ONEOK NGL PIPELINE, LLC

Incident Narrative

ON 9-1-2020 AT 20:43 ONEOK PIPELINE CONTROL RECEIVED A GAS DETECT ALARM AT THE ONEOK WEST TEXAS LPG WEATHERFORD STATION AND DISPATCHED FIELD PERSONNEL. UPON ARRIVING AT THE STATION, THE ONEOK FIELD OPERATOR IDENTIFIED VAPORS LEAKING FROM A 1"" NIPPLE ASSOCIATED WITH THERMAL RELIEF PIPING AT THE ADJACENT ONEOK ARBUCKLE 2 - WEATHERFORD CUSTODY METER SKID. THE METER SKID WAS IMMEDIATELY ISOLATED AND THE PRODUCT EVACUATED. THE 1"" NIPPLE WAS REMOVED, REPLACED AND THE SYSTEM WAS RETURNED TO NORMAL SERVICE. UPON VISUAL INSPECTION OF THE 1"" NIPPLE, A HAIRLINE CRACK WAS FOUND IN THE THREADS. FOLLOW UP CORRECTIVE ACTION HAS BEEN MADE WHICH ELIMINATED THE NEED FOR THE THERMAL RELIEF. ONEOK IS CONTINUING THE INVESTIGATION OF THE 1"" NIPPLE, METER SKID AND ASSOCIATED PIPING AT THE ARBUCKLE 2 - WEATHERFORD CUSTODY METER SKID TO DETERMINE THE CAUSE OF THE RELEASE. A SUPPLEMENTAL REPORT WILL BE SUBMITTED ONCE ONEOK HAS COMPLETED IT'S INVESTIGATION. UPDATE 10/28/2020 THE FAILED 1"" NIPPLE WAS FOUND TO SHOW ELEVATED RESIDUAL STRESS AT THE THREAD CREST AND THREAD ROOTS FROM SEVERE GRAIN DEFORMATION IMPARTED DURING THE INITIAL CUTTING OF THE THREADS AT MANUFACTURE. BECAUSE THE DEFECT IN THE THREADS OCCURRED DURING MANUFACTURE, ONEOK HAS REPLACED THE 1"" NIPPLES IN SIMILAR SERVICE ON THE WEATHERFORD CUSTODY METER SKID.