Fire extinguisher pressure

[LewisM]

What are 4.5kg dry extinguishers tanks pressure regulated to? I have an old one here past expiry that I ceremoniously emptied and now want to convert the tank to a portable air brush painting air tank that i pump up from my compressor. I run my airbrudh at 30psi.

I ASSUME an old extinguisher tank should hold.

[dannat (Daniel)]

dry chemical tank? this thread suggests 120psi, supposedly the tanks are safe to 400psi, but I presume you are modifying & screwing in your own attachments -

[LewisM]

Yes, dry chem.

Will be fitting a regulator, and inlet Schrader valve and an outlet Nitto or perhaps direct 1/4 BSP step down to the airbrush hose thread.

I don't think I'd go above 120 PSI anyway, despite required initial pressure etc.

[leon]

Lewis I used to do some part time work refilling and re pressuring fire extinguishes and they were pressure tested to 1000 Psi.
You will have no problem at 450 or above.

Leon

[LewisM]

Thanks Leon - just what I needed to hear.

[Auster1b (Neil)]

Lewis,
Dry Chem Powder Extinguishers should have a label with working and test pressures listed.

If not, most dry Chem are typically between 1000 to 1350 kPa or 145 to 195 PSI.
Water Extinguishers are typically 700 kPa or ~100 PSI.
Foam Extinguishers are typically 1000 kPa or 145 PSI.
In Australia the Hydrostatic Test pressure is typically 2MPa or 290 PSI unless the manufacturer declares otherwise.

CO2 which run at a much higher pressure, typically tested to around 22MPa or ~3200 PSI.

So at ~30 PSI no problem.

Wash and dry to remove all powder residue, it is a corrosive salt.
Check for corrosion and dents or other damage.
A normal schrader valve is typically used.
Be careful if you use a taper thread fitting it may split the neck.

It is what I do, Neil.

[leon]

Hmmm not sure about this, I had been doing this stuff for a while and don't agree. but I am not perfect.

Leon

[LewisM]

The test pressure on the tag says 4.5 MPa, which is around 650 PSI.

[jenchris (Jennifer)]

A pet soda bottle is good for 180psi

[DarkArts]

I have two dry powder types:
a. bigger one: working pressure 690 kPa, test pressure 2.5 MPa
b. smaller one: working pressure 1035 kPa, test pressure 2.0 MPa.

HTH

[LewisM]

I need to wear my glasses...2.5 MPa...so circa 250 psi

[Auster1b (Neil)]

Lewis, just make sure you regulate the pressure from your compressor to less than 1000 kPa (145 PSI) or what ever working pressure is listed on the extinguisher label.

Leon, from AS1851.
1000 PSI would be a shirtload of pressure for a thin wall extinguisher.

It is what I do, Neil.

[LewisM]

I'd pump in at 100, and regulate out at 20 - 30 PSI.

[dimithri86 (Dimithri)]

I did sometime similar, naturally to make a ball bearing gun.

[acropolite (Phil)]

There's a world of difference between working and test pressure, tests are done hydrostatically, i.e. with water which is incompressible, if the vessel fails a squirt of water is all that ensues, on the other hand the same pressure of air can result in explosive forces if the vessel fails.

[multiweb (Marc)]

Originally Posted by acropolite

There's a world of difference between working and test pressure, tests are done hydrostatically, i.e. with water which is incompressible, if the vessel fails a squirt of water is all that ensues, on the other hand the same pressure of air can result in explosive forces if the vessel fails.

Well said. Compressed air is deadly. Lewis, stick to spray cans