PLAINS PIPELINE, L.P.

Incident Narrative

AN INITIAL INVESTIGATION OF THIS INCIDENT INDICATES THAT THE RELEASE WAS DUE TO THE ACTIVATION OF A THERMAL RELIEF VALVE WHICH FAILED TO RE-SEAT BECAUSE OF THE FOREIGN DEBRIS ON THE VALVE SEAT. THE FLOW RATE FROM THE THERMAL RELIEF VALVE EXCEEDED THE SUMP CAPACITY CAUSING IT TO OVERFLOW. AN ALARM ASSOCIATED WITH THIS SUMP FAILED TO ACTIVATE. THE THERMAL RELIEF VALVE WAS REPLACED AND RE-PIPED TO RELIEVE INTO A STORAGE TANK RATHER THAN A SUMP. THE FAILURES RELATED TO THIS INCIDENT ARE STILL UNDER INVESTIGATION. SUPPLEMENTAL NARRATIVE: AS DESCRIBED IN THE INITIAL REPORT, THIS INCIDENT WAS CAUSED BY THE FAILURE OF A THERMAL RELIEF VALVE TO RE-SEAT AFTER ACTIVATING. THE THERMAL RELIEF VALVE IS INSTALLED BETWEEN A PUMP DISCHARGE AND BACK PRESSURE CONTROL VALVE. THE CONTROL VALVE WAS ORIGINALLY AIR OPERATED. DUE TO EXCESSIVE MAINTENANCE REQUIREMENTS, THE OLD CONTROL VALVE WAS REPLACED BY A NEW, ELECTRIC MOTOR OPERATED VALVE. WHEN THE ELECTRIC OPERATED VALVE WAS INSTALLED, THE ELECTRONIC TECHNICIAN SET THE VALVE TO CLOSE COMPLETELY WHEN THE PIPELINE PUMP WAS STOPPED. THE AIR OPERATED CONTROL VALVE DID NOT CLOSE COMPLETELY WHEN THE PIPELINE PUMP WAS STOPPED. THUS, AFTER THE ELECTRIC OPERATED CONTROL VALVE WAS INSTALLED, THE PUMP WAS STARTING AGAINST A SHUT VALVE. THIS REDUCED THE STARTING CURRENT IN THE PUMP MOTOR BUT ALSO CAUSED THE PRESSURE IN THE LINE BETWEEN THE PUMP AND VALVE TO RISE TO A LEVEL THAT CAUSED THE THERMAL RELIEF VALVE TO ACTIVATE UNTIL THE CONTROL VALVE OPENED ENOUGH TO REDUCE THE PRESSURE TO ALLOW THE THERMAL RELIEF TO RE-SEAT. THE RELIEF VALVE SETTING IS 550 PSIG, THE MOP OF THE LINE IS 800 PSIG AND THE PUMP SHUTOFF HEAD IS 620 PSIG. THIS STARTUP PROCEDURE WAS OCCURRING FOR SOME TIME PRIOR TO THE INCIDENT. THE REPEATED ACTIVATION OF THE RELIEF VALVE DURING SYSTEM STARTUP COULD HAVE CONTRIBUTED TO IT NOT RE-SEATING. THE FLOW RATE FROM THE THERMAL RELIEF NOT RE-SEATING EXCEEDED THE CAPACITY OF THE SMALL SUMP PUMP. THIS RESULTED IN A CONTINUALLY RISING LEVEL IN THE SUMP WHICH ULTIMATELY OVERFLOWED, CAUSING THE RELEASE. ALTHOUGH EQUIPPED WITH A HIGH SUMP LEVEL ALARM, THE ALARM FAILED TO ALERT THE CONTROL ROOM OPERATOR BECAUSE THE ALARM FLOAT BECAME STUCK CAUSING THE ALARM SWITCH NOT TO ACTIVATE. AFTER A THOROUGH INVESTIGATION OF THIS INCIDENT, SEVERAL ACTIONS WERE TAKEN TO PREVENT THE RECURRENCE OF THIS TYPE OF INCIDENT: -A REVIEW OF THE STARTUP PROTOCOL FOR THIS SYSTEM WAS CONDUCTED. AS A RESULT THE CONTROL VALVE SETTING WAS CHANGED SO THAT THE VALVE DID NOT SHUT COMPLETELY WHEN THE PUMP IS SHUTDOWN. THIS IS ALLOWING FLOW THROUGH THE VALVE UPON STARTUP AND MAINTAINING THE PRESSURE UPSTREAM OF THE VALVE BELOW THE SETTING OF THE THERMAL RELIEF VALVE; -A ""EXCESSIVE RUN TIME"" ALARM FEATURE WAS INSTALLED ON THE SUMP PUMP TO ALERT THE CONTROL ROOM OPERATOR WHEN THE SUMP PUMP IS RUNNING LONGER THAN - NORMAL; AND -A NEW THERMAL RELIEF VALVE WAS INSTALLED AND ITS DISCHARGE RE-PIPED TO RELIEF INTO A STORAGE TANK RATHER THAN THE SMALL SUMP.