A member has reported a number of incidents in which a luff ram has parted at the clevis. The first incident occurred during a load test of a remotely operated vehicle (ROV) system. During recovery of the ROV whilst latched into the snubber, another luffing ram on the same launch and recovery system (LARS) parted in the same manner. Subsequently, during an ROV launch of the same system, the replacement starboard luffing ram parted at the clevis. There were no injuries or damage to equipment.
An investigation identified the following:
- No evidence of anti-seize compound or other corrosion inhibitor in the rod end threads or on the rod threads;
- Dead space between rod eye and cylinder rod allows generation and collection of moisture/condensation.
- Excessive corrosion of each clevis (rod eye);
- Dimensional check shows clevis to be deformed.
The company notes that root cause analysis for multiple failures is on-going; however the causes of the corrosion are in part attributable to a missed step during the service and maintenance of the cylinders.
The following actions were taken:
- Updated planned maintenance system with manufacturer’s recommendations for inspection of cylinder rod eyes:
- while A-frame foot is approximately 1″ from the hard stop so the luff cylinders are in tension, use a feeler gauge to determine if there is any gap between the faces of the rod eye and rod. There should be zero gap. If there is a gap, the cylinder should be removed, rod eye removed and inspected
- the counterbalance valves should be verified that they are adjusted properly
- perform a visual inspection of the A-frame operation to focus on cylinder timing or excessive lateral movement
- perform visual inspection of rod eye surface for excessive signs of corrosion at point of rod entry.
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