SHELL PIPELINE CO., L.P.

Incident Narrative

INSULATING GASKET ON THE DOWNSTREAM SIDE OF A MAINLINE BLOCK VALVE AT IOWA PUMP STATION BEGAN LEAKING FOLLOWING THE CONNECTION OF A BYPASS LINE JUST DOWNSTREAM OF THE BLOCK VALVE. THE LEAK WAS FIRST NOTICED AS SMALL ENOUGH TO TIGHTEN THE FLANGE STUDS AND NUTS WHICH STOPPED THE RELEASE FOR OVER ONE HOUR. THE RELEASE BEGAN AGAIN. THE PIPELINE WAS SEGMENTED BY CLOSING OTHER MAINLINE BLOCK VALVE WHICH ISOLATED A 7 MILE LONG SEGMENT OF PIPELINE WHILE ETHYLENE PIPELINE WAS SHUT DOWN. THE ISOLATED SEGMENT WAS BLOWN DOWN THROUGH SEVERAL FLARES. THE FLANGE GASKET CONTINUED TO LEAK UNTIL THE PRESSURE DROPPED TO APPROX. 550 PSI. AT WHICH TIME IT STOPPED. THE ISOLATED PIPELINE SEGMENT CONTINUED TO BE BLOWN DOWN UNTIL IT WAS SAFE TO REMOVE AND REPLACE THE GASKET. THE GASKET WAS REPLACED ON 12/8 AND RESTARTED ON 12/9. THE GASKET WAS A MICARTA INSULATING GASKET USED TO ISOLATE THE PIPELINE SEGMENTS. THIS TYPE OF INSULATING GASKET WAS COMMONLY UTILIZED. IT WAS FOUND TO BE IN GOOD CONDITION. AN INVESTIGATION DETERMINED THE CAUSE OF THE RELEASE WAS DUE TO THE LOSS OF SUPPORT OF THE ABOVEGROUND FLANGE SET WHILE CONNECTING THE TEMPORARY BYPASS PIPING DOWNSTREAM OF THE FLANGE SET. 3/13/2013 - VERIFIED E5F PER REQUEST FROM PHMSA. 11/12/13 - SPOKE WITH BLAINE KEENER, PHMSA - REQUESTED THE RECOVERED VOLUME BE REMOVED FOR THE AMOUNT OF THE INTENTIONAL VOLUME.