ANR PIPELINE CO

Incident Narrative

ON JUNE 29TH, 2015, AT 2:50 AM EDT FAILURE OCCURRED AT APPROXIMATE MP 3.8 ON ANR PIPELINE COMPANY'S 8250 LINE PIPELINE NEAR REED CITY, MICHIGAN. THE PIPELINE, WHICH HAS AN MAOP OF 650 PSIG, IS 24-INCHES OD, X52 GRADE, WITH A NOMINAL WALL THICKNESS OF 0.250 INCHES. THE ELECTRONIC FLASH WELDED PIPE WAS MANUFACTURED BY AO SMITH AND INSTALLED IN 1950. FLOW IN THE PIPELINE IS SEASONALLY BI-DIRECTIONAL AND WAS STATIC AT A PRESSURE OF 634 PSI (58% SMYS BASED ON NOMINAL PROPERTIES) AT THE TIME OF THE FAILURE. GAS RELEASED FROM THE FAILURE LOCATION DID NOT IGNITE. THERE WERE NO INJURIES, FATALITIES OR DAMAGE TO SURROUNDING STRUCTURES OR THE ENVIRONMENT. INVESTIGATIONS SUBSEQUENT TO THE INCIDENT REVEALED THAT A FAILURE OF THE WAX-TYPE COATING APPLIED DURING ORIGINAL CONSTRUCTION CONTRIBUTED TO THE EVENTUAL FORMATION OF TRANSGRANULAR STRESS CORROSION CRACKING (SCC), ALSO KNOW AS NEAR NEUTRAL PH SCC, IN THE PIPE, WHICH ULTIMATELY RESULTED IN THE PIPELINE FAILURE. THUS, THE DIRECT CAUSE OF THE FAILURE WAS THE NEAR NEUTRAL PH SCC, AS DOCUMENTED BY A THIRD-PARTY METALLURGICAL ANALYSIS. AND THE ROOT CAUSE OF THE SCC ON THE RUPTURED PIPE WAS ATTRIBUTED TO THE COATING THAT FAILED TO PERFORM ITS INTENDED PURPOSE OF ELIMINATING THE ENVIRONMENTAL COMPONENT REQUIRED FOR TRANSGRANULAR SCC TO INITIATE AND PROPAGATE. CONCURRENT TO THE ROOT CAUSE FAILURE INVESTIGATION, WHICH INCLUDED A REVIEW OF THE RESPONSE OF OPERATIONS AND GAS CONTROL PERSONNEL DURING THE EVENT, REPAIRS WERE MADE TO THE 8250 LINE, INCLUDING SUBSEQUENT MULTIPLE PRESSURE TESTS TO ASSURE PIPELINE FACILITY INTEGRITY AND SAFETY.