ONEOK NGL PIPELINE, LLC

Incident Narrative

ON 7/17/2023 AT 17:15, A THIRD-PARTY OPERATOR NOTIFIED THE ONEOK PIPELINE CONTROL ROOM OF A POTENTIAL LEAK ON THE STERLING 3 FILTER VESSEL 207 AT ONEOK MONT BELVIEU STORAGE (OMBS). THE ONEOK PIPELINE CONTROLLER DISPATCHED LOCAL ONEOK OPERATORS. EP WAS OBSERVED LEAKING FROM THE VESSEL CLOSURE BY THE RESPONDING OPERATORS. THE PIPELINE CONTROLLER SHUT THE PIPELINE DOWN. THE VESSEL WAS ISOLATED AND DE-INVENTORIED. THE SEALING ELEMENT ON THE VESSEL APPEARED TO BE THE CAUSE OF THE LEAK AND WAS REPLACED; THE VESSEL WAS SUBSEQUENTLY RETURNED TO SERVICE. UPDATE: ONEOK SUBMITTED THE FAILED SEALING ELEMENT AS WELL AS SEVERAL SAMPLES FROM INVENTORY TO A THIRD-PARTY LAB FOR ANALYSIS. THE THIRD-PARTY ANALYSIS DETERMINED THAT THE FAILURE OF THE SEALING ELEMENT APPEARS TO BE RELATED TO GAS-LIQUID EXPANSION RESULTING IN INTERNAL TEARS AND BLISTERS. NO SIGNS OF CHEMICAL DEGRADATION WERE IDENTIFIED WITHIN THE SEALS PROVIDED. ONEOK HAS VERIFIED THAT THE FAILED SEALING ELEMENT WAS INSTALLED PER MANUFACTURER RECOMMENDATIONS. PHMSA REQUESTS: 1. PLEASE INCLUDE SPECIFIC MATERIAL OF SEAL IF KNOWN/LEARNED DURING LAB ANALYSIS: THE MATERIAL WAS FKM RUBBER. 2. PLEASE ADD TO NARRATIVE EXPLANATION OF SYSTEMS AT THIS FACILITY - WHY SCADA AND CPM DID NOT DETECT THE LEAK IN THIS INSTANCE (OR IF THEY DID BUT AFTER IT WAS DETECTED & CONFIRMED): THERE ARE DIFFERENTIAL PRESSURE SENSORS LOCATED AT THE STERLING 3 FILTER VESSEL. THE LEAK WAS SMALL, IMMEDIATELY IDENTIFIED BY A THIRD-PARTY OPERATOR, AND THE VESSEL WAS ISOLATED QUICKLY. AS A RESULT, THERE WAS NO INDICATION OF A LEAK ON SCADA.