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Valero (26003), Norco

LDEQ Accident Report

Accident #133803
PDF AvailablePDF
State Police #11-05461
Accident Date2011-09-04
Report Date 2011-09-09
Follow-up Date 2011-10-28
Follow-up: Yes

Pollutants Released

Pollutant Duration Point Source Greenhouse Gas Criteria Pollutant Ozone forming chemical Amount of Release
Sulfur Dioxide2 h3700 and 30 SRUNOYESNO1,333.5 pounds
Hydrogen Sulfide2 h3700 and 30 SRUNONONOBRQ

Accident Classified As: Reportable Quantity

Cause of Problem: Instrument Failure

The sulfur dioxide levels at 3700 and 30 unit thermal oxidizers were elevated due to failure of a pressure transmitter on the 3700 unit overhead accumulator. Valero estimated that the RQ for sulfur dioxide was exceeded at approximately 1:10 am and the RQ for hydrogen sulfide was not exceeded. The failing transmitter gave false indications in both the overhead accumulator pressure and the stripper overhead pressure. This prompted operational moves in the unit to shift loads in an effort to return the SRUs to stead operation.

Discharge Preventable - Yes

This incident was reasonably preventable.

Notes/Remedial Actions

After the local pressure gauges in the field were verified, it was determined that a single pressure indication was malfunctioning and operational moves were made to restore normal operating conditions. The following corrective actions were identified to prevent recurrence of this incident: (1)Repair both the overhead accumulator and the stripper overhead pressure transmitters and have separate pressure readings on the DCS. (2)Revise the DCS page to reflect both pressure indications. (3) Ensure the DCS and logic changes are covered by the management of change (MOC) process. (4) Conduct training with Operators on this incident. (5)Have the pressure control valve 37-4182-A inspected during the 2014 turnaround.