DOMINION EAST OHIO

Incident Narrative

ON MARCH 25, 2015 AT APPROXIMATELY 9:30 A.M., WHILE WORKING TO REPAIR A GRADE 2 LEAK A CRACK ON A DOMINION FACILITY NEAR THE PAD SADDLE AROUND THE TAP WAS DISCOVERED. ON MARCH 26, 2015, THE SECTION OF PIPE WAS CUT OUT AND REPLACED. PRESSURE WAS RESTORED AND THE LINE WAS PUT BACK INTO SERVICE ON MARCH 28, 2015 AT APPROXIMATELY 1:00 P.M. THE SECTION OF PIPE THAT LEAKED WAS SENT TO A 3RD PARTY LABORATORY FOR FAILURE ANALYSIS. THE RESULT OF THE 3RD PARTY 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.