INTERMOUNTAIN GAS CO

Incident Narrative

SMALL DEBRIS IN THE REGULATOR PUNCTURED THE DIAPHRAGM WHICH CAUSED THE REGULATOR TO FAIL WIDE OPEN. NORMAL CONTROL PRESSURE IS 245 PSIG AND UPSTREAM PRESSURE WAS APPROXIMATELY 650 PSIG. THIS RESULTED IN THE RELIEF TO OPEN AND BLOW TO ATMOSPHERE. THE RELIEF IS SET TO START OPENING AT 265 PSIG AND IT BUILT TO 272 PSIG DURING FULL RELIEF. DUE TO PIPING CONFIGURATION THIS RESULTED IN APPROXIMATELY 280 PSIG OUT OF THE REGULATOR AND PRESSURE LOSSES IN THE PIPE UP TO THE RELIEF. ALL PIPING DOWNSTREAM OF THE RELIEF DID NOT SEE MORE THAN 272 PSIG. ONLY 30' PIPING WAS SUBJECTED TO THE 110% MAOP PRESSURE. OPERATOR PERSONNEL ARRIVED ON SITE AND PROMPTLY SHUT IN THE REGULATOR THAT FAILED BY USING AN UPSTREAM ISOLATION VALVE. THE STATION HAS A REDUNDANT REGULATOR THAT MAINTAINED FEED INTO THE SYSTEM. THE RELIEF WAS REBUILT AND PUT BACK INTO SERVICE. IGC REQUESTED THIS INCIDENT BE RETRACTED, AND WAS DENIED BY BRIAN PIERZINA, PHMSA ACCIDENT INVESTIGATOR. IGC DISAGREES WITH THIS DECISION AND IS WORKING WITH INGAA, WHO IS SEEKING CLARIFICATION FROM PHMSA LEADERSHIP ON THE DEFINITION OF AN INCIDENT, SINCE THE RULEMAKING LANGUAGE IN 2010 SUPPORTS THAT REGULATOR STATION RELIEF'S IN EXCESS OF 3M CUBIC FEET SHOULD NOT BE REPORTED AS INCIDENTS. -LANCE ELROY, IGC DIRECTOR OF OPERATIONS. 2-8-18.