Crude Booster Pump Trip

Date: 09-June-2017
Time: 1050 hrs

Sequence of Events:
1. Out of 4 running crude booster Pumps, 3 pumps tripped. Crude flow decreased from 1820 MT/hr to 650 MT/hr.
2. Another crude booster pump was immediately started and crude flow increased from 620 MT/hr to 1200 MT/hr with in 3-4 minutes.
3. Third and fourth crude pump could not be started immediately, hence flow was maintained @ 1200 MT/hr for about one hour.
4. After an hour third crude pump was started and flow was increased upto 1600 MT/hr.
5. Plant was stabilised at 1600 MT/hr by 1400 hrs and the further throughput increased to 1800 MT/hr by 1800 hrs.

Action Taken in Panel:
1. Since flash drum level started to decrease, Pass flow to CDU furnace reduced gradually. Flash crude pump discharge was pinched.
2. This resulted in decreasing level of CDU column, hence pass flow to VDU furnace was also reduced gradually.
3. Reduction in pass flows, resulted in higher coil outlet temperatures of the CDU and VDU furnaces. Hence Fuel Gas firing was reduced in both the furnace from field as well as from panel.
4. HAGO Internal reflux flow was also reduced and stripping steam to CDU column flow was also reduced gradually.
5. Naphtha, Kerosene, Diesel, Vacuum Diesel, VGO, HVGO flow was gradually reduced keeping an eye on strippers / tray level.
6. Pump around flows through exchangers were reduced by closing cold QVs and opening Hot QVs.
6. Since LAGO pump around flow was not decreased through Stabiliser, De-ethaniser and De-propaniser and Naphtha / LPG flow was reduced, all the bottom materials got evaporated and accumulated at the reflux drum.
7. Presence of heavier in the stabiliser reflux drum resulted in reduction in vapour pressure and hence stabiliser top pressure reduced.
8. Due to low stabiliser top pressure, hot naphtha flow to downstream NHDT unit could not be maintained.
9. Reboiling of Naphtha Stabiliser, Deethaniser, Depropaniser was gradually reduced.
10. Since the LPG was suspected to be off spec, LPG was routed to Off spec LPG bullets from Deethaniser outlet to avoid contamination of good quality LPG in SR-LPG treatment unit and depropaniser.
11. Stabiliser was normalised by putting reflux (pressure restored) and deethniser and depropaniser were also normalised after LPG was on spec.
12. Off Gas compressor load was also decreased to maintain Column Top Pressure.
13. Hot QVs were opened to maintain draw temperature.

Action Taken in Field:
1. Flash Crude Pump discharge valves were pinched to avoid high pressure at furnace inlet and third preheat train to avoid exchange leaks.
2. Fuel firing in CDU and VDU furnace was decreased and after normalisation, it was increased.
3. Off spec LPG was routed to Off spec bullet from Deethnisaer outlet with out contaminating SR-LPG and depropaniser. This has resulted in considerable time saving in recovery of LPG circuit.

Lesson Learnt:
1. Heating through LAGO Pump around in Stabiliser, De-ethaniser and De-propaniser should have been reduced to avoid making naphtha and LPG Off spec.
2. Down stream units who are primarily being run on hot feed viz NHDT, DHDT VGO -HDT and DCU should have been informed about the plant upset.

Actions To be Taken on Complete Crude Failure:
1. Gradually reduce temperature in furnaces.
2. Stop rundown flows of products.
3. Route Naphtha, Kerosene, Diesel, Vac Diesel, VGO, HVGO, VR to Flash drum.
4. Stop stripping steam to columns.
5. Circulate the material till the material cools down.
6. After sufficient cooling, and dilution stop the plant.
7. Flush the VGO, HVGO, VR rundown lines with lighter hydrocarbon to avoid chokage.

 

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