Failure of valve visual position indicator on subsea Christmas tree
During well decommissioning, problems were experienced when attempting to open two annulus swab valves on subsea trees. Several attempts were made to open the valves using diver intervention. Onshore inspection later confirmed that the visual position indicator on both valves had failed rather than the valve themselves, leading to an incorrect representation of the valve status.
The key lessons learned were:
- Indicators of valve position may be prone to failure in service
- Failure of a visual indicator to represent actual valve position could have safety implication for subsea well intervention operations, particularly where there is the involvement of divers
The client has made a number of recommendations including:
- Consideration of valve position indicator failure should be included in the risk assessment for well intervention operations
- Checks on position indicators should be done during routine subsea inspection.
Safety Event
Published: 1 September 1998
Download: 
IMCA SF 04/98
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