PHILLIPS 66 PIPELINE LLC

Incident Narrative

ON OCTOBER 11, 2018, AN ANOMALY REPAIR CREW WAS IN THE PROCESS OF INSTALLING A FULL WRAP SLEEVE ON MX-20 (AT ENG STATION 476+77) AS A REPAIR FOR AN INTERNAL METAL LOSS ILI TOOL RUN FEATURE. AT APPROXIMATELY 11:10 AM, A WELD BURN THROUGH OCCURRED DURING IN-SERVICE WELDING (AT ~6 OCLOCK POSITION) WHILE IN THE PROCESS OF INSTALLING THE FIRST BUTTER PASS/TEMPER BEAD ON A CIRCUMFERENTIAL WELD FOR THE SLEEVE. A SMALL FIRE ENSUED THAT WAS IMMEDIATELY EXTINGUISHED BY THE TWO FIRE-WATCHES ON SITE. NO INJURIES OCCURRED AND THE LINE WAS IMMEDIATELY SHUT DOWN, ISOLATED AND EFFORTS INITIATED TO REDUCE PRESSURE ON THE PIPELINE SEGMENT. THE PIPELINE SEGMENT WAS ISOLATED AND PURGED AND THE AFFECTED AREA OF PIPE WAS REMOVED AND REPLACED WITH NEW PIPE. THE PIPELINE WAS THEN RETURNED TO SERVICE AT 8:00 AM ON MONDAY, OCTOBER 15, 2018. THE PRIMARY CAUSE OF THIS INCIDENT IS RELATED TO A THIN WALL INTERNAL CORROSION AREA ON THE BOTTOM OF THE PIPE AT THE LOCATION OF THE SLEEVE CIRCUMFERENTIAL WELD THAT WAS NOT IDENTIFIED DURING THE UT TESTING OF THE AREA PRIOR TO WELDING. THE PIPE WALL THICKNESS IN THIS AREA WAS TOO THIN TO SUPPORT IN-SERVICE WELDING AND SO THE WELD PENETRATED THE PIPE WALL. AN EPOCH 650 DUAL ELEMENT PROBE WAS USED TO PERFORM THE PIPE WALL THICKNESS TESTING PRIOR TO WELDING OF THE CIRCUMFERENTIAL WELDS FOR THE SLEEVE. WITH THIS TYPE OF UT INSTRUMENT, AND UNDER CERTAIN CIRCUMSTANCES OF PIPE WALL THICKNESS AND CORROSION GEOMETRY, IT IS POSSIBLE TO GET A FALSE INDICATION OF PIPE WALL THICKNESS THAT IS A MULTIPLE OF THE ACTUAL REMAINING WALL THICKNESS. IN THIS CASE, THE NDT TECHNICIAN RECEIVED A FALSE THICKNESS UT READING WHICH WAS BELIEVED TO BE ADEQUATE FOR IN-SERVICE WELDING. P66 IS CURRENTLY EVALUATING IMPROVEMENTS TO UT PROCEDURES AND PROCESSES TO REDUCE THE LIKELIHOOD OF GETTING FALSE THICKNESS INDICATIONS IN SIMILAR SITUATIONS. BASED ON THESE EVALUATIONS, APPROPRIATE CHANGES TO UT PROCEDURES WILL BE IMPLEMENTED. THIS REPORT WAS UPDATED / MODIFIED PER COMMENTS RECEIVED FROM PHMSA ACCIDENT INVESTIGATION DIVISION AND IS SUBMITTED AS A FINAL REPORT.