Air Lift Bags for Marine Salvage

Open bottom air lift bag commonly used for marine salvage

Marine salvage involves recovering a ship and/or its cargo from the seabed following a shipwreck or other maritime accident. Obviously, ships and cargo are heavy objects which cannot be recovered without specialist equipment and knowledge.

Underwater air lifting bags are specifically designed for the recovery of underwater objects that need lifting to the surface. They can also be used as static buoyancy in underwater engineering as they only need a single attachment point and are stable and easy to handle underwater.

Air Lift Bags

Air lifting bags are available in various designs and capacities, so that salvage operators can choose the appropriate level of buoyancy required to lift objects in a controlled fashion. For recovering heavy objects, such as a ship, multiple bags will be necessary to provide a balanced and controlled lift. This is important as objects that are lifted too quickly can reach the surface out of control, posing a risk to the operators and the vessel being salvaged.

Closed or Open?

There are two basic types of lifting bag:

• Closed air lifting bags typically include a safety valve that allows air to be released for a steady, controlled ascent.
• Open bottomed air lift bags work differently as their open bottom allows expanding air to vent freely during an ascent to the surface as pressure decreases.

For this reason, and the ease of handling, open bottomed air lift bags are usually the preferred choice for marine salvage. Their strength, ease of use underwater and predictable behaviour make them the most effective and safest option for most marine lifting operations.

Salvage of the Jean Ricciardi

When the trawler Jean Riccardi suffered a power failure, flooded and sank near the port of Sete, on the French Mediterranean coast, twelve open bottom air lift bags, capable of lifting 20 tonnes each, were used to complete the salvage operation quickly and safely.

Dunkirk ‘little ship’ Recovery

Skylark XI was one of the fleet of ‘little ships’ that rescued Allied soldiers from the beaches of Dunkirk in 1940 in Operation Dynamo. But for the last two years – since the 70th anniversary of Operation Dynamo – she has been lying on the bed of the River Leven at Balloch in West Dunbartonshire.

With the help of the Royal Navy Clearance Divers the Skylark IX was successfully re-floated on the 18th of October.

Skylark salvage – image from http://www.heraldscotland.com

Using inflatable buoyancy bags the Royal Navy divers from the Faslane base on the Clyde undertook a painstaking 12-hour operation to refloat her. They had to abandon their efforts after the first day but eventually the last of the water was pumped out and the successful operation was completed.

The Skylark was one of the smallest of the “little ships” which responded to the call from Winston Churchill in 1940 to rescue the Allied forces trapped on the beaches of Dunkirk. Although her capacity was 90 passengers, on each of the four return trips into Dunkirk she brought out 150 exhausted and wounded soldiers .

Seaflex donated six, 2 tonne Inflatable Buoyancy Units with airlines and manifolds to use in the operation.

STV News article and News video footage on the first day’s attempt.
The Scottish Herald article and images.

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