Incident Report

Subject:                    5 tonne Bobcat mini-digger arm failure    

Date of Email reporting Incident:    16/02/2003

Report Detail:

At approx 11.30 on 10 January 2003, Construction operatives were using a new 5 tonne Bobcat mini-digger to remove 3 metre sheet piles from a completed cable duct excavation prior to back filling. During the morning the operatives had successfully removed approximately 20 sheet piles using this equipment. The sheet piles were fitted with a pile extractor connected to a shackle. A 2 tonne lifting strop was placed around the mini digger bucket and was in turn connected to the shackle. As the sheet pile was extracted from the clay the mini digger arm had to be extended fully in order to clear the side of the excavation and remove the sheet piles. As the sheet pile cleared the clay the mini digger arm went to it's full extension and the hydraulic ram sheared. The sheet pile, bucket and mini digger arm fell down into the trench. The contract company were maintaining an exclusion zone in the line of fire so there were no injuries to personnel.

Findings:

• During the review it was agreed that the removal of sheet piles using a mini digger Bobcat was an accepted practice.  The 5 tonne AMS Bobcat mini digger was brand new and had worked for less than 50 hours.  Immediate actions and underlying causes:
• As the mini digger was being used to lift materials  - local management reported the incident under RIDDOR as a failure of lifting equipment
• The equipment was quarantined and area taped off
• The Hydraulic ram to be sent for metallurgical failure analysis.
• The AMS Bobcat hydraulic system relief pressures to be checked.
• AMS Bobcat to issue a report to ConocoPhillips
• Incident to be communicated to all Contractor companies detailing learnings