Jun 082008
 

MSF advises crane sheave check

Following an accident on 22nd May, 2008, caused by the failure of sheaves to rotate, Marine Safety Forum has recommended  that chief engineers or other competent persons on vessels equipped with a model of Hydralift cranes and similar should check for any signs of wear that would indicate a potential failure of the sheaves to operate as designed.

MSF recommeds that these checks should be daily until the cause of the failure has been established by the crane manufacturer. Any defect found should be reported to the crane manufacturers.

All vessels with cranes that regularly operate Subsea should check sheave integrity and visibly check rotation of all sheaves and should be aware of how quickly a failure of this nature could occur particularly when operating with heave compensated systems.

In the incident the vessel crane was involved in operations where a 20t clump weight was suspended from the crane main hoist wire. The seabed depth of the field was in the region of 1600m. It is not known to what depth the crane was deployed at the time of failure though it is
believed there could have been in excess of 1400m of wire rope deployed.

The crane in operation was a Hydralift Offshore Pedestal Crane Articulated Box Job Active
Heave Compensated. Model OC3432KSCE-(40-150)-(30-11)(21)(10-32). Immediate investigation identified the failure point of the wire rope to have been at the second sheave of the knuckle boom.

Subsequent inspection of the sheave has identified significant damage that would be consistent with the sheave failing to rotate during the operation of the crane. The resultant wear on the wire rope is potentially the cause of the rope failing.

The crane was installed in 2006 has been in operation for no more than two years. At ther time of the accident it was operating with the heave compensation engaged at the time of the failure.

Adises MSF:

• All vessels that are operating cranes of the same model or similar should carry
out as soon as possible an inspection of crane sheaves to identify any signs of
wear that would indicate a potential failure of the sheaves to operate as
designed. This inspection should be carried out by the vessel Chief Engineer or
other competent person.

• These checks should be daily until the cause of the failure has been established
by the crane manufacturer. Any defect found should be reported to the crane
manufacturers.

• All vessels with cranes that regularly operate Subsea should check sheave
integrity and visibly check rotation of all sheaves and should be aware of how
quickly a failure of this nature could occur particularly when operating with heave
compensated systems.

Source: MSF Safety Flash 08-24

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