Archive for the inflatable buoyancy units Category

Laying Underwater Pipelines and Cables

Posted in Air lift bags, inflatable buoyancy units on March 4, 2013 by Seaflex

Laying underwater pipelines and cables is fraught with difficulty and would be almost impossible without the use of buoyancy bags. Buoyancy aids make the process of moving and laying underwater objects a much simpler process through the use of a relatively simple technology based on a simple concept.


IBUs used for pipeline buoyancy

The ‘Overpressure’ Principle

Inflatable buoyancy aids are made from flexible materials and become squashed under pressure but expand as pressure decreases. They work on the principle of overpressure. As the bag is lowered deeper into the water, it decreases in volume because the air inside gets compressed and occupies less volume.

On the other hand, as it is raised the air expands and the volume of the bag increases. Buoyancy is equal to the mass of the water displaced by the bag, which is proportional to the volume of the bag. It follows, therefore, that buoyancy decreases as a bag is lowered deeper into the water and increases as it rises up. Using an air hose attached to the bag, more air can be pumped into it whilst in a compressed state. Then as the bag is raised it expands in volume quickly and a huge amount of buoyancy is created. Even a small buoyancy aid can easily lift a weight equivalent to five family cars.

ALBs and ILBs

The two basic types of buoyancy units are ALBs (Air Lifting Bags) and ILBs (Inflatable Buoyancy Units). ALBs are used in operations such as cable floatation where an object needs lifting from the sea bed. They have just one point of attachment, which means that they will remain upright at all times and can be used at any depth. ILBs are used to increase, for example, pipeline buoyancy close to the surface or the buoyancy of any static object just under the water. They cannot be used at great depths and have multiple points of attachment.

Generally, ALBs are the only option when salvaging a vessel or lifting a cable or pipeline deep under water. If an object such as a pontoon or a section of pipeline that is waiting to be laid needs to be floated on the surface of the water, then ILBs are the correct choice. However, there are many complications when working underwater and the choice is not always so simple so it is well worth consulting the experts before starting any work.

Dunkirk ‘little ship’ Recovery

Posted in inflatable buoyancy units, marine salvage, Underwater air lift bags on November 1, 2012 by Seaflex

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.

Little Ship salvage using Seaflex underwater airlift bags

Skylark salvage – image from

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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Unique Maritime Group acquires Seaflex Ltd.

Posted in Air lift bags, inflatable buoyancy units, marine salvage, Underwater air lift bags on June 2, 2011 by Seaflex

Unique Maritime Group

Unique Maritime Group a leading provider of specialized engineering solutions to the subsea and offshore oil and gas industries worldwide announced the acquisition of Seaflex Ltd today (24th April 2011).  Seaflex Ltd.  is a leading provider of marine buoyancy products and water filled test weights. Seaflex’s product range includes, subsea air lift bags, inflatable buoyancy units, WaterLoad test weights, cable and pipeline buoyancy, lifeboat testing ballast bags, yacht fenders and yacht racing buoys.  Seaflex is a BS EN ISO 9001:2008 company, independently certified by Lloyds Register Quality Assurance and its products comply with current IMCA and EC regulations.

Lifting aircraft airframe using air bags

The purchase of Seaflex Ltd., based in Isle of Wight, further strengthens Unique Maritime Group’s strategic goal  to expand its Manufacturing , Sales & Rental operations for specialized products worldwide. “The acquisition is also expected to result in greater efficiencies and significantly increase our market share” said Harry Gandhi CEO of Unique Maritime Group.

Seaflex will continue to operate under the same name & Graham Brading will take over as Managing Director. Mark Board continues to provide valuable support to him as a consultant for next two years.

“The acquisition of Seaflex was a calculated decision and was accomplished through an exclusive negotiation process under the guidance of Pinsent & Masons as legal advisors.” explained  Harry.