3000 psi and 500 psi testing

[BigRed96]

Having read service manuals and watching great videos on youtube such as Vintage Double Hoses regulator rebuilds and testing I see I should test my rebuilt regulators at both psi. I have a couple of tanks and get them filled by our local fire department. The final psi varies and isn't always at 3000. Is 3000 a hard line or would I be good testing at say 2700 psi? Another question I have is has anyone rigged up an adjustable pressure regulator to a scuba tank so you can adjust from say 2700 to 500 psi without dumping and wasting a bunch of air. I was looking around online and found one regulator the had a 0-6000 psi input and a 0-5000 adjustable output. Problem is its almost $300. Thanks, Timmy

 

[tbone1004]

typically the low pressure start is good to help the seats take their first impression without too much violence. You also do your initial IP sets at this point. The high pressure is to make sure that the IP is behaving because no regulator is perfectly balanced and you'll have IP variation across the tank pressure.

I have an adjustable regulator that I can use, but when I'm doing regulators I usually just have two tanks, one at low ish pressure, and one at high ish pressure *mine are usually at 3600psi from cave country*. I do all the LP side first, then do all the HP final adjustments

 

[victorzamora]

The trick is just to test at "high pressure" and one at "low pressure."

Optimally, you'd test higher than your tanks ever should be and then another at lower than your tanks ever should be. If it tests fine at the extremes, it'll be fine in the middle.

That's overkill, though. Test at 2700ish and at 500ish and make sure that your reg is working as expected. If it is, you can assume that it'll keep being fine at 10% higher pressure than you tested it at. I honestly don't even test at multiple tank pressures anymore and just grab whatever tank I've got nearby.

 

[guruboy]

The main concern is when tuning IP. If you can only pick one, I would test at 500psi.

 

[Couv]

To check the IP at low pressure shut off the tank valve and bleed the pressure down until your SPG reads 500psi. You may want to go just below that, feather the valve and increase the pressure back up to your target.

 

[Scared Silly]

The cadillac way of doing it is to get one of these: H.P. Manager with Bench/Wall Stand

I picked one up years back when a shop was going out of business. By the time I sold off all the tools and other equipment that I did not need it was a great deal. Otherwise one can just jury-rig as suggested by Couv.

 

[halocline]

typically the low pressure start is good to help the seats take their first impression without too much violence.

The seats don't get any extra violence from high tank pressure other than whatever increase in IP is associated with the higher tank pressure. Seats are subjected to IP, not supply pressure. The advantage to checking a just-rebuilt regulator with low supply pressure would be to protect HP o-rings, like DIN/yoke retainers, HP piston o-ring, etc. I've never noticed any difference to be honest.

Edit: I forgot another advantage to initially pressurizing at low supply pressure and that's in case there's something wrong with the HP seat. It's a little easier to shut down and less potentially damaging to the LP side of the regulator if an IP spike is limited to 500PSI, not full tank pressure.