Differential pressure: dummy choke ejected close to divers

A dummy choke insert was ejected from a water injection (WI) tree by force of differential pressure, while divers were working nearby.

A Dive team was removing a dummy choke insert and replacing it with a choke valve insert. The WI tree had been subject to hydrate remediation works. With no hydrates evident, limited trapped or pressurised gas was expected and tested barriers and isolations were in place.

During the removal of the half shell clamps that retained the dummy choke insert,unexpected differential pressure from the flowline forced the dummy choke insert (85kg in water) out of the choke valve body at significant force. The two divers were loosening the clamp bolts around the dummy choke and were therefore close by when it ejected.

Neither diver was in the direct line of fire; both were unharmed.