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|State Police #||11-05461|
|Pollutant||Duration||Point Source||Greenhouse Gas||Criteria Pollutant||Ozone forming chemical||Amount of Release|
|Sulfur Dioxide||2 h||3700 and 30 SRU||NO||YES||NO||1,333.5 pounds|
|Hydrogen Sulfide||2 h||3700 and 30 SRU||NO||NO||NO||BRQ|
Accident Classified As: Reportable Quantity
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.
This incident was reasonably preventable.
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.