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Accident # | 142789 |
State Police # | 12-06034 |
Accident Date | 2012-09-06 |
Report Date | 2012-09-11 |
Follow-up Date | 2013-02-22 |
Follow-up: | Yes |
Pollutant | Duration | Point Source | Greenhouse Gas | Criteria Pollutant | Ozone forming chemical | Amount of Release |
Sulfur Dioxide | 25m | Unit 259 North Ground Flare (EQT #282 EIQ #20A-08) | NO | YES | NO | 896.0 pounds |
Accident Classified As: Reportable Quantity
The U205 coker 1202 drum pressured up causing a corresponding pressure build up in the blow down system. The drum experienced a "refoaming event" where steam is introduced into the drum immediately following a drum swap causing the partial pressure of the unconverted material in the drum to drop. This resulted in over pressuring the fractionator. Pressure relief valves 205-P1511(V1) and 205-P1511(V2) then opened to the North Ground Flare.
The drum inlet temperature was too low for the cycle and after the drum swap, the valve ramp program pinched the combined overhead valve to 40% and the throttling of this valve contributed to over pressuring the drum.
Initial report states that the charge rate to the unit was immediately reduced, but that no specific remedial actions were taken or planned at that time. Follow up report states that a TapRoot Investigation was conducted to determine the cause of the incident. This investigation found that the causal factors were: 1) the drum inlet temperature was too low for the cycle and 2) after the drum swap, the valve ramp program pinched the combined overhead valve to 40% and the throttling of this valve contributed to the overpressure of the drums. The investigation recommended: 1) Implement a low drum inlet temperature alarm on both Coke Drums, 2) Develop a drum inlet temperature controller to allow operations to fire the heater based on drum inlet temperature, and 3) Evaluate removing the combined overhead valve ramp down program after a drum swap. Recommendations 1 and 2 were completed by 11/15/2012. Recommendation 3 was not completed.
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