International Marine Contractors Association (IMCA) provides lessons learned from two incidents in which something went wrong owing to failures in the maintenance process.
Furing lowering of a lifeboat, a small shackle broke. The shackle held the upper sheave guiding the brake release wire, resulting in the sheave falling down on top of the lower sheave. This caused the brake handle not to fall into brake position, with the consequence that the lifeboat did not stop lowering but kept on going down.
The situation did not get out of control: the officer on deck took over control and applied force on the brake handle to stop the boat going any further down. There were no injuries in either incident.
Investigation showed that that the brake release wire drum was stuck/not turning, apparently due to there being an excessive amount of paint (see illustration) applied during the recently done maintenance. Once the paint was removed, the drum could be easily moved by hand.
The main hoist hook block overshot the highest position alarm and ran into the sheaves from the main runner under the jib. The jib was lifted by the force of the main runner and the crane stopped automatically when the slack wire alarm of the topping wire was activated.
Investigation showed that one of the runner sheaves underneath the jib was bent slightly and unable to move freely. During the inspection of the high hook alarm, it was discovered that the flat bar in front of the sensor was not moving. It was stuck in place because of dry paint from maintenance that morning.
Further, the crane operator did not pay sufficient attention when working near the limits of the crane, not looking up to the hook.
In light of these incidents, IMCA informs that the following actions have been taken in order to ensure that similar situation will not happen in the future:
- The damaged sheave was reshaped. Thorough examination of the sheave surface and inspection by means of dye penetration testing showed that there were no cracks;
- Ensure close monitoring the crane movements after each order given and when working near any of the crane limits;
- Test alarms after maintenance on the crane;
- After maintenance/painting check that all equipment parts are still movable and fully operational.