Air pressure control for DIY reg service?

[HenrikBP]

I will at some point begin servicing my own regs. I'm studying and gathering tools, parts and info at this time. For air I only have a 27 cu. ft. pony tank, 3000 PSI max. No direct access to a dive shop, compressor or similar.

So have anyone built a regulating valve w/ gauge to provide a variety of air pressures from one air source for testing IP at high, mid and low pressures, checking SPGs etc.?

Scubatools.com has a very nice (and pricey) unit that does exactly that, but it's outside of my budget:

H.P. Manager with Bench/Wall Stand

Also, what would be an acceptable accuracy of pressure gauges?

I figure my decent quality SPG is good for approximate pressures, but given it's "working environment" and probably having been bumped occasionally, I wouldn't expect it to be accurate within less than a few hundred PSI. My IP gauge is a regular ~$20 unit from Scubatools.com and since it is for less of a pressure range and lives in a waterproof box, is probably reasonably accurate within a few PSI.

But what is "accurate enough" for regulator service and maintenance? I realize there may not be a one single "right" answer.

Thanks

Henrik

 

[redacted]

I use any partial tank to support my service work and then check the reg on a full tank to see if any new problems crop up. My used tanks will usually be in the range of 500 to 1000 psi. I see no need to be precise with the tank pressure. I do use a fairly good quality gauge to measure and adjust IP (a Craftsman compression gauge). I have found IP creep problems on some of my Mk10s when I go to the HP tank (3000 or 3400) due, I'm sure, to some HP piston o-ring extrusion. The cure usually requires going to a urethane o-ring and sometime I have to do some piston swapping to get one that works OK on my HP100. Surprisingly, I have not had the same problems with my Mk5/7s.

 

[dlndavid]

A regulator regulates gas pressure, a valve is either on or off.
I used to work for a very big valve and regulator company, or I'd give you one.

 

[HenrikBP]

I use any partial tank to support my service work and then check the reg on a full tank to see if any new problems crop up.

Thanks for the feed-back. Unfortunately logistics makes the multi-tank solution a no-go for me; I don't own a car, subway transport for everything. It's amazing how much you can move that way - but not ideal for heavy high pressure tanks. And NYPD check points would have a fit

Thanks for the correction David. A pressure regulator is what I'm looking for.

I own a compressor for air tool and such, and it has a simple regulator for controlling output pressure. It is of course much lower than what I'd need for SCUBA purposes. But maybe something like exists for higher pressures as well?

Henrik

 

[dlndavid]

Regulators exist for just about any application.
I'm holding in my hand a reg that would do what you need.
HP port 4000 PSI max inlet with a 0-4000 PSI gauge, and a LP port with a 0-400 gauge, (indication of output range).
I think the LP port outlet pressure is a bit high for testing/setting SCUBA regs though.

 

[HenrikBP]

I think the LP port outlet pressure is a bit high for testing/setting SCUBA regs though.

I'm thinking I will need output pressures to mimmic pressures from full tank to "empty" tank. So from around 3000 PSI to around 500 PSI. That would allow me to test the first stage and adjust for correct/consistent IP throughout the range of pressures the first stage would see.

For the second stages I would use the actual - now properly adjusted - IP from the first stage to test and adjust cracking pressure.

Henrik

 

[Jimmer]

Henrik, I dont have my Praxair catalog in front of me, but they have welding regs for argon/nitrogen etc. that are adjustable from 200-3000 on one model, and 300-4500 on another model. I can find the part #'s tonight if you want.

 

[dlndavid]

I worked for the company that makes Praxair's regulators.

 

[redacted]

By the time you buy that regulator and adapt it to scuba connections, it will probably be a lot cheaper to just purchase another smaller scuba tank and still have $$ left over for a taxi.

 

[HenrikBP]

Jimmer; if you don't mind I'd like that part number. I'll take a look and see if I think it might work - and if the price fits the budget. Thanks.

By the time you buy that regulator and adapt it to scuba connections, it will probably be a lot cheaper to just purchase another smaller scuba tank and still have $$ left over for a taxi.

Gary; I'm afraid you may be right. I know from building race bikes that as soon as you step outside the standard parts and upgrades, the "bang for the buck" factor decreases *rapidly*

Henrik