Failure of anchor winch shaft

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Alert ID: 
Description of Task: 

937 2 pdf

937 1 pdf

Anchor Handler recovered No 7 buoy on deck at 1535 hrs. She attached her work wire to the 400m pennant and at 1553hrs instructed the winch operator on No 7 to pay out 500m of cable, ensuring that the tension did not drop below 80t as per workscope. The winch operator put the winch into Low mechanical and Medium hydraulic and instructed his assistant to put the locking pins in the gears. The scope prior to commencing slacking down was 715m. At 1620hrs the winch driver reported that the cable was running out uncontrollably and that the Anchor Handler should stop running out as he was putting on the brake. Winch operator and Assistant took cover – one in the anchor winch cab and the other moved off the platform aft, underneath the exhaust, well clear of the winch. The brake slowed the release of the cable which eventually came to a halt. The final scope for No 7 was 1145m. The reason for the anchor chain paying out was the failure of the drive shaft. The drive shaft had sheared close to the NDE bearing resulting in the drive gear being loose at this end which in turn caused the bolts in the tension sleeve to shear leaving the drive shaft and gear free. As the winch was paying out at the time this shaft was bouncing about causing substantial damage to the gear wheel and bearings. There was also damage to the drive gear claw coupling and associated equipment.



Lessons Identified: 

High Level of training and experinece of Winch Operator precluded further extensive damage taking place.


Failed Shaft to be examined by metallurgist to establish cause of fracturePM of winch to be reviewed – possibly increase frequency – have individual item of visual inspection of shaft on PMNDT of Drive Shafts to be carried out at least once per year

Information source: 
Stena Drilling Ltd Dave Thomson
Contact Details: 
Step Change in Safety
Specific Equipment: 

Rolls Royce (Norwinch) Anchor Winch

Incident consequence: 
Not Assigned
Any Activity Type
Onshore terminal
Cause of accident or incident: 
Moving machinery or material being machined