IMCA has received a report of an incident wherein a ‘banana sheave’ roller weighing 4.5kg came loose during operations. It fell some 24 metres from the derrick and hit the drill floor. Nobody was injured.
The immediate cause of the accident was identified as being that the bolts which attached the rollers to the sheave had loosened.
The underlying causes were noted as:
- insufficient design;
- insufficient maintenance;
- lack of documentation and drawings describing that the sheaves should be function tested;
- insufficient description of responsibility for involved personnel;
- insufficient maintenance management and follow-up relating to lifting equipment.
The following points were noted:
- Lifting equipment should be examined and valid certificates for equipment in use should be presented;
- Inspection and maintenance should be performed on all sheaves that are in operation, with nuts and bolts inspected;
- All bolts on rollers should be fitted with protective pins to stop the bolt from loosening;
The contractor’s planned maintenance management system in place is to be reviewed accordingly.
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