PRODUCTS (SE) PIPE LINE CORPORATION

Incident Narrative

ON 3/5/21, AN OPERATOR WENT TO TANK 27 TO INVESTIGATE WHY SCADA WAS INDICATING PRODUCT MOVEMENT FOR A TANK THAT WAS NOT INVOLVED IN A DELIVERY. THE OPERATOR DISCOVERED GASOLINE FLOWING FROM THE ROOF DRAIN SYSTEM. THE ROOF DRAIN SYSTEM WAS CLOSED BY THE OPERATOR ON DUTY AND THE DIKE VALVE WAS VERIFIED CLOSED WITH NO GASOLINE OUTSIDE THE IMMEDIATE TANK DIKE. AFTER INITIAL INVESTIGATION, THE TANK ROOF WAS TILTED APPROX. 30-40 DEGREES WITH AN ESTIMATED 6 OF 8 PONTOONS FILLED WITH GASOLINE. THE ROOF WAS ABLE TO MAKE A LEVEL LANDING CORRECTING THE ORIGINAL 30-40 DEGREE TILT FOUND WHILE FLOATING. UPDATE 11/1/21-AFTER BEING RETURNED-TO-SERVICE IN NOVEMBER 2019, TANK 27 SAW INFREQUENT SERVICE AND SAT EMPTY (RESTING ON ROOF LEGS WITH P/V VENTS OPEN) FOR LONG PERIODS. DURING THESE PERIODS, RAINWATER INFILTRATED AND SETTLED INTO THE SUMP. THE HUMID ENVIRONMENT INSIDE THE TANK (DUE TO WATER IN THE SUMP AND THE OPEN P/V VENTS) WOULD HAVE BEEN CONDUCIVE TO CORROSION. ONE PARTICULAR PLACE THAT EXPERIENCED CORROSION WAS A USED MOUNTING BRACKET ON A PONTOON OPPOSITE THE ROLLING LADDER. THIS BRACKET HAD NOT BEEN IDENTIFIED AS NEEDING A PATCH PLATE DURING THE OUT OF SERVICE INSPECTION IN 2019. THIS CORROSION EVENTUALLY COMPROMISED THE INTEGRITY OF THE PONTOON THE TANK'S EXTERNAL FLOATING ROOF BECAME DESTABILIZED WHEN PRODUCT BEGAN TO FILL THE PONTOON FROM THE CORROSION PATHWAY. WITH THE TILTING AND SUBSEQUENT SUBMERGENCE OF THE ROOF, PRODUCT ENTERED THE ROOF DRAIN PIPING AND WAS RELEASED OUTSIDE THE TANK. THE ENTIRE OUTER RIM OF TANK 27'S EXTERNAL FLOATING ROOF HAS BEEN REPLACED.