Gel Lift Bag

[Bombay High]

A new type of lift bag is being tested in Aberdeen right now. It is surface supplied gel filled. This is one of the most exciting new developments in the salvage world in a while. The gel is incompressible, so you can maintain a completely even lift from depth, maintaining the same ascent rate, or even keep a load of several tonnes neutral and it will stay neutral at any position in the water column, and capable of being handled by a single diver in great safety.
Cant wait to get a chance to use it.

 

[Rich Keller]

The gel part is new but the exact same performance could be had by using any liquid that is lighter then water. What is the gel made of exactly?

 

[Darol]

Silly .....
probably a carcinogen to be found out after it's too late..... aka Agent Orange.....

 

[Thalassamania]

My understanding is that the gel is half the density of water, thus making the volume requirement about twice that of a normal air filled lift system. I'm kinda interested in another application, adding inherent buoyancy to submersibles and even scuba rigs (esp, some HP steels) ... that lift capability beats the bejesus out of syntactic foam.

 

[Hickdive]

What is the advantage of this over simply using the correct volume of lifting bags?

For example, if I attach a 6 litre lifting bag to an object that weights 5.5kg in water then it will be 500g positively buoyant at all stages of the lift - expanding air on ascent will simply spill from the bottom of the bag (not allowing for salinity etc. but you get the idea)

Why would you need a diver to control the lift anyway? Inanimate objects don't get the bends. I can lift a 50 tonne object under perfect control with a 1 tonne SWL crane and 49 tonnes of lifting bags.

The only advantage I can see is that the gel, being incompressible, would be able to be pumped down to depth with a relatively lightweight pump and provide buoyancy quickly rather than using a heavy compressor to actually compress gas to the ambient pressure at the depth of the lifting bag.

 

[Thalassamania]

It can be hard, even impossible, to get a bag that is perfectly sized to the task.

 

[Bombay High]

The gel part is new but the exact same performance could be had by using any liquid that is lighter then water. What is the gel made of exactly?

Don't know the composition, but have been told that it is 60% lighter than water.
I will be in Aberdeen next month and will try to get more details.

---------- Post added April 14th, 2012 at 09:05 PM ----------

What is the advantage of this over simply using the correct volume of lifting bags?

For example, if I attach a 6 litre lifting bag to an object that weights 5.5kg in water then it will be 500g positively buoyant at all stages of the lift - expanding air on ascent will simply spill from the bottom of the bag (not allowing for salinity etc. but you get the idea)

Why would you need a diver to control the lift anyway? Inanimate objects don't get the bends. I can lift a 50 tonne object under perfect control with a 1 tonne SWL crane and 49 tonnes of lifting bags.

The only advantage I can see is that the gel, being incompressible, would be able to be pumped down to depth with a relatively lightweight pump and provide buoyancy quickly rather than using a heavy compressor to actually compress gas to the ambient pressure at the depth of the lifting bag.

We dont always know the weight of the object to be manipulated. keeping an object neutral in the water is great for several applications.
You would need an exact sized bag, for it to vent consistently on ascent. We also dont always use open bags for lift.
It is preferable to do a lift under control for several reasons ... none of them involve inanimate objects getting embolisms.

 

[ablebob]

So to lift our "50 ton load" we need to buy, ship, store, handle and dispose of 83.3 tons of this stuff (at 60% of the weight of water being displaced) ? We would also need 40% more bag capacity, correct?

Conventional lift bags are a cheap & easy way to lift big loads. It sounds like this takes the cheap & easy part out of the plan.

It may offer an option in limited situations.

When a lift bag leaks or ruptures (and they do) nobody has ever had to clean up a "air spill"

 

[Bombay High]

True enough. This is obviously not the solution to all lifts. Almost all pioneering work was met with similar scepticism. However, I feel if this technology is pursued and refined, it will have it's place in the repertoire of tools we have at our disposal to make our work safer and easier.