SHELL PIPELINE CO., L.P.

Incident Narrative

LEAKS WERE EXPERIENCED FROM THE FLANGES OF TWO 12INCH 150# VALVES THAT ARE LOCATED BETWEEN ATMOSPHERIC TANKAGE AND PUMP SUCTION. PRODUCT WAS LEAKING FROM THE DOWNSTREAM (PUMP SUCTION) SIDE OF THE VALVES. BOTH VALVES WERE IN THE CLOSED POSITION AT THE TIME THE LEAK WAS DISCOVERED. BECAUSE THESE VALVES ARE ON THE SUCTION SIDE OF THE PUMPS, THE MAXIMUM PRESSURE THEY MAY EVER EXPERIENCE IS HYDROSTATIC HEAD PRESSURE OF AN ATMOSPHERIC TANK AT ITS HIGH LEVEL (<30 PSIG). THE FLANGE LEAKS ARE NOT BELIEVED TO BE PRESSURE-RELATED BECAUSE THE PRESSURES BEFORE AND AT THE TIME OF THE INCIDENT WERE NOT HIGHER THAN NORMAL OPERATIONAL PRESSURES, WHICH ARE WELL BELOW THE PRESSURE RATING OF THE FLANGES AND PIPING SYSTEM. THESE LEAKS OCCURRED DURING THE SUB-FREEZING WINTER TEMPERATURES EXPERIENCED IN FEBRUARY 18, 2021, AND THE SUSPECTED CAUSE IS THAT WATER BETWEEN THE FLANGES FROZE, EXPANDING AND CAUSING THE FLANGES TO BE SEPARATED (VALVES ARE IN THE VERTICAL ORIENTATION, MAKING IT MORE LIKELY FOR WATER TO BE ABLE TO POOL ON THE FLANGE FACE). UPON MAKING REPAIRS, PAPER GARLOCK GASKETS WERE REMOVED (LIKELY FROM ORIGINAL FACILITY CONSTRUCTION) AND REPLACED WITH FLEXITALLIC SPIRAL WOUND GASKETS, WHICH ARE KNOWN TO BE MORE EFFECTIVE.