1st stage regulator question

[Tom Lucas]

Hi folks

Just looking at 1st stage regulators at the moment and have a quick question as never bought one.

Aside from number of ports/water depth suitability etc is there anything special about 1st stage diving regulators versus say a regulator for welding?

I mean if I connected a welding regulator to my 2nd stage and provided the right psi would it even work? Or is there something fundamental that means it wouldn't.

(Not in the real world - I am not suggesting diving with a welding regulator lol).

 

[broncobowsher]

There are some similarities and some differences. Also have to ask, which welding regulator? A welding regulator for arc welding (MIG TIG) is a flow regulator. Has no pressure, just a regulated rate of flow. But if you are looking as an oxy fuel type regulator they are a little closer to a scuba 1st stage. But even then they are way off in operating pressures. The oxy fuel will run in the 0-15 PSI range and is user adjustable. Scuba will run about 165 PSI fixed (above ambient).

So the normal welding regulators won't be anywhere near the correct pressures. I am sure there are some speciality regulators that would work, but they are not the common ones. The principle of the pressure regulating is the same. Just the design specs are way different.

 

[Tom Lucas]

Thanks for that (very helpful) response.

Actually I do have a 2 Stage Nitrogen Regulator which has an adjustable pressure output of up to 230 psi. Not sure what the ramifications of oxygen v nitrogen would be though.

 

[tbone1004]

A second stage is a simple demand valve and one that is designed to provide optimal performance when fed from a supply pressure between 120psi and 170psi *depending on which second stage it is* over ambient pressure. It doesn't really care what is giving the pressure, just that it has it.

 

[Brian G]

A SCUBA first stage is depth compensating. Will a welding regulator do the same thing? I've never taken one apart. At the surface, there is no reason for the second stage to act any differently to air at ~135 psi from a welding regulator as a SCUBA regulator. What kind of flow is expected from a welding regulator? I could see an issue if the flow could not keep up. I think a single second stage at the surface would be drawing less than 1 cubic ft/minute if you are breathing off of it, but would be significantly over that if you are purging it. Interesting question.

 

[tbone1004]

@Brian G it's not so much about average consumption vs. the flow rate required during the actual inhale cycle which is quite a bit more than 1 cfm. Most welding regulators will not supply sufficient flow for depth. IP drop during inhale is a direct function of first stage flow so if the flow rate isn't high enough then the breathing will be a bit difficult during actual inhalation.

most welding regulators will compensate for depth if you submersed. Haven't seen a totally sealed one outside of specialty applications.

 

[Tom Lucas]

I feel kinda pleased that I kicked off an interesting conversation even though it's a thought exercise.

And it looks as though I could use my wielding regulator if it was the only 1st stage at hand, had the right fittings, and house was full of smoke/unexpected flood/gas attack.

 

[2airishuman]

::shrug:: Different devices, different needs. If you're entering a contaminated atmosphere you want an SCBA regulator.

Welding regulator:
- Adjustable output pressure
- Has NPT gauge ports
- Has output ports with a thread form designed to avoid mixups between the fuel and nonfuel noses
- Has thread forms specific to the input gas, again to avoid mixups
- Relatively large form factor for ease of use
- Designed to operate in an atmosphere of air
- Comparatively low flow requirements
- Designed to fail shut so that potentially hazardous gas does not leak out
- Outlet - Torch

SCUBA regulator
- Fixed output pressure
- Has SAE port for SPG
- Has SAE output ports
- Input gas connector is SCUBA-specific (either DIN or yoke)
- Relatively compact form factor for streamlining
- Designed to operate in an atmosphere of water
- Comparatively high flow requirements
- Designed to fail open so that the flow of breathing gas is not interrupted
- Demand valve requires slight suction to open
- Outlet - Mouthpiece

SCBA regulator
- Highly integrated into an SCBA product and designed for regulatory compliance
- CGA 346 or CGA 347 input thread form
- Moderate flow requirements
- etc.
- Demand valve is positive pressure type
- Outlet - facemask