E2

MAPÚA UNIVERSITY Muralla St. Intramuros, Manila School of Mechanical and Manufacturing Engineering

EXPERIMENT NO. 2 STEAM QUALITY DETERMINATION

NAME:

Mahmud, Ali R.

STUDENT NO.:

2015151413

COURSE/SECTION:

31 Aug, 2018

DATE OF SUBMISSION:

7 Sep, 2018

ME144L/A1

GROUP NO.: SEAT NO.:

DATE OF PERFORMANCE:

1 12

GRADE

Engr. Teodulo Valle INSTRUCTOR

Steam Quality Determination

TABLE OF CONTENTS

Objectives

1

Theories and Analysis

7

List of Apparatus

9

Procedure

11

Set-up of Apparatus

12

Final Data Sheet

13

Sample Computations

14

Discussion

15

Conclusion

18

Recommendation

19

References

20

1

Steam Quality Determination

OBJECTIVES 1. To be able to determine the quality of steam produced by the MIT Boiler. 2. To be familiar in the operation of a steam throttling calorimeter THEORY AND ANALYSIS Steam is an odorless invisible gas consisting of vaporized water. It is usually interspersed with minute droplets of water, which gives it a white, cloudy appearance. In nature, steam is produced by the heating of underground water by volcanic processes and is emitted from hot springs, geysers, fumaroles, and certain types of volcanoes. Steam also can be generated on a large scale by technological systems, as, for example, those employing fossil-fuel-burning boilers and nuclear reactors. Steam power constitutes an important power source for industrial society. Water is heated to steam in power plants, and the pressurized steam drives turbines that produce electrical current. The thermal energy of steam is thus converted to mechanical energy, which in turn is converted into electricity. The steam used to drive turbo-generators furnishes most of the world’s electric power. Steam is also widely employed in such industrial processes as the manufacture of steel, aluminum, copper, and nickel; the production of chemicals; and the refining of petroleum. In the home, steam has long been used for cooking and heating. Steam quality is the proportion of saturated steam (vapor) in a saturated condensate (liquid)/ steam (vapor) mixture. A steam quality of 0 indicates 100 % liquid, (condensate) while a steam quality of 100 indicates 100 % steam. One (1) lb of steam with 90 % steam and 10 % percent of liquid entrainment has a steam quality of 0.9. The measurements needed to obtain a steam quality measurement are temperature, pressure, and entrained liquid content. A high percentage (88 % or more) of industrial steam systems use saturated steam for process applications. Steam quality can be mathematically calculated with the help of a steam table. Steam table consist of two sets of tables of the energy transfer properties of water and steam saturated steam tables and superheated steam tables. The saturated steam tables are divided into two parts: temperature tables, which list the properties according to saturation temperature (Tsat) and pressure tables, which list them according to saturation pressure (Psat). Most practical applications using the saturated steam tables involve steam-water mixtures. The key property of such mixtures is steam quality (x), defined as the mass of steam present per unit mass of steam-water mixture, or steam moisture content (y), defined as the mass of water present per unit mass of steam-water mixture. The following notation is used in steam tables

1

Steam Quality Determination

The following relationships exists between the quality of a liquid-vapor mixture and the specific volumes, enthalpies, or entropies of both phases and of the mixture itself. These relationships are used with the saturated steam tables.

2

Steam Quality Determination

Saturated steam/vapor is a vapor at saturation temperature and pressure. It has no liquid or moisture content. Example: Steam at 300-degree C and 8.58 MPa. It exists in complete gaseous form and contains no liquid. The boiler operation uses chemical energy from a fuel source to deliver energy to the boiler water. Inside the boiler, liquid gains energy from the combustion process and changes state into saturated steam. The following diagrams are PV of pure substance:

Pure Substance is a working substance that has homogeneous and invariable chemical composition even though there is a change of phase.

3

Steam Quality Determination

Working Substance is a substance which energy can be stored or from which energy can be removed. Saturation Temperature is the temperature wat which liquid start to boil and vapor start to condense. Compressed Liquid is a liquid at the saturation temperature or pressure whose temperature is equal to the boiling point corresponding to the given pressure. It has no vapor content. Vapor is the term given to a gaseous phase that is in contact with the liquid phase. Superheated Vapor is a vapor whose temperature is higher than the saturation temperature corresponding to the given pressure. Degree Superheat is the difference between the actual superheated temperature and saturation temperature. Degree Subcooled is the difference between the saturation temperature and the actual subcooled temperature. Water Vapor is a mixture of saturated vapor and saturated liquid. Quality of Wet Vapor is the fraction or percentage by weight that is saturated vapor It is the ratio of the mass of saturated vapor to the total mass of the mixture. 𝑥=

𝑚𝑔 𝑚𝑡

Where x = quality of wet vapor 𝑚𝑔 = mass of vapor 𝑚𝑔 = mass of the mixture (wet vapor) Critical Point is a point that represents the pressure and temperature at which liquid and vapor can coexist in equilibrium. Today’s manufacturing techniques of heat transfer, control, and standards are all dedicated to improving and providing the highest quality product to the market place. To attain the highest quality, each manufactured component of the final product is inspected repeatedly, and measured for its quality to ensure that it meets the manufacturer’s and consumer’s expectations. Steam is a vital and critical part in producing the final product; therefore, steam quality should be one of the main measurable points in producing a product in today’s manufacturing facility. All heat transfer components (shell/tube, plate/frame, plate/coil, tracing, etc.) base performance calculations on 100 % steam quality, unless the manufacturer is informed by the end user that the steam quality is lower than 100 %. Unfortunately, steam quality is typically not monitored closely and is assumed to be 100 % quality. Therefore, issues that arise from poor steam quality are blamed on some other item in the system. Based on field documentation by Swagelok Energy Advisors Inc., a high percentage of steam systems are operating below acceptable steam quality levels. 4

Steam Quality Determination

Low steam quality affects steam system operations in many ways. Below is the effect of low steam quality: 1. Reduced heat transfer efficiency: The major problem with low steam quality is the effect on the heat transfer equipment and process. In some cases, low steam quality can reduce heat transfer efficiency by more than 65 %. The liquid entrained in the steam has sensible energy (16 % estimated – varies with pressure) which has a significantly lower amount of energy than the steam vapor’s latent energy (94 %). Therefore, less usable energy is being delivered to the steam process equipment. Also, the additional liquid (low steam quality) collects on the wetted surface of the heat exchanger causing an additional build-up of a liquid which reduces the ability of the steam’s latent energy to be transfer to the product. 2. Premature Valve Failure: Liquid passing through steam control valves will erode the internals of the valves causing premature failure. 3. Internal Turbine Component Failures: Liquid introduced with the steam in a saturated turbine operation will reduce the life expectancy of the internal components. 4. Water hammer Steam systems are usually not designed to accommodate the additional liquid in steam. Additional liquid creates the chance for water hammer to occur. Water hammer is a safety issue and may cause premature failure in the steam system. A true measurement of steam quality can be obtained from the use of a throttling calorimeter and Ganapathy’s steam plant calculations. Unfortunately, most industrial plants do not have the luxury or capability of doing the testing. Another way to measure steam quality is relying on the basics of steam. Saturated steam is a dry invisible gas and only becomes visible with the entrained air or liquid. Therefore, opening a steam valve and allowing steam to be released into the atmosphere provides an estimate of the steam quality in the system. If we have steam that is nearly dry, we make use of a throttling calorimeter as shown in figure. This calorimeter is operated by first opening the stop valve fully so that the steam is not partially throttled as it passes through the apparatus for a while to allow the pressure and temperature to stabilize. If the pressure is very close to atmospheric pressure, the saturation should be around 100°C, it may be assumed that the steam is superheated.

5

Steam Quality Determination

When the conditions have become steady, the gauge pressure before throttling is read from the pressure gauge. After throttling, the temperature and gauge pressure are read from the thermometer and manometer respectively. In the experiment, the researcher is focused on the determination of steam quality. The formula below is utilized to determine the steam quality or the dryness fraction of steam. 𝑥=

ℎ𝑔2 + 𝑐𝑝 (𝑇𝑐 − 𝑇2 ) − ℎ𝑓1 × 100% ℎ𝑓𝑔1

Where: ℎ𝑔2 = is the enthalpy at calorimeter pressure (vapor) 𝑐𝑝 = heat capacity of steam (0.46 BTU/lb) 𝑇𝑐 = calorimeter temperature 𝑇2 = saturated temperature at calorimeter pressure ℎ𝑓1 = enthalpy at steam pressure (liquid) ℎ𝑓𝑔1 = enthalpy at steam pressure (mixture of liquid and vapor)

6

Equation 1

Steam Quality Determination

LIST OF APPARATUS 1. Throttling calorimeter

2. Mercury manometer

3. Thermometer

7

Steam Quality Determination

4. Stop watch

5. Steam Table

6. Personal Protective Equipments

8

Steam Quality Determination

PROCEDURES 1. Purge the water and impurities inside the steam pipeline.

2. Insert the thermometer bulb inside the throttling calorimeter well.

3. Connect the hose of the Hg manometer through the drain valve.

9

Steam Quality Determination

4. Open the gate valve and let the steam enter the calorimeter.

5. Duration of the trial is 3 minutes. 6. Let the condition of the steam inside stabilize before recording the steam line pressure, calorimeter well temperature and Hg manometer reading.

7. Calculate all the necessary requirements needed to complete the data sheet.

10

Steam Quality Determination

SET-UP OF APPARATUS

11

Steam Quality Determination

FINAL DATA SHEET Steam

Calorimeter

Manometer

Calorimeter

Pressure

Temperature

Reading

Pressure

P1 (psi)

tc (F)

“Hg

P2 (psi)

1

23

186.8

¼

14.83

2

24

206.6

¼

3

24

183.2

4

23

5 6

Trial

hf1

hfg1

hg2

X

BTU/lb

BTU/lb

BTU/lb

%

212.42

232.46

936.11

1150.73

96.75

14.83

212.42

206.03

973.67

1150.73

96.75

3⁄ 8

26.68

212.42

479.65

953.78

1083.99

97

185

3⁄ 8

26.68

212.42

475.36

954.90

1083.96

97

23

179.6

1⁄ 4

14.76

212.19

231.36

939.30

1152.95

96.43

20

195.6

¼

14.82

212.42

227.97

941.62

1153.02

97.38

X=

t2 (F)

[hg2 + Cp(t c − t 2 ) − hf1 ] hfg1

Where: Cp=0.46 (steam) P2=pressure inside the calorimeter based on manometer reading t2=saturation temperature of P2 tc=temperature of steam inside the calorimeter P1=steam pipeline pressure

12

Steam Quality Determination

SAMPLE COMPUTATIONS Stream Pressure 𝑃1 = (23 + 14.7𝑝𝑠𝑖𝑎) (

0.101325𝑀𝑃𝑎 ) = 0.2599𝑀𝑃𝑎 14.7 𝑝𝑠𝑖𝑎

Calorimeter Pressure 1 14.7 𝑝𝑠𝑖𝑎 0.101325𝑀𝑃𝑎 𝑃1 = ( + 29.92𝑖𝑛 𝐻𝑔) ( ) = 14.82 𝑝𝑠𝑖𝑎 ( ) = 0.1022 𝑀𝑃𝑎 4 29.92 𝑖𝑛 𝐻𝑔 14.7 𝑝𝑠𝑖𝑎 Saturation Temperature of P2 = 0.1022 MPa 0.100𝑀𝑃𝑎 − 0.1022𝑀𝑃𝑎 99.63 − 𝑇2 = , 𝑇 = 100.23˚𝐶 = 212.414˚𝐹 0.100𝑀𝑃𝑎 − 0.105𝑀𝑃𝑎 99.63 − 101.00 2

0.255𝑀𝑃𝑎 − 0.25986𝑀𝑃𝑎 538.15 − ℎ𝑓1 = 0.255𝑀𝑃𝑎 − 0.26𝑀𝑃𝑎 538.15 − 540.9 ℎ𝑓1 = 232.463

𝐵𝑇𝑈 𝑙𝑏𝑚

2179.7 − ℎ𝑓𝑔1 0.255𝑀𝑃𝑎 − 0.25986𝑀𝑃𝑎 = 0.255𝑀𝑃𝑎 − 0.26𝑀𝑃𝑎 2179.7 − 2177.8 ℎ𝑓𝑔1 = 936.31

𝐵𝑇𝑈 𝑙𝑏𝑚 𝐵𝑇𝑈

ℎ𝑔2 = 1150.73 𝑙𝑏𝑚 Steam Quality 𝑋=

[2676.424 + 1.996(86 − 100.23) − 540.82] 𝑥100% 2177.85

𝑋 = 96.75 % Comparing: ℎ2 = 2676.3264 ℎ𝑓 = 540.90 ℎ𝑓𝑔 = 2177.8 𝑋 = 98.05 %

13

Steam Quality Determination

DISCUSSION OF RESULT

Based on the data gathered by the students, there are 6 trials in the experiment. The gage pressure ranges between 20 psi – 24 psi throughout the trail. The calorimeter temperature was also taken for the calculation of steam quality. The manometer reading was constant throughout the trials as well as the calorimeter pressure and its saturated temperature as the manometer deflects 1/4 inch which results to a pressure of 14.83 psi and its saturation temperature is 212.414 degrees Fahrenheit which is accurate to the boiling temperature of water at sea level. Interpolation of values from the steam table is necessary to achieve a more accurate value. Through interpolation, the values of enthalpy (hf and hfg) were obtained and noticed that the enthalpy decreased when the pressure of steam was increased. The students determined the enthalpy of steam (hf and hfg) since it is composed of mixture of liquid and vapor. The enthalpy of steam at calorimeter was considered in vapor form and determined by interpolation. The steam quality was obtained by using the formula in Theory and Principle, equation 1, and founded out that the steam quality ranges from 96.43%-97.38%. There are discrepancies that the researcher considered since the steam pressure from trial 1 and 2 is different from trial 3 and 4. Also, there are some sources of error that affected the data such as rounding off in calculations and improper measurement of pressure readings. In the pressure reading, the set-up is utilizing a gage which makes difficult for the researcher to read the value on the gage since it looks old. Furthermore, the condition of the equipment must be considered in the sources of error and must be maintained or replaced to gather more accurate data for the experiment.

14

Steam Quality Determination

QUESTION AND ANSWERS 1. Superheated steam at 1.7 MPa and 350 degrees Celsius is expanded in an engine and the final pressure is 0.17 MPa. If the expansion is isentropic, find the dryness fraction of the expanded steam. 1: 𝐴𝑡 1.7 𝑀𝑃𝑎 𝑎𝑛𝑑 350℃; 𝑠 = 7.044 2: 𝐴𝑡 0.17 𝑀𝑃𝑎; 𝑠𝑓 = 1.475

𝑘𝐽 𝑘𝑔 − 𝐾

𝑘𝐽 𝑘𝐽 ; 𝑠𝑓𝑔 = 5.707 𝑘𝑔 − 𝐾 𝑘𝑔 − 𝐾

𝑠 𝑎𝑡 1 = 𝑠 𝑎𝑡 2 1.475 + 𝑥(5.707) = 7.044; 𝑥 = 97.59% 2. Two boilers of equal evaporative capacities generate steam at the same pressure of 1.5 MPa to a common pipe line. One boiler produces superheated steam at 150 degrees Celsius and the other produces wet steam. If the mixture is just dry and saturated, find the dryness fraction of the wet steam from the second boiler. 𝑆𝑡𝑒𝑎𝑚 𝑃𝑟𝑜𝑝𝑒𝑟𝑡𝑖𝑒𝑠: 𝐴𝑡 1.5 𝑀𝑃𝑎 𝑎𝑛𝑑 250℃; ℎ = 2925

𝑘𝐽 𝑘𝑔

𝐴𝑡 1.5 𝑀𝑃𝑎; ℎ𝑓 = 845

𝑘𝐽 𝑘𝐽 𝑘𝐽 ; ℎ𝑓𝑔 = 1947 ; ℎ𝑔 = 2792 𝑘𝑔 𝑘𝑔 𝑘𝑔

𝐸𝑛𝑡ℎ𝑎𝑙𝑝𝑦 𝑏𝑒𝑓𝑜𝑟𝑒 𝑚𝑖𝑥𝑖𝑛𝑔 = 𝐸𝑛𝑡ℎ𝑎𝑙𝑝𝑦 𝑎𝑓𝑡𝑒𝑟 𝑚𝑖𝑥𝑖𝑛𝑔 2925 + (845 + 𝑥(1947)) = 2(2792) → 𝑥 = 93.15% 3. A closed system consisting of 1 kg of superheated steam at 2 MPa and 400 degrees Celsius is cooled at constant volume until the pressure is 1.2 MPa. Determine the condition of the steam at the lower pressure. 𝐴𝑡 2 𝑀𝑃𝑎, 400℃ → ℎ = 3248

𝑘𝐽 0.1511𝑚3 ;𝑣 = 𝑘𝑔 𝑘𝑔

𝑘𝐽 𝑘𝐽 0.1632𝑚3 𝐴𝑡 1.2 𝑀𝑃𝑎 → ℎ𝑓 = 798 ; ℎ = 1986 ;𝑣 = 𝑘𝑔 𝑓𝑔 𝑘𝑔 𝑔 𝑘𝑔 The steam is cooled at constant volume, therefore the volume of 1 kg of steam at 1.2 MPa is the same as it was before cooling which is 0.1511 m3. This is less than the volume of 1 kg of dry saturated steam at 1.2 MPa, therefore it must now be wet and its dryness fraction is:

15

Steam Quality Determination

𝑥=

𝑣 0.1511 = = 92.58% 𝑣𝑔 0.1632

4. In an experiment to determine the dryness fraction of steam, a sample at a pressure of 0.11 MPa was blown into a vessel containing 10 kg of water at 15 degrees Celsius. The final mass of water in the vessel was 10.75 kg and the final temperature is 55 degrees Celsius. Find the dryness fraction of steam, taking the water equivalent of the vessel as 0.45 kg. 𝑆𝑡𝑒𝑎𝑚 𝑃𝑟𝑜𝑝𝑒𝑟𝑡𝑖𝑒𝑠: 𝐴𝑡 0.11 𝑀𝑃𝑎, ℎ𝑓 = 429

𝑘𝐽 𝑘𝐽 ; , ℎ𝑓𝑔 = 2251 𝑘𝑔 𝑘𝑔

𝑊𝑎𝑡𝑒𝑟 𝑃𝑟𝑜𝑝𝑒𝑟𝑡𝑖𝑒𝑠: 𝑎𝑡 55℃; ℎ = 230.2 𝑎𝑡 15 ℃; ℎ = 62.9

𝑘𝐽 𝑘𝑔

𝑘𝐽 𝑘𝑔

𝑀𝑎𝑠𝑠 𝑜𝑓 𝑠𝑡𝑒𝑎𝑚 𝑠𝑎𝑚𝑝𝑙𝑒 = 𝑚 = 10.75 − 10 = 0.75 𝑘𝑔 𝑇𝑎𝑘𝑖𝑛𝑔 𝑖𝑛𝑡𝑜 𝑎𝑐𝑐𝑜𝑢𝑛𝑡 𝑡ℎ𝑎𝑡 𝑡ℎ𝑒 𝑣𝑒𝑠𝑠𝑒𝑙 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑖𝑠 𝑒𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑡 𝑡𝑜 0.45 𝑘𝑔 𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑎𝑡 15℃ = 10 + 0.45 = 10.45𝑘𝑔 𝐹𝑖𝑛𝑎𝑙 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑎𝑡 55℃ = 10.75 + 0.45 = 11.2 𝑘𝑔 𝐸𝑛𝑡ℎ𝑎𝑙𝑝𝑦 𝑜𝑓 𝑠𝑡𝑒𝑎𝑚 𝑎𝑛𝑑 𝑤𝑎𝑡𝑒𝑟 𝑏𝑒𝑓𝑜𝑟𝑒 = 𝐸𝑛𝑡ℎ𝑎𝑙𝑝𝑦 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 𝑎𝑓𝑡𝑒𝑟 0.75(429 + 𝑥(2251)) + 10.45(62.9) = 11.2(230.2) 𝑥 = 94.72% 5. A throttling calorimeter was fitted to pipe carrying steam at 1.2 MPa in order to measure the dryness fraction. The pressure in the calorimeter was 0.12 MPa and its temperature was 116 degrees Celsius. Taking the specific heat of the superheated steam in the calorimeter as 2.0 kJ/kgK, find the dryness fraction of the main steam. 𝑆𝑡𝑒𝑎𝑚 𝑃𝑟𝑜𝑝𝑒𝑟𝑡𝑖𝑒𝑠: 𝑎𝑡 1.2 𝑀𝑃𝑎; ℎ𝑓 = 798

𝑘𝐽 𝑘𝐽 ; ℎ𝑓𝑔 = 1986 𝑘𝑔 𝑘𝑔

𝑎𝑡 0.12 𝑀𝑃𝑎; 𝑡𝑠𝑎𝑡 = 104.8℃; ℎ𝑔 = 2683

𝑘𝐽 𝑘𝑔

𝐷𝑒𝑔𝑟𝑒𝑒 𝑆𝑢𝑝𝑒𝑟ℎ𝑒𝑎𝑡 𝑜𝑓 𝑡ℎ𝑟𝑜𝑡𝑡𝑙𝑒𝑑 𝑠𝑡𝑒𝑎𝑚 = 116 − 104.8 = 11.2℃ 16

Steam Quality Determination

𝐸𝑛𝑡ℎ𝑎𝑙𝑝𝑦 𝑏𝑒𝑓𝑜𝑟𝑒 𝑡ℎ𝑟𝑜𝑡𝑡𝑙𝑖𝑛𝑔 = 𝐸𝑛𝑡ℎ𝑎𝑙𝑝𝑦 𝑎𝑓𝑡𝑒𝑟 𝑡ℎ𝑟𝑜𝑡𝑡𝑙𝑖𝑛𝑔 798 + 𝑥(1986) = 2683 + 2(11.2) 𝑥 = 96.03% 6. A steam generator has an exit enthalpy of 3500 kJ/kg at the rate of 15 kg/s. Calculate the heat lost between the boiler outlet and the turbine inlet if the enthalpy available at the turbine inlet is 3200 kJ/kg. 𝑄 = 𝑚(ℎ2 − ℎ1 ) = 15(3200 − 3500) 𝑄 = −4500 𝑘𝑊

17

Steam Quality Determination

CONCLUSION Steam is useful in power generation because of the unusual properties of water. The manifold hydrogen bonds among water molecules mean that water has a high boiling point and a high latent heat of vaporization compared with other liquids; that is, it takes considerable heat to turn liquid water into steam, which is available when the steam is condensed. The boiling point and the heat of vaporization both depend on ambient pressure. At standard atmospheric pressure of 101 kilopascals (14.7 pounds per square inch), water boils at 100 °C (212 °F). At higher or lower pressures, molecular energy, respectively, is required to allow water molecules to escape from the liquid to the gaseous state. Correspondingly, the boiling point becomes lower or higher. The heat of vaporization, defined as the amount of energy needed to evaporate a unit mass of liquid (in engineering practice, a unit weight), also varies with pressure. At standard atmospheric pressure it is 2,260 kilojoules per kg (972 BTU [British thermal units] per pound). In the experiment, the students were able to determine the steam quality produced by the boiler located at Mapua University. The experiment takes the process of throttling operation in steam throttling calorimeter to determine values of steam pressure, calorimeter pressure and temperature and use steam tables for the determination of enthalpy. The steam quality or also known as the dryness fraction of steam is affected by these enthalpy values obtained from steam tables and the difference between the temperature of the calorimeter and the saturated temperature at the calorimeter pressure. The determination of steam quality is important especially in industrial applications and power generation especially on steam turbines. Steam turbines prefer high quality of steam because if the steam quality or dryness fraction will be low, the moisture content of steam will increase, and it will generate problems on steam turbines such as corrosion which will damage the steam turbine itself and it will be costly for the power-generating company if this damage occurs. The experiment must be performed with the guidance of the lab assistant to prevent accidents and the researcher must wear PPE to ensure safety and to train them for preparation for their work as a mechanical engineer in power-generation industry.

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Steam Quality Determination

RECOMMENDATION There have been several recent incidents where crewmembers have been badly scalded while working on steam systems. Such as Incident One – Not following correct procedures Incident Two – Assumptions can lead to accidents Incident Three – Poor interdepartmental communication These incidents clearly demonstrate the risk of serious injury if procedures are not followed correctly or if adequate precautions are not taken. Given the devastating effects of being hit by a sudden and unexpected release of steam, Members may wish to review their maintenance procedures regarding boilers and steam systems to ensure all eventualities are covered. Inspections and maintenance involving steam plant should be subject to the vessel’s “Permit to Work” process, and no work should be carried out without the knowledge and approval of the instructor. All involved in the operation should be refamiliarized with the applicable procedures and it may also be prudent to carry out a risk assessment beforehand. As a minimum the system should be de-pressurized, drained, cooled and isolated, and warning signs posted. Isolation valves should be locked or tied shut to prevent any backflow of steam or condensate, and blanking plates may also need to be inserted. After emptying a boiler, care should be taken to check that the vacuum has been broken before the manhole doors are removed. Although an air cock may have been opened to break the vacuum, the manhole door nuts should be loosened and the joint broken before the dogs are released. The top manhole doors should be removed first, and personnel should stand well clear when the doors are opened in case of hot vapor. All departments should be kept informed throughout.

19

Steam Quality Determination

REFERENCES •

Steam Quality. (2018). Retrieved from https://www.swagelok.com/~/media/Distributor%20Media/C-G/Chicago/Services/ES%20%20Steam%20Quality_BP_23.ashx

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Importance of Steam Quality. (2018). Retrieved from https://www.forbesmarshall.com/fm_micro/news_room.aspx?Id=boilers&nid=175

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