C-25 Transfill
We've all experienced the problem: bought or leased the biggest cylinder possible, because of the economics, but wished for something smaller to be a bit more portable. I picked up an 80 cf helium cylinder (empty) from Craig's List- same valve as shielding gas, still in hydro date, locally these are owner bottles. Then stopped by the McMaster Carr site to pick up parts for a transfill hose.
First thing I did was draw a vacuum on the bottle with a venturi vacuum pump. The Harbor Freight model shown in the pictures is for HVAC use but the fittings match typical compressed air fittings- the clear vinyl tube in the picture is collapsed due to the vacuum but the braided hose is not.
Next I attached the transfill hose- tight on the donor side and loose on the fill side, and gently cracked the supply valve to purge air from the hose, to avoid contaminating the shielding gas. Then tightened the nut and gently opened the supply valve. A few minutes to let the pressures equalize, closed both valves, and done.
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