Using electronic scales in a pressure vessel
Using electronic scales in a pressure vessel
(OP)
We want to measure the rate of water absorption of rock samples placed in a flooded pressure vessel.
Traditionally to do this you would have to depressurise the chamber, open its top and weigh the sample while it is still suspended in the water. We are looking for a way to skip having to open the chamber by having the scales permanently inside the pressure chamber.
Does anyone know of electronic scales that function in pressure vessels? All of the suppliers I have contacted have been unable to help.
Ideally we would be looking for scales with a 2 kg capacity, 0.1 g resolution and able to function at 5 atmospheres of pressure.
Thanks in advance!
Traditionally to do this you would have to depressurise the chamber, open its top and weigh the sample while it is still suspended in the water. We are looking for a way to skip having to open the chamber by having the scales permanently inside the pressure chamber.
Does anyone know of electronic scales that function in pressure vessels? All of the suppliers I have contacted have been unable to help.
Ideally we would be looking for scales with a 2 kg capacity, 0.1 g resolution and able to function at 5 atmospheres of pressure.
Thanks in advance!





RE: Using electronic scales in a pressure vessel
RE: Using electronic scales in a pressure vessel
RE: Using electronic scales in a pressure vessel
http://www.sensing-systems.com/products/underwater...
RE: Using electronic scales in a pressure vessel
Suspending the sample on a wire that passes through the wall of the pressure vessel would require some pretty good seals and I would be worried about what effect they would have on the recorded weight.
Weighing the whole pressure vessel introduces some interesting problems as well. The pressure vessel, water and sample would have a combined mass of 20-30 kg so as you say it might be hard to find some scales with 0.1 g resolution at that mass. It would also mean that I need to modify how I intend to pressurise the pressure vessel - I was going to use an air compressor to pump air into the flooded pressure vessel. That would mean that I would have a fixed volume of water so the total weight shouldn't change, the water would just be moving into the pores of the rock without entering/leaving the pressure chamber.
Underwater load cells is a great idea - I had only tried the digital scales manufactures. I have now contacted a few load cell suppliers and I am waiting for their response.
RE: Using electronic scales in a pressure vessel
Cheers,
gr2vessels
RE: Using electronic scales in a pressure vessel
RE: Using electronic scales in a pressure vessel
RE: Using electronic scales in a pressure vessel
Forget about suspending wires or rods passing through seals- weighscales are a force balance, and friction is the enemy. Friction such as that occurring through a pressure/vacuum seal will destroy the measurement.
It's possible to do weight measurements inside a pressure vessel- possible, but NOT EASY. You can't just pop a commercial weighscale into that environment and expect it to function properly. You do need to get power and signal in and out of the vessel through sealed connectors or wire passthroughs, but that's the easy part. You need to concern yourself about unbalanced forces on the loadcell parts etc. which are normally exposed to the atmosphere on all sides. Lots of work and suffering, none of it having been done for you by the weighscale vendors. We've done it, successfully, to high accuracy, inside a vessel pressurized with hydrogen to 600 psig, but it's a big job and not to be undertaken lightly.