An incident during which a vessel’s main crane started behaving in an uncontrollable and potentially hazardous way, risking the health of six people.
The incident
When starting up, a vessel’s main crane started behaving in an uncontrollable and potentially hazardous way. The block and hook were hoisted up to the sheave when the auxiliary wire parted due to the forces applied.
The block and hook were ejected forward until they hit a stair railing, approx. 4m forward of the sheave. Then the block and hook fell approx. 3m down to the deck, and bounced before coming to rest.
Six people were involved in the operation and found to have been at high risk had conditions been slightly different.
Two crew were involved in un-hooking; three were in a nearby deck workshop with no barrier in place between them and where the block and hook landed, and the crane operator was in the crane cabin.
When realizing something was wrong, the two personnel on deck quickly vacated the immediate area. No one was harmed.
Probable cause
The main crane auxiliary line encoder unit was damaged due to water ingress, and gave the wrong input to the crane, causing uncontrolled movements of the auxiliary wire as the crane was started up.
In addition:
- The door to the deck workshop was open with no barrier in place to the main deck, leaving the three persons in the workshop exposed to the risk of walking into a hazardous/line of fire area;
- There was also an additional risk for personnel not part of the operation to have accidentally been hit, as there were no barriers in place at the stair from the mezzanine deck to the main deck.
Lessons learned
- Barriers should have been in place to prevent personnel from accessing the area;
- Crane’s start-up routine was not optimal leaving personnel exposed to uncontrolled movement;
- The design of the old encoder did not provide drainage possibilities. The encoder was fitted in a sealed component housing and onboard vessel crew maintenance was not permitted.