CENTERPOINT ENERGY GAS TRANSMISSION

Incident Narrative

CEGT LINE BT-1-AS LEAK 02/18/2011 ON 2/18/2011 AT 20:00 THE PUBLIC REPORTED A POSSIBLE LEAK TO SOUTHERN GAS OPERATIONS (SGO). SGO DISPATCHED AN EMPLOYEE TO INVESTIGATE AND AT 20:15 REPORTED THEY HAD FOUND A LEAK ON CEGT'S ROW FOR THE BT-1 SYSTEM. AT 20:17 SGO CONTACTED THE CEGT PIPELINE TEAM TO ADVISE THEM OF THE LEAK. A TEAM MEMBER WAS SENT TO THE LEAK LOCATION TO VERIFY THE LEAK. AT 20:48 THE LEAK WAS CONFIRMED TO BE ON CEGT'S LINE BT-1-AS AND REPORTED TO SYSTEM CONTROL. IT WAS DETERMINED TO BE A MINOR LEAK. CEGT BEGAN WORKING WITH SGO TO UNDERSTAND THE CUSTOMER LOAD. EMPLOYEES WERE STATIONED AT THE LEAK TO MAN IT UNTIL THE LEAK WAS STOPPED. AT 21:15 CEGT AREA MANAGEMENT NOTIFIED SYSTEM CONTROL THAT THEY HAD GENERATED A PLAN TO LOWER THE PRESSURE ON A 16 MILE SECTION OF BT1-AS FROM 870# TO 400#. AT 22:00 PERSONNEL WERE DISPATCHED TO BEGIN MOVING ALL CUSTOMERS POSSIBLE TO AN ALTERNATIVE CEGT PIPELINE. ON 2/19/2011 AT 01:30 CREWS BEGAN BLOWING DOWN AND THE PRESSURE WAS LOWERED TO 400# BY 03:30. PERSONNEL STAYED AT EACH MLV LOCATION MONITORING PRESSURES (12 HOUR ROTATION FOR DURATION OF INCIDENT). ON 2/21/2011 AT 11:00 EXCAVATION BEGAN TO INSTALL A STOPPLE FITTING 3.5 MILES NORTH OF THE LEAK. ON 2/22/2011 AT 11:00 THE STOPPALL WAS COMPLETED AND CEGT TEAM PERSONNEL BLEW DOWN A 6.6 MILE PIPELINE SECTION CONTAINING THE LEAK. AT 15:00 THE LEAK WAS EXPOSED ENOUGH TO DETERMINE A CAUSE, APPROXIMATELY A 4"" CRACK IN THE PIPE. ON 2/23/2011 AT 16:30 PIPE WAS DELIVERED AND WELD CAPS WERE INSTALLED. AT 19:00 A 4 HOUR HYDRO TEST BEGAN, IT ENDED NEAR 24:00. ON 2/24/2011 AT 07:00 CONTRACTORS BEGAN TO REMOVE THE PIPE TO BE REPLACED. AT 10:00 THE CREW BEGAN INSTALLING THE NEW SECTION OF PIPE. ON 2/25/2011 CREWS COMPLETED THE REPLACEMENT AND AT 17:00 BEGAN PURGING. THE PURGE WAS COMPLETED AT 19:30. ON 2/26/2011 AT 07:30 THE CREW BEGAN BACKFILLING AT LEAK EXCAVATION, RECOATING AT STOPPLE FITTING LOCATION AND THEN RELOADED THE LINE. AT 16:00 THE SYSTEM WAS RETURNED TO NORMAL OPERATIONS. THE SECTION OF PIPE REMOVED WAS SENT TO KIEFNER & ASSOCIATES FOR METALLURGICAL ANALYSIS. IT WAS DETERMINED THAT THE FINAL FAILURE MODE WAS DUCTILE OVERLOAD OF THE REMAINING LIGAMENT BENEATH THE SCC. THE REMAINING LIGAMENT WAS OBSERVED TO BE APPROXIMATELY 50% OF THE PIPE WALL THICKNESS MINIMUM. THE FACT THAT THESE CRACKS WERE CRITICAL AT THIS SIZE INDICATES THE PRESENCE OF A RELATIVELY HIGH AXIAL LOAD. THE FINDINGS ARE AS FOLLOWS: