A crane was lifting a 22,000lbs (10 tons) load. The safe working load (SWL) for the crane was 22,259 lbs.
The operator was swinging the load and booming down to place the basket on the pipe rack.
The designated signal person instructed the crane operator to boom down and hold the load.
The crane operator noticed the boom and load moving up and down.
The fast line slipped 4ft (1.2m), hitting the basket below and damaging a new, uninstalled production riser tensioner control panel.
Why did it happen?
The auxiliary hoist static brake was released.
The counterbalance valve spool was feeding through and the check valves were jammed open.
The crane’s alarms were ignored. The alarms often sounded, which led to a normalisation (they were ignored, thought to be unimportant).
Other factors could have indirectly contributed to the accident:
- The load was very close to the SWL.
- The hydraulic motor and counterbalance valve assembly have been in service for 17 years (longer than originally thought).
- Because of the configuration, it was not possible to be tested whilst in situ.
What did they learn?
Ensure all alarms are investigated and workers are aware of their importance.
Check the age and service life on critical equipment. Ensure the equipment is tested regularly.
Check the manifest weight matches the actual weight of the load (it can differ).
Discuss manifest weights prior to lifting operations.
Ask yourself or your crew
How do you know if a reoccurring alarm indicates a critical part failure?
Which alarms should initiate a stop work?
Should alarms and warnings be discussed after each shift?
How can you check the age and service life of critical parts on your equipment?
How do you know if your equipment has been tested or not? Are you aware of any critical parts that can’t be tested?
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A crane was moving a heavy load onto a pipe rack. When swinging the load into place, the boom was moving up and down. The fast line slipped, causing the basket to fall onto a basket below.