TRANSCONTINENTAL GAS PIPE LINE COMPANY

Incident Narrative

COMPRESSOR STATION 110 MAIN UNIT 04 RELIEF VALVE RELEASE TUBING CONNECTION FAILURE EVENT TIMELINE 08/20/2019 4:47 AM PIPELINE CONTROL (HOUSTON) CONTACTED LOCAL OPERATION TECHNICIAN. CONTROLLER HAD RECEIVED A CALL FROM THE LOCAL DEPUTY THAT WAS ON-SITE OUTSIDE AT THE STATION GATE. LOCAL LANDOWNER NEAR STATION HAD CALLED THE SHERIFF ABOUT THE STATION NOISE AND DEPUTY WAS DISPATCHED TO THE SITE. 5:15 AM OPERATION TECHNICIAN ARRIVED AND HEARD GAS RELEASE, ACCESS WAS HELD-UP BY THE DEPUTY UNTIL IDENTIFIED. 5:20 AM OP TECH MANUALLY SHUT-DOWN THE UNIT AND IDENTIFIED THE PILOT TUBING CONNECTION FAILURE AT THE PRESSURE RELIEF VALVE. THE 3/8-INCH STAINLESS STEEL TUBING CONNECTION FAILED AT THE PRESSURE RELIEF VALVE PILOT AND CAUSED THE RELIEF VALVE TO VENT OPEN (LOSS OF PILOT PRESSURE TO THE RELIEF VALVE). NO OTHER OPERATING ISSUES WERE IDENTIFIED. 6:15 AM OPERATIONS PERSONNEL REVIEWED THE STATION HMI AND TRENDED THE OPERATION DATA BACK TO APPROXIMATELY 2:40 AM FOR NORMAL OPERATION. A 9 PSIG PRESSURE DROP WAS NOTED ON MU04 WITH NO CHANGES IN HORSEPOWER COMMANDS. THERE WERE NO SHUT-DOWN ALARMS. MU04 WAS RUNNING UNTIL MANUALLY SHUT-DOWN AT 5:20 AM. THE REASONABLE GAS RELEASE DURATION IS APPROXIMATELY 2-HOURS AND 40-MINUTES. 7:33 AM OPERATIONS NOTIFIED DIVISION ENGINEER TO DETERMINE THE APPROXIMATE GAS RELEASE VOLUME ASSOCIATED WITH THIS DURATION. 8:41 AM ENGINEER CALCULATED 23,800 MSCF FOR THE GAS RELEASE DURATION. 8:44 AM SECURITY OPERATIONS CENTER WAS CONTACTED AND THE GAS RELEASE VOLUME WAS CONFIRMED WITH PIPELINE SAFETY. THIS GAS RELEASE EVENT WAS DETERMINED TO BE A REPORTABLE INCIDENT DUE TO EQUIPMENT FAILURE AND THE RELEASE VOLUME EXCEEDING 3 MMSCF. 9:00 AM THE PILOT TUBING WAS REPLACED, PILOT RE-SET, CHECKED, AND COMPRESSOR UNIT AND RELIEF VALVE WERE RETURNED BACK TO SERVICE. THE TUBING CONNECTION FAILURE WAS LIKELY DUE TO VIBRATION (RECIPROCATING COMPRESSOR UNIT) AND FATIGUE ON THE MOUNTED TUBING. THE NEW PILOT TUBING INSTALLATION WAS MODIFIED. 9:03 AM/10:03 AM NRC REPORT TIME SOC CONTACTED THE NRC, INCIDENT REPORT # 1255737. 9:17 AM PHMSA AID CONTACTED PIPELINE SAFETY TO DISCUSS THE INCIDENT. THE GENERAL LOCATION AND RELEASE INFORMATION, WAS AN INCIDENT DUE TO EQUIPMENT FAILURE (TUBING) AND THE GAS RELEASE VOLUME EXCEEDING 3 MMSCF, AND WAS NOT AN EMERGENCY. NO SPECIFIC EVENT DETAILS WERE KNOWN AT THIS TIME, OTHER THAN A TUBING FAILURE HAD OCCURRED CAUSING THE MAIN UNIT RELIEF VALVE TO VENT OPEN. 10:00 AM OPERATIONS DISCUSS THE RELEASE EVENT SUMMARY AND TIMELINE WITH PIPELINE SAFETY, GATHERED SITE INFORMATION, AND THE INCIDENT REVIEW PROCESS BEGINS. 08/22/2019 7:57 AM NRC CONTACTED FOR PHMSA 48-HOUR UPDATE, NRC INCIDENT REPORT # 1256000 AND PROVIDED UPDATED INFORMATION. PLEASE NOTE, THE NRC CONTACT REVISED THE INCIDENT DISCOVER DATE AND TIME TO 22-AUG-2019 AT 08:00 LOCAL INCIDENT TIME, WHICH WAS THE APPROXIMATE TIME FOR THE 48-HOUR UPDATE? THE NRC CONTACT MAY HAVE MISUNDERSTOOD THE COMMUNICATION. THE ORIGINAL INCIDENT DATE AND TIME IS STILL 20-AUG-2019 AT 08:44 LOCAL INCIDENT TIME AS NOTED ON NRC INCIDENT REPORT # 1255737. 08/23/2019 THE INCIDENT REVIEW AND CAUSE WERE COMPLETED. INCIDENT REPORT SUBMITTED. ROOT CAUSE ANALYSIS AND REMEDIATION THE NEW PRESSURE RELIEF/SAFETY VALVE (PSV) WAS INSTALLED ON 10/25/2018 WITH THE ORIGINAL VENDOR PILOT FILTER AND TUBING ATTACHED TO THE PSV. THE VENDORS PSV DESIGN HAD THE PILOT FILTER SUPPORTED SOLELY BY THE TUBING CONNECTING THE FILTER TO THE RELIEF VALVE PILOT. THE TUBING FAILED AT THE CONNECTION TO THE PSV PILOT. THIS FAILURE APPEARS TO BE DUE TO VIBRATION INDUCED FATIGUE FROM THE UNSUPPORTED WEIGHT OF THE PILOT FILTER AND THE FAILURE EVENT WAS REVIEWED WITH THE VENDOR. WILLIAMS-TRANSCO HAS REPLACED THE PILOT TUBING AND REMOTE MOUNTED THE PILOT FILTER FOR BETTER SUPPORT WHICH SHOULD PREVENT ANY FUTURE FAILURE FROM OCCURRING. THE TUBING AND PILOT FILTER INSTALLATION WILL BE MONITORED FOR NORMAL OPERATION AND VIBRATION.