Presentation on theme: "1330-Z4 bottom bearing damage due to lubrication clogging."— Presentation transcript:
1330-Z4 bottom bearing damage due to lubrication clogging
1330-Z4 bottom bearing damage Before 1330 section starting up at 7:00 of 20 Oct12, 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 Oct12. 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-V V V13 Residue Bottom of Product column Pure LC SG 1330-Z4 Other TFEs SG Other TFEs Found inlet line and lubricant vessel clogging after HW system stopped on 18 Oct Z7 Found inlet lubricant nozzle clogging and loud noise during starting up
Chronicle of Incident 18 Oct12 0:00 – Shut down 1330-Z4 for Melapack replacement at 1330-C1 in Oct12 8:00, 23:00 – Stop hot water pump for transformer replacement work by 30 minutes. (Wiring temporary cable) 20 Oct12 2:00 – 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 Incident 21 Oct12 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 Oct12 5:00 – Re-start up 1300 unit after product on-specification.
Consequence of this problem 1330-Z4 Bottom bearing Damage - Maintenance cost for repairing – 1 MB tons LC production shortage from delayed starting up of LC plant – 3.78 MB Lactam Lubricant line system clogging 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 damage Root Cause Lack of bottom lubrication due to clogging after re-starting up Lactam Lubrication line clogging Possible 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 Oct12 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 S V15 SG TFE unit Other TFEs 4. Start ejector to produce vacuum Ejector 2-20 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 Oct12 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 S V15 SG 1330-Z4 Other TFEs Found very loud noise after 30 minutes operation Ejector 2-20 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-V V V13 Residue Bottom of Product column Pure LC SG 1330-Z4 Other TFEs SG 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 Oct12 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 Shut down these pumps for 30 min for transformer replacement
Hot water system shut down on 18 Oct12 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 Operate 2 pumps during 1 st 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 1 st day of HW pump re-starting up
LC lubrication system clogging on 21 Oct12 Found HW didnt reach to LC lubricant jacket system, due to air blockage inside the line after HW pump shut down on 18 Oct12 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 4 th 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 Oct12. 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-V V V13 Residue Bottom of Product column Pure LC SG 1330-Z4 Other TFEs SG Other TFEs Found inlet line and lubricant vessel clogging after HW system stopped on 18 Oct Z7 Found inlet lubricant nozzle clogging and loud noise during starting up
Lubrication system at TFE unit Process liquid can be fed to bottom bearing as another lubricant by receiver pot at outlet lubricant line from bottom bearing that the lubricant will always be fed to bearing, although the main lubricant line clogging. There is full HW jacket nozzle at inlet lubricant line which has no any weak point of clogging before starting up. Original TFE unit (1330-Z3, Z5-1, Z6-1, Z7 and Z6-2) Bottom Bearing Process Liquid Rotor HW to jacket RHW Lubricant from head tank Lubricant outlet receiver pot that process liquid can flow to bottom bearing Process Liquid Lubricant From-To Bottom Bearing
Lubrication system at TFE unit Lubricant from head tank is only the one way of this TFE. At inlet lubricant nozzle, there is half jacket line which will has weak point of clogging in no jacket zone (Around 1-2 cm length) during no flow. (We found severe clogging at this point) 1330-Z4 (New DBN3) and 1330-Z5-2 (DBN2) Lubricant from head tank HW for Jacket RHW Acc of LC liquid Rotor Process Liquid Lubricant from head tank Half coupling jacket which has weak point for clogging
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
Conclusion The root cause of bearing damage at 1330-Z4 was come from clogging at lubrication system of all TFEs unit at 1330 section and its inlet nozzle. Clogging at lubrication system was come from shut down of hot water pump for transformer replacement and also missing of HW system re-start up procedure on 18 Oct12. Clogging at the inlet lubricant nozzle was come from its half jacket characteristic which cause lacking of melting during hot water system re-start up. At other TFEs (Except 1330-Z4,Z5-2), it can be operated without lubrication due to there is receiver pot for its process liquid to fulfill inside bottom bearing zone.
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 1 st 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 tank HW 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 4 th and 5 th 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.
LC lubrication system clogging on 21 Oct12 Found HW didnt reach to LC lubricant jacket system, because operator didnt vent HW at the 4 th floor jacket of LC lubrication system until 21 Oct12. Lubricant feed vessel Lubricant to TFE unit Have to open flange to verify flow rate, in case of 1 pump operation due to pressure is too low Locate at 4 th floor of LC plant (35 m EL)