Refinery - II M&I SD Oct-Nov 2018

Chennai Petroleum Corporation Limited (A group company of Indian Oil)
Technical - Inspection
Chennai Petroleum Corporation Limited (A group company of Indian Oil)
Technical - Inspection
metal surface to make it water wet & gets flushed by freeing the coke & releasing the volatile materials.
Subsequently, steam rinsing is carried out & once the rinsing is completed, system will be cooled down keeping
drain closed & vent to atmosphere. Final sampling will be done after ventilation of the equipment in order to
conclude effectiveness of decontamination.
Liquid phase decontamination:
The system is filled up to pre-determined level & circulation is set up. Water sample is checked for HC free &
steam is introduced into water to attain 60 Deg C to 70 Deg C. Then calculated quantity of chemical is injected at
the predefined injection points along with steam & again steam is introduced to raise the temp. to 80 Deg C.
Effluent formed is pumped out to predefined effluent tank for disposal (where oil & water phases will be separated
out. Separated oil can be recycled to slop tank).
Accepted limits after decontamination:
Description Limit Description Limit
Benzene level < 1% PPM LEL < 1%
Odor No odor HC NIL
H2S NIL Pyrophoric Iron NIL
FCCU Main Column (16-C-01)– Shell bulge & FCC Debutanizer (16-C-59) CUI issue:
Due to internal fire in FCCU Main Column especially at the structured packing zone (bed-no.2), inspection was
insisting for removal of packing & providing access inside the fire affected zone and removal of external insulation
along with scaffolding externally to assess & recommend repair procedures. However, access for both got delayed
by the contractor, M/s. Shilpi Engg. due to resource constraints and the same was provided only on 22 nd day of
shutdown (15 days after the fire incident). Multiple bulges were observed at the fire affected zone along with
carburization of external layer of shell internal surface. It was recommended to replace the bulged section of shell
for 6.25 m 2 area with insert plates, but externally patched up (for about 9.0 m 2 ) due to paucity of time.
Event Chronology is as below:
11.10.2018 Internal pyropheric Fire incident reported
16.10.2018 All manways were opened & permit obtained
17.10.2018
Inspection recommended for providing external scaffolding & insulation removal for
detailed inspection at fire affected zone
18.10.2018 Bed packing removal started
21.10.2018 Bed packing removal completed & scaffolding started
INSPECTION EXECUTIVE SUMMARY
Decontamination Process in CDU-2 & FCCU:
Vapor phase decontamination was adopted in majority of the loops (except the pre-heat trains) in CDU-II & FCCU.
Decontamination of 6 loops [(1) pre-heat trains, (2) furnaces, (3) Atm. column, (4) Vacuum column, (5) stabilizer
column & (6) product R/D loops)] & 10 loops was planned/commenced in CDU-II & FCCU respectively at 09:30 hrs
09.10.18. Entire process was being planned to be done by chemical circulation & draining method only. However
on 11.10.18, whitish smoke was noticed from FCCU main column (16-C-01) top section during blinding activities
after completion of decontamination & subsequent check in DCS where temperature increase observed at the
structured packing zone @ LCO section, it was suspected to be an internal fire due to the presence of pyrophoric
iron. In view of this, suspecting ineffective decontamination due to vapour phase decontamination (only
circulation method), it was decided immediately to fill up with liquid in FCCU Main column (oxidizer along with
water & draining) and the liquid phase decontamination method was extended to CDU-2 Atmospheric / vacuum
column also in order to ensure effectiveness of whole process. Due to this exercise of filling, soaking & draining in
CDU columns, decontamination process time got extended by around 24 hours in Atmospheric Column & 57.5
hours in Vacuum column. Further delays were noted for loop separation, decontamination equipment installation
and water filling and the entire decontamination process was completed in 6 days. After opening of equipment,
decontamination process was found ineffective in some of the circuits unlike the previous experience in Ref-3 M &
I S/D in 2015 wherein most of the circuits including vacuum section were found almost clean and ready for box up
stage.
24.10.2018 Bed 1/2/3/4 cleaning completed
26.10.2018 Bed-2 (fire zone) Scaffolding provided for inspection
26.10.2018 Shell bulging/distortion was noticed, Inspection activities done. IWL issued for insert plate
01.11.2018 Bed-2 external patch plating was decided & buffing started
02.11.2018 Extent of external patching was marked by inspection
04.11.2018 External patch plate Fit-up was cleared
06.11.2018 External patch plate welding completed & DPT cleared
08.11.2018 Bed-2 packing job done
10.11.2018 Manway boxed up
Insulation removal job for the debutaniser was taken up in the fag end of the shutdown. Upon removal of
insulation, severe scale was noticed at the insulation support ring area. Inspection was insisting for providing
access externally for detailed inspection. However, scaffolding provision got delayed and the same was provided
only on 28 th day of shutdown. Severe external corrosion & thinning out was noticed upon detailed inspection &
recommended for patch plate provision at 4 ring locations. Welding of the external patches took almost for 8 days
& the job was completed/boxup clearance given on 09.11.2018.
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Refinery - II M&I S/D Oct-Nov 2018 - Inspection Report
Refinery - II M&I S/D Oct-Nov 2018 - Inspection Report
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