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|State Police #||11-05439|
|Pollutant||Duration||Point Source||Greenhouse Gas||Criteria Pollutant||Ozone forming chemical||Amount of Release|
|Sulfur Dioxide||3 h 17 m||(308F-D-1) Low Pressure Flare||NO||YES||NO||1,176.0 pounds|
Accident Classified As: Reportable Quantity
On the morning of 9/3/11 around 4:45 am the 191 Crude Unit Fractionator Overhead Accumulator pump was on-line and tripped off-line unexpectedly. Its back up pump was started and put on-line but after only a few seconds it also tripped off-line. Electricians responded and found blown line fuses for both pump's starters. Further electrical meg testing indicated that the 191-L-10A pump was shorted internally but the 191-L-10B pump did not have any phase-to-ground failure. The blown line fuses were replaced and the 191-L-10A pump was restarted but tripped off-libe after running for only a few minutes. The 191-L-10A pump motor was troubleshooted and meg tested by the electricians at the starter, power cabling, and motor field boxes. All test results found no obvious phase-to-phase fault or issues for tripping. The 191-L010A motor starter was ever replaced and still the motor failed and tripped off line within a few minutes. With both critical (191-L-10) Fractionator Overhead Accumulator pumps off-line and unable to start, it was determined that the Crude Unit was to be shutdown. When the Crude Unit shuts down, the Saturated Gas Unit also must shutdown because of loss of its feed from the Crude Unit. Subsequently, various overhead gases from both the Crude Unit and the Diesel Hydrotreater Unit are routed to the Low Pressure Flare (308-D-1) when the Crude Unit must be shutdown quickly. The root cause investigation determined that an oil mist application called the "Lubrimist System" that had been installed on both of the 191-L-10 motors had a design flaw that allowed a fine oil mist to eventually migrate and run into the interior of the motor housing causing a significant buildup of oil and dirt on the motor's stator, windings, and housing area. The 191-L-10 motors are sleeve bearing motors that use internal fans to force air across their windings for cooling. These windings eventually became oil soaked and attract contaminants and moisture from this air flow which are conductive and degrading to the motor's performance. Contamination within the motor windings caused thermal degradation (due to blocked ventilation) and electrical tracking. Electrical tracking enables currents to flow over the surfaces of the windings insulation. These currents degrade and eventually cause the insulation to fail exposing motor wiring that should be insulated, resulting in the motor having a low resistance to ground and ultimate failing. The investigation also determined that the 191-L-10 pumps had been serviced on a frequent basis in the past but their written repair history was not detailed enough that would have enabled maintenance to anticipate and possibly prevent a motor failure.
Unexpected electrical failure of both Crude Fractionator Overhead Accumulator pumps. Electrical parts to the pumps were tested and replaced with no success in restarting the pumps.
Several attempts were made to get the alternate Crude Fractionator Overhead Accumulator pump on-line, but it continued to trip electrically off-line. Several electrical parts of the pump were replaced but the pump continued to trip electrically off-line. It was determined that the Crude Unit and its affected downstream units were to be shutdown until the pumps could be brought back on-line without tripping off-line electrically. The Crude Unit and its affected downstream units were shutdown safely. Fence line monitoring was performed with no offsite impacts noted throughout the entire shutdown event. The investigation also determined that the "Lubrimist system" had been installed on other motors within the refinery and their installation designs shall be reviewed and improved in order to minimize the chances of oil and dirt buildup on the motor's stator, windings, and housing area. Another corrective action will be to evaluate and determine the adequacy of installing air filters to minimize containment carry through into the motor housing. Weather conditions at the time of the incident: Rainy and Cloudy Wind Direction: 117 degrees ESE Wind speed: 30 mph