1330-Z4 bottom bearing damage due to lubrication clogging

1330-Z4 bottom bearing damage

• Before 1330 section starting up at 7:00 of 20 Oct’12, found loud noise at 1330-Z4 after start LC feeding.

• After inspection, it was caused by bottom bearing damage due to lactam lubrication system shortage from line clogging which cause 394 tons of LC lubrication shortage + 1 MB of repairing cost

Shut down 1330-Z4 due to bottom

bearing damage

1330-Z4, Foot Support Damaged [ New TFE]

Lubrication in from 1330-V15

Lubrication out

Found lubrication (LC) clogged

Found bottom bearing totally damaged by non-lubrication due to clogging at inlet line and clogged at 1330-V15 , Support pin was surface scratched We corrected it by replace new bottom bearing and polishing surface of support pin due to no have spare

Clogging at lubrication system

• Found clogging of lactam lubricant system during shut down period. The suspected cause is shut down of hot water pump for 30 minutes for transformer replacement work on 18 Oct’12.

• Need about 1 day for unclogging line and vessel which cause 360 tons of LC production shortage.

Vacuum unit

1330-E9

LHW

to 1330-V3 or 1320-V7

1330-V15

1330-V13

Residue

Bottom of Product column

Pure LC

SG SG

1330-Z4

Other TFEsSG

Other TFEs

Found inlet line and lubricant vessel

clogging after HW system stopped on

18 Oct’12

1330-Z7

Found inlet lubricant nozzle clogging and loud noise during starting up

Chronicle of Incident18 Oct’12 0:00 – Shut down 1330-Z4 for Melapack replacement at 1330-C1 in Oct’128:00, 23:00 – Stop hot water pump for transformer replacement work by 30 minutes. (Wiring temporary cable)20 Oct’122:00 – Start up 1330-Z4 for washing (Using water as process and lubrication).5:00 – Start total reflux and switch process to LC and actual lubricant after confirmation.7:30 – Shut down this unit after found very loud noise at bottom bearing.8:00 – Found lubricant at the head tank (1330-V13) and total system was freezed to solid.15:00 – Found severe damage at bottom bearing and its accessories after inspection and almost full clogging at 1330-Z4 inlet lubricant nozzle.24:00 – MTN finish bottom bearing replacement and repairing

Chronicle of Incident21 Oct’12 2:00 – Re-start up 1330-Z4 and test run with water.17:00 – Re-start up 1330 section after unclogging and leakage repairing at some points of TFE unit.22 Oct’125:00 – Re-start up 1300 unit after product on-specification.

Consequence of this problem

• 1330-Z4 Bottom bearing Damage - Maintenance cost for repairing – 1 MB - 394 tons LC production shortage from delayed starting up of LC plant – 3.78 MB• Lactam Lubricant line system clogging - 362 tons of LC Production shortage from delayed starting up of LC plant during line unclogging – 3.46 MB

Failure and Possible cause

1330-Z4 Bottom bearing damageRoot Cause• Lack of bottom lubrication due to clogging after re-starting up

Lactam Lubrication line cloggingPossible causes- Clogging of lubricant line of all system- Clogging of lubricant at inlet nozzle to 1330-Z4- Suspected that clogging was come from after hot water pump

shut down on 18 Oct’12 for transformer replacement.

Normal Starting up of lubricant system

• Firstly, all TFE unit have to be washed by water to prevent rotor unbalance due to LC solid accumulation during plant shut down.

• DW will be fed instead of lactam in both main feed line and bottom lubricant.

DW

SC

S11

TFE unit

3. Start rotor for 1 hr.

To ejector

DW to mechanical seal

1. Start DW to mechanical seal

2. Feed DW as lubricant

DW

2. Feed DW for washing

Normal Starting up of lubricant system

• After washing, ejector will be started to produce vacuum condition in TFE unit for readiness in actual operation and elimination of water.

• Before starting up, operator always have to confirm auxillary systems; DW to Mechanical seal and Lactam lubricant to bottom bearing.

• The step of main feed and bottom lubrication will be done before rotor starting up to prevent damage to mechanical part.

Lactam feed

SC

S11

1330-V15

SG SG

TFE unit

Other TFEs

4. Start ejector to produce vacuum

Ejector2-20 torr

DW to mechanical seal

LC lubricant system

5. Start lubricant to bottom

(Observe SG)

6. Start feed and rotor

Use hot water jacket to

maintain liquid

Condition of 1330-Z4 start up on 20 Oct’12

• Normally, the bottom lubrication of TFE unit was come from lactam condensate from 1330-Z7 and pure LC in case of 1330-Z7 shut down

• All sections of lubrication piping have HW jacket for freezing prevention.• However, the lubricant flow rate is quite lower than others which is hard to notice

the flow rate.

Lactam feed

SC

S11

1330-V15

SG SG

1330-Z4

Other TFEs

Found very loud noise after 30

minutes operation

Ejector2-20 torr

DW to mechanical seal

LC lubricant system

Found no lubricant flow after 30

minutes operation

Found clogging of lubricant

inside vessel and make up line

TFE lubricant system

• Normally, the bottom lubrication of TFE unit was come from lactam condensate from 1330-Z7 and pure LC in case of 1330-Z7 shut down

• All sections of lubrication piping have HW jacket for freezing prevention.• However, the lubricant flow rate is quite lower than others which is hard to notice

the flow rate.

Vacuum unit

1330-E9

LHW

to 1330-V3 or 1320-V7

1330-V15

1330-V13

Residue

Bottom of Product column

Pure LC

SG SG

1330-Z4

Other TFEsSG

Other TFEs

Sight glass for gravity flow monitoring

1330-Z7

Use pure LC during start up or lubrication

shortage

Hard to verify the flow rate due to lower flow

rate than others

Hot water system shut down on 18 Oct’12

• Have to shut down hot water pumps which service for hot water jacket of 1330 section for transformer replacement work for 30 minutes

Jacket at 1330 section Jacket at 1330 section

Shut down these pumps for 30 min

for transformer replacement

Hot water system shut down on 18 Oct’12

• Have to shut down hot water pumps which service for hot water jacket of 1330 section for transformer replacement work for 30 minutes

Jacket at 1330 section Jacket at 1330 section

Operate 2 pumps during 1st operation day after HW pump re-starting up to support more heat load

and flow verification.

Boost up flow rate and pressure of hot water to HW jacket users (Oxime

and Lactam) during 1st day of HW pump re-starting up

LC lubrication system clogging on 21 Oct’12

• Found HW didn’t reach to LC lubricant jacket system, due to air blockage inside the line after HW pump shut down on 18 Oct’12 by 30 minutes for electrical transformer replacement.

Lubricant feed vessel

Lubricant to TFE unit

Found lactam clogging in this area

Found no HW come out from vent after opening vent line

due to air blockage

Locate at 4th floor of LC plant (35 m EL)

Clogging at lubrication system

• Found clogging of lactam lubricant system during shut down period. The suspected cause is shut down of hot water pump for 30 minutes for transformer replacement work on 18 Oct’12.

• There is no any confirmation of clogging condition in lubricant feed vessel before re-start up of 1330-Z4.

Vacuum unit

1330-E9

LHW

to 1330-V3 or 1320-V7

1330-V15

1330-V13

Residue

Bottom of Product column

Pure LC

SG SG

1330-Z4

Other TFEsSG

Other TFEs

Found inlet line and lubricant vessel

clogging after HW system stopped on

18 Oct’12

1330-Z7

Found inlet lubricant nozzle clogging and loud noise during starting up

Conclusion of Root cause investigation

Air blockage of hot water jacket at LC lubrication system

after HW Pump shut down

Clogging of lactam lubrication system

1330-Z4 bottom bearing damage due to lubrication shortage

Cause & Effects

360 tons of LC production shortage

(3.5 MB) during unclogging lactam lubricant system

394 tons of LC production Shortage (3.8

MB) & Loss 1 MB of

maintenance cost

Main Root Cause

Loss

Immediate Action

• Replace bottom bearing with new spare part.• Have to repair some parts (Ex. Bottom bearing pin) due to no

spare parts available.• Manually unclog the LC lubricant system by 1-2 days.

Short Term countermeasure

• Reserve all spare parts at the MTN store for emergency case. (Wait 2-4 months for delivery time)

Long Term countermeasure• Try to avoid breakdown of hot water pump in short shut down period.

(Ex. Connect it to generator before electricity shut down.)• Addition of flow verification step of all hot water users by opening vent

line nearby each user after HW pump shut down in any case to prevent air blockage in the line and also operate 2 pumps during 1st operation day of hot water to support more heat load and flow verification step.

• Modify the lubricant inlet nozzle at 1330-Z4 and 1330-Z5-2 from half jacket nozzle to full jacket nozzle or addition of high concentration of steam tracing line in order to avoid clogging at the nozzle throat.

Bottom bearing at

1330-Z4-Z5-2

Lubricant from head

tankHW for Jacket

RHW

Half Jacket Nozzle

Add Steam tracing to prevent lactam clogging in this zone

Hot water flow rate verification step after HW pump re-starting up

• After DBN3 project, the pressure of hot water in some of 4th and 5th floor users is decreased due to more users. Therefore, operator may not notice the flow rate after opening vent line. Therefore, we propose to operate 2 pumps of hot water to boost up flow rate and pressure for easier noticing and also supporting in more heat load (Melting of clogged LC) during plant start up.