 1-3 Exam bookings – please complete pages 1-3
Page 23.14 to 23.16 (144-145) inspection calculations.
PLEASE USE CAPITAL LETTERS THROUGHOUT
Event ref _____________ Event date _________________________ Event title ________________________________________________ _________________________________________________________ Delegate’s first name (s) _________________________________________________________ Delegate’s surname
Page 23.16 (146) relative humidity/dew point calculations.
_________________________________________________________ Date of birth (dd/mm/yy) _____________________________________
Completed event enrolment form
Permanent private address _________________________________________________________ _________________________________________________________
Pages to note: pa10
_________________________________________________________ _________________________________________________________ _________________________
postcode ______________________
Private tel no_______________________________________________
Page 16, section 7 : application of paint.
E-mail____________________________________________________ Correspondence address (if different from above) _________________________________________________________ _________________________________________________________
Confirmation of payment details
_________________________________________________________
Page 21, table spa 1e : preferred systems.
Invoice/Sponsor address (if different from Employer address) _________________________________________________________ _________________________________________________________ Employer name and address
0
_________________________________________________________
Page 27, table spa 3c : hot duty surfaces (above 340 c).
_________________________________________________________ _________________________________________________________ _________________________
postcode ______________________
Contact name ______________________________________________ Telephone_________________________________________________
A valid eyesight test
Page 28, table spa 4a : damp metal surfaces.
Fax ______________________________________________________ E-mail____________________________________________________ Please tick if you are A member of The Welding & Joining Society An employee of an Industrial Member of TWI Member of Institute of Mechanical Engineers (for ATC65 course only)
Page 39, 40, 41 table spa 6a,b,c : non-ferrous surfaces.
Industry Sectors: (Please tick one only) Power Generation Automotive Electronic Oil, Gas & Petrochemical
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Corrosion (Section 1)
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Electrical Circuit
Defined as:
A current flows from positive to negative, from anode to cathode, (+ to -).
The degradation of a material by chemical or Electro-chemical means.
The corrosion is caused by electrons travelling in exactly the opposite direction from cathode to anode, (- to +).
Electro-chemically, implies 2 mechanisms:
An electrical circuit, always dc. A chemical reaction, producing corrosion.
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The corrosion current is the ions returning to the anode in the circuit.
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Corrosion Theory 3 factors needed for corrosion to occur:
Anode, a positively charged area.
Cathode, a negatively charged area.
Electrolyte, a substance which will conduct a current and be broken down by it.
An electrolyte will dissociate into positive and negative ions.
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2
Where the electrons move to -ve, cathode becomes the cathode, negatively charged.
Where electrons move from becomes the anode, positively charged. A corrosion cell – AKA a battery? Copyright © TWI Ltd
+ve, anode
14
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=
Corrosion in a metal object, such as a pipe for example.
1 micron
A negative area of metal (cathode) is connected to a positive area (anode) by the pipe wall itself. As a result, electrons can flow from the anode to the cathode.
2
4600 atoms of iron -
15
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The Combustion Triangle
26 PROTONS
+
-
-
Electrons travel at 18600 miles per second! (1/10 speed of light).
-
Physical size of 1 electron 1 proton = 1836 electrons
-
1 electron
Iron atom = 26 electrons + 26 protons + 30 neutrons Copyright © TWI Ltd
What is Corrosion
Corrosion is like a slow burning fire
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3
The Corrosion Triangle
Cathode
Electrolyte
Electrolyte
Anode
Anode
Shows electrical circuit
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Cathode
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Factors Accelerating Corrosion
Anodes corrode. The combination of elements (oxidation) takes place at the anode. Cathodes are protected, hydrogen is evolved at the cathode as the electrolyte dissociates into positive and negative ions.
Temperature Steel is thermodynamically unstable. As the steel heats up, it gains molecular freedom, becomes more active, and undergoes corrosion more readily.
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Hygroscopic (Osmotic) Blisters
Tiny, pin head size, water filled blisters. Caused by hygroscopic salts (iron sulphates and iron chlorides) grow into larger blisters causing dis-bondment.
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Copyright © TWI Ltd
Factors Accelerating Corrosion Aerobic conditions, (presence of oxygen) Introduce oxygen, double the ions, (twice the number of hydroxyl ions) which will passivate twice the number of iron ions at the anode which will theoretically produce twice the corrosion!
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4
Factors Accelerating Corrosion
Microbial (Anaerobic) Corrosion
Microbial influenced corrosion (MIC)
Sulphate reducing bacteria (SRB) under anaerobic (absence of oxygen) conditions produce hydrogen sulphide.
Presence of some types of bacteria on the metal surface:
Sulphate reducing bacteria (SRB’s).
Metal eating microbes (MEM’s).
SRBs can also form deposits that are linked to under-deposit corrosion. Most aggressive conditions will exist in static water or under deposits where SRBs are protected from disturbance.
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FACTORS INFLUENCING CORROSION 4. BACTERIA ON THE SURFACE SULPHUR REDUCING BACTERIA (S.R.B)
Affected units or equipment
Thrive in oxygen free (or stagnant) areas. They remain dormant until they find oxygen free sites. Hydrogen sulphide (acid) producing bacteria, very active between 25-45°C. Rapid corrosion - often more than 5mm/year. Once established, bacteria colonies are very difficult to eradicate - they exist beneath slimes and deposits where biocide has difficulty reaching them
METAL EATING MICROBES (M.E.M)
Microbial Sulphate Reducing Bacteria Usually form small holes in the direction of Corrosion gravity, similar to weld porosity Severe internal microbial corrosion Copyright © TWI Ltd
Copyright © TWI Ltd
Factors Accelerating Corrosion Acids and alkalies
Bi-metallic Corrosion
Acids and alkalies are both electrolytic. They both dissociate into ions.
Heat exchangers. Bottom water of storage tanks. Piping in contact with some soils. Piping with stagnant or low flow. Systems where cooling water is not treated. Fire water systems.
When 2 different metals are in direct contact or joined by a conductive wire, in an environment where an electrolyte is present, one of the metals will corrode.
The metal which will corrode is dependent on its position in the galvanic list.
For example;
The position in the list determines which metal becomes the anode, and the distance between them determines the electrical potential and rate of corrosion.
HCl, Hydrochloric acid NaOH, Sodium hydroxide (alkalide)
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5
The Galvanic List MATERIAL
POTENTIAL
Graphite Titanium Silver Nickel Lead Admiralty Brass Copper Tin Millscale Low Alloy Steel Mild Steel Aluminium Alloys Zinc Magnesium
+ -
0.25 v 0.0 v 0.1 v 0.15 v 0.2 v 0.3 v 0.3 v 0.35 v 0.4 v 0.7 v 0.7 v 0.9 v 1.0 v 1.6 v
Carbon steel bolts in stainless steel pipework Copyright © TWI Ltd
Copyright © TWI Ltd
Bi-metallic Corrosion When the potentials of the metals are known, the galvanic list can also be known as :
Calculations
Formulae
The electro-motive forces series. The electro-chemical series.
WFT
Solvent V.S%
Note: both the position in the list and the free potential can alter with a different electrolyte and temperature.
Binder
Pigment and Extenders
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Calculations
DFT (% of WFT)
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Volume Calculations
Example: what WFT would be required to provide a DFT of 85 µm, if the paint used was of 66% VS?
Example: how much paint would be required to cover an area of 500m2 to a DFT of 85µm, if the paint used was of 66 % VS?
WFT= 100 %VS
If volume = WFT x area 1000
=
x
1.51 x 85
DFT 1
=
100 x 85 66 1
= 128µm X 500m2 1000
128 microns
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= 64 Litres
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6
Weather Conditions Considerations
Tonight Go to page 23.14 in your course notes, and using the formula on page 11.4, try the WFT, DFT and VS% calculations.
% Relative humidity (max 90%).
Air temperature (dry bulb temperature).
Steel temperature (>30C above dew point).
Calculated dew point temperature.
Manufacturers recommended minimum application temperature (approx 50C typically).
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Whirling Hygrometer (Aspirated Hygrometer) Is mercury in a continuous, unbroken stream? (If not, rectify with a magnet)
Whirling Hygrometer (Aspirated Hygrometer) Pre-use checklist Does the hygrometer spin freely? Is it clearly readable? Is there a wick? Is the wick clean?
Is the reservoir filled? (Distilled water) Is there a wick?
Is the wick wet, (must be distilled water)?
Is the wick clean?
Is the mercury in a continual , unbroken stream?
Is the wick wet?
If not , rectify by pulling back with a magnet.
Is the wick fastened around the bulb neck?
Is the wick fastened around bulb? Copyright © TWI Ltd
Copyright © TWI Ltd
WHIRLING OR ASPIRATED HYGROMETER
Weather Conditions - Dew Point Calculations
Rotate as fast as possible for 30 - 40 seconds (4 metres /sec minimum). Wet bulb reading taken immediately.
Line Up Temp Readings
Example: Dew point 0
Dew Point
Face towards any breeze. If not, walk forward to create an airflow. Test conducted as close to the area of painting as possible. 0
2 consecutive readings within 0.2 c of each other. Copyright © TWI Ltd
Dry bulb = 15 c 0 Wet bulb = 10 c 0
Align 10 c wet (red) 0 With 15 c dry (black) Read DP temp inside the eliptical window opposite the wet bulb 0 temp (DP = 5.5 c) Copyright © TWI Ltd
7
Dew Point Calculator
Read %RH here
To determine % relative humidity 0
Dry bulb 15 c 0 Dew point 5.5 c
Line up Dp and dry bulb Temperatures
Read RH% from tip of black arrow, in the small elliptical window.
Weather Conditions: Definitions Relative humidity (RH) Defined as: The amount of water vapour in the air, expressed as a percentage (%) of the amount of water vapour which could be in the air at that same temperature. Dew point (DP) Defined as: The temperature at which water vapour in the air will condense.
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Surface Preparation (Section 2)
Measuring Steel Temperatures Limpet Gauge Magnetic contact wait 15 Min’s before reading
Thermocouple
Why prepare a surface?
Electronic contact Immediate reading
To remove contaminants and provide a surface to which the paint will readily adhere. This will effectively provide a longer service life from the coating. Two factors for consideration Degree Of Cleanliness. Degree of roughness or surface profile.
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Copyright © TWI Ltd
Surface Preparation by Dry Abrasive Blasting Some surface defects may be revealed after surface cleaning.
Surface Profile The
height of the surface profile is determined by: Size of Abrasive. Velocity of Abrasive. Hardness of Abrasive. Density of Abrasive. Angle of Impingement. Surface cracks
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Surface breaking laminations
Surface pitting
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8
Surface Preparation Methods
Dry Abrasive Blasting
Dry abrasive blast cleaning.
Wet blasting.
Abrasives.
Hand and power tool cleaning.
Profile and adhesion.
Flame cleaning.
Profile measurement and assessment.
Pickling (chemical cleaning).
Rust grades and degree of cleanliness.
Vapour degreasing.
Equipment.
Weathering.
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Dry Abrasive Blasting: Abrasives
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Dry Abrasive Blasting: Abrasives
Copper slag. Expendable. Most commonly used site abrasive.
Contaminated copper slag. Must not be re-used.
Must only be used once, as it shatters upon impact. It is non-metallic.
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Dry Abrasive Blasting: Abrasives
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The Danger of Sand Used as an Abrasive SI 1657: Statutory Instrument (LAW) more than 1% free silica (upon impact) is banned. This information is normally found on COSHH or material safety data sheets.
Garnet. This is a mineral. It can be either expendable, or can be re-cycled, but must be cleaned before re-use.
Causes: silicosis and pneumonicosis Chronic obstructive pulmonary disorders, caused by breathing dust from a variety of minerals, (coal, copper, sand etc). They cause airflow blockage and breathing difficulties, resulting in serious illness, disability and death. Copyright © TWI Ltd
Copyright © TWI Ltd
9
Dry Abrasive Blasting: Abrasives
Dry Abrasive Blasting: Abrasives
Metallic shot
Metallic grit and shot mix.
Used in enclosed systems, needs to be cleansed before reuse. Gradually wears down cycle by cycle.
Mixing ratio depends on spec. As does the particle sizes. Used in enclosed systems. Grit cuts the profile, shot controls the peaks.
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Dry Abrasive Blasting: Abrasives Blasting chamber with under-floor abrasive recovery system.
Metallic grit. Must be recycled for economic reasons. Not used for site work, and it must be cleansed before reuse.
Allows recycling of abrasive grit/shot for economic reasons.
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Dry Abrasive Blasting: Abrasives
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Dry Abrasive Blasting: Abrasives Particle size distribution: sieves to BS 410
Walnut shell Agricultural byproduct, not used on steel. As with other abrasives, it is available in various particle sizes.
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10
Sizing of Abrasives
G = grit. Irregular shape, sharp edges which gradually become blunted after many cycles of use. Stress relieves surface.
Adhesion Defined as: The force required to separate two surfaces in contact.
S = Shot, Spherical shape, work hardens.
There are two theories of adhesion;
There are various systems relating to size:
Molecular interference: a physical method (for example: Velcro).
The SAE, using the J 444 sieve system.
Molecular attraction: a chemical method (for example: a Magnet).
BS 7079 Part E, particle size distribution.
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Profile Irregularities
Prolonged blasting in one area produces rogue peaks
Surface Damage
Blasting can deform a Sliver into an upright shard of metal called a Hackle.
A rogue peak is an isolated peak of excessive amplitude, rectified by abrasion with emery paper or similar. Copyright © TWI Ltd
Laminations
Lamination
< 13mm approx. size
Surface Breaking Lamination, or Sliver
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Profile Measurement: Surface Profile Needle Gauge
Gauge must be calibrated to zero on a flat, smooth glass plate, set to zero, and lock the bezel in place. It can not be used on curved surfaces, such as pipes.
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11
Surface Profile Measurement: Dial Micrometer and Surface Replica Tape
Surface Profile Assessment Surface Comparator to BS 7079 Pt C, ISO 8503 Shot blast comparator. Not used for surface cleanliness. Only for assessment of shot blasted substrates. Grit blast comparator can also be used on substrates blasted with grit/shot mix.
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Rust Grades
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Blast Cleaning Grades (BS EN 7079 Part A)
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Rust Grades
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Blasting Grades A Sa 2.5 and Sa 3
Please note: as closely adherent mill scale can not be removed with light blast cleaning, or even thorough blast cleaning: There are no grade A Sa1 or Sa 2 photographs! In BS 7079 Part A. However we do have:
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12
Blasting Grades B Sa 1 and Sa 2
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Blasting Grades, Comparisons
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Blasting Grades C Sa 2.5 and Sa 3
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Blasting Grades B Sa 2.5 and Sa 3
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Blasting Grades C Sa 1 and Sa 2
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Blasting Grades D Sa 1 and Sa 2
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13
Blasting Grades D Sa 2.5 and Sa 3
SCREEN TEST ONE
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Question 1 Two examples of hygroscopic salts would be:
Iron Iron Iron Iron
phosphates and iron chromates. chlorates and iron oxides. sulphates and iron chlorides. sulphides and iron silicates.
Question 2
What is an electrolyte? It is a mixture of salts and water. A substance which will conduct electricity and cause rusting. Oxidising liquid which will attack steel. A substance which will conduct a current and be broken down by it.
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Copyright © TWI Ltd
Question 3
Question 4
Corrosion is defined as:
Hydrogen is evolved at:
Rusting of the Cathode by electro physical means. Oxidation of a metal in contact with water. Degradation of a material by chemical or electrochemical means. Breakdown of the metal by hydrogen.
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The The The The
anode at all times. cathode as corrosion takes place. cathode in the form of hydrogen gas. anode as corrosion takes place.
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14
Question 5 Which blasting grade best describes thorough Blast cleaning?
Sa Sa Sa Sa
2. 2½. 3. 1.
Question 6 What is the minimum standard of surface cleanliness specified by SPA1a of BGC/PS/PA 10?
Rust Grade C. St 3. Sa 2½. 30 to 75 microns.
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Copyright © TWI Ltd
Question 7 In a corrosion circuit, electrons flow from:
Question 8 Rust grade A can be described as:
Anode to cathode, via electrolyte. Positive to negative. Electrolyte to steel. Cathode to anode, via electrolyte.
Tightly adhering mill scale, with evident heavy pitting. Clean white metal. Tightly adhering mill scale, with no apparent corrosion. Mill scale which has begun to flake, or can be scraped away.
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Copyright © TWI Ltd
Question 9 Abrasive used on site for British Gas projects must be:
Mixed with sand, to reduce cost. Dried in an oven prior to use. Expendable. Used up to a maximum of three times only.
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Question 10 Which is the more noble metal:
Steel. Aluminium. Magnesium. Tin.
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15
Question 11 Mill scale is made up of which three oxide compounds?
Question 12 Two factors to be considered when inspecting a surface preparation, are:
Rust, iron oxide, and scale. RSJ, RSC, and RSA. Wustite, magnetite, and haematite. Iron sulphate, iron chloride, and iron phosphate.
Cleanliness and roughness. Rust grade and material type. Abrasive type and time. Surface area and type of contamination.
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Copyright © TWI Ltd
Question 13
Question 14
The Galvanic List is also known as: Which of the following is Rust Grade C?
The The The The
metallic corrosion potential chart. electromotive forces series. element forces order. electronic chemical series.
Tightly adhering mill scale which can be brushed clean. Loosely adhering mill scale with no evident pitting. Mill scale almost totally removed, visible rust, no heavy pitting. Heavy pitting clearly visible, heavy corrosion.
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Copyright © TWI Ltd
Question 15
Question 16 The thickness of mill scale is approximately:
At the beginning of the corrosion process the iron atom changes it’s polarity from: Neutral to positive. Neutral to negative. Positive to negative. Positive to neutral.
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25μm to 100μm. 100 to 150μm. Zero. Dependant upon the material thickness.
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16
Question 17 The force required to separate two surfaces in contact, can also be termed:
Question 18 Blasting in one area for too long, produces what?
Viscosity. Profile. Adhesion. Blasting.
Hackles. Rogue Peaks. Slivers. Laminations.
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Copyright © TWI Ltd
Question 19 Metallic shot also has which affect upon the material?
Stress relieves. Physically deforms. Work hardens. Causes Slivers.
Question 20 What is the main cause of flash rusting on a substrate?
Rogue peaks. Oxygen. Hackles. Hygroscopic salts.
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Copyright © TWI Ltd
Question 22
Question 21 What is the main advantage of using Testex papers for surface profile measurement?
It also measures cleanliness. Most accurate over a large area. Easy to use. Permanent record.
Which of the following could be classified as a major cause of microbial corrosion:
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Sulphur eating metal. Sulphur reducing bacteria. Rust inhibitive salts. Iron phosphates.
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17
Question 23
Question 24
Three factors which accelerate the rate of corrosion are:
How many abrasive blast cleaning photographs are in BS 7079 part A?
Temperature, time, and coating system. Bi-metallic contact, hygroscopic salts, and bacteria. Coating system, pipe diameter, and ultra violet light. blasting grades, rust grades, and surface profile.
4. 14. 8. 16.
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Copyright © TWI Ltd
Question 25 British Gas PA 10 specifies a surface profile of: Swap your papers please
30 microns to 75 microns. 100 microns to 150 microns. 10 microns to 40 microns. more than 90 microns.
Put your name on your paper, and pass it to someone else to check.
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Copyright © TWI Ltd
Question 1
Question 2
Two examples of Hygroscopic Salts would be:
What is an electrolyte?
a. b. c. d.
a. It is a mixture of salts and water. b. A substance which will conduct electricity and cause rusting. c. Oxidising liquid which will attack steel. d. A substance which will conduct a current and be broken down by it.
Iron Iron Iron Iron
phosphates and iron chromates. chlorates and iron oxides. sulphates and iron chlorides. sulphides and iron silicates.
Answer: C
Answer: D Copyright © TWI Ltd
Copyright © TWI Ltd
18
Question 3
Question 4
Corrosion is defined as:
Hydrogen is evolved at:
a. Rusting of the cathode by electrophysical means. b. Oxidation of a metal in contact with water. c. Degradation of a material by chemical or electrochemical means. d. Breakdown of the metal by hydrogen.
a. b. c. d.
Answer: C
Answer: C
The The The The
anode at all times. cathode as corrosion takes place. cathode in the form of hydrogen gas. anode as corrosion takes place.
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Copyright © TWI Ltd
Question 5
Question 6
Which blasting grade best describes thorough blast cleaning?
What is the minimum standard of surface cleanliness specified by SPA1 of BGC/PS/PA 10?
a. b. c. d.
a. b. c. d.
Sa Sa Sa Sa
2. 2½. 3. 1.
Rust Grade C. St 3. Sa 2½. 30 to 75 microns.
Answer: C Answer: A Copyright © TWI Ltd
Copyright © TWI Ltd
Question 7
Question 8
In a corrosion circuit, electrons flow from:
Rust grade A can be described as:
a. b. c. d.
a. Tightly adhering mill scale, with evident heavy pitting. b. Clean white metal. c. Tightly adhering mill scale, with no apparent corrosion. d. Mill scale which has begun to flake, or can be scraped away.
Anode to cathode, via electrolyte. Positive to negative. Electrolyte to steel. Cathode to anode, via electrolyte.
Answer: D
Answer: C Copyright © TWI Ltd
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19
Question 9 Abrasive used on site for British Gas projects must be: a. b. c. d.
Mixed with sand, to reduce cost. Dried in an oven prior to use. Expendable. Used up to a maximum of three times only.
Question 10 Which is the more noble metal: a. b. c. d.
Steel. Aluminium. Magnesium. Tin.
Answer: D
Answer: C Copyright © TWI Ltd
Copyright © TWI Ltd
Question 11
Question 12
Mill scale is made up of which three oxide compounds?
Two factors to be considered when inspecting a Surface Preparation, are:
a. b. c. d.
a. b. c. d.
Rust, iron oxide, and scale. RSJ, RSC, and RSA. Wustite, magnetite, and haematite. Iron sulphate, iron chloride, and iron phosphate.
Cleanliness and roughness. Rust grade and material type. Abrasive type and time. Surface area and type of contamination.
Answer: A
Answer: C Copyright © TWI Ltd
Copyright © TWI Ltd
Question 13
Question 14
The galvanic list is also known as:
Which of the following is Rust Grade C?
a. b. c. d.
a. Tightly adhering mill scale which can be brushed clean. b. Loosely adhering mill scale with no evident pitting. c. Mill scale almost totally removed, visible rust, no heavy pitting. d. Heavy pitting clearly visible, heavy corrosion.
The The The The
metallic corrosion potential chart. electromotive forces series. element forces order. electronic chemical series.
Answer: B
Answer: C Copyright © TWI Ltd
Copyright © TWI Ltd
20
Question 15 At the beginning of the corrosion process the iron atom changes it’s polarity from: a. b. c. d.
Question 16 The thickness of mill scale is approximately: a. b. c. d.
Neutral to positive. Neutral to negative. Positive to negative. Positive to neutral.
Answer: A
25μm to 100μm. 100 to 150μm. Zero. Dependant upon the material thickness.
Answer: A
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Copyright © TWI Ltd
Question 17 The force required to separate two surfaces in contact can also be termed: a. b. c. d.
Question 18 Blasting in one area for too long, produces what? a. b. c. d.
Viscosity. Profile. Adhesion. Blasting.
Answer: C
Hackles. Rogue Peaks. Slivers. Laminations.
Answer: B
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Copyright © TWI Ltd
Question 20
Question 19 Metallic shot also has which affect upon the material?
What is the main cause of flash rusting on a substrate?
a. b. c. d.
a. b. c. d.
Stress relieves. Physically deforms. Work hardens. Causes Slivers.
Answer: C
Rogue peaks. Oxygen. Hackles. Hygroscopic salts.
Answer: A
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Copyright © TWI Ltd
21
Question 21
Question 22
What is the main advantage of using Testex papers for surface profile measurement?
Which of the following could be classified as a major cause of microbial corrosion:
a. b. c. d.
a. b. c. d.
It also measures cleanliness. Most accurate over a large area. Easy to us. Permanent record.
Answer: D
Sulphate eating metal. Sulphate reducing bacteria. Rust inhibitive salts. Iron phosphates.
Answer: B
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Copyright © TWI Ltd
Question 23
Question 24
Three factors which accelerate the rate of corrosion are:
How many Abrasive Blast Cleaning photographs are in BS 7079 part A?
a. Temperature, time, and coating system. b. Bi-metallic contact, hygroscopic salts, and bacteria. c. Coating system, pipe diameter, and ultra violet light. d. Blasting grades, rust grades, and surface profile.
a. b. c. d.
4. 14. 8. 16.
Answer: B
Answer: B Copyright © TWI Ltd
Copyright © TWI Ltd
Question 25 British Gas PA 10 specifies a surface profile of: a. b. c. d.
30 microns to 75 microns. 100 microns to 150 microns. 10 microns to 40 microns. More than 90 microns.
Answer: A
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22
Wheelabrators (Centrifugal Blast Units) Abrasive Particle Speed 220 Mph Series Of Drums Rotating At 2600 Rpm
ATC 88 BGAS Painting Grade 2/3
100% Surface Coverage
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Wheelabrators or Centrifugal Blast Units
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Automatic Blasting Machines Wheelabrators
Operate at approx. 2600 RPM. Totally enclosed (good operator safety). Automatic chain driven roller feed. Varying number of operating wheels. Gravity fed abrasive (re-usable). Airwash cleansing system for abrasives. Preferred abrasive is metallic shot.
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Centrifugal Blasting Chamber
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Dry Abrasive Blasting Equipment COMPRESSORS pressure rating in psi capacity in cfm. BACK PRESSURE AT NOZZLE hypodermic needle gauge. VAPOUR TRAPS, knock-out pots (removal of oil and water from air stream). PRESSURISED BLAST POTS of suitable capacity. CARBON IMPREGNATED HOSES, to reduce static shock. NOZZLES, Venturi (450 mph) and Straight bore (200 mph). SAFETY TO IGE SR 21 (Institute of Gas Engineers : Safety Regulations).
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1
Typical Set-up of a Dry Abrasive Blasting Operation Internal view of VENTURI NOZZLE increases speed of abrasive from 200 mph to 450 mph.
Pressurised blast pot Compressor Vapour traps (knock out pots)
Whiplash prevention cables Blasting nozzle
Carbon impregnated reinforced hose
External bayonet type couplings
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Blasting Safety
Carbon impregnated hose.
Typical portable site blasting machines.
Hose must have external, Bayonet type couplings, with whiplash restraints.
Reccova valve, fitted to other end of air lines to dead man handle.
Air Filter (breathing air not supplied directly from compressor).
Exhaust beware!
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Blasting Safety
Carbon impregnated hose whiplash cables air-fed helmet protective visor leather apron dead man’s handle gauntlets.
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2
Bayonet Type (Chicago) Couplings
Dead Man’s Handle
Blasting nozzle trigger which must be under the direct control of the operator.
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Measuring Blast Pressure at the Nozzle Hypodermic needle gauge
Method
Alert the operator. Shut off abrasive.
Air Connection Fail Safe Trigger
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Wet Blasting: Methods High pressure pure water blasting <30,000psi. High pressure water plus abrasive injection. Low pressure water plus abrasive injection. Steam cleaning. Air blasting with water injection.
Insert the needle through the hose, with the needle towards the nozzle, at an angle of approximately 45 degrees. Copyright © TWI Ltd
Ultra High Pressure Water Jetting, >30,000 PSI UHP Water Jetting (above 30,000 psi)
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Wet Blasting Abrasive blasting with water injected in to the abrasive stream at the blasting nozzle
Low Pressure water cleaning
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3
Hand and Power Tool Cleaning, (BS 7079 Pt A) High Pressure Water Jetting – up to 30,000 psi
Steam Cleaning
Hand and power wire brushes, chipping hammers, needle guns, emery cloth. St 2 Thorough hand and power tool cleaning. St 3 Very thorough hand and power tool cleaning. Note: because millscale is harder than the brush bristles, (phosphor bronze / beryllium bronze). There is no standard for rust grade A! Copyright © TWI Ltd
Jason’s Hammer and a Needle Gun
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Surface Preparation Hand and power tool cleaning B St 2 and St 3.
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Surface Preparation Hand and power tool cleaning C St 2 and St 3.
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Surface Preparation Hand and power tool cleaning D St 2 and St 3.
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4
Flame Cleaning 1 EXPANSION, co-efficient of expansion. 2 DEHYDRATION, moisture is evaporated. 3 HEAT PENETRATION, heat conducted into substrate.
Pickling is acid bath followed by washing. Footner’s Duplex system. Pickling followed by passivation. Passivation is treatment in phosphoric or chromic acid, which passivates the steel by forming a layer of rust- inhibitive salts which also aid adhesion and provide resistance to cathodic disbondment.
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Footner’s Duplex System Remove oil and grease and check using UVA lamp (contamination shows up yellow/green). Immerse in 5-10% sulphuric acid, 5-25 mins @ 65-700C. Rinse in clean water. Immerse in 2% Phosphoric/chromic acid, with 0.5% iron filings, 1-2 mins @ 800C. Rinse in clean water. Check ph level between 4.5 and 7.0.
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Surface Contaminants and Tests (Section 3) Hygroscopic salts : potassium ferricyanide, (now called potassium hexacyanoferrate)
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Surface Preparation, Chemical Cleaning
PH indicator papers, used to measure acidity or alkalinity of the substrate after final wash. For BGAS the pH should be between 4.5 and 7.
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Surface Contaminants and Tests (Section 3) Soluble chlorides: silver nitrate test. Mill scale: copper sulphate (only for Sa 3 grade). Oil or grease: solvent (not aliphatic) or U/V LAMP. Moisture: talcum or chalk. Dust: sellotape.
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5
Quantitative Tests for Hygroscopic Salts
Merkoquant test
Bresle sample patch
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Salts Detection, Bresle Sample Patch Kit
Paint Technology (Section 4) There are 3 main groups of paint: Paints containing solvents. Solvent free multi-pack, (MCL’s) Powder paints. All have the same basic constituents:
Binder (film former, non-volatile, vehicle).
Solvent. Pigments and other additives. Copyright © TWI Ltd
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Binder properties Binders used in National Grid (BGAS) specifications
Ease of application to: Give adhesion to the substrate. Provide resistance to abrasion. Provide chemical resistance. Provide cohesive strength. Provide dialectric strength. Resist the passage of water. Change from a liquid into a solid. Hold the pigments in suspension.
Acrylics. Alkyds. Epoxies. Ethyl and methyl silicates. Polyurethane silicones
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Other binders (non BGAS)
Cellulose resins. Chlorinated rubber. Emulsions. Natural oils and resins. Phenolic resins. Styrene and vinyl.
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6
Oils
Natural oils are produced from the seeds of a plant. Examples: Linseed, soya, olive, coconut, tung, castor. These oils must combine with oxygen, therefore must be unsaturated. A saturated oil already has enough oxygen bonds, and will not solidify and form a film.
Resins Natural resins are from the main plant, tree trunk). Resins are naturally brittle and fast drying, therefore need modification. This is done by addition of oils. Natural resins are Copals and Dammars and Coumarones, Amber and Laq. Other resins such as frankincense and myrrh are more valued for their perfume qualities.
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Oils Drying Oils Three sets of double bonds along a carbon backbone, react readily in ambient conditions. (unsaturated oils). Semi-drying Oils One or two sets of double bonds, not as reactive as drying oils. Need a catalyst (heat) to start polymerisation. Non-drying Oils (saturated oils) Cannot be used as binders, will not polymerise, no activity points. They are used as plasticisers, to give flexibility and ease application. Modifies the film properties.
Oil Paints LONG OIL PAINT more than 60% Oil to Resin. Elastic and slower drying, mainly used in domestic applications (decorative materials). MEDIUM OIL PAINT between 45% and 60% Oil to Resin. SHORT OIL PAINT less than 45% Oil to Resin. Faster drying, suitable for steelwork. More brittle, with shorter over-coating time. A mixture of oil and resin = oleoresinous.
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Binder - Solvent Compatability
Binder - Solvent Combinations WATER Vinyls, acrylics, epoxies, alkyds, bitumens, polyurethanes, acrylated rubbers.
Compatibility for over-coating.
Correct solvent group for binder.
WHITE SPIRIT Natural oils, natural resins, alkyds, phenolics.
Flashpoint and toxicity considerations.
XYLENE Chlorinated rubber. ACETONE Epoxy.
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7
Solvents
Solvents
Strong solvents for strong binders. Weaker solvents for weaker binders.
Solvent strength: its ability to dissolve the binder.
The stronger solvents have a low number of carbon atoms in the chemical formula.
Evaporation rate: controls polymerisation and drying.
The higher the number of carbon atoms, the higher the boiling point of the solvent,
Flash point: safety factor of the solvent. Toxicity: safety levels of exposure.
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Polymers A string or structure of repeated units Linear Polymer Pre formed, reversible, very sensitive to some HC solvents, thermoplastic. Also called solution polymer.
Linear
Branched polymer Oxidation drying, non-reversible. Natural oils and resins , become very brittle with age. Crosslinked polymer Chemically curing, very strong, multi-directional polymerisation, examples: epoxies, urethanes and polyurethanes.
Polymers are 3 dimensional in the dry paint film. Branched
Cross Linked
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Pigments Animal, vegetable, mineral, or synthetic. Particle size varies from of 1 micron.
1/
10
Pigments
Anti-corrosive: rust inhibitive properties.
th micron to average size
Contribute to cohesive strength, abrasion resistance, durability, opacity and in some instances, impermeability, and resistance to u/v rays.
Metallic: work sacrificially. Opaque: inert, provide opacity and colour. Extenders: add bulk, reduce cost. Laminar: provide impermeability.
Pigments must not dissolve in the vehicle.
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8
Metallic Pigments
Anti-corrosive (Rust Inhibitive) Pigments Primer Red lead (basic) (natural oils and resins) Calcium plumbate White Coal Tar Zinc Chromate
Also used to protect the substrate by cathodic protection.
Colour Toxic Toxic
Red
Toxic Toxic
Black Yellow
Two most commonly used are :
Purple/Grey
ZINC (better for galvanic protection). ALUMINIUM (excellent ultra-violet reflective properties).
Zinc phosphate most common
Material must be below steel in the galvanic list.
Barium Metaborate. Zinc Phosphosilicate. Copyright © TWI Ltd
Copyright © TWI Ltd
Opaque Pigments Inert particles which have excellent light scattering properties in order to give covering (opacity) and colour.
CARBON COBALT CHROMIUM IRON CALCIUM TITANIUM DIOXIDE
Black Blue Greens/Yellows/Oranges Browns/Reds/Yellows Reds/Yellows White
Extender Pigments Low priced, readily available materials, also known as fillers. They add bulk, improve intercoat adhesion, increase cohesive strength, and give extra thickness to paint film at low cost.
CLAYS CHALK TALCUM SLATE FLOUR
Kaolin , China Clay Calcium Carbonate Magnesium Silicate Aluminium Silicate
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(White) (White) (White) (Dark Grey)
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Laminar pigments
Laminar Pigments
Plate-like pigments which provide impermeability. In theory, they have a leafing effect, overlapping as the coating dries. Common laminar pigments:
Graphite. Glass flake. Aluminium flake (ultra-violet reflective). Micaceous Iron Oxide (Mio) (ultra-violet reflective).
Standard Pigment
Mio Theoretical
Attributes of Mio: UV A and B reflection, retards permeation, durability, provides adhesion to next layer. Copyright © TWI Ltd
Delaminated Mio
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9
Critical Pigment Volume Concentration (CPVC)
Other Additives Anti-settling agents:
Aids to shelf life.
Plasticisers: Reduce brittleness, aid application, improves flexibility. Below CPVC
Near CPVC
Above CPVC
Driers: Allow even through drying of oxidising films.
Poor opacity, high gloss, blistering Good opacity, cohesive strength, gloss, impermeability, Porous, low cohesive strength, poor adhesion
Anti-skinning agents: Retard the formation of surface skins.
Pigment/binder ratio can vary from paint to paint. Copyright © TWI Ltd
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Solutions and Dispersions
Solutions and Dispersions (Section 5) SOLVENT: SOLUTE:
Dispersion: a solid or a liquid within another liquid, where there is no solubility.
Will dissolve another material.
There are two types of dispersion
Is dissolved in the solvent
1 Suspension: fine particulate solids dispersed within a liquid, no solubility.
SOLUTION: The resultant liquid produced by dissolving a solute in a solvent.
Example: Sand + Water
EXAMPLE:
2 Emulsion: a liquid dispersed within another liquid where there is no solubility.
Solvent + solute = solution Would be sugar + water = sweet water
Example: Oil + Water
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Drying and curing of Paint Films (Section 6)
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Drying and Curing of Paint Films Oxidation
Solvent evaporation No chemical reaction.
Uses atmospheric oxygen.
Polymers are preformed and saturated.
Oxygen chemically combines with unsaturated double bonds.
Linear polymers closed at the ends by hydrogen and have no double bonds.
Process can be accelerated by addition of driers. Also called convertible or non-reversible.
Also called reversible or non-convertible.
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10
Drying and Curing of Paint Films
Curing Agents Used in 2-pack Epoxies
Chemical curing
AMIDES: Fully cured in 7 days at 20°C.
Must be mixed in the correct ratio (2 pack). Pot life (period after opening and mixing where the paint remains in a usable condition). Induction period (stand time, to allow for wetting of particles and crosslinking to begin).
AMINES: Fully cured in 3 days at 20°C. ISOCYANATES: Suitable for use where low temperatures are unavoidable, fully cured in 16 hours at 20°c. In 1984, at the union carbide plant in bhopal, india, water was accidentally released into a methyl isocyanate storage tank, resulting in 7000 fatalities.
These must be observed and controlled! Convertible or non-reversible. Chemically cross-linking polymers.
Very toxic, CO2 is produced when applied in damp conditions. Great care needed during use and removal! Copyright © TWI Ltd
Copyright © TWI Ltd
Drying and Curing of Paint Films: Coalescence
Solvent Evaporation
High boiling point solvents penetrate the spheres and fuse the binder globules, creating a solid film
Screen Test Two
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Question 1 Which of the following is Rust Grade C?
Question 1 When using a Venturi Nozzle at 100psi, the abrasive exits at approximately what speed?
a. Tightly adhering mill scale which can be brushed clean. b. Loosely adhering mill scale with no evident pitting. c. Mill scale almost totally removed, visible rust, no heavy pitting. d. Heavy pitting clearly visible, heavy corrosion.
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a. b. c. d.
200 mph. 450 mph. 1200 mph. 100 mph.
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11
Question 3
Question 2 The optimum pressure to achieve 100% efficiency in abrasive blast cleaning is?
Sand is not permitted as a dry blast abrasive, as directed by:
a. b. c. d.
a. b. c. d.
75 psi. 450 psi. 100 psi. 220 psi.
BGC/PS/PA10. BS 7079 Part A. COSHH. BS 410.
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Copyright © TWI Ltd
Question 4 How many times can garnet be used as an abrasive for BGAS site use?
Question 5 The correct ratio of a working mix would be: a. b. c. d.
a. Up to 3 times, if cleaning of abrasive is possible. b. None. c. As per the specification. d. 20 times.
70-80% Grit: 20-30% Shot. 50% Grit: 50% Shot. 70-80% Shot: 20-30% Grit. 20-25% Sand:75-80% Copper Slag.
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Copyright © TWI Ltd
Question 6
Question 7
Flame cleaning uses which mechanisms?
Carbon Impregnated hoses are used to:
a. Expansion, decontamination, and force. b. Oxidation, penetration, and de-lamination. c. Heat penetration, expansion, and dehydration. d. Oxidation, weathering, and pressurisation.
a. b. c. d.
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Create static electricity. Prevent static electricity. Reduce friction. Reduce static electricity.
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12
Question 8
Question 9
One of the most important safety items of equipment in abrasive blasting is:
What is the approximate speed of the abrasive particles exiting a wheelabrator?
a. b. c. d.
a. b. c. d.
Dry abrasive mix. The banana gauge. Dead mans handle. 100 psi compressor.
450 mph. 220 mph. Mach 3. 100 psi.
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Copyright © TWI Ltd
Question 10 Where would you normally use a comparator gauge? a. b. c. d.
To To To To
Question 11 Amplitude refers to what? a. The peak-to-trough height of a blast profile. b. The amount of noise a blasting operation creates. c. The velocity of the abrasive particles. d. The roughness of an abrasive particle.
check surface cleanliness. determine surface roughness. control cleaning of abrasives. assess the rust grade of a material.
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Copyright © TWI Ltd
Question 12 What is the material used in surface replica tape, used to measure profile? a. b. c. d.
Question 13 What is the cause of rash rusting? a. b. c. d.
Miler. Testrex. Mylar. Mylon.
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Oxygen. Rogue peaks. Hackles. Hygroscopic salts.
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13
Question 15
Question 14 The test for the presence of hygroscopic salts, is:
How many photographs of flame cleaning standards are shown in BS 7079 Part A?
a. b. c. d.
a. b. c. d.
Potassium hexacyanoferrate test. Copper sulphate test. Iron phosphate test. Iron chromate test.
4. 14. 8. 16.
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Copyright © TWI Ltd
Question 16
Question 17
Which abrasive has the effect of stress relieving the substrate?
Where would it be advisable to use steel grit as an abrasive?
a. b. c. d.
a. b. c. d.
Copper slag. Metallic shot. Steel grit. Garnet.
When a deep profile is required. On high pressure pipework. In enclosed blasting units. On offshore installations.
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Copyright © TWI Ltd
Question 18
Question 19
What is the minimum number of readings required for a Dial Micrometer?
Which test would be used to determine for soluble salts in a marine environment?
a. b. c. d.
a. b. c. d.
Minimum of 10. Minimum of 12. One only. As many as you wish, but the average reading is recorded.
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Potassium hexacyanoferrate. Copper sulphate. Iron phosphate. Silver nitrate.
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14
Question 20
Question 21
The standard for the test sieves used for the sizing of abrasives is:
The most common type of abrasive used for BGAS site work is:
a. b. c. d.
a. b. c. d.
BS 7079 part A. BS 410. BGC/PS/PA10. SI 1657.
Copper slag. Grit and shot mix. Garnet. Metallic shot.
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Copyright © TWI Ltd
Question 22
Question 23
Compared to a venturi nozzle, a straight bore nozzle would give:
Anchor pattern, key, peak-to-trough, are names given to what?
a. b. c. d.
a. b. c. d.
Better paint application. More speed. Larger area coverage. Greater accuracy.
The The The The
abrasive properties. cross section of a blast. total area of blasted substrate. potential of adhesion.
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Copyright © TWI Ltd
Question 24 What is a knock out pot?
Question 25 High pressure wet blasting operates up to which pressure?
a. A drum used for mixing paint and thinners. b. The area on the equipment where static electricity can build up and be hazardous. c. A vessel for removing oil and moisture from the air stream. d. A container where any blockages of the nozzle can be tapped free.
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a. b. c. d.
100 psi. 450 psi. 30,000 psi. 2,250 mph.
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15
Question 1 When using a Venturi Nozzle at 100psi, the abrasive exits at approximately what speed?
SWAP YOUR PAPERS PLEASE Put your name on your paper, and pass it to someone else to check
a. b. c. d.
200 mph. 450 mph. 1200 mph. 100 mph.
Answer: B
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Copyright © TWI Ltd
Question 2
Question 3
The optimum pressure to achieve 100% efficiency in abrasive blast cleaning is?
Sand is not permitted as a dry blast abrasive, as directed by:
a. b. c. d.
a. b. c. d.
75 psi. 450 psi. 100 psi. 220 psi.
BGC/PS/PA10. BS 7079 Part A. COSHH. BS 410.
Answer: C
Answer: C
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Copyright © TWI Ltd
Question 4 How many times can garnet be used as an abrasive for BGAS site use?
Question 5 The correct ratio of a working mix would be: a. b. c. d.
a. Up to 3 times, if cleaning of abrasive is possible. b. None. c. As per the specification. d. 20 times.
70-80% Grit: 50% Grit: 70-80% Shot: 20-25% Sand:
20-30% Shot. 50% Shot. 20-30% Grit. 75-80% Copper Slag.
Answer: C
Answer: B Copyright © TWI Ltd
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16
Question 6
Question 7
Flame cleaning uses which mechanisms?
Carbon Impregnated hoses are used to:
a. Expansion, decontamination, and force. b. Oxidation, penetration, and de-lamination. c. Heat penetration, expansion, and dehydration. d. Oxidation, weathering, and pressurisation.
a. b. c. d.
Answer: C
Create static electricity. Prevent static electricity. Reduce friction. Reduce static electricity.
Answer: D
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Copyright © TWI Ltd
Question 8
Question 9
One of the most important safety items of equipment in abrasive blasting is:
What is the approximate speed of the abrasive particles exiting a wheelabrator?
a. b. c. d.
a. b. c. d.
Dry abrasive mix. The banana gauge. Dead mans handle. 100 psi compressor.
450 mph. 220 mph. Mach 3. 100 psi.
Answer: B
Answer: C
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Copyright © TWI Ltd
Question 10 Where would you normally use a comparator gauge? a. b. c. d.
To To To To
Question 11 Amplitude refers to what? a. The peak-to-trough height of a blast profile. b. The amount of noise a blasting operation creates. c. The velocity of the abrasive particles. d. The roughness of an abrasive particle.
check surface cleanliness. determine surface roughness. control cleaning of abrasives. assess the rust grade of a material.
Answer: A
Answer: B
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Copyright © TWI Ltd
17
Question 12 What is the material used in surface replica tape, used to measure profile? a. b. c. d.
Question 13 What is the cause of rash rusting? a. b. c. d.
Miler. Testrex. Mylar. Mylon.
Oxygen. Rogue peaks. Hackles. Hygroscopic salts.
Answer: B
Answer: C
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Copyright © TWI Ltd
Question 14
Question 15
The test for the presence of hygroscopic salts, is:
How many photographs of flame cleaning standards are shown in BS 7079 Part A?
a. b. c. d.
a. b. c. d.
Potassium hexacyanoferrate test. Copper sulphate test. Iron phosphate test. Iron chromate test.
4. 14. 8. 16.
Answer: A
Answer: A
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Copyright © TWI Ltd
Question 16
Question 17
Which abrasive has the effect of stress relieving the substrate?
Where would it be advisable to use steel grit as an abrasive?
a. b. c. d.
a. b. c. d.
Copper slag. Metallic shot. Steel grit. Garnet.
When a deep profile is required. On high pressure pipework. In enclosed blasting units. On offshore installations.
Answer: C
Answer: C
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Copyright © TWI Ltd
18
Question 18
Question 19
What is the minimum number of readings required for a Dial Micrometer?
Which test would be used to determine for soluble salts in a marine environment?
a. b. c. d.
a. b. c. d.
Minimum of 10. Minimum of 12. One only. As many as you wish, but the average reading is recorded.
Answer: C
Potassium hexacyanoferrate. Copper sulphate. Iron phosphate. Silver nitrate.
Answer: D
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Copyright © TWI Ltd
Question 20
Question 21
The standard for the test sieves used for the sizing of abrasives is:
The most common type of abrasive used for BGAS site work is:
a. b. c. d.
a. b. c. d.
BS 7079 part A. BS 410. BGC/PS/PA10. SI 1657.
Answer: B
Copper slag. Grit and shot mix. Garnet. Metallic shot.
Answer: A
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Copyright © TWI Ltd
Question 22
Question 23
Compared to a venturi nozzle, a straight bore nozzle would give:
Anchor pattern, key, peak-to-trough, are names given to what?
a. b. c. d.
a. b. c. d.
Better paint application. More speed. Larger area coverage. Greater accuracy.
Answer: D
The The The The
abrasive properties. cross section of a blast. total area of blasted substrate. potential of adhesion.
Answer: B
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Copyright © TWI Ltd
19
Question 24
Question 25 High pressure wet blasting operates up to which pressure?
What is a knock out pot? a. A drum used for mixing paint and thinners. b. The area on the equipment where static electricity can build up and be hazardous. c. A vessel for removing oil and moisture from the air stream. d. A container where any blockages of the nozzle can be tapped free.
a. b. c. d.
100 psi. 450 psi. 30,000 psi. 2,250 mph.
Answer: C
Answer: C Copyright © TWI Ltd
Copyright © TWI Ltd
Question 1 Which of the following is not a drying mechanism? a. b. c. d.
Screen Test Three
Coalescence. Oxidation. Stove drying. Chemical curing.
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Copyright © TWI Ltd
Question 2 A solution is: a. The resultant liquid b. The resultant liquid c. The resultant liquid in another liquid. d. The resultant liquid another liquid.
Question 3 Which of the following is a natural oil?
in a polymerisation event. after dispersing a solid. after dissolving a material after dispersing a liquid in
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a. b. c. d.
Dammar. Alkyd. Castor Xylene.
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20
Question 4
Question 5
Which of the following are said to be reversible?
Which of the following are quantitative tests?
a. b. c. d.
a. b. c. d.
Cross-linked polymer. Branched polymer. Linear polymer. Convertible coating.
Potassium hexacyanoferrate. Copper sulphate. Silver nitrate test. Bresle sample patch.
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Copyright © TWI Ltd
Question 6
Question 7
A whirling hygrometer is also called a :
What is the meaning of compliant?
a. b. c. d.
a. In accordance with PA 10. b. In accordance with Environmental Protection Act. c. As per engineers instructions. d. As per manufacturers recommendations.
Pfund cryptometer. A psychrometer. A pyknometer. A rotational viscometer.
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Copyright © TWI Ltd
Question 8 What is the recommended stand-off distance and speed at which the abrasive leaves a Venturi Nozzle? a. b. c. d.
450 220 220 450
mm mm mm mm
and and and and
220 450 220 450
mph. mph. mph. mph.
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Question 9 A typical remedy for burnishing would be: a. b. c. d.
Power brushing. Emery paper or similar. Needle gun. Addition of thinners.
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21
Question 10 Which of the following is part of the Footners Duplex System? a. 1-2% sulphuric acid @ 65-800c for 5-25 mins. b. 5-10% sulphuric acid @ 70-800c for 5-10 mins. c. 5-10% sulphuric acid @ 65-700c for 5-25 mins. d. 5-10% chromic/phosphoric acid @ 65-700c for 1-2 mins.
Question 11 Which of the following is not a natural resin? a. b. c. d.
Copal. Amber. Dammar. Linseed.
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Copyright © TWI Ltd
Question 12
Question 13
Which of the following is not a natural oil?
Which of the following is an extender?
a. b. c. d.
a. b. c. d.
Castor. Amber. Olive. Linseed.
Graphite. Mica. Glass Flake. China Clay.
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Copyright © TWI Ltd
Question 14
Question 15
Which of the following is an opaque pigment?
Which of the following is an additive?
a. b. c. d.
a. b. c. d.
Graphite. Compound of hromium. Zirconium octoate. Zinc phosphate.
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Opaque pigments. Rust inhibitive pigments. Thickening agents. Thinners.
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22
Question 16 What is the specified minimum standard of cleanliness required by BGAS for non-ferrous substrates? a. b. c. d.
Sa 2 ½. Sa 3. St 1. Sa 1.
Question 17 Which of the following binders are reversible? a. b. c. d.
Epoxy. Urethane. Chlorinated rubber. Silicone.
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Copyright © TWI Ltd
Question 18
Question 19
What is the maximum allowable time lapse between surface preparation, and painting?
Which of the following is not a commonly used binder?
a. b. c. d.
a. b. c. d.
24 hours. 4 hours. 20-30 minutes. 7 days.
Epoxy. Zinc. Urethane. Vinyl.
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Copyright © TWI Ltd
Question 20 Wire brushes used for BGAS hand and power tool cleaning, must be made from which material? a. b. c. d.
Question 21 Using the correct calibration shim, a banana gauge can be calibrated on: a. b. c. d.
Tungsten or stainless steel. Copper or brass. Beryllium bronze or phosphor bronze. The same material as the pipe.
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Bare steel. Painted surfaces. Steel with a blast cleaned surface. Any metal surface.
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23
Question 22 Which of the following are commonly used as anti-settling agents? a. b. c. d.
Question 23 A paint drying by chemical reaction is said to be: a. b. c. d.
Heavy metal salts. Bentones and waxes. Saturated oils. Extender pigments.
Linear polymer. Convertible. Non-convertible. Reversible.
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Copyright © TWI Ltd
Question 24 Which of the following is not a laminar pigment? a. b. c. d.
Graphite. Glass flake. Magnesium silicate. Mica.
Question 25 Which two materials are commonly used as sacrificial anodes? a. b. c. d.
Copper and tungsten Aluminium and graphite. Zinc and aluminium. Lead and tin.
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.
Copyright © TWI Ltd
Question 1
Swap your papers please
Which of the following is not a drying mechanism? a. b. c. d.
Put your name on your paper, and pass it to someone else to check.
Coalescence. Oxidation. Stove drying. Chemical curing.
Answer: C
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Copyright © TWI Ltd
24
Question 3
Question 2
A solution is: a. The resultant liquid b. The resultant liquid c. The resultant liquid in another liquid. d. The resultant liquid another liquid.
Which of the following is a natural oil? in a polymerisation event. after dispersing a solid. after dissolving a material after dispersing a liquid in
a. b. c. d.
Dammar. Alkyd. Castor Xylene.
Answer: C Answer: C Copyright © TWI Ltd
Copyright © TWI Ltd
Question 4
Question 5
Which of the following are said to be reversible?
Which of the following are quantitative tests?
a. b. c. d.
a. b. c. d.
Cross-linked polymer. Branched polymer. Linear polymer. Convertible coating.
Answer: C
Potassium hexacyanoferrate. Copper sulphate. Silver nitrate test. Bresle sample patch.
Answer: D
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Copyright © TWI Ltd
Question 6
Question 7
A whirling hygrometer is also called a :
What is the meaning of compliant?
a. b. c. d.
a. b. c. d.
Pfund cryptometer. A psychrometer. A pyknometer. A rotational viscometer.
Answer: B
In accordance with PA 10. In accordance with Environmental Protection Act. As per engineers instructions. As per manufacturers recommendations.
Answer: B
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25
Question 8
What is the recommended stand-off distance and speed at which the abrasive leaves a Venturi Nozzle? a. b. c. d.
450 220 220 450
mm mm mm mm
and and and and
220 450 220 450
mph. mph. mph. mph.
Question 9
A typical remedy for burnishing would be: a. b. c. d.
Power brushing. Emery paper or similar. Needle gun. Addition of thinners.
Answer: B
Answer: D
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Copyright © TWI Ltd
Question 10
Which of the following is part of the Footners Duplex System? a. b. c. d.
0
1-2% sulphuric acid @ 65-80 c for 5-25 mins. 0 5-10% sulphuric acid @ 70-80 c for 5-10 mins. 0 5-10% sulphuric acid @ 65-70 c for 5-25 mins. 0 5-10% chromic/phosphoric acid @ 65-70 c for 12 mins.
Question 11
Which of the following is not a natural resin? a. b. c. d.
Copal. Amber. Dammar. Linseed.
Answer: D
Answer: C Copyright © TWI Ltd
Copyright © TWI Ltd
Question 12
Question 13
Which of the following is not a natural oil?
Which of the following is an extender?
a. b. c. d.
a. b. c. d.
Castor. Amber. Olive. Linseed.
Answer: B
Graphite. Mica. Glass Flake. China Clay.
Answer: D
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26
Question 15
Question 14
Which of the following is an opaque pigment?
Which of the following is an additive?
a. b. c. d.
a. b. c. d.
Graphite. Compound of Chromium. Zirconium octoate. Zinc phosphate.
Answer: B
Opaque pigments. Rust inhibitive pigments. Thickening agents. Thinners.
Answer: C
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Question 16
What is the specified minimum standard of cleanliness required by BGAS for non-ferrous substrates? a. b. c. d.
½
Sa 2 . Sa 3. St 1. Sa 1.
Question 17
Which of the following binders are reversible? a. b. c. d.
Epoxy. Urethane. Chlorinated rubber. Silicone.
Answer: C Answer: D
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Copyright © TWI Ltd
Question 18
Question 19
What is the maximum allowable time lapse between surface preparation, and painting?
Which of the following is not a commonly used binder?
a. b. c. d.
a. b. c. d.
24 hours. 4 hours. 20-30 minutes. 7 days.
Answer: B
Epoxy. Zinc. Urethane. Vinyl.
Answer: B
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27
Question 21
Question 20
Wire brushes used for BGAS hand and power tool cleaning, must be made from which material? a. b. c. d.
Tungsten or stainless steel. Copper or brass. Beryllium bronze or phosphor bronze. The same material as the pipe.
Using the correct calibration shim, a banana gauge can be calibrated on: a. b. c. d.
Bare steel. Painted surfaces. Steel with a blast cleaned surface. Any metal surface.
Answer: C Answer: C
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Copyright © TWI Ltd
Question 22
Which of the following are commonly used as anti-settling agents? a. b. c. d.
Question 23
A paint drying by chemical reaction is said to be: a. b. c. d.
Heavy metal salts. Bentones and waxes. Saturated oils. Extender pigments.
Linear polymer. Convertible. Non-convertible. Reversible.
Answer: B
Answer: B
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Copyright © TWI Ltd
Question 24
Question 25
Which of the following is not a laminar pigment?
Which two materials are commonly used as sacrificial anodes?
a. b. c. d.
a. b. c. d.
Graphite. Glass flake. Magnesium silicate. Mica.
Copper and tungsten Aluminium and graphite. Zinc and aluminium. Lead and tin.
.
Answer: C
Answer: C
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28
Paint Systems (Single or Multilayer) Primer: anti corrosive to protect the steel. Mio: protects primer, provides impermeability.
ATC 88 BGAS Painting Grade 2/3
Mid coat or build coat: protects underlying coating, builds thickness, and provides good adhesion for subsequent layer. Finish coat: aesthetic , correct colour, provide a smooth surface to allow cleaning and shedding of water.
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Primers
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Midcoat or Build Coat
Rust inhibitive pigments passivate the substrate. Mordant or wash primers (t-wash), acid reaction with the substrate produces inhibitive salts. No measurable thickness. Etchant primers, (polyvinyl butyral) similar Reaction but leaves a measurable thickness of 1525 um.
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Extender particles increase surface area to provide adhesion for any subsequent layer.
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Finish Coat Mainly aesthetic, but have other properties. Gloss finish, to assist in shedding water. Solar reflective (white), heat absorbent (black).
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Moisture tolerant:- moisture has no appreciable ill effect. Moisture curing polyurethane:- uses water vapour from the atmosphere to cure, damp or moist, but not wet. Low RH is a problem (min 35%). Damp: no signs of water, but temperature is below dew point. Moist: no standing water, but a noticeable film of water. Wet: droplets or standing water are present Moisture sensitive: moisture reacts with the isocyanates to produce carbon dioxide. Copyright © TWI Ltd
1
Paint Systems
Paint Systems Sacrificial systems
Powder Coatings Thermoplastic or thermosetting.
Zinc
Most commonly thermosetting, needs heat. Steel
Convertible coatings chemically cured. Usually electrostatically applied. Thin plate ,heat applied after powder. Thicker plate, heat applied before powder.
Particles in close contact allow electron circuit when an electrolyte enters the film.
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Waterborne Coatings (Section 8) Use water instead of hydrocarbon solvents.
The zinc acts as a barrier, and corrodes in its own right until there is coating damage and both metals are exposed to electrolyte. Zinc oxides are formed, and repairs Copyright © TWI Ltd the damage.
Paint Manufacture (Section 9) 1. Ball Mill
Most binders now available water borne. Steel balls rotate in cylinder, grind mill base to required particle size (5000 - 40000 lts).
Environmentally friendly, cheap, and compatible with any binder. Many coats can be applied in a day. Disadvantages include smaller application window, storage conditions and weather. Coatings used on BGAS contracts must be compliant. A compliant coating is one which complies with the requirements of the environmental protection act 1991. Copyright © TWI Ltd
Paint Manufacture (Section 9)
2. Attritor Mill
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Paint Manufacture (Section 9)
3. High speed disperser
Upright static cylinder, the steel balls are moved by motorised paddles.
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A 2500 rpm blender, produces mill base. (see Figure 9.2 in course notes for picture of a high speed disperser).
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2
Paint Manufacture (Section 9) 4. Kady Mill (another type is silverson mill) . For the manufacture of emulsions and waterborne paints.
Paint Manufacture (Section 9) 5. Sand Mill (pearl mill or bead mill). Mill base injected at bottom, forced through sand, refined, removed at top. Water cooled.
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13
Paint Manufacture (Section 9)
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Paint Manufacture (Section 9)
Sand Mills
6. Colloid Mill (High speed stone mill) Vertical or horizontal
2 stone discs (approx 10” dia) bottom disc rotates at 3600 rpm. Base is gravity fed to centre of discs. Ground by centrifugal force and friction. Copyright © TWI Ltd
Paint Manufacture (Section 9)
7. Triple Roll Mill
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Paint Manufacture (Section 9)
8. Single Roll Mill
Used to produce mastics, fillers and putties. 3 rolls travel at different speeds, paste sticks to faster of rolls.
Used to produce small batches of expensive materials (gilts, silvers etc.)
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3
Testing of Paints for Properties and Performance (Section 10) BS 3900 Methods of test for paint. BGC PS PA9 Table 2 : RESULTS REQUIRED BY BGAS. Tests subdivided into: Tests on wet materials. Tests on dry materials.
Paint Testing Determination of volatile/non-volatile Procedure: 1. Clean glass plate and rod is weighed. 2. Add 2g of paint, and weigh again. 3. Place into hot air oven (or hot plate). 4. Stir paint to evaporate solvent (volatile). Note: No naked flame! When dry, weigh glass plate to determine ratio of volatile/non-volatile.
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Flash Point of Solvents
Paint Testing Abel closed cup
Flash Point Test carried out in accordance with BS 3900 part A8 using abel cup. Defined as: the temperature at which vapour from a solvent will ignite in the presence of an external source of ignition. High flashpoint is safer than a low flashpoint.
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Copyright © TWI Ltd
Paint Testing The density cup is used to check for addition of thinners, or the correct mix ratio of 2 pack paints.
The density (SG) Cup
PART A (Base)
Pyknometer, SG cup, weight per litre, weight per gallon. Copyright © TWI Ltd
PART B (Catalyst)
Mixing Ratio
Site test result
Caused by Data sheet too much says of PART
1.35
0.95
6:1
1.29
1.35
A
1.28
0.80
6:1
1.21
1.40
A
1.40
0.79
4:1
1.27
1.20
B
1.19
0.75
5:1
1.11
1.39
A
1.22
0.80
7:1
1.16
1.08
B
1.50
0.82
4:1
1.36
1.16
B
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4
Hegman Grind Gauge
Paint Testing Hegman grind gauge For fineness of grind, degree of dispersion.
Particles submerged by scraper bar.
Particles protrude through the film if they are too large to be submerged. The surface changes from gloss to matt, and where between 5 and 10 protrusions is noted, this is the degree of dispersion or fineness of grind. Copyright © TWI Ltd
Copyright © TWI Ltd
Paint Testing
Paint Testing
Viscosity Viscosity Krebs Stormer Viscometer Kinematic Viscosity.
Defined as: A fluid’s resistance to flow. Rotational viscometer with rotothinner measures dynamic viscosity. Units = poises.
Driven by a falling weight, the heavier the weight the faster it rotates. Criteria 200 rpm units stoke or poise.
1 poise = The force required to maintain unit velocity between 2 surfaces separated by 1cm of fluid. Copyright © TWI Ltd
Copyright © TWI Ltd
Paint Testing Flow Viscosity Ford flow cup showing the 4mm hole.
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Ford flow cup in its retort stand.
Lid containing spirit level.
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5
Paint Film Thicknesses (Section 11) WFT measurement: Eccentric Wheel. Ford flow cup in use.
Must be used circumferentially on curved surfaces.
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WFT Measurement: Comb Gauges Must be used longitudinally on curved surfaces.
Last wet tooth
25
First dry tooth
35
45
60
Steel Comb gauge shows WFT reading of 35/45 um Copyright © TWI Ltd
Destructive Test Gauges: The PIG
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Destructive Test Gauges: The PIG Turn PIG 90deg. Light comes on - view graticule scale through eyepiece. Tables in instruction book give conversion factors for each blade, from graticule units into microns.
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Copyright © TWI Ltd
6
Destructive Test Gauges: The PIG Destructive test gauges.
The Saberg test drill.
View through eyepiece with graticule scale. Tables in instruction book give conversion factors for each blade, from graticule units to microns.
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DFT Measurements, Magnetic The banana gauge 211
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Dry Film Thickness Measurement, Magnetic
Calibration shims
The tinsley pencil (foremans gauge)
Scale moves to the curser
Purple Blue Brown White Yellow
25um 50um 125um 250um 500um
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Copyright © TWI Ltd
DFT Measurements: Electronic Gauges Dry film thickness measurement, magnetic, horseshoe gauge (used on TSA). Electrophysic Mini test
The exacto
Elcometer 456
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Copyright © TWI Ltd
7
Tests For Mechanical Properties On Paint
Tests for Mechanical Properties on Paint
Abrasion resistance Sample plates are weighed, and placed beneath abrasive discs for a number of cycles, then weighed again to determine abrasion resistance.
Impact resistance: Tubular impact tester. 1kg weight dropped 1 metre onto the paint surface of a test panel. Assessed for damage, direct or indirect.
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Copyright © TWI Ltd
Accelerated Testing, Weatherometers Flexibility test: conical mandrel Test plate bent over 3mm to 37mm diameter mandrel
0
Humidity cabinets: 95% humidity and 55 C. Salt spray cabinets: Salt laden environment. Water soak test: Panel submerged, weighed. Temperature cycling: hotter and colder than normal operating temperatures. Prohesion testing: (Protective adhesion) 3% salt 0 water spray @ 35 c, (60 min on : 60 min off) no undercut, blisters etc. Beyond 3mm boundary, after test duration of 1000 hours.
Check location where cracking begins Copyright © TWI Ltd
Drying and Curing Tests: Ballotini Test
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Drying and Curing Tests BK (Beck-koller) drying time recorders
Hopper containing small glass beads
Steel block graduated in hours of travel
Glass plate inserted into front slot and the stylus drawn across. Solvent evaporation time, sol/gel transition, surface dry and final dry times recorded.
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Copyright © TWI Ltd
8
Wolff-Wilborn Pencil Scratch Test
Mechanical Thumb Test, Through Drying
Uses the pencil hardness rating.
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Copyright © TWI Ltd
Opacity: The Pfund Cryptometer
Use Of The Pfund Cryptometer
1. View through the glass prism. 2. Record the point where the background can no longer be seen. 3. This is the opacity thickness.
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Copyright © TWI Ltd
Hiding Power Charts and Adjustable Applicator
Gloss Measured with a glossmeter (reflectometer) Gloss can be affected by:
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Pigment volume concentration. Fineness of grind (particle size). Resin type. Refractive index. Solvent type.
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9
Degree of Gloss
Digital Gloss Meter (Reflectometer)
Measures % of light Received, from amount of light transmitted
High
Low
> 80% = Gloss finish < 80% = Matt finish
Air RI, stick appears to bend
Water
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Adhesion Testing: V Cut Test Cut v using craft knife
30 0
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Adhesion Tests: Cross Cut (Cross Hatch) Test
Apply leverage Insert blade tip
Cut 6 lines vertical and 6 lines horizontal, creating 25 x 2mm squares.
Testing for: primer to substrate failure, intercoat adhesion failure and cohesive failure.
Apply an agreed tape. Pull off and compare % area of detachment as per BS 3900 PT E6.
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Copyright © TWI Ltd
Adhesion Tests The Dolly Test
Expendable aluminium dolly
Failure force measured in psi on this scale
Paint adhesion tester dolly test
Circular cutter
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Copyright © TWI Ltd
10
Hydraulic Adhesion Test Equipment Hand Operated Type (with scale of failure force on view)
Re-usable dolly
Units are: Mega- pascales Copyright © TWI Ltd
Copyright © TWI Ltd
Question 1
What is a pyknometer? a. b. c. d.
Screen Test Four
Opacity testing equipment. Whirling hygrometer. Density cup. Windspeed measuring equipment.
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Copyright © TWI Ltd
Question 2
What is the name of the mill used to produce mastics, fillers, and putties? a. b. c. d.
Question 3
Which of the following is not an adhesion test? a. b. c. d.
Triple roll mill. Ball mill. Single roll mill. Bead mill.
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Dolly test. Cross hatch. Krebs Stormer. HATE.
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11
Question 4
Which of the following is not a drying test? a. b. c. d.
Koenig Albert. Beck Koller. Mechanical Thumb. Ballotini.
Question 5
What is the name given to the drying test involving the use of glass beads? a. b. c. d.
Wolff wilborne. Taber. Ballotini. Erichsson.
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Copyright © TWI Ltd
Question 6
Question 7
What type of machinery is used to produce large production runs of popular paints?
A typical pot life of a paint used in BGAS specifications would be:
a. b. c. d.
a. b. c. d.
Triple roll mill. Colloid mill. Kady mill. Sand mill.
20-30 minutes. 12-24 hours. 6-8 hours. 3-7 days.
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Copyright © TWI Ltd
Question 9
Question 8 What is the specified temperature at which a Flash Point Determination test must be carried out? a. b. c. d.
200C. Up to 4500C. There is no specific temperature. 25 0C in seawater.
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HATE is an abbreviation of what? a. b. c. d.
High Adhesive Tension Equipment. Humidity Affected Electrical Tolerance. Hydraulic Adhesion Test Equipment. Hardness and Temperature Evaluation.
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12
Question 10
In paint testing, why is temperature cycling carried out? a. b. c. d.
To To To To
check check check prove
for water absorption. flexibility. contraction cracking. the service life of the coating system.
Question 10
Which of the following would not affect the degree of gloss? a. b. c. d.
Surface profile. Critical Pigment Volume Concentration. Solvent type. Degree of dispersion.
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Copyright © TWI Ltd
Question 12
What diameter is the conical mandrel, which is used in the flexibility test? a. b. c. d.
Question 13 What is the name of the equipment used to determine particle aggregate size? a. b. c. d.
8 mm to 25 mm. 12mm to 18mm. 5mm to 50mm. 3mm to 37mm.
Beck-koller. Hegman gauge. Wolfe-Wilborne. Krebs-Stormer.
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Copyright © TWI Ltd
Question 13
Which specification covers the internal coating of small bore steel pipes? a. b. c. d.
BGC BGC BGC BGC
PS PS PS PS
PA PA PA PA
10. 9. 8. 7.
Question 14
What product should be used for repairs to pipe coatings in damp conditions? a. b. c. d.
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Moisture sensitive isocyanates. Water-borne acrylics. Moisture curing polyurethane. Chlorinated rubber.
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13
Question 15
What surface preparation is specified in PA 10 for weathered galvanised steel? a. b. c. d.
1
Sa 2 /2, followed by T-Wash mordant primer. Sa 3, followed by etch primer. Hand abrasion with a stiff bristled brush only. Sa 1 followed by water washing.
Question 16 What would be the correct course of action upon discovering that the contractor has applied a coat of paint, out of sequence? a. b. c. d.
Blast and re-coat. Apply the correct coating over the top. Inform the engineer. Add an extra protective coating.
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Copyright © TWI Ltd
Question 17
The function of a finish coat is mainly to provide: a. b. c. d.
Impermeability and adhesion. Aesthetic properties and water shedding. Cathodic protection and passivation. Increased thickness at low cost.
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Question 19
Question 18
What is the name of the vessel used to determine the viscosity of free flowing fluids, as per BGAS specifications? a. b. c. d.
Ford Flow cup No 4. Zahn cup. Abel cup. Pyknometer.
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Question 20 The BGas specified site painting conditions are:
Which of the following is not a test for contaminants? a. b. c. d.
Sellotape. Banana gauge. Talcum powder. Solvent.
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a. Maximum wind speed 4 m/sec, relative humidity maximum 95%. 0 b. Maximum 90% relative humidity, dew point 3 C above steel. 0 c. Maximum 90% relative humidity, dew point 3 C less than steel. 0 d. Maximum 27 C, relative humidity 95% maximum.
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14
Question 21
Question 22
Which test would be used to determine for soluble salts in a marine environment?
Which of the following is an extender pigment?
a. b. c. d.
a. b. c. d.
Potassium hexacyanoferrate. Sulphuric acid. Iron phosphate. Silver nitrate.
Magnesium silicate. Aluminium oxide. Manganese napthanate. Barium metaborate.
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Copyright © TWI Ltd
Question 23
With every 11 degree rise in temperature, the air’s ability to hold water: a. b. c. d.
Would Would Would Would
rise by 11%. half. double. decrease by 11%.
Question 24
According to PA10, what is the correct course of action upon discovering foreign bodies embedded in the paint film? a. b. c. d.
Apply an extra protective barrier coat. Re-blast and re-coat. Lightly abrade with emery paper, apply stripe coat. Make a report to the engineer only.
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Copyright © TWI Ltd
Question 25
According to PA10, is the addition of Thinners allowed? a. b. c. d.
Yes, at the engineers discretion, up to 20% max. Only if the paint is difficult to apply. Yes, in accordance with the product data sheets. No, under no circumstances.
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Swap your papers please
Put your name on your paper, and give it to someone else to check
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15
Question 1
What is a pyknometer? a. b. c. d.
Question 2
What is the name of the mill used to produce mastics, fillers, and putties?
Opacity testing equipment. Whirling hygrometer. Density cup. Windspeed measuring equipment.
a. b. c. d.
Triple roll mill. Ball mill. Single roll mill. Bead mill.
Answer: C Answer: A
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Copyright © TWI Ltd
Question 3
Question 4
Which of the following is not an adhesion test?
Which of the following is not a drying test?
a. b. c. d.
a. b. c. d.
Dolly test. Cross hatch. Krebs Stormer. HATE.
Koenig Albert. Beck Koller. Mechanical Thumb. Ballotini.
Answer: A
Answer: C
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Copyright © TWI Ltd
Question 5
Question 6
What is the name given to the drying test involving the use of glass beads?
What type of machinery is used to produce large production runs of popular paints?
a. b. c. d.
a. b. c. d.
Wolff wilborne. Taber. Ballotini. Erichsson.
Answer: C
Triple roll mill. Colloid mill. Kady mill. Sand mill.
Answer: D
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Copyright © TWI Ltd
16
Question 7
What is the specified temperature at which a Flash Point Determination test must be carried out?
A typical pot life of a paint used in BGAS specifications would be: a. b. c. d.
Question 8
20-30 minutes. 12-24 hours. 6-8 hours. 3-7 days.
a. b. c. d.
Answer: C
200C. Up to 4500C. There is no specific temperature. 25 0C in seawater.
Answer: C
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Copyright © TWI Ltd
Question 9
In paint testing, why is temperature cycling carried out?
HATE is an abbreviation of what? a. b. c. d.
Question 10
High Adhesive Tension Equipment. Humidity Affected Electrical Tolerance. Hydraulic Adhesion Test Equipment. Hardness and Temperature Evaluation.
a. b. c. d.
Answer: C
To To To To
check check check prove
for water absorption. flexibility. contraction cracking. the service life of the coating system.
Answer: C
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Copyright © TWI Ltd
Question 11
Question 12
Which of the following would not affect the degree of gloss?
What diameter is the conical mandrel, which is used in the flexibility test?
a. b. c. d.
a. b. c. d.
Surface profile. Critical Pigment Volume Concentration. Solvent type. Degree of dispersion.
Answer: A
8 mm to 25 mm. 12mm to 18mm. 5mm to 50mm. 3mm to 37mm.
Answer: D
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Copyright © TWI Ltd
17
Question 13 What is the name of the equipment used to determine particle aggregate size? a. b. c. d.
Question 13
Which specification covers the internal coating of small bore steel pipes? a. b. c. d.
Beck-koller. Hegman gauge. Wolfe-Wilborne. Krebs-Stormer.
Answer: B
BGC BGC BGC BGC
PS PS PS PS
PA PA PA PA
10. 9. 8. 7.
Answer: C
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Copyright © TWI Ltd
Question 14
Question 15
What product should be used for repairs to pipe coatings in damp conditions?
What surface preparation is specified in PA 10 for weathered galvanised steel?
a. b. c. d.
a. b. c. d.
Moisture sensitive isocyanates. Water-borne acrylics. Moisture curing polyurethane. Chlorinated rubber.
1
Sa 2 /2, followed by T-Wash mordant primer. Sa 3, followed by etch primer. Hand abrasion with a stiff bristled brush only. Sa 1 followed by water washing.
Answer: C
Answer: C
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Copyright © TWI Ltd
Question 17
Question 16 What would be the correct course of action upon discovering that the contractor has applied a coat of paint, out of sequence? a. b. c. d.
The function of a finish coat is mainly to provide: a. b. c. d.
Blast and re-coat. Apply the correct coating over the top. Inform the engineer. Add an extra protective coating.
Impermeability and adhesion. Aesthetic properties and water shedding. Cathodic protection and passivation. Increased thickness at low cost.
Answer: B
Answer: C
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Copyright © TWI Ltd
18
Question 18
What is the name of the vessel used to determine the viscosity of free flowing fluids, as per BGAS specifications? a. b. c. d.
Ford Flow cup No 4. Zahn cup. Abel cup. Pyknometer.
Answer: A
Question 19
Which of the following is not a test for contaminants? a. b. c. d.
Sellotape. Banana gauge. Talcum powder. Solvent.
Answer: B
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Copyright © TWI Ltd
Question 20
The BGas specified site painting conditions are: a. Maximum wind speed 4 m/sec, relative humidity maximum 95%. 0 b. Maximum 90% relative humidity, dew point 3 C above steel. 0 c. Maximum 90% relative humidity, dew point 3 C less than steel. 0 d. Maximum 27 C, relative humidity 95% maximum.
Question 21
Which test would be used to determine for soluble salts in a marine environment? a. b. c. d.
Potassium hexacyanoferrate. Sulphuric acid. Iron phosphate. Silver nitrate.
Answer: D
Answer: C
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Copyright © TWI Ltd
Question 22
Which of the following is an extender pigment? a. b. c. d.
Magnesium silicate. Aluminium oxide. Manganese napthanate. Barium metaborate.
Question 23
With every 11 degree rise in temperature, the air’s ability to hold water: a. b. c. d.
Would Would Would Would
rise by 11%. half. double. decrease by 11%.
Answer: C
Answer: A
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19
Question 24
According to PA10, what is the correct course of action upon discovering foreign bodies embedded in the paint film? a. b. c. d.
Apply an extra protective barrier coat. Re-blast and re-coat. Lightly abrade with emery paper, apply stripe coat. Make a report to the engineer only.
Question 25
According to PA10, is the addition of Thinners allowed? a. b. c. d.
Yes, at the engineers discretion, up to 20% max. Only if the paint is difficult to apply. Yes, in accordance with the product data sheets. No, under no circumstances.
Answer: C
Answer: B
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20
Cathodic Protection: Sacrificial System
ATC 88 BGAS Painting Grade 2/3
Zinc block (anode) Steel pipe (cathode) Must be in direct contact or joined by a conductive cable Copyright © TWI Ltd
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Cathodic Protection: Sacrificial System
Sacrificial zinc anodes
Cathodic Protection: Impressed Current Transformer / rectifier (negative) connected to pipe (Cathode)
There is no current/ electron flow if the coating is in good condition
Positive connection to ground bed (anode)
When barrier coating of buried pipe is damaged, corrosion circuit commences. (Electrons travel from cathode to anode via the electrolyte) Copyright © TWI Ltd
Copyright © TWI Ltd
Cathodic Protection: Monitoring Potentials
Impressed Current Transformer Rectifier Unit
Copper/copper sulphate half-cell reference electrode
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Copyright © TWI Ltd
1
Pinhole/Holiday Detection: Sponge Detector
Cathodic Disbondment Test
Voltage Range 9 to 90v. (Some have only 2 settings) intermediate 67.5v. Sponge is wetted in water with a drop of detergent. Test in progress
Inspection on completion
Excess squeezed out, then passed over the substrate.
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Holiday/Pinhole Detection
Typical high voltage set for pinhole detection. Operates up to 15kv too high for normal paint systems.
Holiday Detection on cross-country pipeline.
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High Voltage Holiday Tester
Test springs now not allowed on BGAS projects
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Holiday Detection of Coated Pipe
Paint Application Application methods
Contoured Brush
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2
Conventional spray
Gravity feed
Suction feed
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Paint application: Conventional Spray
Advantages Inexpensive nozzles. Good atomisation. More Accuracy. Less cleaning after use. Better finish achieved. Lower working pressure. Concentrated spray pattern.
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Paint Application: Airless Spray Airless Spray Gun
Disadvantages Heavy hose lines. Operator fatigue. Specialised containers. Slow application rates.
Portable Pump Copyright © TWI Ltd
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Paint Application: Airless Spray
Air Circuit: Blue Paint Circuit: Red One Way Ball Valve
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3
Paint Application: Airless Spray
Advantages High deposition rates. Can apply high viscosity fluids. Versatile (no air hose). High transfer efficiency. Lower waste. Large area coverage. Uses manufacturers paint containers.
Paint Application: Electrostatic Spraying
Disadvantages
Poor atomisation. Expensive nozzles. Coatings limitations. Increased maintenance. High skill required. Increased safety risk (+ or - 3500 psi). Lower quality finish.
Negatively charged component
Spray gun
Positively charged particles Ionised air volume
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Paint A
Advantages
High transfer efficiency. Good edge cover. Good wraparound. Uniform film thickness. Low wastage.
Hot duty surfaces (> 340 0C)
Disadvantages
(BGC/PS/PA10 PAGE 29 Table SPA 3c)
Bulky, delicate guns. Requires extra cleanliness. Fire/Safety hazard. Component must be conductive. High maintenance costs.
Requires the highest grade of cleanliness: Profile 75um/Grade sa 3 (check for mill scale)
1 Thermally sprayed aluminium. 2 Inorganic zinc silicate. 3 Polysiloxane inorganic coating.
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Copyright © TWI Ltd
TSA: Thermally Sprayed Aluminium
Wire and Pistol Type TSA Applicator Gun
The preferred system, giving longest life. Wire and pistol type (most common). High purity wire. Butane/propane and oxygen fuel gas. Propelled by compressed air onto substrate. Thickness approx 100 - 125 um.
For high temperature service silicone sealer must be applied.
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Wire feed trigger
Fuel gas
Oxygen Compressed air Copyright © TWI Ltd
4
TSA: Thermally Sprayed Aluminium
Visual Inspection
Steel coated with TSA
Wire and Pistol Type
Steel blast cleaned to Sa 21/2
Loss of adhesion (poor surface preparation)
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Copyright © TWI Ltd
Paint, Faults and Bittiness IZS: Inorganic Zinc Silicate Inclusions, either airborn or from the paint itself.
Alternative to TSA. Apply as per manufacturers recommendation. Apply silicone sealer.
Could also be caused by partially cured paint, which is out of shelf life.
Apply heat to cure sealant (turn the system on). Polysiloxane inorganic coating Alternative to TSA and IZS. 0
Will withstand temperatures up to 1100 c. Apply as per manufacturers recommendation. This is not sealed.
(Flocculation) Coating Faults: Blistering
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Coating Faults: Bleeding The solvent from the top coat softens the under lying material and allows it to pass into and through the layer, causing discolouration. (Brown for bitumen, yellow for coal tar).
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Blisters can contain gas, liquid or crystals.
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5
Coating Faults Cissing
Coating Faults: Chalking
Caused by inadequate surface preparation.
Degradation of the binder due to disruptive factors in the environment
A difference in surface energy causes local lack of adhesion. Larger spots known as fish eyes and large areas referred to as crawling.
Epoxies are especially vulnerable.
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Coating Faults: Cracking
Coating Faults: Cissing Mud cracking
Differential expansion and coating age.
Crazing/hair cracking
Crocodiling/alligatoring
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Coating Faults: Cratering
Bowl shaped depressions. Caused by escaping solvent or gases.
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Coating Faults: Curtains, Sags, Runs and Tears Caused by over application. To remedy: remove excess material, lightly abrade and recoat.
High viscosity paint will not flow to fill the depressions. Resulting in small bowls and craters.
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6
Coating Faults: Flaking
As material ages, it gets brittle, cracks and starts to detach. Oxidising paints are especially vulnerable.
Coating Faults: Holidays
Defined as : A void, a miss, or an uncoated area.
(Natural oils and resins).
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Coating Faults: Lifting
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Algae and Mould Growth
Caused by solvent strength and also lack of observance of stated overcoating time.
Remedy: treat with biocidal agent for 24 hours, then clean with detergent/stiff bristle brush/water washing. Copyright © TWI Ltd
Orange Peel
Similar appearance to the skin of a citrus fruit. Caused by paint viscosity problems or by applicator technique.
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Coating Faults: Ropiness
Brushmarks Caused by brushing when film is almost dry, or when paint viscosity is too high.
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7
Coating Faults: Wrinkling and Rivelling
Defect: Rash or Spot Rusting
Cause: rogue peaks, or possibly by contamination of the paint film by foreign matter, such as grit or dirt etc.
Paint forms a skin, trapping solvent below the surface. As this eventually dries, the skin contracts, causing the surface to wrinkle. Copyright © TWI Ltd
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Colour Primary Colours: Red, Yellow and Blue The human eye operates on only these three pigments. Plus, other various colours can be created by combining to various degrees. Colour has 3 main attributes Hue Refers to the basic colour (red, green, yellow, blue etc.) Brightness The darkness or lightness of the colour. Saturation How vivid the colour appears (also known as chroma, intensity, weight).
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Colour: The Munsell System (USA) L= Luminance, chroma
Yellow through green ,blue
a= From green to red
Purple, red and back to yellow
b= From blue to yellow
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BS 4800 Hue From 00 (neutral) to 24 even numbers only. Brightness From A (max white) to E (max black). Saturation 01 to 56 Higher number = stronger colour. Lower number= greyer the colour. Black and white, and all the grey colours in between, are achromatic colours as they lack hue. Anything having colour is said to be chromatic.
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Ral System
System uses cards containing 210 colours.
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8
Product Identification by Pipe Colour Pipe Colour Coding to BS 1710 (Section 13) Uses BS 4800 to identify product Product
Named Colour
BS 4800 APP. REF
Air
Light Blue
20 E 51
Acids and Alkalies
Violet
22 C 37
Gases (except Air)
Yellow Ochre
08 C 35
Fluids
Black
00 E 53
Fresh Water
Auxiliary Blue
18 E 53
Water
Green
12 D 51
Electrical Services
Orange
06 E 51
Brown
06 C 34
Min/Vegetable/Animal Oils, Combustible liquids
Health and Safety COSSH Regulations (Control of substances hazardous to health )
Toxic or Very Toxic
Harmful or Irritant
Corrosive
Hazard warning symbols.
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Health And Safety: (COSHH Regulations)
Hazard Warning Symbols Abbreviations
Explosive
Oxidizing
Extremely flammable
Highly flammable
Can be found on safety data sheets and on the paint tin label. Dangerous for the environment
EH 40
HSE guidance notes: list of all known harmful substances.
OEL
Occupational exposure limit ( there are 2 types).
MEL
Maximum exposure limit must never be exceeded! The maximum exposure to airborne substance over a reference period. Occupational exposure standard
OES
The concentration level of an airborne substance (averaged over a reference period) which is considered safe to be exposed to, day after day (ppm). RAQ
Required air quantity
HASAWA
Health and safety at work act (1974)
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Protective Masks
Dust only!
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Health And Safety: Drager Tube and Bellows
Solvents
Each depression of the bellows draws 100 cc of air Copyright © TWI Ltd
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9
Drager Tube and Bellows
Duties of a Painting Inspector
Ensure that all work is carried out in accordance with the specification requirements.
To test the air quality when using solvents. Varying crystal types for different solvents.
No deviation from specification unless permission given in writing from a higher authority, ie clients engineer.
Example: Xylene (OEL: 100 ppm) Raq: 500 cc (5 depressions). Crystals will change colour, (white to red/brown). Toxicity levels read from the scale on the tube.
Report any deviation from specifications. Especially malpractices.
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Visual Inspection Blast cleaned surfaces: Slivers, hackles, laminations, cracks, pitting. Wet paint films: Runs, sags, cissing, uneven coverage.
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Report Writing
All information requested on a report sheet should be completed. The information provides traceability in the event of any future breakdown.
Dry paint films: Quality of finish, paint faults, opacity (grinning), coverage, holidays.
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Day To Day Activities – Record 1. Environmental conditions. 2. Confirmation of materials used (abrasives, paint, pipe data etc). 3. Confirmation of equipment (calibrations etc). 4. Adherence to specification application faults 5. Adverse weather conditions (start and stop times etc).
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Good reports and documentation are essential to ensure efficient handover to another inspector in the event of illness or other emergencies.
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Daily Checks Beginning of the day Environment, equipment, materials, previous days work. During the day Environment, equipment, materials, each operators work, application faults, the standards. At the end of the day The days work, housekeeping, all daily reports.
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10
Purpose of a Quality Plan
Records - End of Contract
All daily records signed off. A complete register of control documents. A complete record of test results. All NCR’s should be closed out. Complete waste disposal records. A complete correspondance file.
To ensure stated paramenters are met.
Establish the integrity of the system.
To provide tracable records.
To reduce the risk of error.
Inspection Is not quality assurance. Inspection is not quality control.
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Question 1
This paint defect is referred to as:
Screen Test Five
a. b. c. d.
Flaking. Chalking. Grinning. Cissing.
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Copyright © TWI Ltd
Question 2
Question 3
The main difference between airless and conventional spray is:
What is the name of the equipment used to determine particle aggregate size?
a. b. c. d.
a. b. c. d.
Conventional spray gives better deposition rate. Conventional spray gives less waste. Airless spray gives better quality finish. Conventional spray gives better atomisation.
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Beck-koller. Hegman gauge. Wolfe-Wilborne. Krebs-Stormer.
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11
Question 4
What are the 3 attributes, which make up the colour of a paint? a. b. c. d.
White, black, and primary colour. Hue, brightness and saturation. Red, yellow, and blue. Contrast, density, and definition.
Question 5
What voltage settings are commonly used for sponge test holiday detection? a. b. c. d.
5 Kv to 15 Kv. 15 Kv maximum. 9v to 90 v. 110v or 240v.
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Copyright © TWI Ltd
Question 6
This is the hazard warning symbol for: a. b. c. d.
Toxic or very toxic. Harmful or irritant. Corrosive. Explosive.
Question 7
Another name for a vapour trap is? a. b. c. d.
Air wash cup. Dry out pot. Knock out pot. Pressure regulator.
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Copyright © TWI Ltd
Question 8
Beryllium Bronze is a material used in the manufacture of: a. b. c. d.
Question 9
Which of the following are primary colours? a. b. c. d.
Welding electrodes. Power wire brushes. Comb gauges. Venturi Nozzle liners
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Blue yellow and green. Red green and white. Red white and blue. Red yellow and blue.
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12
Question 10
When carrying out holiday detection using the sponge tester, what can we add to the water? a. b. c. d.
Question 11
What would be the main problem of a low CPVC? a. b. c. d.
Salt. Detergent. Xylene. Inhibitor.
High opacity. Permeability. Low Gloss. Low opacity.
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Copyright © TWI Ltd
Question 12
Question 13
BGC/PS/PA10 contains which table, specifying the preferred coating systems?
Thermally sprayed aluminium is normally applied by which system?
a. b. c. d.
a. b. c. d.
Spa Spa Spa Spa
6a. 1e. 4a. 3c.
Electric arc spray. Sheradising. Wire and Pistol. Electro-plating.
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Copyright © TWI Ltd
Question 14
Padding refers to what?
Question 15
Which of the following is not a system for paint colour classification?
a. Protection for pipes during transport and storage. b. Protective clothing for TSA application. c. A paint application method. d. Material used to soak spillages.
a. b. c. d.
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BS 4800. BS 5252. Munsell. BGC/PS/CW5.
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13
Question 16
When testing for Xylene using a Drager Bellows, the crystals will change colour: a. b. c. d.
Orange to black. White to red/brown. White to green. White to black.
Question 17
Which pH range covers acids? a. b. c. d.
7 0 0 5
to to to to
14. 7. 14. 10.
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Copyright © TWI Ltd
Question 18
Question 19
What is the specified abrasive overlap requirement on repair areas? a. b. c. d.
The specified method of removal of this of type of contamination is:
250 mm. Twice pipe diameter. 100 mm. 1 metre.
a. b. c. d.
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Copyright © TWI Ltd
Question 21
Question 20
Where a silicone sealer is applied to an Inorganic Zinc Silicate coating system, how is the sealer cured? a. b. c. d.
Propane torch. Electric induction pads. It cures when the system begins to operate. It does not require curing.
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Dry abrasive blasting. Hand abrasion. Xylene. High pressure washing.
Which would be considered to be the most toxic? a. b. c. d.
Acetone. Xylene. Ethanol. Toluene.
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14
Question 22
Question 23
The document issued by the HSE listing all known harmful substances, is:
In the electrostatic spray painting process, the component must be:
a. b. c. d.
a. b. c. d.
COSHH. SI 1657. EH40. IGE SR 21.
Positively charged. Negatively charged. 9 volts DC. 15 Kv DC.
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Copyright © TWI Ltd
Question 24
Question 25
Where bleeding is evident on a pipe which was previously coated with coal tar, the staining would be which colour? a. b. c. d.
This is caused by: a. b. c. d.
Black Brown Yellow Red
Expansion and contraction. Age and environment. Solvent strength. Surface contamination.
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Copyright © TWI Ltd
Question 1
Swap your papers please This paint defect is referred to as: a. b. c. d.
Put your name on your paper, and pass it to someone else to check
Flaking. Chalking. Grinning. Cissing.
Answer: B Copyright © TWI Ltd
Copyright © TWI Ltd
15
Question 3
Question 2 The main difference between airless and conventional spray is: a. b. c. d.
What is the name of the equipment used to determine particle aggregate size?
Conventional spray gives better deposition rate. Conventional spray gives less waste. Airless spray gives better quality finish. Conventional spray gives better atomisation.
a. b. c. d.
Answer: D
Beck-koller. Hegman gauge. Wolfe-Wilborne. Krebs-Stormer .
Answer: B
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Question
4
What are the 3 attributes, which make up the colour of a paint? a. b. c. d.
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White, black, and primary colour. Hue, brightness and saturation. Red, yellow, and blue. Contrast, density, and definition.
Question 5
What voltage settings are commonly used for sponge test holiday detection? a. b. c. d.
5 Kv to 15 Kv. 15 Kv maximum. 9v to 90 v. 110v or 240v.
Answer: C
Answer: B
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Copyright © TWI Ltd
Question 6
This is the hazard warning symbol for: a. b. c. d.
Toxic or very toxic. Harmful or irritant. Corrosive. Explosive.
Question 7
Another name for a Vapour Trap is? a. b. c. d.
Air wash cup. Dry out pot. Knock out pot. Pressure regulator.
Answer: C
Answer: B
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Copyright © TWI Ltd
16
Question 8
Beryllium bronze is a material used in the manufacture of: a. b. c. d.
Question 9
Which of the following are primary colours? a. b. c. d.
Welding electrodes. Power wire brushes. Comb gauges. Venturi nozzle liners.
Blue yellow and green. Red green and white. Red white and blue. Red yellow and blue.
Answer: D
Answer: B
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Copyright © TWI Ltd
Question 10
When carrying out holiday detection using the sponge tester, what can we add to the water? a. b. c. d.
Question 11
What would be the main problem of a low CPVC? a. b. c. d.
Salt. Detergent. Xylene. Inhibitor.
Answer: B
High opacity. Permeability. Low gloss. Low opacity
Answer: D
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Copyright © TWI Ltd
Question 12
Question 13
BGC/PS/PA10 contains which table, specifying the preferred coating systems?
Thermally sprayed aluminium is normally applied by which system?
a. b. c. d.
a. b. c. d.
Spa Spa Spa Spa
6a. 1e. 4a. 3c.
Electric arc spray. Sheradising. Wire and pistol. Electro-plating.
Answer: C
Answer: B
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Copyright © TWI Ltd
17
Question 14
Padding refers to what? a. b. c. d.
Protection for pipes during transport and storage. Protective clothing for TSA application. A paint application method. Material used to soak spillages.
Answer: C
Question 15
Which of the following is not a system for paint colour classification? a. b. c. d.
BS 4800. BS 5252. Munsell. BGC/PS/CW5.
Answer: D
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Copyright © TWI Ltd
Question 16
When testing for Xylene using a Drager Bellows, the crystals will change colour : a. b. c. d.
Question 17
Which pH range covers acids? a. b. c. d.
Orange to black. White to red/brown. White to green. White to black.
7 0 0 5
to to to to
14. 7. 14. 10.
Answer: B
Answer: B
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Copyright © TWI Ltd
Question 18
Question 19
What is the specified abrasive overlap requirement on repair areas? a. b. c. d.
The specified method of removal of this of type of contamination is:
250 mm. Twice pipe diameter. 100 mm. 1 metre.
a. b. c. d.
Answer: C
Dry abrasive blasting. Hand abrasion. Xylene. High pressure washing.
Answer: D Copyright © TWI Ltd
Copyright © TWI Ltd
18
Question 20
Where a silicone sealer is applied to an inorganic zinc silicate coating system, how is the sealer cured? a. b. c. d.
Question 21
Which would be considered to be the most toxic? a. b. c. d.
Propane torch. Electric induction pads. It cures when the system begins to operate. It does not require curing.
Acetone. Xylene. Ethanol. Toluene
Answer: D
Answer: C
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Copyright © TWI Ltd
Question 22
Question 23
The document issued by the HSE listing all known harmful substances, is:
In the electrostatic spray painting process, the component must be:
a. b. c. d.
a. b. c. d.
COSHH. SI 1657. EH40. IGE SR 21.
Positively charged. Negatively charged. 9 volts DC . 5 Kv DC.
Answer: B
Answer: C
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Question
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Question 25
24
Where bleeding is evident on a pipe which was previously coated with coal tar, the staining would be which colour? a. b. c. d.
This is caused by: a. b. c. d.
Black. Brown. Yellow. Red.
Answer: C
Expansion and contraction. Age and environment. Solvent strength. Surface contamination.
Answer: C
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19
To recognise and identify the benefits/disadvantages of paint systems. To understand the importance of surface preparation. To understand methods of application and testing. To understand paint system inspections. To interpret requirements of standards. To meet the syllabus requirements for the BGASCSWIP Painting Inspector Examination.
ATC 88 BGAS Painting Grade 2/3
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A cascade system of two grades:
Course Times Break Times/Prayer Times
Smoking/Mobile Phones
Grade one, offshore grade. Grade two, painting inspector.
Homework (every evening) Course material Practical equipment
You must have grade 2 to obtain grade 1.
Queries
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Examination Details Grade 2 Theory: 50 Multi Choice one and a half hours allowed.
Practical Examination Abrasives: identification and uses. Rust grade – identification. Blast cleaning grade – identification.
Practical (Includes use of gauges etc) 50 multichoice, In two parts 25 questions Practical Theory and 25 Practical). One and a half hours allowed.
Hand and power tool grade – identification.
This is a closed book exam.
Use of whirling hygrometer and scales.
Profile measurement: testex and needle gauge. Dry film thickness measurements. Identification of equipment. Paint fault identification.
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1
Candidate Requirements Prior to Course Event enrolment form PLEASE SEND A PHOTOCOPY WITH YOUR PAYMENT AND THE NECESSARY ENCLOSURES TO:
Pages to note: course text
TWI Training & Examination Services
2 x passport photographs: (print name, and sign on the back)
Customer Services Granta Park Great Abington Cambridge CBI 6AL Tel.: +44 (0)1223 891162 Fax. +44 (0)1223 891630 E-mail: [email protected]
OR
TWI North Aurora Court, Barton Road Riverside Middlesbrough TS2 1RY Tel.: +44 (0)1642 210512 Fax: +44 (0)1642 252218 E-mail: [email protected]
Page 23.1 to 23.13 (131-143) revision questions.
Course bookings – please complete page 1 Course and Exam packages – please complete pages 1-3 Exam bookings – please complete pages 1-3
Page 23.14 to 23.16 (144-145) inspection calculations.
PLEASE USE CAPITAL LETTERS THROUGHOUT
Event ref _____________ Event date _________________________ Event title ________________________________________________ _________________________________________________________ Delegate’s first name (s) _________________________________________________________ Delegate’s surname
Page 23.16 (146) relative humidity/dew point calculations.
_________________________________________________________ Date of birth (dd/mm/yy) _____________________________________
Completed event enrolment form
Permanent private address _________________________________________________________ _________________________________________________________
Pages to note: pa10
_________________________________________________________ _________________________________________________________ _________________________
postcode ______________________
Private tel no_______________________________________________
Page 16, section 7 : application of paint.
E-mail____________________________________________________ Correspondence address (if different from above) _________________________________________________________ _________________________________________________________
Confirmation of payment details
_________________________________________________________
Page 21, table spa 1e : preferred systems.
Invoice/Sponsor address (if different from Employer address) _________________________________________________________ _________________________________________________________ Employer name and address
0
_________________________________________________________
Page 27, table spa 3c : hot duty surfaces (above 340 c).
_________________________________________________________ _________________________________________________________ _________________________
postcode ______________________
Contact name ______________________________________________ Telephone_________________________________________________
A valid eyesight test
Page 28, table spa 4a : damp metal surfaces.
Fax ______________________________________________________ E-mail____________________________________________________ Please tick if you are A member of The Welding & Joining Society An employee of an Industrial Member of TWI Member of Institute of Mechanical Engineers (for ATC65 course only)
Page 39, 40, 41 table spa 6a,b,c : non-ferrous surfaces.
Industry Sectors: (Please tick one only) Power Generation Automotive Electronic Oil, Gas & Petrochemical
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Corrosion (Section 1)
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Electrical Circuit
Defined as:
A current flows from positive to negative, from anode to cathode, (+ to -).
The degradation of a material by chemical or Electro-chemical means.
The corrosion is caused by electrons travelling in exactly the opposite direction from cathode to anode, (- to +).
Electro-chemically, implies 2 mechanisms:
An electrical circuit, always dc. A chemical reaction, producing corrosion.
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The corrosion current is the ions returning to the anode in the circuit.
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Corrosion Theory 3 factors needed for corrosion to occur:
Anode, a positively charged area.
Cathode, a negatively charged area.
Electrolyte, a substance which will conduct a current and be broken down by it.
An electrolyte will dissociate into positive and negative ions.
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2
Where the electrons move to -ve, cathode becomes the cathode, negatively charged.
Where electrons move from becomes the anode, positively charged. A corrosion cell – AKA a battery? Copyright © TWI Ltd
+ve, anode
14
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=
Corrosion in a metal object, such as a pipe for example.
1 micron
A negative area of metal (cathode) is connected to a positive area (anode) by the pipe wall itself. As a result, electrons can flow from the anode to the cathode.
2
4600 atoms of iron -
15
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The Combustion Triangle
26 PROTONS
+
-
-
Electrons travel at 18600 miles per second! (1/10 speed of light).
-
Physical size of 1 electron 1 proton = 1836 electrons
-
1 electron
Iron atom = 26 electrons + 26 protons + 30 neutrons Copyright © TWI Ltd
What is Corrosion
Corrosion is like a slow burning fire
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3
The Corrosion Triangle
Cathode
Electrolyte
Electrolyte
Anode
Anode
Shows electrical circuit
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Cathode
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Factors Accelerating Corrosion
Anodes corrode. The combination of elements (oxidation) takes place at the anode. Cathodes are protected, hydrogen is evolved at the cathode as the electrolyte dissociates into positive and negative ions.
Temperature Steel is thermodynamically unstable. As the steel heats up, it gains molecular freedom, becomes more active, and undergoes corrosion more readily.
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Hygroscopic (Osmotic) Blisters
Tiny, pin head size, water filled blisters. Caused by hygroscopic salts (iron sulphates and iron chlorides) grow into larger blisters causing dis-bondment.
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Factors Accelerating Corrosion Aerobic conditions, (presence of oxygen) Introduce oxygen, double the ions, (twice the number of hydroxyl ions) which will passivate twice the number of iron ions at the anode which will theoretically produce twice the corrosion!
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Factors Accelerating Corrosion
Microbial (Anaerobic) Corrosion
Microbial influenced corrosion (MIC)
Sulphate reducing bacteria (SRB) under anaerobic (absence of oxygen) conditions produce hydrogen sulphide.
Presence of some types of bacteria on the metal surface:
Sulphate reducing bacteria (SRB’s).
Metal eating microbes (MEM’s).
SRBs can also form deposits that are linked to under-deposit corrosion. Most aggressive conditions will exist in static water or under deposits where SRBs are protected from disturbance.
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FACTORS INFLUENCING CORROSION 4. BACTERIA ON THE SURFACE SULPHUR REDUCING BACTERIA (S.R.B)
Affected units or equipment
Thrive in oxygen free (or stagnant) areas. They remain dormant until they find oxygen free sites. Hydrogen sulphide (acid) producing bacteria, very active between 25-45°C. Rapid corrosion - often more than 5mm/year. Once established, bacteria colonies are very difficult to eradicate - they exist beneath slimes and deposits where biocide has difficulty reaching them
METAL EATING MICROBES (M.E.M)
Microbial Sulphate Reducing Bacteria Usually form small holes in the direction of Corrosion gravity, similar to weld porosity Severe internal microbial corrosion Copyright © TWI Ltd
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Factors Accelerating Corrosion Acids and alkalies
Bi-metallic Corrosion
Acids and alkalies are both electrolytic. They both dissociate into ions.
Heat exchangers. Bottom water of storage tanks. Piping in contact with some soils. Piping with stagnant or low flow. Systems where cooling water is not treated. Fire water systems.
When 2 different metals are in direct contact or joined by a conductive wire, in an environment where an electrolyte is present, one of the metals will corrode.
The metal which will corrode is dependent on its position in the galvanic list.
For example;
The position in the list determines which metal becomes the anode, and the distance between them determines the electrical potential and rate of corrosion.
HCl, Hydrochloric acid NaOH, Sodium hydroxide (alkalide)
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The Galvanic List MATERIAL
POTENTIAL
Graphite Titanium Silver Nickel Lead Admiralty Brass Copper Tin Millscale Low Alloy Steel Mild Steel Aluminium Alloys Zinc Magnesium
+ -
0.25 v 0.0 v 0.1 v 0.15 v 0.2 v 0.3 v 0.3 v 0.35 v 0.4 v 0.7 v 0.7 v 0.9 v 1.0 v 1.6 v
Carbon steel bolts in stainless steel pipework Copyright © TWI Ltd
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Bi-metallic Corrosion When the potentials of the metals are known, the galvanic list can also be known as :
Calculations
Formulae
The electro-motive forces series. The electro-chemical series.
WFT
Solvent V.S%
Note: both the position in the list and the free potential can alter with a different electrolyte and temperature.
Binder
Pigment and Extenders
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Calculations
DFT (% of WFT)
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Volume Calculations
Example: what WFT would be required to provide a DFT of 85 µm, if the paint used was of 66% VS?
Example: how much paint would be required to cover an area of 500m2 to a DFT of 85µm, if the paint used was of 66 % VS?
WFT= 100 %VS
If volume = WFT x area 1000
=
x
1.51 x 85
DFT 1
=
100 x 85 66 1
= 128µm X 500m2 1000
128 microns
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= 64 Litres
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Weather Conditions Considerations
Tonight Go to page 23.14 in your course notes, and using the formula on page 11.4, try the WFT, DFT and VS% calculations.
% Relative humidity (max 90%).
Air temperature (dry bulb temperature).
Steel temperature (>30C above dew point).
Calculated dew point temperature.
Manufacturers recommended minimum application temperature (approx 50C typically).
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Whirling Hygrometer (Aspirated Hygrometer) Is mercury in a continuous, unbroken stream? (If not, rectify with a magnet)
Whirling Hygrometer (Aspirated Hygrometer) Pre-use checklist Does the hygrometer spin freely? Is it clearly readable? Is there a wick? Is the wick clean?
Is the reservoir filled? (Distilled water) Is there a wick?
Is the wick wet, (must be distilled water)?
Is the wick clean?
Is the mercury in a continual , unbroken stream?
Is the wick wet?
If not , rectify by pulling back with a magnet.
Is the wick fastened around the bulb neck?
Is the wick fastened around bulb? Copyright © TWI Ltd
Copyright © TWI Ltd
WHIRLING OR ASPIRATED HYGROMETER
Weather Conditions - Dew Point Calculations
Rotate as fast as possible for 30 - 40 seconds (4 metres /sec minimum). Wet bulb reading taken immediately.
Line Up Temp Readings
Example: Dew point 0
Dew Point
Face towards any breeze. If not, walk forward to create an airflow. Test conducted as close to the area of painting as possible. 0
2 consecutive readings within 0.2 c of each other. Copyright © TWI Ltd
Dry bulb = 15 c 0 Wet bulb = 10 c 0
Align 10 c wet (red) 0 With 15 c dry (black) Read DP temp inside the eliptical window opposite the wet bulb 0 temp (DP = 5.5 c) Copyright © TWI Ltd
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Dew Point Calculator
Read %RH here
To determine % relative humidity 0
Dry bulb 15 c 0 Dew point 5.5 c
Line up Dp and dry bulb Temperatures
Read RH% from tip of black arrow, in the small elliptical window.
Weather Conditions: Definitions Relative humidity (RH) Defined as: The amount of water vapour in the air, expressed as a percentage (%) of the amount of water vapour which could be in the air at that same temperature. Dew point (DP) Defined as: The temperature at which water vapour in the air will condense.
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Surface Preparation (Section 2)
Measuring Steel Temperatures Limpet Gauge Magnetic contact wait 15 Min’s before reading
Thermocouple
Why prepare a surface?
Electronic contact Immediate reading
To remove contaminants and provide a surface to which the paint will readily adhere. This will effectively provide a longer service life from the coating. Two factors for consideration Degree Of Cleanliness. Degree of roughness or surface profile.
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Surface Preparation by Dry Abrasive Blasting Some surface defects may be revealed after surface cleaning.
Surface Profile The
height of the surface profile is determined by: Size of Abrasive. Velocity of Abrasive. Hardness of Abrasive. Density of Abrasive. Angle of Impingement. Surface cracks
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Surface breaking laminations
Surface pitting
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Surface Preparation Methods
Dry Abrasive Blasting
Dry abrasive blast cleaning.
Wet blasting.
Abrasives.
Hand and power tool cleaning.
Profile and adhesion.
Flame cleaning.
Profile measurement and assessment.
Pickling (chemical cleaning).
Rust grades and degree of cleanliness.
Vapour degreasing.
Equipment.
Weathering.
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Dry Abrasive Blasting: Abrasives
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Dry Abrasive Blasting: Abrasives
Copper slag. Expendable. Most commonly used site abrasive.
Contaminated copper slag. Must not be re-used.
Must only be used once, as it shatters upon impact. It is non-metallic.
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Dry Abrasive Blasting: Abrasives
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The Danger of Sand Used as an Abrasive SI 1657: Statutory Instrument (LAW) more than 1% free silica (upon impact) is banned. This information is normally found on COSHH or material safety data sheets.
Garnet. This is a mineral. It can be either expendable, or can be re-cycled, but must be cleaned before re-use.
Causes: silicosis and pneumonicosis Chronic obstructive pulmonary disorders, caused by breathing dust from a variety of minerals, (coal, copper, sand etc). They cause airflow blockage and breathing difficulties, resulting in serious illness, disability and death. Copyright © TWI Ltd
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9
Dry Abrasive Blasting: Abrasives
Dry Abrasive Blasting: Abrasives
Metallic shot
Metallic grit and shot mix.
Used in enclosed systems, needs to be cleansed before reuse. Gradually wears down cycle by cycle.
Mixing ratio depends on spec. As does the particle sizes. Used in enclosed systems. Grit cuts the profile, shot controls the peaks.
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Dry Abrasive Blasting: Abrasives Blasting chamber with under-floor abrasive recovery system.
Metallic grit. Must be recycled for economic reasons. Not used for site work, and it must be cleansed before reuse.
Allows recycling of abrasive grit/shot for economic reasons.
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Dry Abrasive Blasting: Abrasives
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Dry Abrasive Blasting: Abrasives Particle size distribution: sieves to BS 410
Walnut shell Agricultural byproduct, not used on steel. As with other abrasives, it is available in various particle sizes.
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Sizing of Abrasives
G = grit. Irregular shape, sharp edges which gradually become blunted after many cycles of use. Stress relieves surface.
Adhesion Defined as: The force required to separate two surfaces in contact.
S = Shot, Spherical shape, work hardens.
There are two theories of adhesion;
There are various systems relating to size:
Molecular interference: a physical method (for example: Velcro).
The SAE, using the J 444 sieve system.
Molecular attraction: a chemical method (for example: a Magnet).
BS 7079 Part E, particle size distribution.
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Profile Irregularities
Prolonged blasting in one area produces rogue peaks
Surface Damage
Blasting can deform a Sliver into an upright shard of metal called a Hackle.
A rogue peak is an isolated peak of excessive amplitude, rectified by abrasion with emery paper or similar. Copyright © TWI Ltd
Laminations
Lamination
< 13mm approx. size
Surface Breaking Lamination, or Sliver
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Profile Measurement: Surface Profile Needle Gauge
Gauge must be calibrated to zero on a flat, smooth glass plate, set to zero, and lock the bezel in place. It can not be used on curved surfaces, such as pipes.
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Surface Profile Measurement: Dial Micrometer and Surface Replica Tape
Surface Profile Assessment Surface Comparator to BS 7079 Pt C, ISO 8503 Shot blast comparator. Not used for surface cleanliness. Only for assessment of shot blasted substrates. Grit blast comparator can also be used on substrates blasted with grit/shot mix.
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Rust Grades
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Blast Cleaning Grades (BS EN 7079 Part A)
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Rust Grades
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Blasting Grades A Sa 2.5 and Sa 3
Please note: as closely adherent mill scale can not be removed with light blast cleaning, or even thorough blast cleaning: There are no grade A Sa1 or Sa 2 photographs! In BS 7079 Part A. However we do have:
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Blasting Grades B Sa 1 and Sa 2
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Blasting Grades, Comparisons
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Blasting Grades C Sa 2.5 and Sa 3
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Blasting Grades B Sa 2.5 and Sa 3
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Blasting Grades C Sa 1 and Sa 2
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Blasting Grades D Sa 1 and Sa 2
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13
Blasting Grades D Sa 2.5 and Sa 3
SCREEN TEST ONE
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Question 1 Two examples of hygroscopic salts would be:
Iron Iron Iron Iron
phosphates and iron chromates. chlorates and iron oxides. sulphates and iron chlorides. sulphides and iron silicates.
Question 2
What is an electrolyte? It is a mixture of salts and water. A substance which will conduct electricity and cause rusting. Oxidising liquid which will attack steel. A substance which will conduct a current and be broken down by it.
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Question 3
Question 4
Corrosion is defined as:
Hydrogen is evolved at:
Rusting of the Cathode by electro physical means. Oxidation of a metal in contact with water. Degradation of a material by chemical or electrochemical means. Breakdown of the metal by hydrogen.
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The The The The
anode at all times. cathode as corrosion takes place. cathode in the form of hydrogen gas. anode as corrosion takes place.
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14
Question 5 Which blasting grade best describes thorough Blast cleaning?
Sa Sa Sa Sa
2. 2½. 3. 1.
Question 6 What is the minimum standard of surface cleanliness specified by SPA1a of BGC/PS/PA 10?
Rust Grade C. St 3. Sa 2½. 30 to 75 microns.
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Question 7 In a corrosion circuit, electrons flow from:
Question 8 Rust grade A can be described as:
Anode to cathode, via electrolyte. Positive to negative. Electrolyte to steel. Cathode to anode, via electrolyte.
Tightly adhering mill scale, with evident heavy pitting. Clean white metal. Tightly adhering mill scale, with no apparent corrosion. Mill scale which has begun to flake, or can be scraped away.
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Question 9 Abrasive used on site for British Gas projects must be:
Mixed with sand, to reduce cost. Dried in an oven prior to use. Expendable. Used up to a maximum of three times only.
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Question 10 Which is the more noble metal:
Steel. Aluminium. Magnesium. Tin.
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Question 11 Mill scale is made up of which three oxide compounds?
Question 12 Two factors to be considered when inspecting a surface preparation, are:
Rust, iron oxide, and scale. RSJ, RSC, and RSA. Wustite, magnetite, and haematite. Iron sulphate, iron chloride, and iron phosphate.
Cleanliness and roughness. Rust grade and material type. Abrasive type and time. Surface area and type of contamination.
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Question 13
Question 14
The Galvanic List is also known as: Which of the following is Rust Grade C?
The The The The
metallic corrosion potential chart. electromotive forces series. element forces order. electronic chemical series.
Tightly adhering mill scale which can be brushed clean. Loosely adhering mill scale with no evident pitting. Mill scale almost totally removed, visible rust, no heavy pitting. Heavy pitting clearly visible, heavy corrosion.
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Question 15
Question 16 The thickness of mill scale is approximately:
At the beginning of the corrosion process the iron atom changes it’s polarity from: Neutral to positive. Neutral to negative. Positive to negative. Positive to neutral.
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25μm to 100μm. 100 to 150μm. Zero. Dependant upon the material thickness.
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16
Question 17 The force required to separate two surfaces in contact, can also be termed:
Question 18 Blasting in one area for too long, produces what?
Viscosity. Profile. Adhesion. Blasting.
Hackles. Rogue Peaks. Slivers. Laminations.
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Question 19 Metallic shot also has which affect upon the material?
Stress relieves. Physically deforms. Work hardens. Causes Slivers.
Question 20 What is the main cause of flash rusting on a substrate?
Rogue peaks. Oxygen. Hackles. Hygroscopic salts.
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Question 22
Question 21 What is the main advantage of using Testex papers for surface profile measurement?
It also measures cleanliness. Most accurate over a large area. Easy to use. Permanent record.
Which of the following could be classified as a major cause of microbial corrosion:
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Sulphur eating metal. Sulphur reducing bacteria. Rust inhibitive salts. Iron phosphates.
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Question 23
Question 24
Three factors which accelerate the rate of corrosion are:
How many abrasive blast cleaning photographs are in BS 7079 part A?
Temperature, time, and coating system. Bi-metallic contact, hygroscopic salts, and bacteria. Coating system, pipe diameter, and ultra violet light. blasting grades, rust grades, and surface profile.
4. 14. 8. 16.
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Question 25 British Gas PA 10 specifies a surface profile of: Swap your papers please
30 microns to 75 microns. 100 microns to 150 microns. 10 microns to 40 microns. more than 90 microns.
Put your name on your paper, and pass it to someone else to check.
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Question 1
Question 2
Two examples of Hygroscopic Salts would be:
What is an electrolyte?
a. b. c. d.
a. It is a mixture of salts and water. b. A substance which will conduct electricity and cause rusting. c. Oxidising liquid which will attack steel. d. A substance which will conduct a current and be broken down by it.
Iron Iron Iron Iron
phosphates and iron chromates. chlorates and iron oxides. sulphates and iron chlorides. sulphides and iron silicates.
Answer: C
Answer: D Copyright © TWI Ltd
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18
Question 3
Question 4
Corrosion is defined as:
Hydrogen is evolved at:
a. Rusting of the cathode by electrophysical means. b. Oxidation of a metal in contact with water. c. Degradation of a material by chemical or electrochemical means. d. Breakdown of the metal by hydrogen.
a. b. c. d.
Answer: C
Answer: C
The The The The
anode at all times. cathode as corrosion takes place. cathode in the form of hydrogen gas. anode as corrosion takes place.
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Question 5
Question 6
Which blasting grade best describes thorough blast cleaning?
What is the minimum standard of surface cleanliness specified by SPA1 of BGC/PS/PA 10?
a. b. c. d.
a. b. c. d.
Sa Sa Sa Sa
2. 2½. 3. 1.
Rust Grade C. St 3. Sa 2½. 30 to 75 microns.
Answer: C Answer: A Copyright © TWI Ltd
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Question 7
Question 8
In a corrosion circuit, electrons flow from:
Rust grade A can be described as:
a. b. c. d.
a. Tightly adhering mill scale, with evident heavy pitting. b. Clean white metal. c. Tightly adhering mill scale, with no apparent corrosion. d. Mill scale which has begun to flake, or can be scraped away.
Anode to cathode, via electrolyte. Positive to negative. Electrolyte to steel. Cathode to anode, via electrolyte.
Answer: D
Answer: C Copyright © TWI Ltd
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19
Question 9 Abrasive used on site for British Gas projects must be: a. b. c. d.
Mixed with sand, to reduce cost. Dried in an oven prior to use. Expendable. Used up to a maximum of three times only.
Question 10 Which is the more noble metal: a. b. c. d.
Steel. Aluminium. Magnesium. Tin.
Answer: D
Answer: C Copyright © TWI Ltd
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Question 11
Question 12
Mill scale is made up of which three oxide compounds?
Two factors to be considered when inspecting a Surface Preparation, are:
a. b. c. d.
a. b. c. d.
Rust, iron oxide, and scale. RSJ, RSC, and RSA. Wustite, magnetite, and haematite. Iron sulphate, iron chloride, and iron phosphate.
Cleanliness and roughness. Rust grade and material type. Abrasive type and time. Surface area and type of contamination.
Answer: A
Answer: C Copyright © TWI Ltd
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Question 13
Question 14
The galvanic list is also known as:
Which of the following is Rust Grade C?
a. b. c. d.
a. Tightly adhering mill scale which can be brushed clean. b. Loosely adhering mill scale with no evident pitting. c. Mill scale almost totally removed, visible rust, no heavy pitting. d. Heavy pitting clearly visible, heavy corrosion.
The The The The
metallic corrosion potential chart. electromotive forces series. element forces order. electronic chemical series.
Answer: B
Answer: C Copyright © TWI Ltd
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20
Question 15 At the beginning of the corrosion process the iron atom changes it’s polarity from: a. b. c. d.
Question 16 The thickness of mill scale is approximately: a. b. c. d.
Neutral to positive. Neutral to negative. Positive to negative. Positive to neutral.
Answer: A
25μm to 100μm. 100 to 150μm. Zero. Dependant upon the material thickness.
Answer: A
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Question 17 The force required to separate two surfaces in contact can also be termed: a. b. c. d.
Question 18 Blasting in one area for too long, produces what? a. b. c. d.
Viscosity. Profile. Adhesion. Blasting.
Answer: C
Hackles. Rogue Peaks. Slivers. Laminations.
Answer: B
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Question 20
Question 19 Metallic shot also has which affect upon the material?
What is the main cause of flash rusting on a substrate?
a. b. c. d.
a. b. c. d.
Stress relieves. Physically deforms. Work hardens. Causes Slivers.
Answer: C
Rogue peaks. Oxygen. Hackles. Hygroscopic salts.
Answer: A
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21
Question 21
Question 22
What is the main advantage of using Testex papers for surface profile measurement?
Which of the following could be classified as a major cause of microbial corrosion:
a. b. c. d.
a. b. c. d.
It also measures cleanliness. Most accurate over a large area. Easy to us. Permanent record.
Answer: D
Sulphate eating metal. Sulphate reducing bacteria. Rust inhibitive salts. Iron phosphates.
Answer: B
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Question 23
Question 24
Three factors which accelerate the rate of corrosion are:
How many Abrasive Blast Cleaning photographs are in BS 7079 part A?
a. Temperature, time, and coating system. b. Bi-metallic contact, hygroscopic salts, and bacteria. c. Coating system, pipe diameter, and ultra violet light. d. Blasting grades, rust grades, and surface profile.
a. b. c. d.
4. 14. 8. 16.
Answer: B
Answer: B Copyright © TWI Ltd
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Question 25 British Gas PA 10 specifies a surface profile of: a. b. c. d.
30 microns to 75 microns. 100 microns to 150 microns. 10 microns to 40 microns. More than 90 microns.
Answer: A
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Wheelabrators (Centrifugal Blast Units) Abrasive Particle Speed 220 Mph Series Of Drums Rotating At 2600 Rpm
ATC 88 BGAS Painting Grade 2/3
100% Surface Coverage
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Wheelabrators or Centrifugal Blast Units
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Automatic Blasting Machines Wheelabrators
Operate at approx. 2600 RPM. Totally enclosed (good operator safety). Automatic chain driven roller feed. Varying number of operating wheels. Gravity fed abrasive (re-usable). Airwash cleansing system for abrasives. Preferred abrasive is metallic shot.
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Centrifugal Blasting Chamber
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Dry Abrasive Blasting Equipment COMPRESSORS pressure rating in psi capacity in cfm. BACK PRESSURE AT NOZZLE hypodermic needle gauge. VAPOUR TRAPS, knock-out pots (removal of oil and water from air stream). PRESSURISED BLAST POTS of suitable capacity. CARBON IMPREGNATED HOSES, to reduce static shock. NOZZLES, Venturi (450 mph) and Straight bore (200 mph). SAFETY TO IGE SR 21 (Institute of Gas Engineers : Safety Regulations).
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1
Typical Set-up of a Dry Abrasive Blasting Operation Internal view of VENTURI NOZZLE increases speed of abrasive from 200 mph to 450 mph.
Pressurised blast pot Compressor Vapour traps (knock out pots)
Whiplash prevention cables Blasting nozzle
Carbon impregnated reinforced hose
External bayonet type couplings
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Blasting Safety
Carbon impregnated hose.
Typical portable site blasting machines.
Hose must have external, Bayonet type couplings, with whiplash restraints.
Reccova valve, fitted to other end of air lines to dead man handle.
Air Filter (breathing air not supplied directly from compressor).
Exhaust beware!
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Blasting Safety
Carbon impregnated hose whiplash cables air-fed helmet protective visor leather apron dead man’s handle gauntlets.
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2
Bayonet Type (Chicago) Couplings
Dead Man’s Handle
Blasting nozzle trigger which must be under the direct control of the operator.
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Measuring Blast Pressure at the Nozzle Hypodermic needle gauge
Method
Alert the operator. Shut off abrasive.
Air Connection Fail Safe Trigger
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Wet Blasting: Methods High pressure pure water blasting <30,000psi. High pressure water plus abrasive injection. Low pressure water plus abrasive injection. Steam cleaning. Air blasting with water injection.
Insert the needle through the hose, with the needle towards the nozzle, at an angle of approximately 45 degrees. Copyright © TWI Ltd
Ultra High Pressure Water Jetting, >30,000 PSI UHP Water Jetting (above 30,000 psi)
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Wet Blasting Abrasive blasting with water injected in to the abrasive stream at the blasting nozzle
Low Pressure water cleaning
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3
Hand and Power Tool Cleaning, (BS 7079 Pt A) High Pressure Water Jetting – up to 30,000 psi
Steam Cleaning
Hand and power wire brushes, chipping hammers, needle guns, emery cloth. St 2 Thorough hand and power tool cleaning. St 3 Very thorough hand and power tool cleaning. Note: because millscale is harder than the brush bristles, (phosphor bronze / beryllium bronze). There is no standard for rust grade A! Copyright © TWI Ltd
Jason’s Hammer and a Needle Gun
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Surface Preparation Hand and power tool cleaning B St 2 and St 3.
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Surface Preparation Hand and power tool cleaning C St 2 and St 3.
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Surface Preparation Hand and power tool cleaning D St 2 and St 3.
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4
Flame Cleaning 1 EXPANSION, co-efficient of expansion. 2 DEHYDRATION, moisture is evaporated. 3 HEAT PENETRATION, heat conducted into substrate.
Pickling is acid bath followed by washing. Footner’s Duplex system. Pickling followed by passivation. Passivation is treatment in phosphoric or chromic acid, which passivates the steel by forming a layer of rust- inhibitive salts which also aid adhesion and provide resistance to cathodic disbondment.
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Footner’s Duplex System Remove oil and grease and check using UVA lamp (contamination shows up yellow/green). Immerse in 5-10% sulphuric acid, 5-25 mins @ 65-700C. Rinse in clean water. Immerse in 2% Phosphoric/chromic acid, with 0.5% iron filings, 1-2 mins @ 800C. Rinse in clean water. Check ph level between 4.5 and 7.0.
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Surface Contaminants and Tests (Section 3) Hygroscopic salts : potassium ferricyanide, (now called potassium hexacyanoferrate)
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Surface Preparation, Chemical Cleaning
PH indicator papers, used to measure acidity or alkalinity of the substrate after final wash. For BGAS the pH should be between 4.5 and 7.
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Surface Contaminants and Tests (Section 3) Soluble chlorides: silver nitrate test. Mill scale: copper sulphate (only for Sa 3 grade). Oil or grease: solvent (not aliphatic) or U/V LAMP. Moisture: talcum or chalk. Dust: sellotape.
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Quantitative Tests for Hygroscopic Salts
Merkoquant test
Bresle sample patch
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Salts Detection, Bresle Sample Patch Kit
Paint Technology (Section 4) There are 3 main groups of paint: Paints containing solvents. Solvent free multi-pack, (MCL’s) Powder paints. All have the same basic constituents:
Binder (film former, non-volatile, vehicle).
Solvent. Pigments and other additives. Copyright © TWI Ltd
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Binder properties Binders used in National Grid (BGAS) specifications
Ease of application to: Give adhesion to the substrate. Provide resistance to abrasion. Provide chemical resistance. Provide cohesive strength. Provide dialectric strength. Resist the passage of water. Change from a liquid into a solid. Hold the pigments in suspension.
Acrylics. Alkyds. Epoxies. Ethyl and methyl silicates. Polyurethane silicones
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Other binders (non BGAS)
Cellulose resins. Chlorinated rubber. Emulsions. Natural oils and resins. Phenolic resins. Styrene and vinyl.
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Oils
Natural oils are produced from the seeds of a plant. Examples: Linseed, soya, olive, coconut, tung, castor. These oils must combine with oxygen, therefore must be unsaturated. A saturated oil already has enough oxygen bonds, and will not solidify and form a film.
Resins Natural resins are from the main plant, tree trunk). Resins are naturally brittle and fast drying, therefore need modification. This is done by addition of oils. Natural resins are Copals and Dammars and Coumarones, Amber and Laq. Other resins such as frankincense and myrrh are more valued for their perfume qualities.
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Oils Drying Oils Three sets of double bonds along a carbon backbone, react readily in ambient conditions. (unsaturated oils). Semi-drying Oils One or two sets of double bonds, not as reactive as drying oils. Need a catalyst (heat) to start polymerisation. Non-drying Oils (saturated oils) Cannot be used as binders, will not polymerise, no activity points. They are used as plasticisers, to give flexibility and ease application. Modifies the film properties.
Oil Paints LONG OIL PAINT more than 60% Oil to Resin. Elastic and slower drying, mainly used in domestic applications (decorative materials). MEDIUM OIL PAINT between 45% and 60% Oil to Resin. SHORT OIL PAINT less than 45% Oil to Resin. Faster drying, suitable for steelwork. More brittle, with shorter over-coating time. A mixture of oil and resin = oleoresinous.
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Binder - Solvent Compatability
Binder - Solvent Combinations WATER Vinyls, acrylics, epoxies, alkyds, bitumens, polyurethanes, acrylated rubbers.
Compatibility for over-coating.
Correct solvent group for binder.
WHITE SPIRIT Natural oils, natural resins, alkyds, phenolics.
Flashpoint and toxicity considerations.
XYLENE Chlorinated rubber. ACETONE Epoxy.
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7
Solvents
Solvents
Strong solvents for strong binders. Weaker solvents for weaker binders.
Solvent strength: its ability to dissolve the binder.
The stronger solvents have a low number of carbon atoms in the chemical formula.
Evaporation rate: controls polymerisation and drying.
The higher the number of carbon atoms, the higher the boiling point of the solvent,
Flash point: safety factor of the solvent. Toxicity: safety levels of exposure.
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Polymers A string or structure of repeated units Linear Polymer Pre formed, reversible, very sensitive to some HC solvents, thermoplastic. Also called solution polymer.
Linear
Branched polymer Oxidation drying, non-reversible. Natural oils and resins , become very brittle with age. Crosslinked polymer Chemically curing, very strong, multi-directional polymerisation, examples: epoxies, urethanes and polyurethanes.
Polymers are 3 dimensional in the dry paint film. Branched
Cross Linked
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Pigments Animal, vegetable, mineral, or synthetic. Particle size varies from of 1 micron.
1/
10
Pigments
Anti-corrosive: rust inhibitive properties.
th micron to average size
Contribute to cohesive strength, abrasion resistance, durability, opacity and in some instances, impermeability, and resistance to u/v rays.
Metallic: work sacrificially. Opaque: inert, provide opacity and colour. Extenders: add bulk, reduce cost. Laminar: provide impermeability.
Pigments must not dissolve in the vehicle.
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8
Metallic Pigments
Anti-corrosive (Rust Inhibitive) Pigments Primer Red lead (basic) (natural oils and resins) Calcium plumbate White Coal Tar Zinc Chromate
Also used to protect the substrate by cathodic protection.
Colour Toxic Toxic
Red
Toxic Toxic
Black Yellow
Two most commonly used are :
Purple/Grey
ZINC (better for galvanic protection). ALUMINIUM (excellent ultra-violet reflective properties).
Zinc phosphate most common
Material must be below steel in the galvanic list.
Barium Metaborate. Zinc Phosphosilicate. Copyright © TWI Ltd
Copyright © TWI Ltd
Opaque Pigments Inert particles which have excellent light scattering properties in order to give covering (opacity) and colour.
CARBON COBALT CHROMIUM IRON CALCIUM TITANIUM DIOXIDE
Black Blue Greens/Yellows/Oranges Browns/Reds/Yellows Reds/Yellows White
Extender Pigments Low priced, readily available materials, also known as fillers. They add bulk, improve intercoat adhesion, increase cohesive strength, and give extra thickness to paint film at low cost.
CLAYS CHALK TALCUM SLATE FLOUR
Kaolin , China Clay Calcium Carbonate Magnesium Silicate Aluminium Silicate
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(White) (White) (White) (Dark Grey)
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Laminar pigments
Laminar Pigments
Plate-like pigments which provide impermeability. In theory, they have a leafing effect, overlapping as the coating dries. Common laminar pigments:
Graphite. Glass flake. Aluminium flake (ultra-violet reflective). Micaceous Iron Oxide (Mio) (ultra-violet reflective).
Standard Pigment
Mio Theoretical
Attributes of Mio: UV A and B reflection, retards permeation, durability, provides adhesion to next layer. Copyright © TWI Ltd
Delaminated Mio
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9
Critical Pigment Volume Concentration (CPVC)
Other Additives Anti-settling agents:
Aids to shelf life.
Plasticisers: Reduce brittleness, aid application, improves flexibility. Below CPVC
Near CPVC
Above CPVC
Driers: Allow even through drying of oxidising films.
Poor opacity, high gloss, blistering Good opacity, cohesive strength, gloss, impermeability, Porous, low cohesive strength, poor adhesion
Anti-skinning agents: Retard the formation of surface skins.
Pigment/binder ratio can vary from paint to paint. Copyright © TWI Ltd
Copyright © TWI Ltd
Solutions and Dispersions
Solutions and Dispersions (Section 5) SOLVENT: SOLUTE:
Dispersion: a solid or a liquid within another liquid, where there is no solubility.
Will dissolve another material.
There are two types of dispersion
Is dissolved in the solvent
1 Suspension: fine particulate solids dispersed within a liquid, no solubility.
SOLUTION: The resultant liquid produced by dissolving a solute in a solvent.
Example: Sand + Water
EXAMPLE:
2 Emulsion: a liquid dispersed within another liquid where there is no solubility.
Solvent + solute = solution Would be sugar + water = sweet water
Example: Oil + Water
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Drying and curing of Paint Films (Section 6)
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Drying and Curing of Paint Films Oxidation
Solvent evaporation No chemical reaction.
Uses atmospheric oxygen.
Polymers are preformed and saturated.
Oxygen chemically combines with unsaturated double bonds.
Linear polymers closed at the ends by hydrogen and have no double bonds.
Process can be accelerated by addition of driers. Also called convertible or non-reversible.
Also called reversible or non-convertible.
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10
Drying and Curing of Paint Films
Curing Agents Used in 2-pack Epoxies
Chemical curing
AMIDES: Fully cured in 7 days at 20°C.
Must be mixed in the correct ratio (2 pack). Pot life (period after opening and mixing where the paint remains in a usable condition). Induction period (stand time, to allow for wetting of particles and crosslinking to begin).
AMINES: Fully cured in 3 days at 20°C. ISOCYANATES: Suitable for use where low temperatures are unavoidable, fully cured in 16 hours at 20°c. In 1984, at the union carbide plant in bhopal, india, water was accidentally released into a methyl isocyanate storage tank, resulting in 7000 fatalities.
These must be observed and controlled! Convertible or non-reversible. Chemically cross-linking polymers.
Very toxic, CO2 is produced when applied in damp conditions. Great care needed during use and removal! Copyright © TWI Ltd
Copyright © TWI Ltd
Drying and Curing of Paint Films: Coalescence
Solvent Evaporation
High boiling point solvents penetrate the spheres and fuse the binder globules, creating a solid film
Screen Test Two
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Copyright © TWI Ltd
Question 1 Which of the following is Rust Grade C?
Question 1 When using a Venturi Nozzle at 100psi, the abrasive exits at approximately what speed?
a. Tightly adhering mill scale which can be brushed clean. b. Loosely adhering mill scale with no evident pitting. c. Mill scale almost totally removed, visible rust, no heavy pitting. d. Heavy pitting clearly visible, heavy corrosion.
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a. b. c. d.
200 mph. 450 mph. 1200 mph. 100 mph.
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11
Question 3
Question 2 The optimum pressure to achieve 100% efficiency in abrasive blast cleaning is?
Sand is not permitted as a dry blast abrasive, as directed by:
a. b. c. d.
a. b. c. d.
75 psi. 450 psi. 100 psi. 220 psi.
BGC/PS/PA10. BS 7079 Part A. COSHH. BS 410.
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Copyright © TWI Ltd
Question 4 How many times can garnet be used as an abrasive for BGAS site use?
Question 5 The correct ratio of a working mix would be: a. b. c. d.
a. Up to 3 times, if cleaning of abrasive is possible. b. None. c. As per the specification. d. 20 times.
70-80% Grit: 20-30% Shot. 50% Grit: 50% Shot. 70-80% Shot: 20-30% Grit. 20-25% Sand:75-80% Copper Slag.
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Copyright © TWI Ltd
Question 6
Question 7
Flame cleaning uses which mechanisms?
Carbon Impregnated hoses are used to:
a. Expansion, decontamination, and force. b. Oxidation, penetration, and de-lamination. c. Heat penetration, expansion, and dehydration. d. Oxidation, weathering, and pressurisation.
a. b. c. d.
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Create static electricity. Prevent static electricity. Reduce friction. Reduce static electricity.
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12
Question 8
Question 9
One of the most important safety items of equipment in abrasive blasting is:
What is the approximate speed of the abrasive particles exiting a wheelabrator?
a. b. c. d.
a. b. c. d.
Dry abrasive mix. The banana gauge. Dead mans handle. 100 psi compressor.
450 mph. 220 mph. Mach 3. 100 psi.
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Copyright © TWI Ltd
Question 10 Where would you normally use a comparator gauge? a. b. c. d.
To To To To
Question 11 Amplitude refers to what? a. The peak-to-trough height of a blast profile. b. The amount of noise a blasting operation creates. c. The velocity of the abrasive particles. d. The roughness of an abrasive particle.
check surface cleanliness. determine surface roughness. control cleaning of abrasives. assess the rust grade of a material.
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Copyright © TWI Ltd
Question 12 What is the material used in surface replica tape, used to measure profile? a. b. c. d.
Question 13 What is the cause of rash rusting? a. b. c. d.
Miler. Testrex. Mylar. Mylon.
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Oxygen. Rogue peaks. Hackles. Hygroscopic salts.
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13
Question 15
Question 14 The test for the presence of hygroscopic salts, is:
How many photographs of flame cleaning standards are shown in BS 7079 Part A?
a. b. c. d.
a. b. c. d.
Potassium hexacyanoferrate test. Copper sulphate test. Iron phosphate test. Iron chromate test.
4. 14. 8. 16.
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Copyright © TWI Ltd
Question 16
Question 17
Which abrasive has the effect of stress relieving the substrate?
Where would it be advisable to use steel grit as an abrasive?
a. b. c. d.
a. b. c. d.
Copper slag. Metallic shot. Steel grit. Garnet.
When a deep profile is required. On high pressure pipework. In enclosed blasting units. On offshore installations.
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Copyright © TWI Ltd
Question 18
Question 19
What is the minimum number of readings required for a Dial Micrometer?
Which test would be used to determine for soluble salts in a marine environment?
a. b. c. d.
a. b. c. d.
Minimum of 10. Minimum of 12. One only. As many as you wish, but the average reading is recorded.
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Potassium hexacyanoferrate. Copper sulphate. Iron phosphate. Silver nitrate.
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14
Question 20
Question 21
The standard for the test sieves used for the sizing of abrasives is:
The most common type of abrasive used for BGAS site work is:
a. b. c. d.
a. b. c. d.
BS 7079 part A. BS 410. BGC/PS/PA10. SI 1657.
Copper slag. Grit and shot mix. Garnet. Metallic shot.
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Copyright © TWI Ltd
Question 22
Question 23
Compared to a venturi nozzle, a straight bore nozzle would give:
Anchor pattern, key, peak-to-trough, are names given to what?
a. b. c. d.
a. b. c. d.
Better paint application. More speed. Larger area coverage. Greater accuracy.
The The The The
abrasive properties. cross section of a blast. total area of blasted substrate. potential of adhesion.
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Copyright © TWI Ltd
Question 24 What is a knock out pot?
Question 25 High pressure wet blasting operates up to which pressure?
a. A drum used for mixing paint and thinners. b. The area on the equipment where static electricity can build up and be hazardous. c. A vessel for removing oil and moisture from the air stream. d. A container where any blockages of the nozzle can be tapped free.
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a. b. c. d.
100 psi. 450 psi. 30,000 psi. 2,250 mph.
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15
Question 1 When using a Venturi Nozzle at 100psi, the abrasive exits at approximately what speed?
SWAP YOUR PAPERS PLEASE Put your name on your paper, and pass it to someone else to check
a. b. c. d.
200 mph. 450 mph. 1200 mph. 100 mph.
Answer: B
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Copyright © TWI Ltd
Question 2
Question 3
The optimum pressure to achieve 100% efficiency in abrasive blast cleaning is?
Sand is not permitted as a dry blast abrasive, as directed by:
a. b. c. d.
a. b. c. d.
75 psi. 450 psi. 100 psi. 220 psi.
BGC/PS/PA10. BS 7079 Part A. COSHH. BS 410.
Answer: C
Answer: C
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Copyright © TWI Ltd
Question 4 How many times can garnet be used as an abrasive for BGAS site use?
Question 5 The correct ratio of a working mix would be: a. b. c. d.
a. Up to 3 times, if cleaning of abrasive is possible. b. None. c. As per the specification. d. 20 times.
70-80% Grit: 50% Grit: 70-80% Shot: 20-25% Sand:
20-30% Shot. 50% Shot. 20-30% Grit. 75-80% Copper Slag.
Answer: C
Answer: B Copyright © TWI Ltd
Copyright © TWI Ltd
16
Question 6
Question 7
Flame cleaning uses which mechanisms?
Carbon Impregnated hoses are used to:
a. Expansion, decontamination, and force. b. Oxidation, penetration, and de-lamination. c. Heat penetration, expansion, and dehydration. d. Oxidation, weathering, and pressurisation.
a. b. c. d.
Answer: C
Create static electricity. Prevent static electricity. Reduce friction. Reduce static electricity.
Answer: D
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Copyright © TWI Ltd
Question 8
Question 9
One of the most important safety items of equipment in abrasive blasting is:
What is the approximate speed of the abrasive particles exiting a wheelabrator?
a. b. c. d.
a. b. c. d.
Dry abrasive mix. The banana gauge. Dead mans handle. 100 psi compressor.
450 mph. 220 mph. Mach 3. 100 psi.
Answer: B
Answer: C
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Copyright © TWI Ltd
Question 10 Where would you normally use a comparator gauge? a. b. c. d.
To To To To
Question 11 Amplitude refers to what? a. The peak-to-trough height of a blast profile. b. The amount of noise a blasting operation creates. c. The velocity of the abrasive particles. d. The roughness of an abrasive particle.
check surface cleanliness. determine surface roughness. control cleaning of abrasives. assess the rust grade of a material.
Answer: A
Answer: B
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Copyright © TWI Ltd
17
Question 12 What is the material used in surface replica tape, used to measure profile? a. b. c. d.
Question 13 What is the cause of rash rusting? a. b. c. d.
Miler. Testrex. Mylar. Mylon.
Oxygen. Rogue peaks. Hackles. Hygroscopic salts.
Answer: B
Answer: C
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Copyright © TWI Ltd
Question 14
Question 15
The test for the presence of hygroscopic salts, is:
How many photographs of flame cleaning standards are shown in BS 7079 Part A?
a. b. c. d.
a. b. c. d.
Potassium hexacyanoferrate test. Copper sulphate test. Iron phosphate test. Iron chromate test.
4. 14. 8. 16.
Answer: A
Answer: A
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Copyright © TWI Ltd
Question 16
Question 17
Which abrasive has the effect of stress relieving the substrate?
Where would it be advisable to use steel grit as an abrasive?
a. b. c. d.
a. b. c. d.
Copper slag. Metallic shot. Steel grit. Garnet.
When a deep profile is required. On high pressure pipework. In enclosed blasting units. On offshore installations.
Answer: C
Answer: C
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Copyright © TWI Ltd
18
Question 18
Question 19
What is the minimum number of readings required for a Dial Micrometer?
Which test would be used to determine for soluble salts in a marine environment?
a. b. c. d.
a. b. c. d.
Minimum of 10. Minimum of 12. One only. As many as you wish, but the average reading is recorded.
Answer: C
Potassium hexacyanoferrate. Copper sulphate. Iron phosphate. Silver nitrate.
Answer: D
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Copyright © TWI Ltd
Question 20
Question 21
The standard for the test sieves used for the sizing of abrasives is:
The most common type of abrasive used for BGAS site work is:
a. b. c. d.
a. b. c. d.
BS 7079 part A. BS 410. BGC/PS/PA10. SI 1657.
Answer: B
Copper slag. Grit and shot mix. Garnet. Metallic shot.
Answer: A
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Copyright © TWI Ltd
Question 22
Question 23
Compared to a venturi nozzle, a straight bore nozzle would give:
Anchor pattern, key, peak-to-trough, are names given to what?
a. b. c. d.
a. b. c. d.
Better paint application. More speed. Larger area coverage. Greater accuracy.
Answer: D
The The The The
abrasive properties. cross section of a blast. total area of blasted substrate. potential of adhesion.
Answer: B
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Copyright © TWI Ltd
19
Question 24
Question 25 High pressure wet blasting operates up to which pressure?
What is a knock out pot? a. A drum used for mixing paint and thinners. b. The area on the equipment where static electricity can build up and be hazardous. c. A vessel for removing oil and moisture from the air stream. d. A container where any blockages of the nozzle can be tapped free.
a. b. c. d.
100 psi. 450 psi. 30,000 psi. 2,250 mph.
Answer: C
Answer: C Copyright © TWI Ltd
Copyright © TWI Ltd
Question 1 Which of the following is not a drying mechanism? a. b. c. d.
Screen Test Three
Coalescence. Oxidation. Stove drying. Chemical curing.
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Copyright © TWI Ltd
Question 2 A solution is: a. The resultant liquid b. The resultant liquid c. The resultant liquid in another liquid. d. The resultant liquid another liquid.
Question 3 Which of the following is a natural oil?
in a polymerisation event. after dispersing a solid. after dissolving a material after dispersing a liquid in
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a. b. c. d.
Dammar. Alkyd. Castor Xylene.
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20
Question 4
Question 5
Which of the following are said to be reversible?
Which of the following are quantitative tests?
a. b. c. d.
a. b. c. d.
Cross-linked polymer. Branched polymer. Linear polymer. Convertible coating.
Potassium hexacyanoferrate. Copper sulphate. Silver nitrate test. Bresle sample patch.
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Copyright © TWI Ltd
Question 6
Question 7
A whirling hygrometer is also called a :
What is the meaning of compliant?
a. b. c. d.
a. In accordance with PA 10. b. In accordance with Environmental Protection Act. c. As per engineers instructions. d. As per manufacturers recommendations.
Pfund cryptometer. A psychrometer. A pyknometer. A rotational viscometer.
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Copyright © TWI Ltd
Question 8 What is the recommended stand-off distance and speed at which the abrasive leaves a Venturi Nozzle? a. b. c. d.
450 220 220 450
mm mm mm mm
and and and and
220 450 220 450
mph. mph. mph. mph.
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Question 9 A typical remedy for burnishing would be: a. b. c. d.
Power brushing. Emery paper or similar. Needle gun. Addition of thinners.
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21
Question 10 Which of the following is part of the Footners Duplex System? a. 1-2% sulphuric acid @ 65-800c for 5-25 mins. b. 5-10% sulphuric acid @ 70-800c for 5-10 mins. c. 5-10% sulphuric acid @ 65-700c for 5-25 mins. d. 5-10% chromic/phosphoric acid @ 65-700c for 1-2 mins.
Question 11 Which of the following is not a natural resin? a. b. c. d.
Copal. Amber. Dammar. Linseed.
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Copyright © TWI Ltd
Question 12
Question 13
Which of the following is not a natural oil?
Which of the following is an extender?
a. b. c. d.
a. b. c. d.
Castor. Amber. Olive. Linseed.
Graphite. Mica. Glass Flake. China Clay.
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Copyright © TWI Ltd
Question 14
Question 15
Which of the following is an opaque pigment?
Which of the following is an additive?
a. b. c. d.
a. b. c. d.
Graphite. Compound of hromium. Zirconium octoate. Zinc phosphate.
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Opaque pigments. Rust inhibitive pigments. Thickening agents. Thinners.
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22
Question 16 What is the specified minimum standard of cleanliness required by BGAS for non-ferrous substrates? a. b. c. d.
Sa 2 ½. Sa 3. St 1. Sa 1.
Question 17 Which of the following binders are reversible? a. b. c. d.
Epoxy. Urethane. Chlorinated rubber. Silicone.
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Copyright © TWI Ltd
Question 18
Question 19
What is the maximum allowable time lapse between surface preparation, and painting?
Which of the following is not a commonly used binder?
a. b. c. d.
a. b. c. d.
24 hours. 4 hours. 20-30 minutes. 7 days.
Epoxy. Zinc. Urethane. Vinyl.
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Copyright © TWI Ltd
Question 20 Wire brushes used for BGAS hand and power tool cleaning, must be made from which material? a. b. c. d.
Question 21 Using the correct calibration shim, a banana gauge can be calibrated on: a. b. c. d.
Tungsten or stainless steel. Copper or brass. Beryllium bronze or phosphor bronze. The same material as the pipe.
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Bare steel. Painted surfaces. Steel with a blast cleaned surface. Any metal surface.
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23
Question 22 Which of the following are commonly used as anti-settling agents? a. b. c. d.
Question 23 A paint drying by chemical reaction is said to be: a. b. c. d.
Heavy metal salts. Bentones and waxes. Saturated oils. Extender pigments.
Linear polymer. Convertible. Non-convertible. Reversible.
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Copyright © TWI Ltd
Question 24 Which of the following is not a laminar pigment? a. b. c. d.
Graphite. Glass flake. Magnesium silicate. Mica.
Question 25 Which two materials are commonly used as sacrificial anodes? a. b. c. d.
Copper and tungsten Aluminium and graphite. Zinc and aluminium. Lead and tin.
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.
Copyright © TWI Ltd
Question 1
Swap your papers please
Which of the following is not a drying mechanism? a. b. c. d.
Put your name on your paper, and pass it to someone else to check.
Coalescence. Oxidation. Stove drying. Chemical curing.
Answer: C
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Copyright © TWI Ltd
24
Question 3
Question 2
A solution is: a. The resultant liquid b. The resultant liquid c. The resultant liquid in another liquid. d. The resultant liquid another liquid.
Which of the following is a natural oil? in a polymerisation event. after dispersing a solid. after dissolving a material after dispersing a liquid in
a. b. c. d.
Dammar. Alkyd. Castor Xylene.
Answer: C Answer: C Copyright © TWI Ltd
Copyright © TWI Ltd
Question 4
Question 5
Which of the following are said to be reversible?
Which of the following are quantitative tests?
a. b. c. d.
a. b. c. d.
Cross-linked polymer. Branched polymer. Linear polymer. Convertible coating.
Answer: C
Potassium hexacyanoferrate. Copper sulphate. Silver nitrate test. Bresle sample patch.
Answer: D
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Copyright © TWI Ltd
Question 6
Question 7
A whirling hygrometer is also called a :
What is the meaning of compliant?
a. b. c. d.
a. b. c. d.
Pfund cryptometer. A psychrometer. A pyknometer. A rotational viscometer.
Answer: B
In accordance with PA 10. In accordance with Environmental Protection Act. As per engineers instructions. As per manufacturers recommendations.
Answer: B
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Copyright © TWI Ltd
25
Question 8
What is the recommended stand-off distance and speed at which the abrasive leaves a Venturi Nozzle? a. b. c. d.
450 220 220 450
mm mm mm mm
and and and and
220 450 220 450
mph. mph. mph. mph.
Question 9
A typical remedy for burnishing would be: a. b. c. d.
Power brushing. Emery paper or similar. Needle gun. Addition of thinners.
Answer: B
Answer: D
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Copyright © TWI Ltd
Question 10
Which of the following is part of the Footners Duplex System? a. b. c. d.
0
1-2% sulphuric acid @ 65-80 c for 5-25 mins. 0 5-10% sulphuric acid @ 70-80 c for 5-10 mins. 0 5-10% sulphuric acid @ 65-70 c for 5-25 mins. 0 5-10% chromic/phosphoric acid @ 65-70 c for 12 mins.
Question 11
Which of the following is not a natural resin? a. b. c. d.
Copal. Amber. Dammar. Linseed.
Answer: D
Answer: C Copyright © TWI Ltd
Copyright © TWI Ltd
Question 12
Question 13
Which of the following is not a natural oil?
Which of the following is an extender?
a. b. c. d.
a. b. c. d.
Castor. Amber. Olive. Linseed.
Answer: B
Graphite. Mica. Glass Flake. China Clay.
Answer: D
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Copyright © TWI Ltd
26
Question 15
Question 14
Which of the following is an opaque pigment?
Which of the following is an additive?
a. b. c. d.
a. b. c. d.
Graphite. Compound of Chromium. Zirconium octoate. Zinc phosphate.
Answer: B
Opaque pigments. Rust inhibitive pigments. Thickening agents. Thinners.
Answer: C
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Copyright © TWI Ltd
Question 16
What is the specified minimum standard of cleanliness required by BGAS for non-ferrous substrates? a. b. c. d.
½
Sa 2 . Sa 3. St 1. Sa 1.
Question 17
Which of the following binders are reversible? a. b. c. d.
Epoxy. Urethane. Chlorinated rubber. Silicone.
Answer: C Answer: D
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Copyright © TWI Ltd
Question 18
Question 19
What is the maximum allowable time lapse between surface preparation, and painting?
Which of the following is not a commonly used binder?
a. b. c. d.
a. b. c. d.
24 hours. 4 hours. 20-30 minutes. 7 days.
Answer: B
Epoxy. Zinc. Urethane. Vinyl.
Answer: B
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Copyright © TWI Ltd
27
Question 21
Question 20
Wire brushes used for BGAS hand and power tool cleaning, must be made from which material? a. b. c. d.
Tungsten or stainless steel. Copper or brass. Beryllium bronze or phosphor bronze. The same material as the pipe.
Using the correct calibration shim, a banana gauge can be calibrated on: a. b. c. d.
Bare steel. Painted surfaces. Steel with a blast cleaned surface. Any metal surface.
Answer: C Answer: C
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Copyright © TWI Ltd
Question 22
Which of the following are commonly used as anti-settling agents? a. b. c. d.
Question 23
A paint drying by chemical reaction is said to be: a. b. c. d.
Heavy metal salts. Bentones and waxes. Saturated oils. Extender pigments.
Linear polymer. Convertible. Non-convertible. Reversible.
Answer: B
Answer: B
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Copyright © TWI Ltd
Question 24
Question 25
Which of the following is not a laminar pigment?
Which two materials are commonly used as sacrificial anodes?
a. b. c. d.
a. b. c. d.
Graphite. Glass flake. Magnesium silicate. Mica.
Copper and tungsten Aluminium and graphite. Zinc and aluminium. Lead and tin.
.
Answer: C
Answer: C
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28
Paint Systems (Single or Multilayer) Primer: anti corrosive to protect the steel. Mio: protects primer, provides impermeability.
ATC 88 BGAS Painting Grade 2/3
Mid coat or build coat: protects underlying coating, builds thickness, and provides good adhesion for subsequent layer. Finish coat: aesthetic , correct colour, provide a smooth surface to allow cleaning and shedding of water.
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Primers
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Midcoat or Build Coat
Rust inhibitive pigments passivate the substrate. Mordant or wash primers (t-wash), acid reaction with the substrate produces inhibitive salts. No measurable thickness. Etchant primers, (polyvinyl butyral) similar Reaction but leaves a measurable thickness of 1525 um.
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Extender particles increase surface area to provide adhesion for any subsequent layer.
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Finish Coat Mainly aesthetic, but have other properties. Gloss finish, to assist in shedding water. Solar reflective (white), heat absorbent (black).
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Moisture tolerant:- moisture has no appreciable ill effect. Moisture curing polyurethane:- uses water vapour from the atmosphere to cure, damp or moist, but not wet. Low RH is a problem (min 35%). Damp: no signs of water, but temperature is below dew point. Moist: no standing water, but a noticeable film of water. Wet: droplets or standing water are present Moisture sensitive: moisture reacts with the isocyanates to produce carbon dioxide. Copyright © TWI Ltd
1
Paint Systems
Paint Systems Sacrificial systems
Powder Coatings Thermoplastic or thermosetting.
Zinc
Most commonly thermosetting, needs heat. Steel
Convertible coatings chemically cured. Usually electrostatically applied. Thin plate ,heat applied after powder. Thicker plate, heat applied before powder.
Particles in close contact allow electron circuit when an electrolyte enters the film.
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Waterborne Coatings (Section 8) Use water instead of hydrocarbon solvents.
The zinc acts as a barrier, and corrodes in its own right until there is coating damage and both metals are exposed to electrolyte. Zinc oxides are formed, and repairs Copyright © TWI Ltd the damage.
Paint Manufacture (Section 9) 1. Ball Mill
Most binders now available water borne. Steel balls rotate in cylinder, grind mill base to required particle size (5000 - 40000 lts).
Environmentally friendly, cheap, and compatible with any binder. Many coats can be applied in a day. Disadvantages include smaller application window, storage conditions and weather. Coatings used on BGAS contracts must be compliant. A compliant coating is one which complies with the requirements of the environmental protection act 1991. Copyright © TWI Ltd
Paint Manufacture (Section 9)
2. Attritor Mill
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Paint Manufacture (Section 9)
3. High speed disperser
Upright static cylinder, the steel balls are moved by motorised paddles.
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A 2500 rpm blender, produces mill base. (see Figure 9.2 in course notes for picture of a high speed disperser).
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2
Paint Manufacture (Section 9) 4. Kady Mill (another type is silverson mill) . For the manufacture of emulsions and waterborne paints.
Paint Manufacture (Section 9) 5. Sand Mill (pearl mill or bead mill). Mill base injected at bottom, forced through sand, refined, removed at top. Water cooled.
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13
Paint Manufacture (Section 9)
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Paint Manufacture (Section 9)
Sand Mills
6. Colloid Mill (High speed stone mill) Vertical or horizontal
2 stone discs (approx 10” dia) bottom disc rotates at 3600 rpm. Base is gravity fed to centre of discs. Ground by centrifugal force and friction. Copyright © TWI Ltd
Paint Manufacture (Section 9)
7. Triple Roll Mill
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Paint Manufacture (Section 9)
8. Single Roll Mill
Used to produce mastics, fillers and putties. 3 rolls travel at different speeds, paste sticks to faster of rolls.
Used to produce small batches of expensive materials (gilts, silvers etc.)
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3
Testing of Paints for Properties and Performance (Section 10) BS 3900 Methods of test for paint. BGC PS PA9 Table 2 : RESULTS REQUIRED BY BGAS. Tests subdivided into: Tests on wet materials. Tests on dry materials.
Paint Testing Determination of volatile/non-volatile Procedure: 1. Clean glass plate and rod is weighed. 2. Add 2g of paint, and weigh again. 3. Place into hot air oven (or hot plate). 4. Stir paint to evaporate solvent (volatile). Note: No naked flame! When dry, weigh glass plate to determine ratio of volatile/non-volatile.
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Flash Point of Solvents
Paint Testing Abel closed cup
Flash Point Test carried out in accordance with BS 3900 part A8 using abel cup. Defined as: the temperature at which vapour from a solvent will ignite in the presence of an external source of ignition. High flashpoint is safer than a low flashpoint.
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Paint Testing The density cup is used to check for addition of thinners, or the correct mix ratio of 2 pack paints.
The density (SG) Cup
PART A (Base)
Pyknometer, SG cup, weight per litre, weight per gallon. Copyright © TWI Ltd
PART B (Catalyst)
Mixing Ratio
Site test result
Caused by Data sheet too much says of PART
1.35
0.95
6:1
1.29
1.35
A
1.28
0.80
6:1
1.21
1.40
A
1.40
0.79
4:1
1.27
1.20
B
1.19
0.75
5:1
1.11
1.39
A
1.22
0.80
7:1
1.16
1.08
B
1.50
0.82
4:1
1.36
1.16
B
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4
Hegman Grind Gauge
Paint Testing Hegman grind gauge For fineness of grind, degree of dispersion.
Particles submerged by scraper bar.
Particles protrude through the film if they are too large to be submerged. The surface changes from gloss to matt, and where between 5 and 10 protrusions is noted, this is the degree of dispersion or fineness of grind. Copyright © TWI Ltd
Copyright © TWI Ltd
Paint Testing
Paint Testing
Viscosity Viscosity Krebs Stormer Viscometer Kinematic Viscosity.
Defined as: A fluid’s resistance to flow. Rotational viscometer with rotothinner measures dynamic viscosity. Units = poises.
Driven by a falling weight, the heavier the weight the faster it rotates. Criteria 200 rpm units stoke or poise.
1 poise = The force required to maintain unit velocity between 2 surfaces separated by 1cm of fluid. Copyright © TWI Ltd
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Paint Testing Flow Viscosity Ford flow cup showing the 4mm hole.
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Ford flow cup in its retort stand.
Lid containing spirit level.
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5
Paint Film Thicknesses (Section 11) WFT measurement: Eccentric Wheel. Ford flow cup in use.
Must be used circumferentially on curved surfaces.
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WFT Measurement: Comb Gauges Must be used longitudinally on curved surfaces.
Last wet tooth
25
First dry tooth
35
45
60
Steel Comb gauge shows WFT reading of 35/45 um Copyright © TWI Ltd
Destructive Test Gauges: The PIG
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Destructive Test Gauges: The PIG Turn PIG 90deg. Light comes on - view graticule scale through eyepiece. Tables in instruction book give conversion factors for each blade, from graticule units into microns.
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6
Destructive Test Gauges: The PIG Destructive test gauges.
The Saberg test drill.
View through eyepiece with graticule scale. Tables in instruction book give conversion factors for each blade, from graticule units to microns.
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DFT Measurements, Magnetic The banana gauge 211
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Dry Film Thickness Measurement, Magnetic
Calibration shims
The tinsley pencil (foremans gauge)
Scale moves to the curser
Purple Blue Brown White Yellow
25um 50um 125um 250um 500um
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DFT Measurements: Electronic Gauges Dry film thickness measurement, magnetic, horseshoe gauge (used on TSA). Electrophysic Mini test
The exacto
Elcometer 456
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7
Tests For Mechanical Properties On Paint
Tests for Mechanical Properties on Paint
Abrasion resistance Sample plates are weighed, and placed beneath abrasive discs for a number of cycles, then weighed again to determine abrasion resistance.
Impact resistance: Tubular impact tester. 1kg weight dropped 1 metre onto the paint surface of a test panel. Assessed for damage, direct or indirect.
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Accelerated Testing, Weatherometers Flexibility test: conical mandrel Test plate bent over 3mm to 37mm diameter mandrel
0
Humidity cabinets: 95% humidity and 55 C. Salt spray cabinets: Salt laden environment. Water soak test: Panel submerged, weighed. Temperature cycling: hotter and colder than normal operating temperatures. Prohesion testing: (Protective adhesion) 3% salt 0 water spray @ 35 c, (60 min on : 60 min off) no undercut, blisters etc. Beyond 3mm boundary, after test duration of 1000 hours.
Check location where cracking begins Copyright © TWI Ltd
Drying and Curing Tests: Ballotini Test
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Drying and Curing Tests BK (Beck-koller) drying time recorders
Hopper containing small glass beads
Steel block graduated in hours of travel
Glass plate inserted into front slot and the stylus drawn across. Solvent evaporation time, sol/gel transition, surface dry and final dry times recorded.
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8
Wolff-Wilborn Pencil Scratch Test
Mechanical Thumb Test, Through Drying
Uses the pencil hardness rating.
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Opacity: The Pfund Cryptometer
Use Of The Pfund Cryptometer
1. View through the glass prism. 2. Record the point where the background can no longer be seen. 3. This is the opacity thickness.
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Hiding Power Charts and Adjustable Applicator
Gloss Measured with a glossmeter (reflectometer) Gloss can be affected by:
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Pigment volume concentration. Fineness of grind (particle size). Resin type. Refractive index. Solvent type.
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9
Degree of Gloss
Digital Gloss Meter (Reflectometer)
Measures % of light Received, from amount of light transmitted
High
Low
> 80% = Gloss finish < 80% = Matt finish
Air RI, stick appears to bend
Water
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Adhesion Testing: V Cut Test Cut v using craft knife
30 0
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Adhesion Tests: Cross Cut (Cross Hatch) Test
Apply leverage Insert blade tip
Cut 6 lines vertical and 6 lines horizontal, creating 25 x 2mm squares.
Testing for: primer to substrate failure, intercoat adhesion failure and cohesive failure.
Apply an agreed tape. Pull off and compare % area of detachment as per BS 3900 PT E6.
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Adhesion Tests The Dolly Test
Expendable aluminium dolly
Failure force measured in psi on this scale
Paint adhesion tester dolly test
Circular cutter
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10
Hydraulic Adhesion Test Equipment Hand Operated Type (with scale of failure force on view)
Re-usable dolly
Units are: Mega- pascales Copyright © TWI Ltd
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Question 1
What is a pyknometer? a. b. c. d.
Screen Test Four
Opacity testing equipment. Whirling hygrometer. Density cup. Windspeed measuring equipment.
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Question 2
What is the name of the mill used to produce mastics, fillers, and putties? a. b. c. d.
Question 3
Which of the following is not an adhesion test? a. b. c. d.
Triple roll mill. Ball mill. Single roll mill. Bead mill.
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Dolly test. Cross hatch. Krebs Stormer. HATE.
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11
Question 4
Which of the following is not a drying test? a. b. c. d.
Koenig Albert. Beck Koller. Mechanical Thumb. Ballotini.
Question 5
What is the name given to the drying test involving the use of glass beads? a. b. c. d.
Wolff wilborne. Taber. Ballotini. Erichsson.
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Question 6
Question 7
What type of machinery is used to produce large production runs of popular paints?
A typical pot life of a paint used in BGAS specifications would be:
a. b. c. d.
a. b. c. d.
Triple roll mill. Colloid mill. Kady mill. Sand mill.
20-30 minutes. 12-24 hours. 6-8 hours. 3-7 days.
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Question 9
Question 8 What is the specified temperature at which a Flash Point Determination test must be carried out? a. b. c. d.
200C. Up to 4500C. There is no specific temperature. 25 0C in seawater.
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HATE is an abbreviation of what? a. b. c. d.
High Adhesive Tension Equipment. Humidity Affected Electrical Tolerance. Hydraulic Adhesion Test Equipment. Hardness and Temperature Evaluation.
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12
Question 10
In paint testing, why is temperature cycling carried out? a. b. c. d.
To To To To
check check check prove
for water absorption. flexibility. contraction cracking. the service life of the coating system.
Question 10
Which of the following would not affect the degree of gloss? a. b. c. d.
Surface profile. Critical Pigment Volume Concentration. Solvent type. Degree of dispersion.
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Question 12
What diameter is the conical mandrel, which is used in the flexibility test? a. b. c. d.
Question 13 What is the name of the equipment used to determine particle aggregate size? a. b. c. d.
8 mm to 25 mm. 12mm to 18mm. 5mm to 50mm. 3mm to 37mm.
Beck-koller. Hegman gauge. Wolfe-Wilborne. Krebs-Stormer.
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Question 13
Which specification covers the internal coating of small bore steel pipes? a. b. c. d.
BGC BGC BGC BGC
PS PS PS PS
PA PA PA PA
10. 9. 8. 7.
Question 14
What product should be used for repairs to pipe coatings in damp conditions? a. b. c. d.
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Moisture sensitive isocyanates. Water-borne acrylics. Moisture curing polyurethane. Chlorinated rubber.
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13
Question 15
What surface preparation is specified in PA 10 for weathered galvanised steel? a. b. c. d.
1
Sa 2 /2, followed by T-Wash mordant primer. Sa 3, followed by etch primer. Hand abrasion with a stiff bristled brush only. Sa 1 followed by water washing.
Question 16 What would be the correct course of action upon discovering that the contractor has applied a coat of paint, out of sequence? a. b. c. d.
Blast and re-coat. Apply the correct coating over the top. Inform the engineer. Add an extra protective coating.
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Question 17
The function of a finish coat is mainly to provide: a. b. c. d.
Impermeability and adhesion. Aesthetic properties and water shedding. Cathodic protection and passivation. Increased thickness at low cost.
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Question 19
Question 18
What is the name of the vessel used to determine the viscosity of free flowing fluids, as per BGAS specifications? a. b. c. d.
Ford Flow cup No 4. Zahn cup. Abel cup. Pyknometer.
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Question 20 The BGas specified site painting conditions are:
Which of the following is not a test for contaminants? a. b. c. d.
Sellotape. Banana gauge. Talcum powder. Solvent.
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a. Maximum wind speed 4 m/sec, relative humidity maximum 95%. 0 b. Maximum 90% relative humidity, dew point 3 C above steel. 0 c. Maximum 90% relative humidity, dew point 3 C less than steel. 0 d. Maximum 27 C, relative humidity 95% maximum.
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14
Question 21
Question 22
Which test would be used to determine for soluble salts in a marine environment?
Which of the following is an extender pigment?
a. b. c. d.
a. b. c. d.
Potassium hexacyanoferrate. Sulphuric acid. Iron phosphate. Silver nitrate.
Magnesium silicate. Aluminium oxide. Manganese napthanate. Barium metaborate.
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Copyright © TWI Ltd
Question 23
With every 11 degree rise in temperature, the air’s ability to hold water: a. b. c. d.
Would Would Would Would
rise by 11%. half. double. decrease by 11%.
Question 24
According to PA10, what is the correct course of action upon discovering foreign bodies embedded in the paint film? a. b. c. d.
Apply an extra protective barrier coat. Re-blast and re-coat. Lightly abrade with emery paper, apply stripe coat. Make a report to the engineer only.
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Copyright © TWI Ltd
Question 25
According to PA10, is the addition of Thinners allowed? a. b. c. d.
Yes, at the engineers discretion, up to 20% max. Only if the paint is difficult to apply. Yes, in accordance with the product data sheets. No, under no circumstances.
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Swap your papers please
Put your name on your paper, and give it to someone else to check
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15
Question 1
What is a pyknometer? a. b. c. d.
Question 2
What is the name of the mill used to produce mastics, fillers, and putties?
Opacity testing equipment. Whirling hygrometer. Density cup. Windspeed measuring equipment.
a. b. c. d.
Triple roll mill. Ball mill. Single roll mill. Bead mill.
Answer: C Answer: A
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Copyright © TWI Ltd
Question 3
Question 4
Which of the following is not an adhesion test?
Which of the following is not a drying test?
a. b. c. d.
a. b. c. d.
Dolly test. Cross hatch. Krebs Stormer. HATE.
Koenig Albert. Beck Koller. Mechanical Thumb. Ballotini.
Answer: A
Answer: C
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Copyright © TWI Ltd
Question 5
Question 6
What is the name given to the drying test involving the use of glass beads?
What type of machinery is used to produce large production runs of popular paints?
a. b. c. d.
a. b. c. d.
Wolff wilborne. Taber. Ballotini. Erichsson.
Answer: C
Triple roll mill. Colloid mill. Kady mill. Sand mill.
Answer: D
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16
Question 7
What is the specified temperature at which a Flash Point Determination test must be carried out?
A typical pot life of a paint used in BGAS specifications would be: a. b. c. d.
Question 8
20-30 minutes. 12-24 hours. 6-8 hours. 3-7 days.
a. b. c. d.
Answer: C
200C. Up to 4500C. There is no specific temperature. 25 0C in seawater.
Answer: C
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Copyright © TWI Ltd
Question 9
In paint testing, why is temperature cycling carried out?
HATE is an abbreviation of what? a. b. c. d.
Question 10
High Adhesive Tension Equipment. Humidity Affected Electrical Tolerance. Hydraulic Adhesion Test Equipment. Hardness and Temperature Evaluation.
a. b. c. d.
Answer: C
To To To To
check check check prove
for water absorption. flexibility. contraction cracking. the service life of the coating system.
Answer: C
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Copyright © TWI Ltd
Question 11
Question 12
Which of the following would not affect the degree of gloss?
What diameter is the conical mandrel, which is used in the flexibility test?
a. b. c. d.
a. b. c. d.
Surface profile. Critical Pigment Volume Concentration. Solvent type. Degree of dispersion.
Answer: A
8 mm to 25 mm. 12mm to 18mm. 5mm to 50mm. 3mm to 37mm.
Answer: D
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17
Question 13 What is the name of the equipment used to determine particle aggregate size? a. b. c. d.
Question 13
Which specification covers the internal coating of small bore steel pipes? a. b. c. d.
Beck-koller. Hegman gauge. Wolfe-Wilborne. Krebs-Stormer.
Answer: B
BGC BGC BGC BGC
PS PS PS PS
PA PA PA PA
10. 9. 8. 7.
Answer: C
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Copyright © TWI Ltd
Question 14
Question 15
What product should be used for repairs to pipe coatings in damp conditions?
What surface preparation is specified in PA 10 for weathered galvanised steel?
a. b. c. d.
a. b. c. d.
Moisture sensitive isocyanates. Water-borne acrylics. Moisture curing polyurethane. Chlorinated rubber.
1
Sa 2 /2, followed by T-Wash mordant primer. Sa 3, followed by etch primer. Hand abrasion with a stiff bristled brush only. Sa 1 followed by water washing.
Answer: C
Answer: C
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Copyright © TWI Ltd
Question 17
Question 16 What would be the correct course of action upon discovering that the contractor has applied a coat of paint, out of sequence? a. b. c. d.
The function of a finish coat is mainly to provide: a. b. c. d.
Blast and re-coat. Apply the correct coating over the top. Inform the engineer. Add an extra protective coating.
Impermeability and adhesion. Aesthetic properties and water shedding. Cathodic protection and passivation. Increased thickness at low cost.
Answer: B
Answer: C
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18
Question 18
What is the name of the vessel used to determine the viscosity of free flowing fluids, as per BGAS specifications? a. b. c. d.
Ford Flow cup No 4. Zahn cup. Abel cup. Pyknometer.
Answer: A
Question 19
Which of the following is not a test for contaminants? a. b. c. d.
Sellotape. Banana gauge. Talcum powder. Solvent.
Answer: B
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Copyright © TWI Ltd
Question 20
The BGas specified site painting conditions are: a. Maximum wind speed 4 m/sec, relative humidity maximum 95%. 0 b. Maximum 90% relative humidity, dew point 3 C above steel. 0 c. Maximum 90% relative humidity, dew point 3 C less than steel. 0 d. Maximum 27 C, relative humidity 95% maximum.
Question 21
Which test would be used to determine for soluble salts in a marine environment? a. b. c. d.
Potassium hexacyanoferrate. Sulphuric acid. Iron phosphate. Silver nitrate.
Answer: D
Answer: C
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Copyright © TWI Ltd
Question 22
Which of the following is an extender pigment? a. b. c. d.
Magnesium silicate. Aluminium oxide. Manganese napthanate. Barium metaborate.
Question 23
With every 11 degree rise in temperature, the air’s ability to hold water: a. b. c. d.
Would Would Would Would
rise by 11%. half. double. decrease by 11%.
Answer: C
Answer: A
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Copyright © TWI Ltd
19
Question 24
According to PA10, what is the correct course of action upon discovering foreign bodies embedded in the paint film? a. b. c. d.
Apply an extra protective barrier coat. Re-blast and re-coat. Lightly abrade with emery paper, apply stripe coat. Make a report to the engineer only.
Question 25
According to PA10, is the addition of Thinners allowed? a. b. c. d.
Yes, at the engineers discretion, up to 20% max. Only if the paint is difficult to apply. Yes, in accordance with the product data sheets. No, under no circumstances.
Answer: C
Answer: B
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20
Cathodic Protection: Sacrificial System
ATC 88 BGAS Painting Grade 2/3
Zinc block (anode) Steel pipe (cathode) Must be in direct contact or joined by a conductive cable Copyright © TWI Ltd
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Cathodic Protection: Sacrificial System
Sacrificial zinc anodes
Cathodic Protection: Impressed Current Transformer / rectifier (negative) connected to pipe (Cathode)
There is no current/ electron flow if the coating is in good condition
Positive connection to ground bed (anode)
When barrier coating of buried pipe is damaged, corrosion circuit commences. (Electrons travel from cathode to anode via the electrolyte) Copyright © TWI Ltd
Copyright © TWI Ltd
Cathodic Protection: Monitoring Potentials
Impressed Current Transformer Rectifier Unit
Copper/copper sulphate half-cell reference electrode
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Copyright © TWI Ltd
1
Pinhole/Holiday Detection: Sponge Detector
Cathodic Disbondment Test
Voltage Range 9 to 90v. (Some have only 2 settings) intermediate 67.5v. Sponge is wetted in water with a drop of detergent. Test in progress
Inspection on completion
Excess squeezed out, then passed over the substrate.
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Holiday/Pinhole Detection
Typical high voltage set for pinhole detection. Operates up to 15kv too high for normal paint systems.
Holiday Detection on cross-country pipeline.
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High Voltage Holiday Tester
Test springs now not allowed on BGAS projects
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Holiday Detection of Coated Pipe
Paint Application Application methods
Contoured Brush
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2
Conventional spray
Gravity feed
Suction feed
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Paint application: Conventional Spray
Advantages Inexpensive nozzles. Good atomisation. More Accuracy. Less cleaning after use. Better finish achieved. Lower working pressure. Concentrated spray pattern.
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Paint Application: Airless Spray Airless Spray Gun
Disadvantages Heavy hose lines. Operator fatigue. Specialised containers. Slow application rates.
Portable Pump Copyright © TWI Ltd
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Paint Application: Airless Spray
Air Circuit: Blue Paint Circuit: Red One Way Ball Valve
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3
Paint Application: Airless Spray
Advantages High deposition rates. Can apply high viscosity fluids. Versatile (no air hose). High transfer efficiency. Lower waste. Large area coverage. Uses manufacturers paint containers.
Paint Application: Electrostatic Spraying
Disadvantages
Poor atomisation. Expensive nozzles. Coatings limitations. Increased maintenance. High skill required. Increased safety risk (+ or - 3500 psi). Lower quality finish.
Negatively charged component
Spray gun
Positively charged particles Ionised air volume
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Paint A
Advantages
High transfer efficiency. Good edge cover. Good wraparound. Uniform film thickness. Low wastage.
Hot duty surfaces (> 340 0C)
Disadvantages
(BGC/PS/PA10 PAGE 29 Table SPA 3c)
Bulky, delicate guns. Requires extra cleanliness. Fire/Safety hazard. Component must be conductive. High maintenance costs.
Requires the highest grade of cleanliness: Profile 75um/Grade sa 3 (check for mill scale)
1 Thermally sprayed aluminium. 2 Inorganic zinc silicate. 3 Polysiloxane inorganic coating.
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TSA: Thermally Sprayed Aluminium
Wire and Pistol Type TSA Applicator Gun
The preferred system, giving longest life. Wire and pistol type (most common). High purity wire. Butane/propane and oxygen fuel gas. Propelled by compressed air onto substrate. Thickness approx 100 - 125 um.
For high temperature service silicone sealer must be applied.
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Wire feed trigger
Fuel gas
Oxygen Compressed air Copyright © TWI Ltd
4
TSA: Thermally Sprayed Aluminium
Visual Inspection
Steel coated with TSA
Wire and Pistol Type
Steel blast cleaned to Sa 21/2
Loss of adhesion (poor surface preparation)
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Copyright © TWI Ltd
Paint, Faults and Bittiness IZS: Inorganic Zinc Silicate Inclusions, either airborn or from the paint itself.
Alternative to TSA. Apply as per manufacturers recommendation. Apply silicone sealer.
Could also be caused by partially cured paint, which is out of shelf life.
Apply heat to cure sealant (turn the system on). Polysiloxane inorganic coating Alternative to TSA and IZS. 0
Will withstand temperatures up to 1100 c. Apply as per manufacturers recommendation. This is not sealed.
(Flocculation) Coating Faults: Blistering
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Coating Faults: Bleeding The solvent from the top coat softens the under lying material and allows it to pass into and through the layer, causing discolouration. (Brown for bitumen, yellow for coal tar).
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Blisters can contain gas, liquid or crystals.
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5
Coating Faults Cissing
Coating Faults: Chalking
Caused by inadequate surface preparation.
Degradation of the binder due to disruptive factors in the environment
A difference in surface energy causes local lack of adhesion. Larger spots known as fish eyes and large areas referred to as crawling.
Epoxies are especially vulnerable.
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Coating Faults: Cracking
Coating Faults: Cissing Mud cracking
Differential expansion and coating age.
Crazing/hair cracking
Crocodiling/alligatoring
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Coating Faults: Cratering
Bowl shaped depressions. Caused by escaping solvent or gases.
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Coating Faults: Curtains, Sags, Runs and Tears Caused by over application. To remedy: remove excess material, lightly abrade and recoat.
High viscosity paint will not flow to fill the depressions. Resulting in small bowls and craters.
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Copyright © TWI Ltd
6
Coating Faults: Flaking
As material ages, it gets brittle, cracks and starts to detach. Oxidising paints are especially vulnerable.
Coating Faults: Holidays
Defined as : A void, a miss, or an uncoated area.
(Natural oils and resins).
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Coating Faults: Lifting
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Algae and Mould Growth
Caused by solvent strength and also lack of observance of stated overcoating time.
Remedy: treat with biocidal agent for 24 hours, then clean with detergent/stiff bristle brush/water washing. Copyright © TWI Ltd
Orange Peel
Similar appearance to the skin of a citrus fruit. Caused by paint viscosity problems or by applicator technique.
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Copyright © TWI Ltd
Coating Faults: Ropiness
Brushmarks Caused by brushing when film is almost dry, or when paint viscosity is too high.
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7
Coating Faults: Wrinkling and Rivelling
Defect: Rash or Spot Rusting
Cause: rogue peaks, or possibly by contamination of the paint film by foreign matter, such as grit or dirt etc.
Paint forms a skin, trapping solvent below the surface. As this eventually dries, the skin contracts, causing the surface to wrinkle. Copyright © TWI Ltd
Copyright © TWI Ltd
Colour Primary Colours: Red, Yellow and Blue The human eye operates on only these three pigments. Plus, other various colours can be created by combining to various degrees. Colour has 3 main attributes Hue Refers to the basic colour (red, green, yellow, blue etc.) Brightness The darkness or lightness of the colour. Saturation How vivid the colour appears (also known as chroma, intensity, weight).
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Colour: The Munsell System (USA) L= Luminance, chroma
Yellow through green ,blue
a= From green to red
Purple, red and back to yellow
b= From blue to yellow
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BS 4800 Hue From 00 (neutral) to 24 even numbers only. Brightness From A (max white) to E (max black). Saturation 01 to 56 Higher number = stronger colour. Lower number= greyer the colour. Black and white, and all the grey colours in between, are achromatic colours as they lack hue. Anything having colour is said to be chromatic.
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Ral System
System uses cards containing 210 colours.
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8
Product Identification by Pipe Colour Pipe Colour Coding to BS 1710 (Section 13) Uses BS 4800 to identify product Product
Named Colour
BS 4800 APP. REF
Air
Light Blue
20 E 51
Acids and Alkalies
Violet
22 C 37
Gases (except Air)
Yellow Ochre
08 C 35
Fluids
Black
00 E 53
Fresh Water
Auxiliary Blue
18 E 53
Water
Green
12 D 51
Electrical Services
Orange
06 E 51
Brown
06 C 34
Min/Vegetable/Animal Oils, Combustible liquids
Health and Safety COSSH Regulations (Control of substances hazardous to health )
Toxic or Very Toxic
Harmful or Irritant
Corrosive
Hazard warning symbols.
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Copyright © TWI Ltd
Health And Safety: (COSHH Regulations)
Hazard Warning Symbols Abbreviations
Explosive
Oxidizing
Extremely flammable
Highly flammable
Can be found on safety data sheets and on the paint tin label. Dangerous for the environment
EH 40
HSE guidance notes: list of all known harmful substances.
OEL
Occupational exposure limit ( there are 2 types).
MEL
Maximum exposure limit must never be exceeded! The maximum exposure to airborne substance over a reference period. Occupational exposure standard
OES
The concentration level of an airborne substance (averaged over a reference period) which is considered safe to be exposed to, day after day (ppm). RAQ
Required air quantity
HASAWA
Health and safety at work act (1974)
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Protective Masks
Dust only!
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Health And Safety: Drager Tube and Bellows
Solvents
Each depression of the bellows draws 100 cc of air Copyright © TWI Ltd
Copyright © TWI Ltd
9
Drager Tube and Bellows
Duties of a Painting Inspector
Ensure that all work is carried out in accordance with the specification requirements.
To test the air quality when using solvents. Varying crystal types for different solvents.
No deviation from specification unless permission given in writing from a higher authority, ie clients engineer.
Example: Xylene (OEL: 100 ppm) Raq: 500 cc (5 depressions). Crystals will change colour, (white to red/brown). Toxicity levels read from the scale on the tube.
Report any deviation from specifications. Especially malpractices.
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Visual Inspection Blast cleaned surfaces: Slivers, hackles, laminations, cracks, pitting. Wet paint films: Runs, sags, cissing, uneven coverage.
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Report Writing
All information requested on a report sheet should be completed. The information provides traceability in the event of any future breakdown.
Dry paint films: Quality of finish, paint faults, opacity (grinning), coverage, holidays.
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Day To Day Activities – Record 1. Environmental conditions. 2. Confirmation of materials used (abrasives, paint, pipe data etc). 3. Confirmation of equipment (calibrations etc). 4. Adherence to specification application faults 5. Adverse weather conditions (start and stop times etc).
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Good reports and documentation are essential to ensure efficient handover to another inspector in the event of illness or other emergencies.
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Daily Checks Beginning of the day Environment, equipment, materials, previous days work. During the day Environment, equipment, materials, each operators work, application faults, the standards. At the end of the day The days work, housekeeping, all daily reports.
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10
Purpose of a Quality Plan
Records - End of Contract
All daily records signed off. A complete register of control documents. A complete record of test results. All NCR’s should be closed out. Complete waste disposal records. A complete correspondance file.
To ensure stated paramenters are met.
Establish the integrity of the system.
To provide tracable records.
To reduce the risk of error.
Inspection Is not quality assurance. Inspection is not quality control.
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Copyright © TWI Ltd
Question 1
This paint defect is referred to as:
Screen Test Five
a. b. c. d.
Flaking. Chalking. Grinning. Cissing.
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Copyright © TWI Ltd
Question 2
Question 3
The main difference between airless and conventional spray is:
What is the name of the equipment used to determine particle aggregate size?
a. b. c. d.
a. b. c. d.
Conventional spray gives better deposition rate. Conventional spray gives less waste. Airless spray gives better quality finish. Conventional spray gives better atomisation.
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Beck-koller. Hegman gauge. Wolfe-Wilborne. Krebs-Stormer.
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11
Question 4
What are the 3 attributes, which make up the colour of a paint? a. b. c. d.
White, black, and primary colour. Hue, brightness and saturation. Red, yellow, and blue. Contrast, density, and definition.
Question 5
What voltage settings are commonly used for sponge test holiday detection? a. b. c. d.
5 Kv to 15 Kv. 15 Kv maximum. 9v to 90 v. 110v or 240v.
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Copyright © TWI Ltd
Question 6
This is the hazard warning symbol for: a. b. c. d.
Toxic or very toxic. Harmful or irritant. Corrosive. Explosive.
Question 7
Another name for a vapour trap is? a. b. c. d.
Air wash cup. Dry out pot. Knock out pot. Pressure regulator.
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Copyright © TWI Ltd
Question 8
Beryllium Bronze is a material used in the manufacture of: a. b. c. d.
Question 9
Which of the following are primary colours? a. b. c. d.
Welding electrodes. Power wire brushes. Comb gauges. Venturi Nozzle liners
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Blue yellow and green. Red green and white. Red white and blue. Red yellow and blue.
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12
Question 10
When carrying out holiday detection using the sponge tester, what can we add to the water? a. b. c. d.
Question 11
What would be the main problem of a low CPVC? a. b. c. d.
Salt. Detergent. Xylene. Inhibitor.
High opacity. Permeability. Low Gloss. Low opacity.
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Copyright © TWI Ltd
Question 12
Question 13
BGC/PS/PA10 contains which table, specifying the preferred coating systems?
Thermally sprayed aluminium is normally applied by which system?
a. b. c. d.
a. b. c. d.
Spa Spa Spa Spa
6a. 1e. 4a. 3c.
Electric arc spray. Sheradising. Wire and Pistol. Electro-plating.
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Copyright © TWI Ltd
Question 14
Padding refers to what?
Question 15
Which of the following is not a system for paint colour classification?
a. Protection for pipes during transport and storage. b. Protective clothing for TSA application. c. A paint application method. d. Material used to soak spillages.
a. b. c. d.
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BS 4800. BS 5252. Munsell. BGC/PS/CW5.
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13
Question 16
When testing for Xylene using a Drager Bellows, the crystals will change colour: a. b. c. d.
Orange to black. White to red/brown. White to green. White to black.
Question 17
Which pH range covers acids? a. b. c. d.
7 0 0 5
to to to to
14. 7. 14. 10.
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Copyright © TWI Ltd
Question 18
Question 19
What is the specified abrasive overlap requirement on repair areas? a. b. c. d.
The specified method of removal of this of type of contamination is:
250 mm. Twice pipe diameter. 100 mm. 1 metre.
a. b. c. d.
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Copyright © TWI Ltd
Question 21
Question 20
Where a silicone sealer is applied to an Inorganic Zinc Silicate coating system, how is the sealer cured? a. b. c. d.
Propane torch. Electric induction pads. It cures when the system begins to operate. It does not require curing.
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Dry abrasive blasting. Hand abrasion. Xylene. High pressure washing.
Which would be considered to be the most toxic? a. b. c. d.
Acetone. Xylene. Ethanol. Toluene.
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14
Question 22
Question 23
The document issued by the HSE listing all known harmful substances, is:
In the electrostatic spray painting process, the component must be:
a. b. c. d.
a. b. c. d.
COSHH. SI 1657. EH40. IGE SR 21.
Positively charged. Negatively charged. 9 volts DC. 15 Kv DC.
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Copyright © TWI Ltd
Question 24
Question 25
Where bleeding is evident on a pipe which was previously coated with coal tar, the staining would be which colour? a. b. c. d.
This is caused by: a. b. c. d.
Black Brown Yellow Red
Expansion and contraction. Age and environment. Solvent strength. Surface contamination.
Copyright © TWI Ltd
Copyright © TWI Ltd
Question 1
Swap your papers please This paint defect is referred to as: a. b. c. d.
Put your name on your paper, and pass it to someone else to check
Flaking. Chalking. Grinning. Cissing.
Answer: B Copyright © TWI Ltd
Copyright © TWI Ltd
15
Question 3
Question 2 The main difference between airless and conventional spray is: a. b. c. d.
What is the name of the equipment used to determine particle aggregate size?
Conventional spray gives better deposition rate. Conventional spray gives less waste. Airless spray gives better quality finish. Conventional spray gives better atomisation.
a. b. c. d.
Answer: D
Beck-koller. Hegman gauge. Wolfe-Wilborne. Krebs-Stormer .
Answer: B
Copyright © TWI Ltd
Question
4
What are the 3 attributes, which make up the colour of a paint? a. b. c. d.
Copyright © TWI Ltd
White, black, and primary colour. Hue, brightness and saturation. Red, yellow, and blue. Contrast, density, and definition.
Question 5
What voltage settings are commonly used for sponge test holiday detection? a. b. c. d.
5 Kv to 15 Kv. 15 Kv maximum. 9v to 90 v. 110v or 240v.
Answer: C
Answer: B
Copyright © TWI Ltd
Copyright © TWI Ltd
Question 6
This is the hazard warning symbol for: a. b. c. d.
Toxic or very toxic. Harmful or irritant. Corrosive. Explosive.
Question 7
Another name for a Vapour Trap is? a. b. c. d.
Air wash cup. Dry out pot. Knock out pot. Pressure regulator.
Answer: C
Answer: B
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Copyright © TWI Ltd
16
Question 8
Beryllium bronze is a material used in the manufacture of: a. b. c. d.
Question 9
Which of the following are primary colours? a. b. c. d.
Welding electrodes. Power wire brushes. Comb gauges. Venturi nozzle liners.
Blue yellow and green. Red green and white. Red white and blue. Red yellow and blue.
Answer: D
Answer: B
Copyright © TWI Ltd
Copyright © TWI Ltd
Question 10
When carrying out holiday detection using the sponge tester, what can we add to the water? a. b. c. d.
Question 11
What would be the main problem of a low CPVC? a. b. c. d.
Salt. Detergent. Xylene. Inhibitor.
Answer: B
High opacity. Permeability. Low gloss. Low opacity
Answer: D
Copyright © TWI Ltd
Copyright © TWI Ltd
Question 12
Question 13
BGC/PS/PA10 contains which table, specifying the preferred coating systems?
Thermally sprayed aluminium is normally applied by which system?
a. b. c. d.
a. b. c. d.
Spa Spa Spa Spa
6a. 1e. 4a. 3c.
Electric arc spray. Sheradising. Wire and pistol. Electro-plating.
Answer: C
Answer: B
Copyright © TWI Ltd
Copyright © TWI Ltd
17
Question 14
Padding refers to what? a. b. c. d.
Protection for pipes during transport and storage. Protective clothing for TSA application. A paint application method. Material used to soak spillages.
Answer: C
Question 15
Which of the following is not a system for paint colour classification? a. b. c. d.
BS 4800. BS 5252. Munsell. BGC/PS/CW5.
Answer: D
Copyright © TWI Ltd
Copyright © TWI Ltd
Question 16
When testing for Xylene using a Drager Bellows, the crystals will change colour : a. b. c. d.
Question 17
Which pH range covers acids? a. b. c. d.
Orange to black. White to red/brown. White to green. White to black.
7 0 0 5
to to to to
14. 7. 14. 10.
Answer: B
Answer: B
Copyright © TWI Ltd
Copyright © TWI Ltd
Question 18
Question 19
What is the specified abrasive overlap requirement on repair areas? a. b. c. d.
The specified method of removal of this of type of contamination is:
250 mm. Twice pipe diameter. 100 mm. 1 metre.
a. b. c. d.
Answer: C
Dry abrasive blasting. Hand abrasion. Xylene. High pressure washing.
Answer: D Copyright © TWI Ltd
Copyright © TWI Ltd
18
Question 20
Where a silicone sealer is applied to an inorganic zinc silicate coating system, how is the sealer cured? a. b. c. d.
Question 21
Which would be considered to be the most toxic? a. b. c. d.
Propane torch. Electric induction pads. It cures when the system begins to operate. It does not require curing.
Acetone. Xylene. Ethanol. Toluene
Answer: D
Answer: C
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Copyright © TWI Ltd
Question 22
Question 23
The document issued by the HSE listing all known harmful substances, is:
In the electrostatic spray painting process, the component must be:
a. b. c. d.
a. b. c. d.
COSHH. SI 1657. EH40. IGE SR 21.
Positively charged. Negatively charged. 9 volts DC . 5 Kv DC.
Answer: B
Answer: C
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Question
Copyright © TWI Ltd
Question 25
24
Where bleeding is evident on a pipe which was previously coated with coal tar, the staining would be which colour? a. b. c. d.
This is caused by: a. b. c. d.
Black. Brown. Yellow. Red.
Answer: C
Expansion and contraction. Age and environment. Solvent strength. Surface contamination.
Answer: C
Copyright © TWI Ltd
Copyright © TWI Ltd
19
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