"MISSISSIPPI HUB, LLC"

Incident Narrative

"AT 20:52 CDT ON 4/12/2025, AN 8-INCH PRESSURE RELIEF VALVE (PRV) ATTACHED TO A 42-INCH HEADER AT THE MISSISSIPPI HUB UNGSF AND COMPRESSOR STATION WAS EJECTED DUE TO A RUPTURE OF THE PIPE SPOOL BELOW THE VALVE. AS A RESULT OF THE EVENT, THE ON-SITE OPERATIONS CONTROLLER EXPERIENCED A LOSS OF COMMUNICATIONS WITH THE SCADA SYSTEM. HOWEVER, THE STATION ESD SYSTEM FUNCTIONED AS DESIGNED AND SHUT IN THE FACILITY AUTOMATICALLY. THE FACILITY WAS IN THE PROCESS OF PREPARING TO WITHDRAW GAS FROM STORAGE WHEN THE EVENT OCCURRED. THE ON-SITE OPERATOR WAS JOINED BY OTHER LOCAL EMPLOYEES AND BEGAN INVESTIGATING THE SOURCE OF THE FAILURE WHEN THE EJECTED PRV WAS DISCOVERED. THE PRV WAS LOCATED BETWEEN THE GAS HEATERS AND SEPARATORS DOWNSTREAM OF THE PRESSURE REGULATORS FOR THE COMINGLED GAS STREAM WHICH WAS NOT WITHIN THE UNGSF DEMARCATION. IT WAS DETERMINED THAT THE EXTENT OF PHYSICAL DAMAGE AND CORRECTIONS TO COMMUNICATIONS COULD NOT BE FULLY EVALUATED UNTIL DAYLIGHT, BUT THERE WAS NO CONCERN FOR THE SAFETY OF EMPLOYEES OR THE PUBLIC. THERE WERE NO INJURIES TO PERSONNEL, IGNITION OF THE GAS, EVACUATIONS, ROAD CLOSURES, OR MEDIA INQUIRIES. THE FOLLOWING MORNING, PERSONNEL DETERMINED THE PRV HAD BEEN EJECTED VERTICALLY AND THROUGH A CABLE TRAY, RESULTING IN MULTIPLE DAMAGED CABLES. ONCE THE PRELIMINARY EXTENT OF THE DAMAGE HAD BEEN ASSESSED, IT WAS DETERMINED THE FACILITY WOULD BE SHUT IN WHILE REPAIRS WERE MADE. THE EVENT WAS REPORTED TO THE NRC AT 11:09 CDT ON 4/13/2025 SINCE REPAIRS COULD HAVE EXCEEDED $145,400 AND WE DETERMINED AT THAT TIME THAT THE EVENT RESULTED IN THE EMERGENCY SHUTDOWN OF AN UNGSF. THE REPAIR WAS COMPLETED ON 4/16/2025, AND COMMUNICATIONS FOR THE FACILITY WERE RESTORED, ALLOWING THE FACILITY TO BE PLACED BACK INTO SERVICE ON 4/18/2025. THE FAILED PIPE UNDERWENT METALLURGICAL EXAMINATION, AND A ROOT CAUSE ANALYSIS WAS UNDERTAKEN TO DETERMINE THE CAUSE OF THE FAILURE. THE METALLURGICAL ANALYSIS DETERMINED THE PIPE SPOOL FAILURE WAS THE RESULT OF AN EXTERNAL OVERLOAD OF THE ASSEMBLY CREATED BY A PRESSURE RELEASE EVENT. THE PRESSURE RELEASE CAUSED A DOWNWARD FORCE AND BENDING MOMENT, TRIGGERING BUCKLING INSTABILITY JUST BELOW THE PRESSURE RELIEF VALVE. THE COMPONENTS OF THE ASSEMBLY ABOVE THE BUCKLE ROTATED NEARLY 45