CENTERPOINT ENERGY - MISSISSIPPI RIVER GAS TRANSMISSION CORP

Incident Narrative

ON 01/26/2011 AT 12:30 A THIRD PARTY WORKING NEAR MRT LINE ML-2 CALLED CEGT SYSTEM CONTROL AND REPORTED A LEAK NEAR MILE POST 13. SYSTEM CONTROL NOTIFIED AN AREA PIPELINE TECHNICIAN. AT 12:39 THE TECHNICIAN CONTACTED THE THIRD PARTY THAT REPORTED THE LEAK TO GET FURTHER DETAILS. AT 12:45 HE THEN CONTACTED TWO ADDITIONAL TECHNICIANS TO ASSIST IN INVESTIGATING THE LEAK. THEY ARRIVED AT THE LEAK SITE AT 13:24 AND MADE THE DETERMINATION THAT THERE WAS A LEAK ON ML-2. A TECHNICIAN AT THE SCENE CALLED SYSTEM CONTROL TO CONFIRM THE LEAK AT 13:38. AT 13:40 TECHNICIANS ON LOCATION CONTACTED TECHNICIANS NEAR MILE POST 23 AND HAD THEM GO TO THE VALVE TO AWAIT NOTIFICATION FROM SYSTEM CONTROL TO ISOLATE THE LEAK. TECHNICIANS AT THE SITE OF THE LEAK SECURED THE AREA AND STOOD BY AWAITING INSTRUCTIONS FROM SYSTEM CONTROL. AT 15:45 TECHNICIANS WERE INSTRUCTED TO SETUP VALVES TO CROSS OVER GAS FROM ML-2 TO ML-3 AND THEN CLOSE THE VALVE AT MILE POST 23. AT 15:46 THE TECHNICIANS AT MILE POST 13 WAS INSTRUCTED TO PUT VALVES IN SEQUENCE TO CROSS OVER GAS FROM ML-2 TO ML-3 TO ISOLATE THE LEAK. AT 16:15 THE TECHNICIANS REDUCED THE FLOW ON ML-3 TO PULL DOWN ML-2 PRESSURE AND THEN CLOSED THE VALVE AT MILE POST 13. TECHNICIANS THEN BEGAN BLOWING DOWN ML-2 AT 17:24 PM. AT 17:38 ALL VALVES WERE LOCKED AND TAGGED. AT 18:25 THEY HAD THE PRESSURE DOWN AND REPAIR CONTRACTORS MADE THE CUT AND SPOOLED IN A JOINT OF PIPE. ON JANUARY 27TH AT 2:40 WELD X-RAYS BEGAN. THE X-RAYS RESULTS WERE GOOD AND SYSTEM CONTROL WAS NOTIFIED THAT THE REPAIR CREW WAS READY TO PURGE AND PACK. SYSTEM CONTROL HAD ARRANGED FOR ALTERNATIVE GAS SUPPLIES AND ADVISED THE REPAIR CREW TO HOLD OFF ON THE PURGE UNTIL 6:30. THE CREW RETURNED TO THE REPAIR SITE AT 6:15 AND AT 6:34 BEGAN THE PURGE. THE PURGE WAS COMPLETED AT 7:04 AND THE PACK BEGAN AT 7:05. THE PIPELINE EQUALIZED AT 8:19 AT 600#. ALL VALVES WERE PUT BACK IN THE NORMAL OPERATING POSITIONS AND CONTROL OF THE PIPELINE WAS TURNED OVER TO SYSTEM CONTROL AT 8:40. THE SECTION OF PIPE REMOVED WAS SENT TO KIEFNER & ASSOCIATES FOR METALLURGICAL ANALYSIS. THE CONCLUSION IS AS FOLLOWS: THE LEAK WAS ATTRIBUTABLE TO PREVIOUS MECHANICAL DAMAGE. THE LEAK ORIGINATED AT A CRACK MEASURING APPROXIMATELY 5 1/2 INCHES LONG LOCATED WITHIN A 9-INCH LONG GOUGE. THE GOUGE WAS ORIENTED AT APPROXIMATELY 45 DEGREES TO THE AXIS OF THE PIPE. THE DENT OR DEFORMATION ASSOCIATED WITH THE GOUGE WAS MINOR, MEASURING LESS THAN 1% OF THE PIPE OD. THE CRACK LIKELY GREW THROUGH THE PIPE WALL THICKNESS BY FATIGUE IN RESPONSE TO PRESSURE-CYCLE INDUCED FATIGUE. THE MECHANICAL PROPERTIES AND CHEMICAL COMPOSITION OF THE PIPE SPECIMEN MET THE REQUIREMENTS OF API SPECIFICATION 5LX APPROPRIATE TO THE PIPE VINTAGE AND GRADE.