Emergency diver lifting system has yacht racing to thank

Space in a dive unit can be limited, so Harken’s DRS fits the bell. Photo: Stork Subsea Space in a dive unit can be limited, so Harken’s DRS fits the bell (Photo: Stork Subsea)
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Diver recovery is a meticulously investigated subject but Andy Ash-Vie of Harken admitted it’s called for improvisation along the way.

“A chap phoned me up last year wanting to buy one of our winches. When I asked what he wanted it for: he said - pulling divers up into a diving bell. The next question was the obvious one- Do you have room to swing the handle fully?”

On reflection the answer was, it seems, ‘No’ – although a partial movement was just about achievable. Mr Ash-Vie suspected a winch was less than ideal, but there was obviously a pressing need and evidently more to this request than first met the eye.

It transpired that a diver fatality in the North Sea had caused a revision of accepted practices, and the standard tackle solution for getting injured or unconscious people back to safety inside the bell had been found wanting. So the diving fraternity was on the hunt for an alternative.

But Mr Ash-Vie was certain they were overlooking a more straightforward answer, so within the hour he had videoed himself lifting his own body weight on a quickly rigged up 6:1 tackle in the Harken workshop – tackle originally developed for sailing boats. However hastily improvised, the recording demonstrated that this kind of system really could bring the combined weight of unconscious diver, suit and cylinders up in a vertical lift from the moonpool. Most importantly, it would also be achievable even given just one man operating the system from inside the cramped environment of a dive bell.

So, why does this tackle work better than other solutions? “It’s a combination,” explained Ash Vie. Firstly, the 6:1 ratio has clear advantages over the other, more common 4:1 or even 2:1 rigs which make much harder work of lifting a potentially helpless, 150kg load. Further, the central sheave is ratcheted to hold the weight on the line without dropping – a characteristic enhanced by the cam cleat, lending efficiency to each upward movement. Lastly, usability is significantly improved by a bearing arrangement designed to minimise the system’s inherent friction.

Bring it all together, “and things that weren’t possible with standard equipment became possible with Harken kit”, said Mr Ash-Vie.

The new diver recovery system was soon picked up and taken almost directly to an IMCA committee meeting which decided that it provided the necessary answer.

As a result, “we’ve recently been selling that tackle system all around the world” explained Mr Ash-Vie, “supplied set up for operation with tamper-evident terminations, proof tested and given the necessary certification before it goes out”.

No winches needed.

By Stevie Knight

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