Context - I run an u-sun XB30 booster.
Disclaimer… I claim no expertise, only a strong desire to dive as much as I can stretch my budget - and if I don't take the time to put things in writing, I find it much harder to recall and structure my thoughts.
I have purchased the following compressor to drive it when at home
Stanley Air Compressor Silenced 2.75HP 50 Litre tank
www.supercheapauto.com.au
(more filtration work underway, its really needed when boosting into S80s and its running pretty much continuously)
Here are some notes on how to drive a booster I put together when sharing thoughts with a mate. I've also written up some on single/double/two-stage etc., collated stuff, its not my work! but I'll post that some time too.
Again, these were some of my thoughts at the time, happy to take constructive feedback.
So, notes...
To get a cycle out of a booster, you need to fill its chamber to a given pressure. That means a given volume of gas at at suffient pressure to get that chamber to the tripping pressure. Its a max of 8 bar in the small u-sun range. The required trigger pressure will vary throughout the fill as the relative pressures in source and target cylinder change.
So, it’s not just pressure you need, but volume, or flow rate, to fill that chamber in a given time and cause a cycle.
In the context of "shop" compressors, really stress you need a compressor that *operates* in the 8-10bar range. So keep an eye out for working pressure as opposed to max pressure.
An 8bar max compressor will cut off at 8bar, but only kick back in at 6 bar. If you need 7 bar for that next booster cycle, you're stalled. You could add a secondary bleed, but that's another story.
More detail.... the tank acts as a buffer, and only starts refilling at 6bar (stopping at 8). So you can't drive when you need more than 6bar because the compressor won't start if the tank is above 6bar. The u-suns will need more than 6bar to fill a small butt cylinder with o2.
Again, you need a 10bar max that starts to refill at 8bar.
This also plays into "Duty Cycle", that is the time a compressor can run before it needs a rest.
Sure, a “buffer” cylinder helps and it’s the same as a bank, but it’s also really helpful to generate more gas at a given pressure to keep things moving so you don't fall asleep in the outhouse. Volume of air delivered is often referred to as FAD, or "Free Air Delivery".
My use-case sees me filling “2l ally butt cylinders” to 200bar. I don’t need a big compressor to drive my booster, and filling slowly is also a bonus. Far less than one cycle a second, possibly as much as 2-3 seconds per cycle. I’ve bought a small garage type compressor for AUD400, the type often used to drive a single air tool (nail gun etc). This is a 2.5hp, 50l.
A few other peeps I know use belt-drive air compressors. These peeps do large boosting jobs, and like to “scavenge” as much of the source gas as possible (helium is expensive huh).
These larger "shop" compressors are still cheap-ish, but start at the $7-800 range, and can put out 8-10bar at a much higher *flow* rate (total air volume at given pressure) than the smaller one I’m buying, so you'd not have to wait around forever boosting into an S80 from a half empty O2 bottle.
You can also get these larger flow rate “shop” & belt drive compressors in electric. Not sure myself of all the trade offs of these higher powered ones, probably same as any electric v Petrol engine argument though.
Either way, these will keep up with larger S80 boosting needs so you don’t have to empty banks nor wait on a smaller (cheap!) one like I'm buying.
There are a few oil traps and “dryer” options on Amazon etc. to help clean up the output from these cheaper compressors which will protect your booster’s internal bits on the drive gas side.
All up, much cheaper than running a scuba-grade air compressor to drive a booster.
