I've been looking at solutions to compress gases and getting stunned by the cost and maintenance requirements of existing systems to fill cylinders (whether for SCBA or chemical storage) to 2000-4000psi: The cost of entry is over 4 figures, with commercial systems like those used in fire stations and SCUBA shops running into 5 figures. And, as far as I can tell, they are all direct mechanically driven multi-stage pneumatic pistons.
Meanwhile, sitting in my garage I have a manually-driven hydraulic bottle cylinder that can lift 20 tons, and typical hydraulic systems circulate hydraulic fluid at 5000-10000psi.
So I have in mind a very simple gas compressor: a single piston sealed on both ends. On one side it is driven by a single hydraulic pump line. On the other are two gas valves: An intake and an output. Operation is simple:
- Hydraulic pressure shut off.
- Gas intake valve open.
- Hydraulic flow reversed until piston has drawn in the maximum capacity of gas.
- Intake valve closed.
- Hydraulic pressure run until piston has reached maximum compression
- Output valve opened (if not one-way and hence automatic), then closed once pressure equalized with output cylinder.
If the piston lacks the compression ratio to reach the desired psi, then the charged cylinder is switched to the input line and another cylinder to the output.
Am I missing a reason this won't work? Or does it already exist in some form close to this?
If not, where and under what name might I find a long two-sided piston with pressure fittings on each end?