@iain/hsm even if I can get basically a new old stock unit for about $2000USD and have my electricians fit a VFD to it?
How is that going to help? You are already in USA running at 181RPM it's our lot that needs the VFD drive to jack our speeds up from 150 RPM to match your 181 RPM at 60Hz I can't see the point of going any faster than 181 RPM except maybe 200 RPM. But the cost to do that is a diminished return for the slight increase in flow rate.
Only if you want to reduce the speed of the booster/compressor to match your generator flow rate, but again a much cheaper option would be just to run the oxygen generator flat out and let the discharge pressure decay match the HP booster. There comes a point where they will match as the discharge pressure from your generator reduces to match the charging rate of the booster, the pair will end up at a matched position but at a reduced flow rate. (if its designed to do this of course)
I did this with a modified 3 stage SA block and a modified electric oxygen booster as in the photo below, worked well in that you could deliver a 16 scfm charging rate with a small 1.5HP motor on the booster to the customer, filling on the fly directly to his cylinders quick and fast then later you could fill the intermediate bank back up to 2000 psi at your leisure using a 3.7 Kw motor on the HP compressor. The 2000psi intermediate bank was also used as the source supply drive gas through the booster.
To fully charge the main HP storage bank to 5000psi (not oxygen) you ran the intermediate bank through the booster and to gas route to a medium pressure 3 cylinder 2000 psi bank all running single phase. Further when working both at the same time a reduced flow rate was achieved from 16 scfm to 7 cfm when both the compressor and bank were both balanced using pressure decay to match both performance rates.
From memory the design philosophy was tad more complicated but for this post the intermediate bank (for the booster supply gas could be made 50/50 by continuous blending from ambient pressure though the compressor thereby scavenging all the oxygen (and helium) in storage down to zero.
Then either the pure oxygen or pure helium banks could be routed to the storage for make up gas or oil free HP air used to dilute the mix.
Or when making any other nitrox mix to the main storage banks say 32-36% at 300 bar you used the intermediate bank with anything in and use either the booster or the compressor to top up the percentage or reduce down the percentage with either running the oil free compressor or booster.
It was a basically a poor mans "Mix Maker" with a "waste not want not" advantage in that all the bought in pure gas was used to make up anything you needed either for storage or on the fly. And all running single phase (or 3P) with minimum power and all bench mounted well off the dirt dust and rubbish blowing about on the floor LOL
I should add:
Note that all the HP gas pipework in the 1/4" size is not in stainless. It's important.
16 scfm is too high a gas velocity for oxygen at high pressure unless you want to use the gas lines to heat the building up with I guess.
The only stainless tube you see are static pressure lines to the HP gauges these are OK in stainless but note it's in 1/8 tubing to avoid ignition in the event of a bourdon tube failure, dead heading the gauge movement or when you turn on and blasting the delicate movement with a massive pressure shock load and the requisite adiabatic shock.
Heck this is a long process, Oxygen Hackers Handbook for Professionals I guess.
Or what happens when you let the old gas monkey loose with a pair of pipe benders
and a roll of pretty green electrical tape. ROFL
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