WBI ENERGY TRANSMISSION, INC.

Incident Narrative

NATURAL GAS WAS VENTED THROUGH EMERGENCY SHUTDOWN (ESD) VALVES AS A RESULT OF A PARTIAL FREEZE OFF OF THE ESD SYSTEM. THE SUPPLY GAS REGULATOR FROZE OFF WHICH RESULTED IN THE SUPPLY GAS SYSTEM PRESSURE DROPPING TO 0 PSIG. THE LOSS OF PRESSURE TO THE SUPPLY GAS SYSTEM CAUSED THE ESD BLOW DOWN VALVES TO OPEN AS DESIGNED AND VENT NATURAL GAS TO THE ATMOSPHERE. THE NATURAL GAS WAS VENTED FOR APPROXIMATELY 54 MINUTES UNTIL PERSONNEL WERE ABLE TO REACH THE SITE AND RESTORE NORMAL OPERATION. DURING A FOLLOW UP INVESTIGATION, A SMALL LEAK WAS FOUND ON A 3/8"" TUBING UNION DOWNSTREAM OF THE SUPPLY GAS REGULATOR WHICH WOULD HAVE CAUSED GAS TO FLOW THROUGH THE SUPPLY GAS REGULATOR. THE FLOWING CONDITIONS THROUGH THE SUPPLY GAS REGULATOR IN CONJUNCTION WITH THE AMBIENT TEMPERATURE OF -30 DEGF WOULD HAVE ALLOWED THE SUPPLY GAS REGULATOR TO FREEZE OFF WITH SUBSEQUENT LEAKING THROUGH THE TUBING UNION CAUSING THE LOSS OF PRESSURE TO THE SUPPLY GAS SYSTEM. THE LEAK IN THE 3/8"" TUBING UNION HAS BEEN FIXED; AND HEAT TRACE AND AN INSULATION BLANKET HAVE BEEN INSTALLED ON THE SUPPLY GAS REGULATOR TO PREVENT THIS SITUATION FROM REOCCURRING. THIS INCIDENT OCCURRED IN A RURAL LOCATION AT A COMPRESSOR STATION APPROXIMATELY 4 MILES NORTH OF GLEN ULLIN, ND.