Scuba Tank Pressure Too high?

[oldbulldog]

Our clubs scuba tanks were filled by the local fire company. I was told by the parent volunteer that they were filled to 3500 psi. Would an air cylinder or air rifle be damaged by this pressure? How can I adjust the pressure in the tanks to 2900 psi?

[Jimro]

Add a SCUBA yolk with air pressure gauge and bleed off the pressure until you hit 2900 psi/200 BAR.

Jimro

[TenMetrePeter]

Your scuba tank is rated at 232 bar (3365 psi) and if you are LUCKY they give you a bit extra. Be thankful! The more in there the more fills you get.
YES if you filled the gun cylinder to that pressure it would be damaging so take the advice above, fill slowly and shut off the valve at 200 bar checking the tank gauge and the gun gauge together. You MUST have a gauge fitted on the scuba tank.

Remember many shooters use 300 bar tanks and that would probably render gun cylinders unusable or worse if you let it go to full pressure.

[John Marchant]

All air gun cylinders have a maximum operating pressure stamped on them, often this is 200bar. A few might have 300bar stamped on them.
The second number that is stamped on them is the maximum test pressure which is usually 1.5 times the maximum operating pressure.
Do not exceed the maximum operating pressure or your could potentially cause high pressure damage to the cylinder.
It is always preferrable to have a gauge on the outlet of your scuba tank to indicate the pressure that exists in your airgun cylinder, to ensure that you do not overfill this.
Some of the Air Arms air rifles do not recommend filling past 160-170 bar.
If in doubt, read the instructions for the gun cylinder that you are filling.

[Hemmers]

As tenmetrepeter says, it is usual to use a 232bar tank. Less commonly people will use 300bar.

If you have your scuba tank at 200bar, then after the first couple of fills you'll not be able to get a good fill on your 200bar airgun cylinders (because you're starting at 200bar and dropping below immediately). You're going to be refilling your scuba tank very regularly.

The usual thing would be to have a 232 bar cylinder, open the valve slowly and monitor the pressure, shutting it off when the cylinder gets to the 200bar mark.

You shouldn't just whack the cylinder on, open the valve and let the two equalise. If you do that, then although you should be within the safety envelope for the airgun cylinder, you will be overpressure it and risk damaging the cylinder.

[SlartyBartFast]

I used to be very interested in paintball. Same sort of pressures for compressed air.

For safety, if you're using a tank that has a higher working pressure than pressure of your cylinder. You should have a regulator.

If you want to maximize your use of your tanks, you should have at least two tanks and use cascade filling.

[Rover]

Fugeddaboutit.

[TenMetrePeter]

...
For safety, if you're using a tank that has a higher working pressure than pressure of your cylinder. You should have a regulator.

If you want to maximize your use of your tanks, you should have at least two tanks and use cascade filling.

I have never seen a 200 bar regulator to fit a scuba tank. Do you have a link?

I have had a 7 litre 232bar tank for 18 years. It lasts 6 months between top-ups. Never seen the need for cascade. Maybe thats a CO2 paintball thing?

[SlartyBartFast]

...
For safety, if you're using a tank that has a higher working pressure than pressure of your cylinder. You should have a regulator.

If you want to maximize your use of your tanks, you should have at least two tanks and use cascade filling.

I have never seen a 200 bar regulator to fit a scuba tank. Do you have a link?

I have had a 7 litre 232bar tank for 18 years. It lasts 6 months between top-ups. Never seen the need for cascade. Maybe thats a CO2 paintball thing?

Quick search: http://jdsairman.com/Regs.html

Cascading might be a tiny issue for AP and AR cylinders. Painball cylinders are 45, 68, and even 80 cubic inch at 3000 or 4500psi (http://www.ansgear.com/Empire_Paintball_Tank_s/2465.htm). So to get as high a pressure as possible for as many fills as possible, cascading was almost critical.

Guess it dates me, because pressure was an issue when compressed air started and the cylinders for the guns were ~2000 psi.

For CO2, the most hi-fangled way to fill tanks was by using a CO2 pump. Few used that though.

[TenMetrePeter]

With respect those regs are for connecting large capacity tanks to bench rested guns and shooting them whilst still connected. Not for normal scuba tank filling.
A gauge and stop valve on one scuba tank per gun is quite sufficient and normal for our sport.

Note to oldbulldog - sounds like you have young shooters (you talked of a "parent volunteer"). You need to have risk assessments documented, training for newcomers and preferably a rule that nobody under 16 fills their own gun cylinders.

[SlartyBartFast]

With respect those regs are for connecting large capacity tanks to bench rested guns and shooting them whilst still connected.

Well, looking at the page more, I was wrong, but you were too. Those are tank regulators which are fitted directly to tanks that are connected directly to the guns.
http://jdsairman.com/TanksRegs.html

Searching for "regulated HPA paintball fill station" first hit is http://www.ninjapaintball.com/fillstations

First product is a regulated output fill station.

Another result https://www.nuvair.com/paintball/fill-panels/

Has regulated fill panels. Connect hose to tank (while still on gun), pull lever, release lever, disconnect.

Idea: scope out the local paintball community. Paintball air fills might help finance a 6000psi ASME bulk tank, compressor, and fill panels and provide income to a air pistol/rifle club. Might also attract new members/customer for the pistol/rifle club as paintball players discover the challenge of precision shooting (as opposed to shooting 30 balls per second or more trying to hit moving people).

[TenMetrePeter]

Those are tank regulators which are fitted directly to tanks that are connected directly to the guns.

That is exactly what I said so not sure why we were both wrong.

With respect those regs are for connecting large capacity tanks to bench rested guns and shooting them whilst still connected. Not for normal scuba tank filling.

Maybe the host will add Paintball section but until then I'll stick to precision rifle topics.

[SlartyBartFast]

That is what I said

With respect those regs are for connecting large capacity tanks to bench rested guns and shooting them whilst still connected. Not for normal scuba tank filling.

Maybe the host will add Paintball section but until then I'll stick to precision rifle topics.

No that isn't what you said. There is nothing about bench resting guns with those regulators. You connect scuba or bulk to the regulator to fill tank while the tank remains on the gun then disconnect to use the gun.

What you need is to regulate the supplied air to the 2200, 3000, or 4500 psi working pressure of the tanks.

You asked "I have never seen a 200 bar regulator to fit a scuba tank. Do you have a link?". I've now provided links. Just connect a hose to the scuba yoke or DIN fitting and to the regulated fill station or panel.

There's no need to be so dismissive of an available safe alternative for filling precision rifles and pistols. Never did I suggest the host or any shop cater to paintball.

I was suggested a possibility for clubs to gain club equipment, make money from it, and ultimately have safer air fills from foolproof push button fill stations.

[TenMetrePeter]

Well we will have to just disagree on all points. It happens.

[SlartyBartFast]

Well we will have to just disagree on all points. It happens.

There are two facts under discussion with which you cannot disagree:
- No one shoot paintball guns connected to the bulk tank on a bench.
- There are regulators and solutions to fill AP and AR cylinders quickly and safely from any size or pressure of supply tank.

So the only points remaining are whether those systems are a good investment and whether a club could make money or pay for their equipment by filling cylinders for local paintball players and other air gun users.

You're free to disagree with those points.

[TenMetrePeter]

You're free to disagree with those points.

Thank you. I claim that freedom.

[Mtl_Biker]

Hey TenMetrePeter... how come you can't be sent a PM?

[TenMetrePeter]

Hey TenMetrePeter... how come you can't be sent a PM?

Fixed.

[dc.fireman]

Here in the US, we in the fire service use either low pressure (2216 psi) systems, or high pressure (4500 psi) systems. Most departments have phased out the older low pressure bottles, and have switched to the kevlar wrapped composite cylinders - thereby negating the need for the low pressure systems.

Generally, the in-station units are cascade type filling systems, so that we only have to run the noisy compressors once or twice a week, to keep the refill tanks full. This system will generally use a compressor capable of creating 6000 psi, and it's internally regulated to send 4500 psi to the bottles.

Are you sure they said 3500 psi, and not 4500 psi?

[hundert]

all 200 bar air pistols withstand 300 bar pressure, they're tested for that.
A typical body of an air pistol will hold out a even more pressure than 300, the material is thicker than in the cylinder.