NUSTAR PERMIAN TRANSPORTATION AND STORAGE, LLC

Incident Narrative

A THIRD-PARTY PRODUCER NOTIFIED NUSTAR OPERATIONS PERSONNEL OF A LEAK AT NUSTAR'S XTO NAIL RANCH SITE. A CRUDE OIL LEAK WAS DISCOVERED ORIGINATING AT AN ABOVE-GRADE HORIZONTAL 8-INCH FLANGE CONNECTING NUSTAR'S SOUTH CURTIS RANCH LATERAL AND THE NAIL RANCH MAINLINE. THE SYSTEM WAS IMMEDIATELY SHUTDOWN, AND THE LEAK WAS ISOLATED USING VALVES BETWEEN THE TRAP FACILITIES AT THE SITE. THE APPARENT CAUSE OF THE LEAK IS INTERNAL CORROSION AT THE 6 O'CLOCK POSITION OF THE FLANGE. THE FAILED FLANGE WAS REMOVED FROM SERVICE AND REPLACED. THE CONTRIBUTING CAUSE(S) OF THE LEAK IS UNDER INVESTIGATION. UPDATE - THE CORROSION WAS CAUSED BY CURRENT LEAVING THE INTERNAL SURFACE OF THE PIPE CLOSE TO THE ISOLATING JOINT ON THE ANODIC SIDE. IT IS LIKELY MULTIPHASE PRODUCTS AND WATER CREATED AN ELECTROLYTIC PATH ACROSS THE ISOLATION FLANGE AND CONTRIBUTED TO THE CORROSION. NUSTAR INVESTIGATED THE RESPONSE TO A LEAK DETECTION ALARM RECEIVED PRIOR TO THE DISCOVERY OF THE RELEASE, AND IT WAS DETERMINED THE ALARM WAS MISTAKEN FOR ONE OF SEVERAL FALSE ALARMS ON ANOTHER SEGMENT EARLIER IN THE SHIFT. THIS DID NOT CAUSE THE ACCIDENT, BUT LIKELY, IN PART, CONTRIBUTED TO THE TOTAL VOLUME OF THE RELEASE.