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Louisiana Refinery Accident Database

Valero (1238), Meraux

LDEQ Accident Report

Pollutants Released

Accident Classified As: Reportable Quantity

Cause of Problem: Maintenance/Procedures

On May 3rd 2013, starting at approximately 2:00, Valero experienced excess emissions of sulfur dioxide and Hydrogen Sulfide at the north flare during startup of the gas oil Hyrdocracker/ Hrydrotreater Unit (HCU) following a planned maintenance outage and catalyst replacement. Excess emissions during the HCU startup were associated with the following events: 1. The Pressure Safety Valve (PSV) on the Fractionator Tower opened to the flare 2. The PSV on the cold seperator was found to be opened to the flare 3. The Recycle Gas Compressor (RGC) tripped and activated an automatic unit depressurization to the flare. 4. The PSV on the Cold Seperator Opened to the Flare 5. The PSV on the Fractionator Tower opened to the flare a second time Valero determined the root cause of the PSV actuations to be inadequate startup procedure. Valero determined the root cause of the RGC trip to be an instrument technician lifting the instrument wires for a thermocouple that provided a shutdown interlock. Contributing factors to this root cause were: 1. Neither the operator nor the instrument technician was aware that this thermocouple provided a shutdown interlock 2. The instrument technician did not reference any documentation to verify that this transmitter was a possible Safety Critical Instrument 3. The reference documentation was inadequate 4. The instrument was not labeled in the field as a Safety Critical Instrument contrary to Valero standard procedure 7/2/2013 report states that written notification was submitted on 5/10/2013. This documentation is not available on the LDEQ document database.

Discharge Preventable - Yes

Notes/Remedial Actions

Valero reduced pressure to reseat PSVs that had lifted and attempted to stop the leakage on the Cold Separator PSV. Valero shut down the HCU on 5/13/13 and replaced the Cold Separator PSV. Valero will revise HCU startup procedure to include a maximum charge rate limit and maximum Cold Separator pressure limit during sulfiding and also to ensure that the Cold Separator pressure control valve is initially lined up for feed introduction into the unit. Valero repaired the thermocouple and corrected the documentation to reflect that it is a Safety Critical Instrument. Valero has also labeled this instrument in the field. Valero will also finalize a Safety Critical Instrument List in the HCU to provide a reference document for all critical instruments and to label these instruments in the field.