Dropped Object from Crane Boom Tip Causing Injury to IP Foot

Description of Incident

During normal platform lifting operations, under no load, an object fell from the crane boom tip, descending a height of approximately 20m before deflecting off a container and striking the IP on the foot who was situated approximately 5m away.

Subsequent investigation determined the dropped object to be a rope sheave guide bar (Weight: 1.03Kg) that had become detached from the boom tip due to failure of the nylon locking nut. On further review, it was found that the nylon locking nut was badly corroded and had been removed during recent maintenance operations and then re-used as a temporary measure until a replacement nut could be sourced. The subsequent operation of the crane introduced sufficient dynamic loading to loosen the nut, resulting in it falling from the crane and allowing the rope guard bar to fall to deck.

The drops calculator showed that a direct impact of the object from this height could have resulted in a fatality.

Good Practice Guidance

• Maintenance tasks not to commence until an inventory check of all consumables, parts, tooling, and procedures has been completed.

• Nylon locking nuts are an accepted and well-used form of secondary retention. It must be noted that they are designed for single use only, and re-use can compromise the integrity of the component when used as a means of secondary retention.

• Refer to https://dropsonline.org/for further information and guidance.

• Temporary solutions must be risk assessed and approved under an Operational Risk Assessment (ORA) or equivalent measure with a time-bound period to rectify.