ONEOK NGL PIPELINE, LLC

Incident Narrative

AT APPROXIMATELY 4:42 PM ON 8/15/2022, A ONEOK OMBS OPERATOR IDENTIFIED VAPORS FROM THE DOOR OF STERLING 3 FILTER VESSEL 204. THE OPERATOR IMMEDIATELY NOTIFIED PIPELINE CONTROL, AND THE STERLING 3 TRAP VALVES WERE CLOSED TO ISOLATE THE SYSTEM. THE STERLING 3 FILTER VESSEL INLET VALVE WAS CLOSED TO FURTHER ISOLATE THE FILTER VESSEL, AND HYDROCARBONS WERE REMOVED. AN OPERATOR IDENTIFIED THE VESSEL DOOR GASKET AS THE SOURCE OF THE VAPORS. THE OPERATOR REMOVED AND REPLACED THE FILTER VESSEL DOOR GASKET AND THE FILTER VESSEL WAS RETURNED TO SERVICE. THE FAILED GASKET HAS BEEN SENT FOR MATERIAL ANALYSIS TO IDENTIFY THE CONTRIBUTING FACTORS OF THE FAILURE. A SUPPLEMENTAL REPORT WILL BE SUBMITTED PENDING THE MATERIAL ANALYSIS AND ONEOK COMPLETING ITS INVESTIGATION. SUPPLEMENTAL UPDATE 11/3/2022 FAILURE ANALYSIS OF THE O-RING/GASKET IDENTIFIED THAT THE CAUSE OF FAILURE WAS DUE TO HIGH VELOCITY MECHANICAL SHEAR FRACTURE IN A DIRECTION PARALLEL TO THE VESSEL RADIUS. DEFORMATION AND STRETCHING OF THE POLYMER LATERAL AND IN-PLANE OCCURRED OVER THE ENTIRE BREAK SURFACE, AND THE METALLIC HELICAL SPRING HAD ALSO FAILED DUE TO RAPID SHEAR OVERLOAD. POLYMER MATERIAL CHARACTERISTICS, SUCH AS COMPOUNDS PRESENT, GLASS TRANSITION TEMPERATURE, AND DUROMETER HARDNESS CONFIRMED THAT FUNDAMENTAL MATERIAL PROPERTIES OF THE FAILED O-RING DID NOT CONTRIBUTE TO THE CAUSE OR MECHANISM OF O-RING FAILURE. AS A RESULT OF THE FAILURE ANALYSIS REPORT AND ONEOKS CAUSEMAP INVESTIGATION, THE FOLLOWING MITIGATION STEPS HAVE BEEN TAKEN TO PREVENT FUTURE RE-OCCURRENCE OF O-RING/GASKET FAILURE. 1. ONSITE TRAINING WITH THE MANUFACTURE OF THE FILTER DOOR OCCURRED ON AUGUST 31, 2022 TO ENSURE ONEOK IS COMPLETING PROPER INSTALLATION OF THE O-RING/GASKET DURING A FILTER CHANGE. 2. A WORK ORDER WILL BE CREATED AFTER EACH FILTER CHANGE AT THIS LOCATION TO CHECK THE FILTER DOOR FOR LEAKS.