SUNOCO PIPELINE L.P.

Incident Narrative

CONSTRUCTION CREW WAS WORKING TO INSTALL NEW PIPING AND RECONFIGURE EXISTING STATION PIPING ASSOCIATED WITH TANK 2660. MUD PLUGS WERE INSTALLED TO ISOLATE THE WORK AREA FROM ANY POTENTIAL VAPORS. A PART OF THE MUD PLUG PROCEDURE REQUIRES AN OPEN VENT TO ENSURE NO PRESSURE BUILDS ON PIPING WHILE THE MUD PLUGS ARE IN PLACE. A 4"" VALVE NEAR TANK 2660 WAS SELECTED TO PROVIDE THE VENTING. OIL WAS RELEASED FROM THIS VALVE WHEN PRESSURE BUILT ON THE ASSOCIATED PIPING. THE ROOT CAUSE ANALYSIS DETERMINED THIS SELECTED VENT LOCATION WAS NOT APPROPRIATE DUE TO A LOW PORTION OF THE PIPING FORMING A LIQUID TRAP BETWEEN THE MUD PLUG AND THE VENT. THIS ALLOWED THERMAL PRESSURE BUILD UP BETWEEN THE VENT AND THE MUD PLUG WHICH CAUSED THE MUD PLUG TO FAIL. AFTER THE MUD PLUG FAILED, WELDING ACTIVITIES CAUSED THE SUSPECTED IGNITION OF CRUDE OIL VAPORS INSIDE THE PIPE. THIS CREATED PRESSURE SUFFICIENT ENOUGH TO FORCE CRUDE OUT OF THE 4"" VENT VALVE AT TANK 2660. AT THE TIME OF THE RELEASE COMBUSTION OF THE VAPORS INSIDE THE PIPE WAS NOT SUSPECTED, HENCE NRC NOTIFICATION WAS NOT MADE. VIA THE ROOT CAUSE ANALYSIS PROCESS IT WAS DETERMINED THAT COMBUSTION OF VAPORS BEHIND THE MUD PLUG HAD LIKELY OCCURRED AND CAUSED THE RELEASE HOWEVER THE NRC REPORTING TIMELINE HAD ALREADY BEEN EXCEEDED.