CENTERPOINT ENERGY GAS TRANSMISSION

Incident Narrative

ON 12/28/10 AT APPROXIMATELY 13:30 HRS. CEGT FIELD PERSONNEL WERE RAISING THE PRESSURE ON LINE BT-3 PER A REQUEST FROM SYSTEM CONTROL FROM 585 PSIG TO 685 PSIG. AT 17:00 HRS. 685 PSIG WAS OBTAINED. WHILE LETTING THE PRESSURE SETTLE OUT FROM LINE J TO LINE BT-3, SYSTEM CONTROL CALLED THE FIELD PERSONNEL AND ADVISED THAT PRESSURE WAS DROPPING FROM LINE BT-3 TO LINE B. THE FIELD PERSONNEL WENT TO CHECK THE BT-3 TO B DELIVERY JUNCTION AND DISCOVERED NO GAS AT THE JUNCTION. A LOCAL GAME AND FISH COMMISSION OFFICER CALLED AND REPORTED A BLOWOUT IN A CREEK BED IN ED GORDON WILDLIFE REFUGE ABOUT 1/2 MILE NORTH OF I-40 AT THE BLACKWELL EXIT AND GUIDED CEGT'S PERSONNEL TO THE LEAK LOCATION. AT 18:34 HRS. PIPELINE FIELD PERSONNEL ISOLATED LINE BT-3 BOTH UP AND DOWNSTREAM FROM THE RUPTURE SITE. THE RUPTURE SITE WAS MONITORED THROUGH THE NIGHT. ON THE MORNING OF 12/28/2011 CREWS ARRIVED ON SITE, WELDED CAPS ON EACH END OF THE RUPTURED PIPE AND RESTORED SERVICE ON THE PIPELINE AT A PRESSURE OF 200 PSIG. ON THURSDAY, 1/6/11 THE REPAIR CREW REPLACED 60 FEET OR PRE-TESTED PIPE AND THE TIE-INS WERE COMPLETED. THE PIPELINE WAS PRESSURED TO 548 PSIG, 80 % OF THE PREVIOUS OPERATING PRESSURE, UNTIL AN INVESTIGATION IS COMPLETED. THE PIPELINE WAS PUT BACK INTO SERVICE AT 16:00 HRS ON 01/07/2011. KIEFNER & ASSOCIATES, INC. REPORT CONCLUSION: THE FAILURE WAS CAUSED BY EXTERNAL CORROSION. THE EXTERNAL CORROSION HAD REDUCED THE PIPE WALL THICKNESS TO 0.010 INCH. THE REMAINING WALL THICKNESS FAILED BY DUCTILE TENSILE OVERLOAD RESULTING IN A RUPTURE MEASURING APPROXIMATELY 17 INCHES LONG. THE CAUSE OF THE EXTERNAL CORROSION COULD NOT BE CONCLUSIVELY IDENTIFIED, BUT IT DID NOT APPEAR TO HAVE BEEN CAUSED BY MICROBIOLOGICALLY INFLUENCED CORROSION. THE MECHANICAL PROPERTIES AND CHEMICAL COMPOSITION OF THE FAILED PIPE SPECIMEN MET THE REQUIREMENTS OF API 5L FOR THE PIPE GRADE AND VINTAGE.