Gas release from 3 part ¾” ball valve

Cause & Consequence

• Uncontrolled release of a flammable gas or liquid

Incident Consequence

Hydrocarbon release

Incident Location

Fixed Installation

Incident Activity

Production operations

Incident Info Source

Gary Begg&

Specific Incident Equipment

3 part stainless steel ball valve with various selectable options on studs and nuts

Lessons Identified

The nuts which did not fail looked to be in good condition, however examination revealed slight cracking in the thread troughs. When sectioned they were found to be severely corroded and cracked to the point one shattered during the inspection This valve type has been manufactured since 1981, and specification options have varied. Users could have inadvertently specified the valves with lower grade 303/304 grade fasteners in the period between 1989 and 1999, as marine grade 316 studs and nuts had to be specifically requested at the time. Visual inspection of the fasteners are of little value in determining integrity and it is possible that our operations have a significant number in service, allowing for a risk of further leaks

Incident Recommendations

Inspect all 3 part valves of this design and confirm all nuts and studs are in place Where possible this valve type should be isolated and a change out programme instigated as soon as practical. The preferred replacement option is a solid block type valve which does away with the two flanged joints on the valve and hence two potential leak points.