TALLGRASS INTERSTATE GAS TRANSMISSION, LLC

Incident Narrative

AT APPROXIMATELY 02:18 LOCAL TIME ON MAY 4, 2013, A PIPE SECTION OF THE 20"" TALLGRASS PONY EXPRESS PIPELINE (PXP) MAINLINE IN UNINCORPORATED (CLASS 1 AREA) KIMBALL COUNTY, NE RUPTURED DUE TO THEN-UNKNOWN CAUSES. THE PIPELINE WAS OPERATING AT 845 PSIG AT THE TIME OF THE INCIDENT, WITH AN ESTABLISHED MAXIMUM ALLOWABLE OPERATING PRESSURE (MAOP) OF 1052 PSIG. THERE WAS NO FIRE, EXPLOSION, INJURY/DEATH, OR MAJOR PRIVATE PROPERTY DAMAGE ASSOCIATED WITH THE RUPTURE. THE RUPTURE WAS IDENTIFIED BY TALLGRASS GAS CONTROL OPERATORS AT 02:31 WHEN A DOWNSTREAM COMPRESSOR STATION ALARMED ON A LOW COMPRESSION RATE. PRESSURE TRENDING INDICATED ABNORMAL OPERATING CONDITIONS (AOC) ON THE 135 MILE-LONG PXP GUERNSEY-STERLING SEGMENT. LOCAL FIELD OPERATORS WERE CONTACTED AND BEGAN SHUTTING IN THE SEGMENT VIA ISOLATION VALVES AT INTERCONNECT POINTS. THE GUERNSEY-ROCKPORT INTERCONNECT POINT (35 MILES UPSTREAM OF STERLING) SEGMENT WAS ISOLATED BY 02:54, 23 MINUTES AFTER AOC IDENTIFICATION. FIELD OPERATIONS CONTINUED SYSTEMATIC VALVE CLOSURES AS THEY MOVED ALONG THE PIPELINE TOWARDS THE RUPTURE; THE LOCAL 15.9 MILE VALVE-TO-VALVE SEGMENT WITH THE RUPTURED SECTION WAS ISOLATED BY 06:29. FIELD OPERATIONS SUPERVISED AN INTENTIONAL AND CONTROLLED BLOWDOWN OF THE LOCAL SEGMENT UNTIL IT WAS SAFE TO APPROACH THE RUPTURE SITE TO BEGIN INVESTIGATION. FIELD INVESTIGATION REVEALED A CATASTROPHIC RUPTURE OF A PIPE SECTION APPROXIMATELY 45 FEET IN LENGTH, WITH COMPLETE SEPARATION OF THE RUPTURED SECTION FROM THE PIPELINE. THE FRAGMENTS OF THE PIPE (API-5L X52, EFW, MANUFACTURED IN 1954 BY AO SMITH) WERE SENT TO A METALLURGICAL FIRM FOR STUDY. METALLOGRAPHY DETERMINED THAT THE RUPTURE ORIGINATED IN A ""HARD SPOT"" MILL DEFECT IN THE BODY WALL. THE SEAM AND GIRTH WELDS WERE NOT PART OF THE ROOT CAUSE. THE PIPELINE WAS RETURNED TO SERVICE ON MAY 9, 2013 UNDER A TEMPORARY PRESSURE RESTRICTION OF 676 PSIG (80% OF THE OPERATING FAILURE PRESSURE).