MARATHON PIPE LINE LLC

Incident Narrative

INCIDENT OCCURRED AS PART OF A PROCEDURE TO RE-FILL A SEGMENT OF THE SYSTEM THAT WAS PURGED AND REPAIRED DUE TO A FIRE (INCIDENT ID# 20230179-38361). FIELD PERSONNEL BEGAN LOOSENING A FLANGE ON A 2"" BLOW DOWN VALVE PER PROCEDURE AND THE VALVE WAS NOT HOLDING. THIS ALLOWED PROPANE TO BE INTRODUCED TO THE ATMOSPHERE IN THE FORM OF VAPOR. THE PROCEDURE DID NOT SPECIFY TO CLOSE/VERIFY CLOSED THE 2"" BLOWN DOWN, BUT IT WAS CLOSED BECAUSE OF AN OBVIOUS NEED TO DO SO FOR ISOLATION, AND IT WAS DETERMINED THAT THE VALVE WAS NOT FULLY CLOSED/SEATED AND REMAINED 1/16 OF AN INCH OPEN. THE PROCEDURE WAS HALTED AND THE VALVE WAS FULLY CLOSED AND RE-PACKED BEFORE PROCEEDING. SUPPLEMENTAL UPDATE. CAUSE HAS BEEN ADJUSTED TO REFLECT NEW INFORMATION THAT THE PROCEDURE FOR THIS OPERATION DID NOT SPECIFY TO CLOSE/VERIFY CLOSED THE VALVE PRIOR TO REMOVAL OF THE BLIND. SUPPLEMENTAL UPDATE #2, THE SOUTH HALLS BAYOU (MP16) BLOCK VALVE IS LOCATED LESS THAN A FOOT DOWNSTREAM FROM THE BLOW-DOWN VALVE THAT IN WHICH THE FAILURE OCCURRED. THE MP16 VALVE WAS OPENED AFTER ISOLATING THE SEGMENT IN WHICH THE RELEASE WAS OCCURRING FROM THE UPSTREAM PORTION OF THE PIPE. ISOLATION FROM THE UPSTREAM SEGMENT WAS ACHIEVED BY CLOSURE OF THE MP 15 NORTH HALLS BLOCK VALVE. OPENING THE MP 16 BLOCK VALVE DOWNSTREAM ALLOWED THE PRODUCT TO FLOW INTO AN EMPTY SECTION OF PIPE AND REDUCED THE PRESSURE TO A LEVEL THAT ALLOWED FOR THE INJECTION OF GREASE INTO THE BLOWDOWN VALVE TO STOP THE LEAK. THIS METHOD WAS REQUIRED DUE TO THE FORMATION OF ICE IN THE BLOWDOWN VALVE PREVENTING ITS OPERATION.