KINDER MORGAN TEJAS PIPELINE

Incident Narrative

ON MARCH 30, 2018 AT 8:00 AM, A TEJAS PIPELINE COMPANY (TEJAS) EMPLOYEE ARRIVED AT THE RIO GRANDE CS OFFICE IN STARR COUNTY, TEXAS AND HEARD THE SOUND OF AIR OR GAS VENTING. THE EMPLOYEE ACCESSED THE STATION DATA TO SAFELY IDENTIFY THE CAUSE OF THE SOUND. HE OBSERVED NO PRESSURES EXCEEDING MAOP. HE THEN APPROACHED THE COMPRESSOR BUILDING AND AT 8:25 AM CONFIRMED THAT THE SOUND WAS NATURAL GAS VENTING FROM THE RELIEF VALVE (RV) ON DISCHARGE PIPING DOWNSTREAM OF COMPRESSOR NO. 80. HE SHUT NO. 80 DOWN AND ISOLATED THE RV BY 8:30 AM STOPPING THE RELEASE OF NATURAL GAS. THE REPORTED CAPACITY OF THE RV (FARRIS ENGINEERING SERIES 2600 PRESSURE RELIEF VALVE TYPE 26KC1-4-920) WAS 39,333 SCFM WITH A SET PRESSURE OF 1,100 PSIG. THE NRC WAS NOTIFIED OF THE RELEASE ON MAY 30, 2018 AT 09:19 AM. THE TOTAL VOLUME OF THE RELEASE REPORTED WAS ESTIMATED TO BE 24,000 MCF. AT 9:43 AM, THE RRC OF TEXAS WAS ALSO NOTIFIED OF THE INCIDENT. ON APRIL 1, 2018 AT 5:52 AM, A REVISED RELEASE VOLUME (17,414 MCF) WAS REPORTED WITH THE 48-HOUR UPDATE TO THE NRC (NRC NO. 1208193). THE VOLUME WAS BASED ON THE MAXIMUM CAPACITY, ORIFICE DIAMETER OF 3 INCHES AT 940 PSIG FOR 325 MINUTES, ASSUMING THE RELEASE BEGAN AT 3:24 AM, BASED ON AVAILABLE DATA AT THE STATION. THIS TIME WAS SELECTED AS THE EARLIEST POSSIBLE MOMENT THE INCIDENT BEGAN AND WAS BASED ON AN OBSERVED PRESSURE DROP RECORDED ON DISCHARGE PIPING FOR NO. 80 THE MORNING OF THE EVENT. IT WOULD BE DETERMINED LATER IN THE INVESTIGATION THAT THIS OBSERVED PRESSURE DROP WAS CAUSED BY A STOP COMMAND ISSUED BY GAS CONTROL ON COMPRESSOR UNIT NO. 79; DETERMINED TO BE UNRELATED TO THE EVENT. ON APRIL 2, 2018, THE RV WAS INSPECTED BY TEJAS AND THEY WERE UNABLE TO LOCATE ANY SIGNS OF PHYSICAL DAMAGE TO THE UNIT BUT THEY DID NOTICE THE UNIT CONTINUED TO LEAK GAS. ON APRIL 11, 2018, TEJAS DECIDED TO SEND THE RV TO THE SUPPLIER FOR FURTHER INSPECTION AND REPAIR. THE VENDOR REPORTED THAT THE DISC HOLDER AND SOFT RETAINER SCREW WERE FOUND TO BE DAMAGED. AT THAT TIME, THE UNIT WAS REPAIRED WITH NEW PARTS AND ADJUSTED TO REESTABLISH THE REQUIRED SET POINT AND TESTED BY THE VENDOR. THE RV UNIT WAS REINSTALLED APRIL 16TH 2018. HOWEVER, NO.80 WAS NOT PLACED BACK INTO SERVICE UNTIL APRIL 23, 2018 AS THE UNIT WAS NOT NEEDED UNTIL THAT TIME. ON APRIL 11, 2018, TEJAS RE-ESTIMATED THE RELEASE VOLUME USING THE ACTUAL RV SPECIFICATIONS USING THE MAXIMUM CAPACITY FOR A TOTAL DURATION OF 325 MINUTES WITH THE RELEASE BEGINNING AT 3:24 AM AND ESTIMATED THE VOLUME TO BE 13,591 MCF. THIS WAS THE VALUE REPORTED WITH THE INITIAL 30-DAY INCIDENT REPORT TO PHMSA AND THE TRRC. ON MAY 3, 2018, THE RELEASE VOLUME WAS RE-ESTIMATED USING HOURLY GAS VOLUME MEASUREMENT DATA TO ESTABLISH AN HOURLY VOLUME LOSS THROUGH THE STATION DURING THE EVENT. THE TOTAL RELEASE VOLUME WAS 3,920 MCF. THE ESTIMATED DURATION OF THE EVENT USING THIS DATA REVEALED THE EVENT TRIGGERED A REPORTING REQUIREMENT BETWEEN 5:00 AM AND 6:00 AM AND LASTING UNTIL THE UNIT WAS ISOLATED AT 8:30 AM THAT MORNING. THEREFORE, TEJAS CHANGED THE RESPONSE TO PART A Q4 FROM 3:24 AM TO 5:00 AM WITH THIS REPORT. TEJAS BELIEVES THE HOURLY GAS LOSS REMAINS THE BEST ESTIMATE OF ACTUAL RELEASE VOLUME SINCE THE RV COULD NOT OPEN TO FULL CAPACITY DUE TO THE INTERNAL DAMAGE TO THE DISC PLATE AND SEAL THAT WOULD NOT ALLOW IT TO PROPERLY RESEAT. THIS EXPLAINS WHY THE RV WAS FOUND TO BE VENTING AT A PRESSURE BELOW THE ESTABLISHED SET POINT. THE RELEASE VOLUME IS ALSO UPDATED TO REFLECT 3,920 MCF DISCUSSED ABOVE. ON MAY 4, 2018, THE DAMAGED RV COMPONENTS WERE SENT TO AN-TECH LAB IN HOUSTON, TEXAS. ON JUNE 29, 2018, THE RESULTS OF THEIR METALLURGICAL INVESTIGATION SHOWED THE IMMEDIATE CAUSE WAS DUE A FRACTURED DISC LOCKING SCREW WHICH PREVENTED THE DISC FROM SEALING PROPERLY AGAINST THE ASSOCIATED O-RING. THE FRACTURE MORPHOLOGY IN THE DISC LOCKING SCREW WAS TORSIONAL OVERLOAD INDICATING THE LOCKING SCREW WAS OVER TORQUED DURING ASSEMBLY; REPRESENTING THE ROOT CAUSE.