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Louisiana Refinery Accident Database

ExxonMobil Chemical Plant (286), Baton Rouge

LDEQ Accident Report

Pollutants Released

Accident Classified As: Reportable Quantity

Cause of Problem: Equipment Failure

An electrical fault in a transformer caused the Halobutyl unit (RLA-1) C-751 compressor to trip. Subsequently, the unit was shut down. During shutdown processes, safety valve 828-023 (D-751) and 769-021 (D-100) vented methyl chloride the the flare system per design. The combustion of methyl chloride resulted in reportable quantities hydrochloric acid and methyl chloride being released from the flare system. Upon completion of startup, flare gas flow remained slightly elevated from expected baseline. An investigation discovered that safety valve 828-023 did not completely reseat after malfunction, which resulted in low pressure flow in the line causing the trip of the compressor. Material routed to the flare system until the SV was blocked in approximately 20 minutes later. The leaking safety valve resulted in an extended incident duration. According to all refinery letters the quantity of Hydrochloric Acid released was 62,480 pounds and the amount of methyl chloride was 438.0000 pounds. According to the LDEQ report dated March 26, 2013 - the total amount of Hydrochloric Acid released was 24,383 pounds and the amount of methyl chloride was 170 pounds.

Discharge Preventable - No

The prevent-ability of this accident was under investigation during the initial verbal notification and the initial written notification AKA the 7 day letter. According to the 60 day letter dated Feb. 5th 2013: The root cause investigation did not reveal any mechanical failure of the lube oil pump or components. It is believed that either the check valve on the pump discharge or the pressure was obstructed or stuck resulting in the low lube oil pressure. The emergency lube oil pump (P-751C) did start, but was unsuccessful at recovering the system pressure to prevent a trip on low lube oil pressure. This failure mechanism has not presented itself in the past and was unforeseen.

Notes/Remedial Actions

The combustion of methyl chloride resulted in 62,480 pounds of HCl and 434 pounds of methyl chloride being released from the flare system. The RQs for methyl chloride and HCl wer exceeded as a result of this event. The restart of RLA-1 C-751 compressor began on 12/1/12 at 11:50 am and was completed at approximately 3:58 pm. Drier regeneration activities were conducted per normal operating procedures from 12/1/12 at 6:54 pm until 12/2/12 at 6:02 pm. These activities resulted in permitted flows of methyl chloride to flare system. According to the 60 day letter dated Feb. 5th 2013: The unit was shut-down and the leaking valve was blocked to isolate the release. The reliability of the lube oil system has been improved by replacing the low pressure kick-in switches, adjust kick-in pressure set point, and conducting on-line testing of the lube oil system. Also, unit operator training on the lube oil systmem for C-751 will be conducted. This event is under investigation to determine the root cause and path forward to prevent recurrence.