Cause & Consequence
- Moving, flying or falling object
Any Location Type
Lifting, crane, rigging, deck operations
Incident Info Source
Brian Smith, Sparrows Offshore Services Ltd
Specific Incident Equipment
The loss of drive due to grease contamination - and thus hoist up motion on the boom hoist - resulted in the boom going into a free fall descent. The operator initially pulled the boom lever back further in order to try to prevent the boom running away. When this failed, the auxiliary foot (slow down) brake was applied which due to no drive on the boom winch shaft had no effect in slowing down the boom decent. The operator then engaged the boom pawl device in an effort to stop all boom movement. This resulted in 4 teeth being sheared off the boom winch drum. With the boom now reaching critical speed, the RSI (rope speed indicator) detected an overspeed which activated the main brakes stopping the boom freefall motion.
As a result of this incident regarding the loss of control of a boom we feel this bulletin should not just be directed to installations where friction clutch cranes are employed. Other important lessons should be learnt from this incident which some may overlook in the heat of the moment should a similar boom, load or slew motion not react as planned.We advise that maintainers of similar 1st generation friction clutch cranes carry out inspection of the clutch drum assemblies to ensure that any excess grease collecting in drum behind clutch assembly has been cleaned off to prevent the potential for contamination of clutch shoes.Maintainers of similar 1st generation friction clutch cranes should also grease clutch assemblies sparingly to avoid potential of over greasing and thus contamination.
•Advised resident and all ad-hoc operators of similar 1st generation friction clutch cranes in Shell contract of the correct response to clutch failure – “HANDS OFF” controllers and allow them to return to neutral thus allowing main brakes to actuate.Advised resident and all ad-hoc operators of similar 1st generation friction clutch cranes of the correct usage of the boom pawl device, i.e. boom pawl to be utilised as static parking brake and safety device when booming up and not as a dynamic brake. DO NOT ENGAGE BOOM PAWL WHEN BOOM IN DOWNWARD MOTION.we recommend that Manual application of the boom pawl as per the clutch contamination scenario will not apply to all. However, this is just a reminder to ensure that we are aware of its purpose. If fitted, use it as a safety/security devise when:
•Lifting loads at long radii
•Lifting heavy loads
•Lifting the boom out of its rest
•Lifting loads across the deck
•When the crane is parked
•If the crane is under maintenance
•Consider using it when loads are clear of vessels during offload or backload operations.DO NOT ENGAGE THE BOOM PAWL WHEN THE BOOM IS IN A DOWNWARD MOTION
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