Regulator and fittings: not quite a welding question but I hope you can help

[Cobbler]

I can't remember the exact figure, but the first stage of a two stage diving regulator supplies air at about the same pressure as a good compressor. You can run windy tools from them, it's slightly safer than trying to use an electric drill underwater.

Dependant on the make, but most are in the region of about 125 to 150 psi from what I recall from my diving days. I’ve still got the remains of a Poseidon Cyclon 300 in the Shed I think, hoses all rotten, but can’t quite face bunging it in the bin.

 

[hotponyshoes]

I can't remember the exact figure, but the first stage of a two stage diving regulator supplies air at about the same pressure as a good compressor. You can run windy tools from them, it's slightly safer than trying to use an electric drill underwater.

When I was diving 10bar was the standard outlet although they all had at least 1 HP port for a contents gauge

 

[hotponyshoes]

I need two operating modes:
- main one is 10 bar for quite a short period, no more than a few minutes,
- secondary one is 5 to 8 bar over a 30ish minute period.

Might be worth pricing up both, a bottle to run the 10bar and then a smaller silent compressor for the other stuff?

If you get a dive bottle get a steel one not alloy. The alloy ones are a lot easier to carry up stairs but if I remember rightly they needed testing more often than the steel ones. Dont remember what the testing cost but it might be worth checking as it might make the rental option more attractive?

 

[Cobbler]

Could you run it on CO2? Being as it’s liquid in the cylinder, effectively you get a lot more for your money, I don’t know what the expansion ratio from liquid to gas is, but it’s quite considerable. A rent free bottle isn’t a lot of money, or use a CO2 fire extinguisher.

 

[Robm]

Hehe, air wired to the loft, another interesting possibility. Unfortunately it's the air tank of the current compressor that the leak has sprung from.

On the turbines, it's kind of a long-term experiment thing, all the gory details here: https://www.meades.org/misc/all_things_nikola/all_things_nikola.html.

 

[Robm]

CO2 is an interesting idea: I guess that would have quite a low exit temperature though? Might cause problem with my 3D printed plastic parts.

 

[Cobbler]

If using a diving bottle & the first stage of a demand valve, make sure you fit a safety valve on the low pressure side. All modern second stages to my knowledge are downstream valves, this acts as a safety valve as it lifts off its seat. If there is any leakage on the first stage, without a safety valve you could have bottle pressure build up on the low pressure side. There can’t be many of the old upstream valves with a safety valve on the first stage around now like the original Snark, remember them anyone?

 

[Kram]

Hehe, air wired to the loft, another interesting possibility. Unfortunately it's the air tank of the current compressor that the leak has sprung from.

On the turbines, it's kind of a long-term experiment thing, all the gory details here: https://www.meades.org/misc/all_things_nikola/all_things_nikola.html.

Interesting stuff.
I would want a compressor for that.
CO2 is a bad idea in an enclosed area, it only takes a few % to have bad effects without displacing much normal air.