VRM Roller Bearing (R3) Maintenance Report

By: DMC Maintenance Department(Mechanical) July 2015 i

VRM Roller Bearing (R3) Maintenance Report Down time Duration 2015 (June 24-Jully07)

By: DMC Maintenance Department(Mechanical) July 2015 ii

Index

i. Scope of the Work ........................................................................................................................... iii

ii. Overview ............................................................................................................................................... 1

a) Safety Considerations ....................................................................................................................... 1

b) Main procedure for Removal of Roller from Mill ............................................................................ 1

1. Man power and Work Duration ............................................................................................................ 2

2. Consumable Materials........................................................................................................................... 3

3. Tools and Equipment Required............................................................................................................. 4

4. Dis-assembling of the Grinding Rollers ................................................................................................ 5

4.1 Safety and Site Preparation ....................................................................................................... 6

4.2 Dismantling from the Carrier .................................................................................................... 7

4.3 Roller Dismantling .......................................................................................................................... 9

5. Involvement and the Role of the DMC, Pfeiffer Expert ..................................................................... 10

6. Bearing Failure Analysis and Decisions ............................................................................................. 11

a. Unusual dis-assembling procedure ............................................................................................. 11

b. Electric grounding conditions during welding VRM area .......................................................... 11

c. Low Material bed height ............................................................................................................. 12

7. Installation of New Bearing on Roller Tire Assembly ........................................................................ 13

7.1 Sub assembly one (Roller bushing, the two bearing and the distance ring) .................................... 13

7.2 Sub-assembly two (Roller shaft, Ceramic Bushing, inner spacer (Inner rase) bushing, and outer

spacer bushing ) ...................................................................................................................................... 14

7.3 Assemble 7.1 and 7.2 ...................................................................................................................... 14

7.4 Assembly of pressure yoke ............................................................................................................. 15

8. Growth to the Mill ............................................................................................................................. 16

9. Problems and Abnormal Conditions ................................................................................................... 18

a. Shortage of full material for dismantling .................................................................................... 18

b. Lack of experience for dismantling ............................................................................................ 19

By: DMC Maintenance Department(Mechanical) July 2015 iii

i. Scope of the Work

The report only considers the disassembly and the assembly procedures taken, equipment and

labor required and the problem encountered during practical work. The main objective of the

maintenance work is to sustain the system in a required working condition, to escape the down

time, to keep the maintenance cost as low as possible at the same time to keep the design life

time of the equipment. In broad tem maintenance may indicate inspection and servicing,

lubrication procedures and maintenance repair work.

This maintenance work is performed on the VRM grinding roller 3 due to bearing failure. The

most probable cause for this bearing failure may be

Due to grounding of the shaft at hard facing of roller tire since last summer.

Material bed is too low.

Grind-ability and material size.

Lubrication type and regularity of follow up.

Generally the maintenance procedure taken is dreary and time consuming as well as the

maintenance cost required is very high. The main factor for this is none ready maintenance

material and lack of experience.

By: DMC Maintenance Department(Mechanical) July 2015 1

Company Name

Derba MIDROC Cement Document No. DMC/OF/

Title

VRM Roller Bearing Maintenance Report Issue No. 01 Page 1of 23

ii. Overview

For the Removing of the grinding roller from the mill assembly, make sure that they are

positioned on the grinding table at an angle of 1500.5. If the angle is wider, lift the grinding

rollers briefly with the hydraulic tensioning causing them to swing to the inside. After lowering

the grinding rollers, get them to the right angle, using the auxiliary (maintenance) drive.

a) Safety Considerations

Any accidental restart of the m/c may cause heavy injuries or casualty.

For any power interruptions make sure it cannot be switched on unintendedly.

For any work inside the mill, make proper ventilations i.e. when there is lack of oxygen

or the presence of toxic kiln gases, it may cause problem to human life.

To the maintenance personnel it is required to use a harness and/or enlarge the firmly

installed floor by an appropriate working plat form.

A tilting grinding roller may cause injuries /squeeze a body and cause high injuries, thus

the tightening torques specified in the manual must be observed.

b) Main procedure for Removal of Roller from Mill

Open the maintenance door and swing it aside.

Remove the segments of the lining of the air guide cone from around the door as well as

the detachable segment of the nozzle ring.

Remove the parts of the water injection system from the grinding zone.

Loosen the covers from the pressure yokes so that the grinding roller stop parts hang

freely.

Dismantle and remove the three seal air ducts from the grinding roller.


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1. Man power and Work Duration Table 1-1

Manpower CNBM DMC Pfeiffer Expert

Expert Labor force Expert Labor force(security) 1

5 9 5 4

Date(from June 24-July 2015) Effort performed

24 Removal (isolation) of the physically investigated roller (Roller 3) from Raw

meal

25 Mounting of the lift and swing system

26 Roller (R3) dismantling

27 Roller ring disassembled

28 Pressure frame dismantled

29 Removal of high torque bolt by heating and chain block simultaneously

30 Pulling up the bearing shaft assembly with hydraulic jack

01 Preparation for new Extractor(50mm,1000mm) mechanism for 500t

hydraulic jack extractor

02 Bearing disassembly

03 Heating the scratched bearing inner raise

Probing for assembling workshop

04 Preparation for assembly, tent preparation (rain prevention), roller Bushing

support(jigs) preparation, Heating material(butane gas, acetylene-oxygen gas, wood),

7.1, and 7.2 assembled

05 Assembly of Shaft cup and roller bushing cup

06 Assembly of pressure yoke, safety disc (pr. Yoke side) , Inner seal air sealing

ring (item 322 manual), clamp bow

07 Assembly to the carrier


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2. Consumable Materials Table 2-1

Material

Description

Estimated Unit Cost

Est. total cost

Quantity ( Birr )

Oxygen gas For accetyline steel cutting 4 cyls

Acetylene gas For accetyline steel cutting 2 cyls

CHS tube, 1200mm – 220mmØ For suporting bearing shaft assemb. 3pcs

Steel Plates (1000Øx50mm thicness), berg CHS Basement and for extraction 4pcs

Eye bolts, nuts, M56 x 50mm, M24, For crane handling 3 pcs

oil

Extracting oil, Oil for Lift and

swing, Lubrication oil, grease oil

-

Cleaning detergent For cleaning purpose -

Welding rod, 7018 – 4mmØ - 12 kgs

Roller tyre bearing diassembly 1unit 1 sets.

Protection/Shed Preventing dust and rain 1

Butane gas For heating the bearing 3units(26.3kg) 3 cyls


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3. Tools and Equipment Required

Equipment

Description

Estimated Estimated Est. total cost

Quantity N° of Hours ( Birr )

Lift and swing system to remove the roler outside

Crane, 150 tons to lower or retain the roller assembly 1 unit

Crane, 55 tons To move disassembled roller part 1 unit

Fork lift For different purpose 1 unit

ladder 1unit

Chain block, 5t,3t, 2t For different purposse 3,4,2units respectively

Welding machine, 300 A 1 unit

Grinder 1 unit

Toolbox Different size tools 1 box

Shackle,(Padlocks(Deadbolts))

different size

connect the wire rope and the roller part

for moving tenacity 8-12pcs

eye bolt tightened to the part body to handle the

crane, chain block, forklift

3x12t 5x25t, 4x40kg,

3x250kg

Crowbar, hammer, spacer,etc. For different purposse

Rubber hose, Hose for butane gas, compressor dust

cleaning 20 mtrs

Hand pump For lubrication 3units

Wire rope cable sling. 40mmØ x 3m,

spliced eyes on both ends

For moving componenents 6 pcs

Wood blocks, 300mmx 300 mmx

152mm

Support 10-15 pcs

Hydraulic crick jacks,60t, 100t, 500t

To dis-assemble the shirink fit shaft

and roller bushing, assemble and

disassebly of the presure yoke and shaft

4 units(1, 2, 1 resp.)

IR Thermometer(-32-10500c), To mesure the temperature 1pcs

Wire rope sling cables, 20mmØ -55t x

6m, spliced eyes on both ends

3pcs

Wire rope sling cables, 50mmØ x

150t x3m, spliced eyes on both ends

2 pcs

Nylon rope, 10mmØ x 1m, spliced on

both ends

3 pcs

Hydraulic torque wrench, electric driven

(Power Team USA)

to loosening or tightening the bolt,nut 1 set

Steel plate & supporting CHS jigs for

bearing pre-setting disassembly

Supports the roller at a fixed leveled

height

3CHS pcs with spacer at

the top +2steel plates


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4. Dis-assembling of the Grinding Rollers

The disassembly and assembly of the grinding rollers from the mill is performed by the means of

lift-swing system.

Figure 4-1 Lift and Swing Mechanism

Note. Please check the manual drawing of hydraulic circuit to properly identify the lift hose and

the two swing hose. i.e. the problem Which we have seen during the work.


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4.1 Safety and Site Preparation

Workers, shall at all times wear safety helmets, safety shoes, safety goggles when doing

grinding or chipping works, welding mask during welding, working and welding gloves,

human harness or safety belts when climbing more than three ( 3 ) meters.

Prepare, inspect & test integrity of a 5-t lever block to be used for the job. Ensure this is fit

for use. Likewise, inspect, check the integrity a 40-t wire rope slings to be used.

Prepare, inspect & test integrity of the oxygen-acetylene hoses & gauges to be used for the

job. Ensure this is fit for use.

Prepare & inspect the integrity of the welding cables to be used. Test the welding machine to

be used for the job. Ensure this is fit for use.

Haul to site the oxygen-acetylene hoses & gauges, oxy-acetylene cylinders, lever block, wire

rope sling, tool box, welding rods.

Clean and clear the site / work area from dust, garbage & scraps.

Position the platform and crossed-jig on the area and leveling of the same. You need some

wedges in order to level the platform to 0-0 (at least 99%). Fix & tuck weld all wedges.

Also, position at site wood blocks & fabricated stand that will be used for holding the roller

assembly.

Position the fabricated freezing pan on the area and leveling of same. You need some

wedges in order to level this.

Apply all Safety Aspects & Procedures during the duration of the work. Refer the

maintenance manual applications & all Safety Procedures.


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4.2 Dismantling from the Carrier

Initially by using the lift and swing system wrench out the roller assembly from the carrier

and swing out for handling by 150t crane.

After pulling out the roller, Using 150t & 55t cranes, position the roller assembly on the

ground at side rest - so that the roller bushing flat side on the ground while the pressure yoke

side is on the top position.

a. Lift, swing system and Roller Connector assembly

b. Disconnecting and handling by 150t crane

a. b.


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1. 2.

3. 4.

1. Slowly lowering, 2. Place on the ground,

3. Using the two cranes for positioning, 4. Roller flat side to the ground


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4.3 Roller Dismantling

Loosen all 24 pcs locking bolts of shaft damper plate with striking hydraulic wrench.

Then, loosen the 12 pcs bearing clamping stud bolts. Remove also all remaining 24 pcs

damper ring stud bolts.

Using 500t hydrauulic cricks dis-assemble the roller yoke.

Using the 55t crane, lift up the roller yoke very slowly to free from the carrier shaft and put in a

safe place without reversing. Pull out the roller bushing ringplate, all oil seals, and o-rings. Use

shackles to connect wire rope sling. Using the two cranes reverse the rolle bushing flat side up

and put on the leveled prepared supporting jigs of about 1200mm hieght and dis asseble the

roller bushing cup.

Now using 55t reverse the roller bushing flat side up and start the shaft lifting up by 500t

hydraulic cricks.When the roller bushing and shaft are disassembled, screw the bolt on the shaft

cup plate and remove the shaft cup.

Then heat up the distance ring and inner race of the bearing, You may gas cut the inner race if

need arises. Using the 55t crane, lift this bearing to be free from the carrier shaft. Lay this

bearing near the mountain side–free from the work area. Remove all lifting pads & wire rope

slings.

Dismantle the outer races of both inner & outer bearings. Use the 500t hydraulic jacks for this

purpose

Visually check the shaft and the bearing for any signs of cracks or spalling. Use crack

detector or visualisation. Smooth grind with emery cloth & solvent


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5. Involvement and the Role of the DMC, Pfeiffer Expert The CNBM maintenance professionals ordered them to follow rigidly whatever they want.

After removing the shaft cup three bolts from the self-aligned roller end side they have tried

to disassemble horizontally using 5t chain block, which could have damage the sensitive

bronze sleeve ceramics. After strong command they reverse up-down by 55t crane which is

the easiest, normal and safe way of removing the bearing.

CNBM working force did not care for the plant design life hence they do modification, weld

on very expensive VRM casting part

5t chain block

Welding heat that Could damage the cast cup

Bronze sleeve

We can use this to handle

Malfunction Weight


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6. Bearing Failure Analysis and Decisions

a. Unusual dis-assembling procedure

The most likely cause for the damage of self-aligned roller bearing is the hydraulic pressure during dis-

assembly.

b. Electric grounding conditions during welding VRM area

When we make welding around the mill we need to take care of the electric grounding

condition.

As an example if the grounding distance is too far from the welding point, i.e. long flow

distance, the electric charge loss is higher and hence the spark heat on the circuit make

bonding of the two mating metal of bearing inner race and the roller.

Even if the grounding distance is also lower, the lower welding current adjustment also

make the same problem and may damage the bearing as well.

Crack propagate from the bottom to the top

a. Self-aligned roller Bearing

500t

Pressure

W


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c. Low Material bed height

Low material bed height may cause bearing damage when coarse material inflowing may result

in high pressure on the roller that may result abnormal condition. Thus the proper material bed

should set based on the given design value of mill operation.

22

5

14

18

b. Upper 4 Rollers

Damaged

(Cylindrical Roller bearing)

a. Pressure side Bearing inner-race

(Cylindrical roller bearing)


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7. Installation of New Bearing on Roller Tire Assembly

7.1 Sub assembly one (Roller bushing, the two bearing and the distance ring)

Using the 55t crane, position one new roller Bushing vertically (i.e. wider part uper)into

the pre-leveled crossed-jig(i.e. 3 supporter circular hollow section CHS). Clean the bearing

housings. Use emery cloth and solvent to smoothly grind the bearing housings.

Start heating the Roller bushinig externally for (5-6)hrs untill the temperature reaches about

1000c(manual design value).

When the temperature reaches the required value, using 55t crane put the self-aligned roller

bearing to the roller bushing. To fix it at the bottom ded center use some retainer (L

profile=50x150x100mm)which is tightened to the bushing. Then assemble the distance ring

(oil distributer ring). Rapidly assemble the cylinderical roller bearing.

1. Bearing bushing

2. Cylindrical Roller bearing

3. Distance ring

(Outer spacer bushing)

4. Self-aligned Roller

bearing

3

1

4

2


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7.2 Sub-assembly two (Roller shaft, Ceramic Bushing, inner spacer

(Inner rase) bushing, and outer spacer bushing )

Fix the roller shaft up making the pressure yoke side down ward (i.e. stand it on safe

condition without support.).

Then smoothly keep ceramic bushing safe. Using the butane gas heater heat up the

cylindrical roller bearing inner rase approximately up to 75-85 0c and assemble up-down

ward on the shaft using 55t crane, move it down untill it reaches the ceramic bushing. Then

assemble the second inner rase downward untill it reaches the first one.

7.3 Assemble 7.1 and 7.2

Fix the 7.2and using 55t crane directly putting it up and then assemble 7.1 on 7.2. from the

below When the cylindrical roller bearing tip concedes its inner rase on the shat stop moving

it down and make support at three equal point distance (approximately 1200). Then assemble

the shaft cup on the top by allowing some tolerance to shaft (about 20mm). Thus now

assemble the roller cup on the top to the roller bushing and the shaft cup.

After completing these, using the two cranes, reverse the total assembly down ward. (i.e.

shaft pressure yoke side on the top.). Now clean the roller bearing, shaft, ceramic bushing (if

any) and assemble bushing inner cup ring plate to the system assembly.

1

2

4

3

1. Roller shaft 2. Ceramic bushing

3. Inner spacer bushing

4. Outer spacer bushing


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7.4 Assembly of pressure yoke 7.5


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8. Growth to the Mill

Clean and clear the site / area for storing.

With the use of 150t crane, slowly lift each roller pair assembly to the storage area. You may

need some wood blocks to wedge each tyre to prevent from rolling. Remove all sling cables.

Cover the assembly.

Clean area from all scraps & waste materials. Safe keep all sling cables for re-use.

Haul all oxygen-acetylene cylinders. Empty cylinders should be returned back to the warehouse.

All remaining full cylinders should be safekeep at the workshop for further use. Clean all tools

& return to Toolroom.

Turn off the power of the welding machine. Safekeep the ground cable as well as the welding

machine cables.


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To be under the roller

Put on lift & swing


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9. Problems and Abnormal Conditions

a. Shortage of full material for dismantling

As it can be seen above, for loosening of the pressure yoke cup screw the loosening torque is so

high that they have use both chain block and heating up of the cup body. The heating result may

affect the thermal property of the structure.

Heat effected


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b. Lack of experience for dismantling

The best practice for dismantling of the roller bush and bearing is to remove roller bushing first

and then the bearing and the shaft. But as a result of experience they have used different capacity

hydraulic jack to remove the shaft bearing assembly against the gravity using 50mm extraction

plate which may the cause for the damage of self-aligned roller bearing.


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Date post:	06-May-2023
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VRM Roller Bearing (R3) Maintenance Report

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