During pigging operations on a temporary water transfer line, a pig became stuck due to an ice blockage and pressure was trapped upstream of the pig. When it was freed, the pig and trapped pressure behind it traveled down the line causing a loose clamp to unfasten. The pressure release caused the disconnected hose to swing and strike a worker on the leg, causing serious injury.
Proper heating operations were not in place. This resulted in ice/slush build-up in the line, which caused the pig to become stuck.
A loose connection downstream of the stuck pig failed when the pig was freed, and pressure traveled downstream.
Connection points in the water transfer line were not additionally secured with restraint devices (whip checks) to prevent movement in the event of a connection failure.
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