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# Foam Block

## Foam Block

(OP)
Hi All,

I am designing a subsea equipment, which will be using a foam block to make the equipment neutrally buoyant. While we can calculate the buoyant force needed to make the equipment neutrally buoyant in seawater, I have another question.
Suppose the equipment is neutrally buoyant in water at a depth or 100m. But when the equipment goes to a depth of 3000 m, there will be pressure of 3000m of the sea above acting on the equipment. What calculations do I have to confirm that I measure the correct volume of Foam Block for that kind of depth? Thanks in advance.

Regards,

HD

### RE: Foam Block

Basically you need to work out how much it will compress at depth.

One material commonly used for buoyancy subsea is Syntactic.

I think I would contact a supplier like Balmoral. See the link below. They have tables published for their products which might help you. For example, buoy MCMB1 has a buoyancy of 77kg at the surface, reducing to 28kg at 2000m

http://www.balmoral-group.com/balmoral-offshore/im...

### RE: Foam Block

Syntactic foams are often made on site from 3m glass microspheres, and epoxy resin, the ratio of resin to microspheres determining the density and hardness of the foam. Phenolic Micro balloons in epoxy can also be used, but the Micro balloons are softer than the Micro spheres.
B.E.

You are judged not by what you know, but by what you can do.

### RE: Foam Block

Trelleborg specializes in syntactic foams for buoyancy. Glass micro-baloons are used for their relatively high compression strength and modulus. Polymer micro-baloons will not take the pressure at depth. Solid micro-spheres of any type are not used for buoyancy control because then you may as well just use solid materials.

### RE: Foam Block

Apparently 3M has also caught onto this discrepancy They are now calling their hollow microspheres " Glass Bubbles".
B.E.

You are judged not by what you know, but by what you can do.

### RE: Foam Block

syntatic is relatively stiff. that said, if you need to absolutely neutral at 3000m, you have a challenge. depending on salinity and temp, water density will not be constant anyway. Syntec or balmoro will hopefully be able to give you some guidance, though keep in mind, syntactic production is not a precision operation, so allow for a good safety margin anyway.

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