Towing Hook and Quick Release
Tug towing hooks: geometry, the load test to bollard pull, the upward angle release test, remote release, and why casualties find them unusable.
A towing hook takes the towline on a tug that does not work off a winch drum, and its quick release is the fitting the crew reach for when the tug is being girted. DNV requires the hook to be load tested with a load equal to the vessel’s bollard pull, and the quick release to be tested against a towline direction 60 degrees or 45 degrees above the horizontal, which is the geometry that matters once the tug is heeling.
The casualty record is unflattering. ATSB investigation MO-2011-005 into the capsize of Adonis at Gladstone on 11 June 2011 found that the crew could not release the towline using the towing hook’s quick release before the capsize, and MAIB report 17/2024 concluded that given the rapid capsize the crew of Biter were unlikely to have had time to operate the emergency tow release. The fitting is required and it is not a reliable last line of defence in the seconds available.
The full article will cover hook types, the release mechanism and its actuation forces, remote and bridge release, operation during a blackout, load testing and survey, and the arrangement of H bitts and towing points around the hook.