DOMINION EAST OHIO

Incident Narrative

ON MARCH 16, 2016, DOMINION EMPLOYEES WERE NOTIFIED OF A POTENTIAL GAS LEAK IN PORT WASHINGTON, OHIO. DOMINION REPRESENTATIVES REPORTED TO THE AREA AND VERIFIED A LEAK. GAS CONTROL WAS NOTIFIED TO BEGIN PRESSURE REDUCTIONS IN THE LINE BEGINNING AT APPROXIMATELY 14:00, AND A BLOW DOWN PROCEDURE WAS COMPLETED AROUND 18:00 ON THE SAME DAY. THE SITE WAS EXCAVATED ON MARCH 17, 2016 AND THE LEAK WAS VALIDATED. THE LEAK WAS REPAIRED BY REPLACEMENT OF THE AFFECTED SECTION OF PIPE ON MARCH 19, 2016 AND THE LINE RESTORED TO SERVICE. THE SECTION OF PIPE THAT LEAKED WAS ANALYZED INTERNALLY DUE TO THE CIRCUMSTANTIAL SIMILARITIES FROM A RECENTLY REPORTED FAILURE, WHICH WAS SENT TO A 3RD PARTY LABORATORY FOR ANALYSIS. AFTER COMPLETION OF THE INTERNAL ANALYSIS, IT WAS CONFIRMED THAT THE CONDITIONS SURROUNDING THIS FAILURE ARE IDENTICAL. THE PREVIOUS FAILURE ANALYSIS DETERMINED THAT THE FAILURE WAS CAUSED BY DUCTILE OVERLOAD OF THE PIPE WALL AT THE WELD TOE. THE PRIMARY FACTOR TO THE FAILURE WAS SETTLEMENT OF THE BRANCH CONNECTION DUE TO IMPROPER SUPPORT. THE SETTLEMENT CAUSED BENDING STRESSES IN THE CARRIER PIPE AT THE SADDLE REINFORCEMENT FILLET WELD WHICH RESULTED IN THE FORMATION OF A CRACK. THE GEOMETRY OF THE FILLET WELD THAT ATTACHED THE SADDLE REINFORCEMENT PAD TO THE CARRIER PIPE WAS ALSO A CONTRIBUTING FACTOR TO THE FAILURE. THE SADDLE THICKNESS WAS 2.5 TIMES THE THICKNESS OF THE CARRIER PIPE WHICH CONTRIBUTED TO A STRESS CONCENTRATION IN THE THINNER PIPE AT THE FILLET WELD TOE. UNDERCUT AT THE TOE OF THE FILLET WELD FURTHER CONCENTRATED THE STRESS AND CONTRIBUTED TO THE FORMATION OF A CRACK.