COLUMBIA GAS TRANSMISSION, LLC

Incident Narrative

ON OCTOBER 23RD, 2017, A 8-INCH SINGLE BOLT HINGED CLOSURE FAILED AFTER AN UNINTENDED NATURAL GAS RELEASE WAS NOTED BY THE ONSITE COMPANY PERSONNEL. THE FACILITY IS KNOWN AS EDC-TIMKEN MEASURING STATION 730886. THE FACILITY IS OWNED BY EDC-TIMKEN, OPERATED AND MAINTAINED BY COLUMBIA GAS TRANSMISSION, LLC (COMPANY). THE TWO COMPANY PERSONNEL WERE PERFORMING ROUTINE PREVENTIVE MAINTENANCE TO THE MS. THE LINE WAS DEPRESSURIZED AND THE CLOSURE WAS OPENED IN ORDER TO PERFORM THE MAINTENANCE. AT THE COMPLETION OF THE MAINTENANCE ACTIVITY, THE CLOSURE WAS CLOSED AND SECURED WITH A SWING BOLT. THE LINE WAS PRESSURIZED AND AN UNINTENDED RELEASE WAS IDENTIFIED AT THE HEAD OF THE CLOSURE. UPON COMPLETING THE MAINTENANCE TASKS AND RETURNING THE FACILITY BACK INTO SERVICE BEFORE LEAVING THE SITE, THE SOUND OF A POTENTIAL RELEASE WAS HEARD BY ONE OF THE MEASUREMENT AND REGULATION (M&R) TECHNICIANS. BASED ON REPORTED WITNESS STATEMENTS, WHILE INVESTIGATING THE NATURE OF THE UNINTENDED RELEASE, THE SINGLE BOLT MAY HAVE BEEN IN THE PROCESS OF BEING TIGHTENED IN AN EFFORT TO STOP THE POTENTIAL LEAK AT THE TIME OF THE FAILURE. THE CLOSURE FAILURE FATALLY INJURED THE M&R TECHNICIAN INVESTIGATING THIS UNINTENDED RELEASE. THE FAILED SECTIONS WERE SENT TO A METALLURGICAL LABORATORY FOR FAILURE ANALYSIS INVESTIGATION, TO DETERMINE THE PROBABLE CAUSE BEHIND THE FAILURE OF THE SWING BOLT. THE LABORATORY REPORT IDENTIFIED THE INCIDENT WAS CAUSED DUE TO THE FAILURE OF THE SWING BOLT PIN. THE VERTICAL ORIENTATION OF THE DUCTILE SHEAR OBSERVED ON THE FRACTURE SURFACE OF THE SWING BOLT PIN IS CONSISTENT WITH A LOADING DIRECTION IMPACTED WHILE TIGHTENING THE SWING BOLT NUT AND PLACING THE SWING BOLT PIN INTO DOUBLE SHEAR. TWO SAFETY ALERTS WERE ISSUED COMPANY-WIDE AS A RESULT OF THIS INCIDENT, WITH CAREFUL ATTENTION PAID TO SIMILAR APPLICATIONS, WITH THE GOAL OF PREVENTING SIMILAR INCIDENTS FROM RE-OCCURRING. (INCIDENT NRC REPORT NO. 1194041 AND 48-HR NRC REPORT NO. 1194188)