ANR PIPELINE CO

Incident Narrative

ON JUNE 20, 2014, PRODUCER PERSONNEL NOT UNDER THE DIRECT SUPERVISION OF ANR PERSONNEL WERE IN THE PROCESS OF REMOVING A PORTION OF THE MEASUREMENT PIPING FACILITIES ON THE OFFSHORE SHIP SHOAL 207 PLATFORM TO COMPLY WITH CERTAIN REQUIREMENTS STIPULATED BY THE DOI/BSEE. THE PRODUCER WAS TO REMOVE TWO METER RUNS. THE VALVES AT THE ENDS OF EACH METER RUN HAD BEEN CLOSED AND LOCKED AT SOME EARLIER DATE BY ANR PERSONNEL. AT THE TIME OF PLANNED FACILITY DISCONNECTION AND REMOVAL, THE PRODUCER PERSONNEL DETERMINED THAT THE METER RUN ISOLATION VALVES WERE LEAKING AND DECIDED TO ISOLATE ADDITIONAL PIPING ON THE PLATFORM IN ORDER TO ASSURE THAT NO GAS COULD MIGRATE TO THE MEASUREMENT PIPING. TO FACILITATE THIS ADDITIONAL ISOLATION ACTIVITY, WHICH WAS NOT PART OF THE PROJECT SCOPE AND HAD NOT BEEN AUTHORIZED BY ANR MANAGEMENT, PRODUCER PERSONNEL CLOSED VALVES TO GAS SOURCES, OPENED THE PIG TRAP KICKER LINE VALVE, AND THEN OPENED THE 4' PIG TRAP VENT VALVE THROUGH WHICH THIS ISOLATED PIPING WAS EVACUATED. AS THE PIPING AND PIG TRAP WERE BLOWING DOWN, IT WAS DETERMINED THAT THE PRESSURE IN THE PIG TRAP AND ASSOCIATED PIPING WOULD NOT DROP TO ATMOSPHERIC. PRODUCER PERSONNEL PRESUMED THAT ONE OF THE VALVES THEY HAD CLOSED TO ISOLATED THE PIPING FROM A GAS SOURCE MUST NOT HAVE COMPLETELY CLOSED. IT WAS DECIDED TO ATTEMPT TO FURTHER CLOSE THE VALVE. HOWEVER, RATHER THAN USING THE HAND PUMP TO OPERATE THE VALVE, PRODUCER PERSONNEL USED THE POWER GAS OPERATOR AND MISTAKENLY PARTLY OPENED THE VALVE. THIS ALLOWED HIGH PRESSURE GAS (APPROXIMATELY 860 PSIG) TO ENTER THE PARTIALLY BLOWN DOWN PIPING WITH A HIGH DIFFERENTIAL PRESSURE ACROSS THE OPENED VENT VALVE. IT SHOULD BE NOTED THAT THE PIG TRAP VENT ASSEMBLY, WHICH WAS MOUNTED AT THE 12 O'CLOCK POSITION ON THE TRAP BOTTLE, INCLUDED A VENT STACK THAT WAS CONFIGURED WITH A 90 DEGREE BEND INTENDED TO VENT GAS AWAY FROM THE PLATFORM. DUE TO THE SUDDEN INCREASE IN GAS PRESSURE AND FLOW THROUGH THE VENT VALVE ASSEMBLY AND THE RESULTANT HIGH VELOCITY GAS EXITING THE 90 DEGREE VENT STACK, ENOUGH FORCE WAS PRODUCED TO CAUSE THE ENTIRE VENT ASSEMBLY TO FAIL AND DISCONNECT NEAR THE PIG TRAP BOTTLE. FOLLOWING THE FAILURE, THE VENT VALVE ASSEMBLY HAS BEEN REBUILT AND REINSTALLED ON THE PIG TRAP. THE SYSTEM WAS THEN PLACED BACK INTO SERVICE ON JUNE 28, 2014.