SUNOCO PIPELINE L.P.

Incident Narrative

ON 1/14/2015 A 30 BBL RELEASE OF PROPANE OCCURRED AT THE WEST PORT ARTHUR RD. MLV SITE ON THE MARINER SOUTH SYSTEM. A LOSS OF LINE PRESSURE WAS IDENTIFIED VIA SCADA IN THE CONTROL CENTER. THE LINE WAS IMMEDIATELY SHUT DOWN AND MLV'S ON EITHER SIDE OF THE AFFECTED SEGMENT WERE CLOSED REMOTELY BY THE CONTROLLER. FIELD PERSONNEL WERE DISPATCHED TO THE LOCATION TO INVESTIGATE. WHEN THE FAILURE LOCATION WAS IDENTIFIED AT A 3/4' PIPE NIPPLE THAT HAD CRACKED AT THE THREADED CONNECTION TO AUXILIARY PIPING AT THE MLV SITE IT WAS DETERMINED THAT THE LINE SEGMENT WOULD HAVE TO BE PURGED TO AFFECT PERMANENT REPAIR. PURGE WAS ACCOMPLISHED AND PERMANENT REPAIRS WERE COMPLETED AND THE LINE WAS RETURNED TO SERVICE ON 1/22/15. INVESTIGATION REVEALED THAT THE NITROGEN SUPPLY SYSTEM REGULATOR FOR THE PNEUMATICALLY OPERATED MLV FAILED WHICH CAUSED HIGH NITROGEN PRESSURE TO BE EXERTED ON THE PNEUMATIC ACTUATOR. THE HIGH PRESSURE ON THE ACTUATOR CAUSED IT TO FAIL AND IMPACT THE ADJACENT AUXILIARY PIPING AT THE MLV SITE. THIS IMPACT BENT THE PIPING ASSEMBLY AND ULTIMATELY CAUSED THE CRACK OF A 3/4' PIPE NIPPLE AT THE THREADED CONNECTION. THIS CRACK WAS THE SOURCE POINT OF THE RELEASE OF PROPANE. THE PERMANENT REPAIRS INCLUDED INSTALLATION OF A DUAL REGULATOR AND A PRESSURE SAFETY VALVE (PSV) IN THE NITROGEN SUPPLY SYSTEM FOR THE PNEUMATICALLY OPERATED MLV. THIS CONFIGURATION WILL RELIEVE NITROGEN PRESSURE SHOULD THE REGULATOR FAIL THUS PREVENTING A REOCCURRENCE OF THIS FAILURE SCENARIO.