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 150
0.5. 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.

Company Name
Derba MIDROC Cement
Title
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

Company Name
Derba MIDROC Cement
Title
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

Company Name
Derba MIDROC Cement
Title
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(-32-10500
c), 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

Company Name
Derba MIDROC Cement
Title
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.

Company Name
Derba MIDROC Cement
Title
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.

Company Name
Derba MIDROC Cement
Title
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.

Company Name
Derba MIDROC Cement
Title
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

Company Name
Derba MIDROC Cement
Title
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

Company Name
Derba MIDROC Cement
Title
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
MalfunctionWeight

Company Name
Derba MIDROC Cement
Title
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

Company Name
Derba MIDROC Cement
Title
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)

Company Name
Derba MIDROC Cement
Title
7. Installation of New Bearing on Roller Tire Assembly
7.1Sub 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
1000
c(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

Company Name
Derba MIDROC Cement
Title
7.2Sub-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 0
c 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.
7.3Assemble 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

Company Name
Derba MIDROC Cement
Title
7.4Assembly of pressure yoke
7.5

Company Name
Derba MIDROC Cement
Title
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.

Company Name
Derba MIDROC Cement
Title
To be under the roller
Put on lift & swing

Company Name
Derba MIDROC Cement
Title
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

Company Name
Derba MIDROC Cement
Title
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.

Company Name
Derba MIDROC Cement
Title

Vrm roller bearing_r3_maintenance_report

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