In article .com,
says...

I will drill a few test holes as suggested earlier to get an idea of
what may be inside and relieve any possible differences in pressure if
it is a double wall. If it turns out that there is some insulating
material that can not be removed or has a temperature problem then it
may not be possible to use the tank.

Most liquid cryogen tanks are double-walled with a vacuum jacket.

If so then there will be a pumpout bung someplace in the vacuum
jacket and you could pull out the plug and vent it before working
on it.

Chances are it is superinsulated (alternating layers of aluminized
mylar and open weave nexus cloth) and it may have intermediate
thermal shields attached to the neck of the inner vessel.

The neck may be made of G-10 fiberglass.

The mylar will stink and maybe catch on fire if you try to cut
through it. If I were doing this, I would a) purge the vessel
with an inert gas a few times b) vent the vacuum jacket up to
air, c) cut around the top of the outer vessel.

At this point the inner vessel can be lifted out, with all the
insulation still on it. You will be left with the larger, outer
tank basically bare.

The inner tank can be gotten at by unwrapping all the insulation
and heat shields, if any.

Jim


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