For natural gas transmission pipelines, a low probability but high consequence failure event is a large, ignited gas release (rupture) which potentially could adversely impact the surrounding area. However, prudent emergency response planning and actions taken by operators and first responders may be able to help reduce the impact.

One operator response action is closing isolation valves and shutting down the ruptured pipeline segment. Past industry studies have shown that the rapid shutdown of a ruptured natural gas pipeline segment has minimal effect on reducing consequences since the most of the thermal radiation impact occurs before isolation valves can be activated. However, insights from past pipeline incidents, including investigations of the National Transportation Safety Board (NTSB) in the United States, have indicated that rapid shutdown (e.g., isolation of the impacted segment to limit the gas release) in conjunction with other emergency response measures (e.g., firefighting of secondary fires) may reduce the severity of building damage.

This paper introduces a technical approach for evaluating the emergency response effectiveness with the rapid closure of isolation valves in combination with firefighter intervention to extinguish secondary building fires following a hypothetical rupture. In addition, the paper will present findings from applying this methodology to the system of a natural gas pipeline operator, to guide decision-making in prioritizing mitigative actions, including installation of automatic shut-off valves or remote-control valves to achieve rapid valve closure.