Heidelbergcement Group Guidance Paper: High Bearing Temperature In Ball Mills

HeidelbergCement Group Guidance Paper Edition:

01

Date:

28.01.2015

High Bearing Temperature in Ball Mills Process/MTN

Expert Group: Grinding / Maintenance

75ºC 53ºC

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HTC Management System High Bearing Temperature in Ball Mills

Edition:

01

Date:

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Table of contents

Introduction ................................................................................................................. 3 1.1 1.2 1.3

Process reasons for high bearing temperature ....................................................... 6 2.1 2.1.1 2.1.2 2.1.3

2.2

3

High temperature inside the mill ...................................................................................... 6 Process arrangement .................................................................................................................................. 6 System operation ........................................................................................................................................ 7 External heat source ................................................................................................................................... 8

High environmental temperature ...................................................................................... 9

Measures to prevent high bearing temperature ....................................................... 9 3.1 3.2

Process design measures ............................................................................................... 9 System operation........................................................................................................... 13

4

Mechanical reasons for high bearing temperature ................................................ 14

5

Description of mill and running aspects ................................................................ 15 5.1 5.2

6

Measure to prevent high bearing temperature ....................................................... 17 6.1 6.2 6.2.1 6.2.2

6.3

7

The sliding rings ........................................................................................................................................ 19 The slide shoe bearings ............................................................................................................................. 21

Checking of mill internal insulation and lining ................................................................. 23

Process recommended measures to avoid high bearing temperature situations: ........... 24 Maintenance recommended measures to avoid high bearing temperature situations: ... 24

Up-gradation of Tender docs ................................................................................... 27 8.1 8.2

9

Lubrication units ............................................................................................................ 17 Mill bearings system ...................................................................................................... 19

General summary and conclusions ........................................................................ 24 7.1 7.2

8

Generalities for MTN section ......................................................................................... 15 Mill supports and bearings system ................................................................................. 15

Process/ operational ...................................................................................................... 27 Maintenance .................................................................................................................. 27

Further applicable documents................................................................................. 28

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PROCESS/GRINDING SECTION

2

Background ..................................................................................................................... 3 Expert Group Objectives and Scope ................................................................................ 4 Used terms and definitions: ............................................................................................. 5

MAINTENANCE SECTION

1

HTC Management System High Bearing Temperature in Ball Mills

Edition:

01

Date:

28.01.2015

1 Introduction 1.1 Background In recent years HC has installed several Chinese ball mills for cement grinding as for example: -

CM#4, TPCC, Tanzania

-

CM#1, #2 & #3, Tula Cement, Russia

-

CM#2, Kanchpur, Bangladesh

-

CM#9C & #10B, Indocement, Cirebon, Indonesia; etc.

-

CM#1, Shetpe, Kazakhstan

There are also several Chinese ball mills for cement grinding presently in the execution phase such as: -

CM#5, Takoradi, Ghana

-

CM#5, TPCC, Tanzania

-

Burkina Faso

-

Togo Kara; etc.

It appears that the above mentioned mills which are in operation are having similar problems with high bearing temperature, especially at mill outlet. All mills are equipped with slide shoe bearings. Apparently, the design has been copied from European suppliers, mainly FLS. After some operating period these Chinese cement mills are facing problems with high bearing temperature, especially at the discharge end of the mill. This high bearing temperature is leading to shut downs with increasing frequency and thus creating production loss and bottlenecking. Especially in countries with seasonally high environmental temperatures this issue has become critical. The Plants have tackled the problem individually and tried to overcome these issue. Since the problem is similar in all these plants, it is investigated by HTC and expert group maintenance and grinding. The appropriate solutions are listed in the following pages of the guidance paper.

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HTC Management System High Bearing Temperature in Ball Mills

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1.2 Expert Group Objectives and Scope Overheating of bearings of a ball mill for cement is a well-known phenomenon. This phenomenon generally occurs after a long period of operation, due to normal wear of surfaces in relative motion. It may be considered normal if we face issue of bearing overheating after several years of operation of the mill. The well-known usual maintenance methods for tracking and repairs are able to avoid such issues. With planned routine maintenance this can be done without limiting the equipment normal production. However, almost all ball mills for cement from Chinese suppliers have similar problems, overheating of slide shoe bearings. This phenomenon seems to exist since commissioning of the mills. High bearing temperature regularly leads to an emergency stop of the cement mills and limits the production capacity as well as increases the specific power consumption and maintenance costs. The objective of this document is to provide effectively proven solutions to overcome this problem. The numerous aspects which can contribute to the overheating of the bearings are quality, storage, delivery, mounting, operation and maintenance. Hence, they have to be taken care and to be followed up carefully. In this section you will find other recommendations that are usually not part of the manufacturer's documentation. These were applied for several mills and have given good results. The scope of both sections, Maintenance and Process, are to enumerate and describe the most important requests and checks for a cement mill before and after commissioning. It is guidance for Maintenance, Process, as well as for Investment and Purchasing Departments. To deal with, the task is split into three main subjects: 1. Investigation of root cause of the problem 2. Recommendations to solve the problem 3. Modification/ Up-gradation of concerned Tender documents It is a good possibility to find RCFA for installed mills and share with others.

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1.3 Used terms and definitions: (term)

(definition)

RCFA

RCFA is a method of problem solving by attempting to identify and correct the root causes of events, as opposed to simply addressing their symptoms. By focusing correction on root causes, problem recurrence can be prevented. An ultrasound transducer is passed over the object being inspected and sends ultrasound waves into it. Reflected ultrasound comes from an interface, such as the back wall of the object or from an imperfection within the object. The diagnostic machine displays these results Is based upon capillary action. Low surface tension fluid penetrates into the cracks of a clean and dry surface. The excess penetrant is removed and a developer is applied. The developer helps to draw penetrant out of the flaw so that an invisible indication becomes visible. Is for detecting surface and slightly subsurface discontinuities in ferroelectric materials. The process works with magnetic fields. Discontinuities will cause differences in the magnet field. Ferrous iron particle are applied to indicate them. The care and servicing by personnel for the purpose of maintaining equipment and facilities in normal operating condition by providing for systematic inspection, detection and correction of incipient failures either before they occur or before they develop into major defects. All techniques which are designed to help determine the condition of in-service equipment in order to predict when maintenance should be performed. This approach promises cost savings over routine or time-based preventive maintenance, because tasks are performed only when warranted. To evaluate equipment condition, predictive maintenance utilizes nondestructive testing technologies such as infrared, acoustic (partial discharge and airborne ultrasonic), corona detection, vibration analysis, sound level measurements, oil analysis , and other specific monitoring measurements

(UT)Ultrasonic Testing

(DP)Dye penetration Test

(MPT)Magnetic Particle Test

Preventive Maintenance

Predictive Maintenance

OPC PID Controller

DCS

Ordinary Portland Cement Proportional-Integrative-Derivative controller which calculates an error value as the difference between a measured process variable and a desired setpoint. Design Criteria and Standards

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HTC Management System High Bearing Temperature in Ball Mills

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A-PROCESS/GRINDING SECTION 2 Process reasons for high bearing temperature From process/ operational point of view high bearing temperature is caused by high temperature inside the mill and high temperature of the environment. High bearing temperature caused by  High temperature inside mill  High environmental temperature

2.1 High temperature inside the mill High mill temperature can be caused by the process arrangement or system operation or can be introduced from external source.

2.1.1 Process arrangement Factors influencing mill temperature related to process arrangement are:  Open or closed circuit mill -

Open circuit mills for example are traditionally operated with lower material filling and less ventilation air to achieve the desired cement quality. Both factors are increasing temperature inside the mill. Above mentioned Chinese mills are all closed circuits.

 Capacity of mill ventilation -

The mill ventilation shall allow min. 1.5 m/s ventilation speed above ball charge. Mill ventilation has 3 basic functions: 

Removal of fine dust to avoid coating



Material transport



Cooling

 Separator de-dusting -

The bigger the separator de-dusting volume the higher the amount of fresh air which can be introduced to the separator for cooling. Best arrangement in this regard is direct separator de-dusting in bag-house with 100 % fresh air operation

 Separator efficiency -

The lower the separator efficiency the higher the circulating load and the higher the temperature inside the mill. Separator should be state of the art 3rd generation cage separator with sufficient reserve. If separator design is too tight then efficiency will drop accordingly.

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HTC Management System High Bearing Temperature in Ball Mills

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 Water injection -

Is the system equipped with a proper water injection? Water injection will help lowering the temperature inside the mill.

 System instrumentation -

The mill system should be equipped with sufficient instrumentation to allow a proper operation of the mill. Such instruments should include reject weighing, mill outlet pressure, acoustic mill level, elevator power consumption (KW) etc.. High level of automation is another plus.

2.1.2 System operation Factors influencing mill temperature related to system operation are:  Ball charge -

Ball charge should be kept in proper condition. Resorting of charge to be done every year for chamber 1 and every second year for chamber 2. Regular top-up to be done to keep constant filling level. Improper ball charge will lower efficiency and increase circulation load.

 Mill condition -

The ball mill should be regularly inspected, e.g. once a month to check the condition of the mill internals, the filling degree, the slot openings in the diaphragms, the water injection nozzle etc. This will ensure best efficiency of grinding.

 Circulating load -

Mill should be operated at optimum circulation load to avoid both overfilling and empty ball mill which both may lead to higher temperature in the grinding chamber.

 Mill ventilation -

Sufficient mill ventilation is important to fulfil basic functions of the same (see above). Mill ventilation should be adjusted to the cement type and fineness of the product. Regular airflow measurements should be executed to check the actual airflow at the mill ventilation. The ventilation bag filter should be properly maintained to ensure constant operating conditions in terms of pressure drop. The bag filter cleaning cycle should be adjusted adequately.

 Water injection -

Water injection is generally used for quality control by means of temperature control of mill outlet material and most efficient in chamber 2. Proper adjustment of the same can also help to prevent high bearing temperature. A typical setting is 115 °C start injection and 110 °C stop injection. The water valve should be controlled by PID controller which needs to be optimised. Also the injection

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HTC Management System High Bearing Temperature in Ball Mills

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equipment, especially the nozzle, has to be properly maintained. Before and after usage, the injection system shall be automatically cleaned with compressed air to avoid clogging.  Separator -

The separator should be inspected regularly e.g. once a month. The efficiency of the separator should also be checked from time to time by circuit sampling. Good separator efficiency is reducing the circulating load. If the separator allows for fresh air operation, the same should be maximized to reduce the mill temperature.

 Mill system automation -

The mill system should have a good level of automation especially proper tuned control loop for the circulating load and fresh material feeding. Information of the mill filling level beside the mill KW e.g. acoustic mill sound measurement is very helpful to avoid both overfilling and running empty. Mill should be also properly interlocked to shut down the mill when fresh material feeding is interrupted for more than 10 min.

2.1.3 External heat source Factors influencing mill temperature related to external heat source are:  High clinker temperature -

In especially integrated plants and older kiln process arrangement it can appear that clinker temperature is quite high. In peak season with low clinker stock clinker temperature can be as high as 140 °C. This will have of course a big impact on mill and bearing temperature. In such case water injection is a must. Also injection in chamber 1 shall be considered then. Besides separator cooling, reject cooling also could be an option. Reject cooling can be a better option than cement cooling since it is effective at an earlier stage of the process and helps to control temperature in the mill circuit.

 High oil temperature -

If slide shoe lubrication oil is not properly cooled will also lead to higher bearing temperature. This issue will be covered in the maintenance section of this document.

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HTC Management System High Bearing Temperature in Ball Mills

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2.2 High environmental temperature Factors influencing mill temperature related to environmental temperature are.  Mill building ventilation -

High environmental temperature will also increase mill and bearing temperature especially in summer in “hot” countries. If mill building is not open for noise emission reasons then there should be a proper ventilation of the mill building. If bearing temperature is critical, forced ventilation by means of fans could be considered.

 Circuit cooling -

If environmental temperature is higher, then separator cooling also will be less efficient. As an alternative reject cooling with water cooler could be considered. Forced cooling of e.g. mill shell by means of fans could be also an option for temporarily emergency cooling.

3 Measures to prevent high bearing temperature Process / operational measures to avoid high bearing temperature can be split into two sections:  Process design  System operation

3.1 Process design measures Optimisation of process arrangement in view of high mill temperature and thus also high bearing temperature shall include the following.  Mill system -

-

State of the art mill system is closed circuit with below advantages: 

efficient production of high quality cement



easy operation and quality control



ball mill outlet must not be finish cement



good ball mill optimisation potential



independent grinding ( ball mill) and quality control ( separator)



lower energy consumption increasingly with higher cement quality

New open circuit mills shall only be installed in markets with permanent request for low quality OPC cement

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HTC Management System High Bearing Temperature in Ball Mills

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 Mill ventilation -

The mill ventilation shall be designed for min. 1.5 m/s ventilation speed above ball charge. This will allow to properly fulfil and optimise the 3 basic functions of the mill ventilation: o

Removal of fine dust to avoid coating

o

Material transport

o

Cooling

 Separator de-dusting -

Separator de-dusting can be arranged through cyclones or bag-filter. Cyclone arrangement still requires a small bag-filter to remove the fine dust. Usual size is then 5 – 10 % of separator airflow. The bigger the separator de-dusting volume the higher the amount of fresh air which can be introduced to the separator for cooling. Best arrangement in this regard is direct separator de-dusting in bag-house with 100 % fresh air operation (see flow-sheet above). Beside better cooling and positive impact of bearing temperature, this arrangement also has the below advantages: 

no fine material circulation resulting in higher separator efficiency

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HTC Management System High Bearing Temperature in Ball Mills

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

efficient cement collection even for high Blaine



no vibration at separator fan due to fine dust deposit on fan impellor



less equipment

 Separator type -

The lower the separator efficiency the higher the circulating load and the higher the temperature inside the mill. Separator for new mill project should be state of the art 3rd generation cage separator with sufficient reserve. If separator design is too tight then efficiency will drop accordingly.

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HTC Management System High Bearing Temperature in Ball Mills

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 Water injection -

If clinker temperature is an issue like e.g. in integrated Plants or cement temperature is to be limited or separator de-dusting is in cyclones then water injection should be considered.

-

Water injection should be limited to 2 % of fresh feed amount. Water injection is more efficient in chamber 2. Arrangement can be co or counter-current. Water injection in chamber 1 shall be considered at high clinker temperatures.

System instrumentation -

The mill system should be equipped with sufficient instrumentation to allow a proper operation of the mill. Such instruments should include reject weighing, mill outlet pressure, acoustic mill level, elevator kW etc. High level of automation is another plus. New mills should be equipped with state of the art instrumentation and control. Old mills should be updated to allow operators efficient process control at optimum mill condition.

-

Water injection should be high enough to cool the cement temperature and low enough not to cause any pre-hydration of cement. Sufficient mill ventilation must be ensured when water is sprayed in the mill to avoid any condensation of water.

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HTC Management System High Bearing Temperature in Ball Mills

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3.2 System operation Operational measures to avoid high mill temperature include the following:  Operator training -

Only professionally trained people can operate mill systems in optimum condition. Therefore mill operators should be regularly trained and updated.

 System inspection -

All key equipment should be regularly inspected to check mechanical condition and detect optimisation potential. The Expert Group Grinding has created specific guidelines for this purpose such as “Guideline on plant and process evaluation for grinding plants or “Ball Mill Grinding Process Handbook“. The same are available on HC INTRANET.

 Mill system maintenance -

Only properly maintained mill circuits can run in optimum condition and achieve best performance. This should include mechanics e.g. mill internals and ball charge but also electrical and instrumentation. Also Plant control system and automation should be kept up to date. The details of mechanical aspects are presented on the next section.

 System optimisation -

According to inspection analyses Plant should be continuously optimised. Also changes in raw material properties or composition as well as product qualities shall result in adequate system optimisation. Also here are useful guidelines available such as “Guideline for Sulfate Optimization of Cement” or “Best practice in the production of composite cements“. Optimisation measures should include control loop tuning and standard start up and shut down procedures etc.

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B-MAINTENANCE SECTION 4 Mechanical reasons for high bearing temperature From Maintenance point of view high bearing temperature can be caused by various reasons such as: 

equipment design and dimensioning



material quality and compatibilities



geometrical precision



surfaces quality



transport conditions



storage conditions



commissioning



mechanical adjustments



lubricant quality



operation



Environment conditions (dust, humidity, etc.)

75ºC 53ºC

All above mentioned reasons are significantly influenced by high temperature of the environment or process inadequate parameters. To eliminate or minimise the high bearing temperature problems, it is recommended to follow carefully all instructions from the technical documentations and this guidance paper. All these aspects should be accomplished by a nominated responsible person, starting with contracting period. After commissioning and running test period, the Maintenance department has a very important role to maintain the normal condition in operation as well as the Production department to operate in proper operational parameters.

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5 Description of mill and running aspects 5.1 Generalities for MTN section The two chambers of the ball mills are equipped with different liners and balls according to the specific needs of customer and the design of the manufacturer. The intermediate diaphragm between the two grinding chambers and the discharge diaphragm from the outlet ensure an optimum of free area for ventilation and minimize the loss pressure in the system. The temperature has important impact on the mill shell and sliding surfaces of the bearings. In the next picture you can see the main elements of a ball mill and the air and material flow. You can see that the outlet sliding ring is influenced more by the higher temperature from inside in this area.

Cold air T<45 ºC

Feed [t/h]=constant (Fresh feed + rejects from separator

Inlet sliding ring

Mill ventilation [m/s]

Outlet sliding ring Inlet

First Chamber Diaphragm

Hot air and material

Second Chamber

T > 70ºC Outlet

5.2 Mill supports and bearings system The mill support is provided by four slide shoe bearings (two slide shoe bearings for the inlet sliding ring and two slide shoe bearings for the outlet sliding ring The bearing shoe is placed in a concave ball cup on the lower part of the sliding shoe.

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The sliding ring together with their shoe bearings is covered by a protection cover with special sealing preventing the entry of dust, dirt, humidity, etc. and the leakage of oil.

Thermic influence of sliding ring and mill shell

The mill bearings have a separate and an independent lubrication system. The systems are included in the automation system of the mill interlocking. The lubrication system usually consists of one high pressure pump and one low pressure pump, double oil filters, oil/air/water coolers.

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HTC Management System High Bearing Temperature in Ball Mills

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Measure to prevent high bearing temperature 6.1 Lubrication units

Therefore, a responsible person should be assigned to check the equipment in accordance with the supplier’s instructions and the specific instructions prepared by cement plants. The following aspects should be emphasized:  For a new mill, the lubrication oil for the sliding-shoes bearings should be replaced with fresh oil when the mill has been operated first test period according supplier recommendations. The oil tank and the installation (e.g. filters, pipes, pumps etc.) should be cleaned before the fresh oil is filled up. The cleaning must be executed by careful flushing and cleaning the dirty and particle inside of installation according supplier instructions.  The oil level in the oil tank should be checked regularly. Oil should be added when the oil level is lower than the minimum standard level. Supplementary investigations will be executed if the periodicity of filling is lower and if the quantity of completion is bigger.  The oil quality should be checked regularly by sampling and specialized analyses. The dirt in the oil tank and in the rest of installations should be checked and cleaned regularly. Supplementary investigations have to be executed if dirt appeared in the system (e.g. to identify the source) Please see below an example of a very bad situation of oil contamination with dust. Particles of dust deposited outside the rubber sealing escaped through the seal, in to the sliding ring cage.



Periodical inspection should be made for the sealing condition. Please check the compatibility of rubber with the oil.

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HTC Management System High Bearing Temperature in Ball Mills

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The high-pressure oil lubrication station should be checked regularly for the oil sufficiency and for the blockage of the piping. The automation control instrumentation and the signalization devices should be checked regularly for normal function and interlock. The temperature change of the supporting bush and the lubrication oil should be checked regularly. Attention should be paid to the abnormal vibration and noise of the equipment. The flow of the cooling water should be checked regularly. The temperature of fresh water and the proper filtration of fresh water should be checked regularly.

Example of measurements of water and oil temperature at the inlet and outlet can reveal differences between similar installations of mills or low efficiency of coolers OIL temperature in operation

WATER temperature in operation

Mill No. inlet

outlet

Difference of temperature

inlet

outlet

Difference of temperature

CM1

27.8

25.6

2.2

18.2

19.9

1.7

CM2

28.6

25.1

3.5

18.3

22.1

3.8

…

…

…

….

….

….

….

CMn

32.5

30.5

2

18.4

21

2.5

In the previous example we could see that the lubrication system of mill no 2 is more efficient than CM1 and CM2 which is similar. In this case an inspection should be planned.

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6.2 Mill bearings system 6.2.1 The sliding rings The sliding rings are parts of the mill sustaining bearings. The main aspects which should be checked from commissioning period are ovality, surface form and the surface condition of both slide rings (inlet and outlet ring).

Mill shell

D left

D right

Sliding ring

Discharging holes

Outlet head of CM

Example of ovality measurement of sliding ring: Measurements consists of ovality checking of the slide rings by measuring on the upper position of two circles ‘’D left’’ and ‘’D right’’. Please see an example below:

Example: Allowed value of ovality : acc. producer 0,36 Diameter left

: 0, 22 mm

Diameter right : 0, 32 mm

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Example of surface form / shape measurements of sliding ring: Measurements consisted of checking the surface shape of slide rings by measuring on the bottom position (near to the shoes bearing) of two circles ‘’series 1’’ and ‘’series 2’’. It is revealed in this representation the alternation of surface inclination and the maximum of inclinations (in the points 5,13, 19)

[mm]

Generally, the state of slide ring surfaces is related to the corrosion and mechanical damages in the form of scratches / pitting. Transport, storage and commissioning are the most important phases to check and to maintain the surfaces in the best condition. The recommendations from the producer as well as standard conditions should be assured during these phases (specific package and surface protection against corrosion). Therefore, a responsible person should be assigned to check these aspects in accordance with supplier’s instructions and specific instructions prepared by cement plants starting with commissioning period. The following aspects should be emphasized: 

The surfaces should be protected by specific methods during :  Transport (especially for shipping transport)  Storage  Commissioning  Running test and starting in operation

Below are the pictures with examples of different types of corrosion and the infrared diagrams of temperature distribution and the effects on the surfaces:

Dust and corrosion



Pronounced corrosion

Infrared view of hot spots

The surfaces should be protected against mechanical damages or scratches.

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A deep scratch and the distribution of the temperature near to scratch

It is visible the correspondence between infrared and visible scratch.

Generally, the hot spots increase the average of temperature of all system. The target is to have approximately constant temperature on the slide bearing and slide ring surfaces.

6.2.2 The slide shoe bearings The instructions from the producer should be assured for the slide shoes bearings surfaces: Therefore, a responsible person should be assigned to check these aspects in accordance with supplier’s instructions and specific instructions prepared by cement plants starting with commissioning period. The following aspects should be emphasized: 

The blue print method: Example of the contact surface of the slide shoes bearing with sliding ring Invert method printing

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A

A

A-A without pocket

A-A with pocket

Example of blue print method (direct imprint)

Example of slide shoe bearing geometry sketch (geometrical aspects, according each supplier)

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6.3 Checking of mill internal insulation and lining One of the major reasons that lead to increase the bearing temperature of sliding ring area is the insulation from inside of the mill. Please see below an example of proper insulation (see the correspondence of numbers from sketch and pictures)

Mill shell

Thermic insulation 1

Thermic insulation 3

The liners 2 Outlet wall 4 (screen)

Discharging holes

Outlet head of CM 

The mill shell insulation and protection

1



4

1

The insulation under the sliding ring

3

3 4

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

Routine maintenance on the inner parts is an importance measure for keeping the equipment in good condition and for long term safe operation.



All the connection bolts of liners for a new mill or a repaired mill should be checked regularly.



The wearing condition of the liners in the feeding chute should be checked regularly.



When the equipment is running, it is necessary to check out visually (five senses method e.g. leakages, unusual noises, etc.).

7 General summary and conclusions High bearing temperature can be either related to process or mechanical reasons as well as design and manufacturing. These potential reasons can be covered considering Expert Group recommendations. Please note that the measures recommended above are not exhaustive and they can be supplemented with other specific measures that may result from the specific conditions, risk assessments, producer, local laws, etc.

7.1 Process recommended measures to avoid high bearing temperature situations: 1. Installation of sufficient mill ventilation capacity 2. Proper control of mill inlet/outlet temperature ( water injection, separator cooling etc.) 3. Adequate operation of the mill system ( avoid overloading, insufficient separator or mill ventilation airflow etc.) 4. Regular inspection of the mill system (ball sorting, diaphragm cleaning, nibs trap working…)

7.2 Maintenance recommended measures to avoid high bearing temperature situations: 1. Checking during commissioning for: a. General situation of equipment

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b. Condition of active surfaces(e.g. slide ring, slide shoes bearings, sealing, etc) c. Storage conditions d. Transport conditions e. Protection of surfaces f.

Installation of proper insulation under sliding rings

g. Installation of proper insulation under the liner plates h. Checking the alignment i.

Checking of proper blue print adjustment (see related chapter)

j.

Used materials and spares

k. Assembly and adjustments acc. technical documentation

2. Checking during running test a. Lubricants quality and quantity b. Cooling systems 

Water flow and quality



Oil flow and quality



Temperature inlet/outlet for water



Temperature inlet/outlet for oil



System functionality

c. Sealing systems/elements d. Temperature monitoring and comparing e. Vibration monitoring and comparing f.

Leakages and reasons

3. Checking in guarantee period a. Temperature monitoring and scanning b. Vibration monitoring and scanning c. Sealing systems

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d. Insulation systems e. Cooling and aeration systems f.

Lubricants and lubrication systems

g. Condition of active surfaces h. Mill mechanical conditions The most important aspects for checking, according to previous experiences, are marked

.

4. Other regular MTN activities Maintenance in normal operation, according to the maintenance procedures and specific technical documentations of equipment needs to be ensured. The following recommended specific checks needs to be executed: a. Ultrasonic Testing (UT) – periodically when a crack was observed during periodic inspections b. Dye penetration Test (DP) – periodically or when a crack was observed during periodic inspections c. Magnetic Particle Test (MPT) – annually or when a crack was observed during periodic inspections d. Preventive Maintenance plans e. Predictive Maintenance plans The most common methodology is DP test. The other methods can be executed when a crack is detected. MTN Conclusions: Some of the recommended activities have to be carried out every day or every shift, some have considerably longer intervals, e.g. bi-monthly or annually. It is mandatory to document all checks and observations and maintain a history record (e.g. in SAP PM). More information can be found in Library CoP Maintenance. After the commissioning period and the operation tests, a careful regular check of the machinery combined with scheduled replacement of wear parts, lubrication oil, etc. is needed to ensure steady operation and long service life. Even if the mill is in the warranty period, maintenance inspections must be executed without fail. Usually during this period, clear signs of problems may appear which will become acute later. In practice, careful regular checks of the machinery combined with scheduled replacement of wear parts, lubrication oil, etc. is needed to ensure steady operation and long service life.

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8 Up-gradation of Tender docs In view of avoiding problems with high bearing temperature for future projects the relevant Tender docs should be updated.

8.1 Process/ operational In terms of process, the most relevant documents are Flow-sheet, Limits and Requirements and project specific Process DCS as well as General DCS. In above documents the following items should be clearly specified: -

Mill system process arrangement

-

Kind of separator de-dusting

-

Separator type

-

Minimum mill ventilation amount

-

Water injection yes/no, where and quantity.

-

System instrumentation and mill control

8.2 Maintenance In terms of Maintenance, the most relevant docs are MTN documentation, Limits and Requirements, Periodicity of MTN activities, Quality Certificates for materials and execution according standards, Certificates for all specific intermediary and final phases during commissioning and running test periods(e.g. alignments, adjustments and recorded parameters), as well as General DCS. In above documents the following items should be clearly specified: -

Mill insulation systems and materials

-

Mill sealing systems and materials

-

Alignment conditions, used standards and specifications(e.g. runout, etc)

-

Vibration conditions, used standards and specifications

-

Running conditions and parameters

-

Measurement points and periodicity for :

-

o

Vibrations

o

Temperatures

o

Other specific measurements

System monitoring instrumentation and compatibilities with others

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-

Mechanical documentation

-

List of spare parts for standardised elements (e.g. bearings, simmering, thermocouples, etc.)

9 Further applicable documents Please see other related documents in WoK: - SMP-Ball Mill Maintenance - SMP-Plant Mothballing - PM Guideline warranty - Guideline on plant and process evaluation of grinding plants (Ball mills) - Ball mill grinding process handbook - Separator inspection and optimization guideline

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