Cause & Consequence
Other Cause & ConsequenceFailure of stored pressure from single nitrogen pressure accumulator
Description of Process
Lowering a Totally Enclosed Motor Propelled Safety Craft (TEMPSC) from an offshore installation (exercise).
Description of Incident
When some designs of TEMPSC are lowered from an installation, the hydraulic brake is released using stored pressure from a single nitrogen accumulator.
When the brake release lever on a TEMPSC was activated during an exercise, it was found that the accumulator had failed and held no pressure. As a result, the brake could not be released and the TEMPSC could not be lowered.
In the event of an evacuation, the installation could not have been abandoned.
- Hydraulic system and nitrogen accumulator pressure were checked every 6 months under a planned maintenance regime, but not during weekly, bi-weekly and monthly planned maintenance.
- The accumulator was not fitted with a gauge or any means to monitor the pressure within the system between checks.
- Whilst the installation had planned to execute change to the system to include a pressure gauge, this had not yet been completed.
Good Practice Guidance
- Operators should ensure that any accumulators fitted to TEMPSC brake release systems are frequently monitored to ensure they are in good condition, and filled to the appropriate pressure at all times.
- Operators should assure themselves that any single point failures within TEMPSC systems are subject to Failure Mode Cause and Effects Analysis and that the outputs from these analyses are addressed.
- Operators should assure themselves that personnel tasked with maintaining such systems are assessed to a recognised standard which is aligned with their competency requirements.
- Do not assume facility original design aligns with current good practice or manufacturers recommendations.