# Fire Extuinguisher Workig Pressure?



## Andre (Jun 4, 2016)

I wish to use a steel (or aluminum?) fire extinguisher tank as a low pressure vessel,  and am wondering the usual working pressure of a fire extinguisher from the manufacturer as a comparison. I will make a new top plug with the inlet and outlet barbs for tubing to replace the regular nozzle.

It was a dry chemical extinguisher that expired, I believe made by Kiddie. It had a metal head.


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## ScrapMetal (Jun 4, 2016)

I just looked at the label on the dry chemical extinguisher sitting next to my desk, brand "First Alert" (not that it matters).  On the label it says "tested to 360 psi.

Hope that helps,

-Ron


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## FLguy (Jun 4, 2016)

My Kiddie unit says to charge it to 195 psi and test for 30 seconds  at 585 psi.. For your safety stay under 200. Hope this helps.


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## francist (Jun 4, 2016)

I just looked at three here, quite a range. An older Pyrene is tested to 525 with a working pressure of 175, a Sentry tested to 600 and sitting at 195, and a one year old Kidde from a Home Depot hydro tested to 300 and sitting at 100 working pressure. All above are psi.

-frank


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## Grumpy Gator (Jun 4, 2016)

_Please keep in mind that the test pressure was done in a hydro tank. _
_  Look on the tank for the last time it was tested stamped close to the neck._
_ They should be tested every ten years._
_ It doesn't cost that much to test one. _
_  Extinguisher's are filled with dry nitrogen to keep the corrosion out._
_That said you should be safe to 120psi._
_          *G*_


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## Andre (Jun 4, 2016)

Thanks guys, I realized I could also just add pressure to the gauge until it read in the green, then read the pressure in the air line to test for working pressure.

This is going to stay under 120 PSI because that's the highest pressure compressor I have. A small volume air tank for a project.


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## David VanNorman (Jun 4, 2016)

Remember any thing you do to weld or screw into this tank to test it also . You might want to add a safety to your tank also.


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## TommyD (Jun 5, 2016)

Grumpy is correct, it is the pressure at which the tank was tested at in a water filled tank ( hydro test) to contain rupture. If I remember correctly, I serviced  fire extinguishers a number of years ago, it was only CO2 tanks we pressure tested and stamped and I don't remember ever doing dry cylinders but I'm old and have forgotten a lot. CO2 tanks are heavy walled where dry chem cylinders are only sheet metal and don't like being stamped, we'd place inspection stickers on the dry chem and would only refill them after changing out the internal components after they were discharged. Steel tanks can develop rust and being internal you can't see any cratering caused by the rust. If you can open the top take a peek in with a light to see if there is any rust. A bit of pucker happened every time we put the pressure to the tank, I never heard one repture so I don't have that experience, luckily.

 During the Summer months I'd take the CO2 extinguishers outside and discharge them when they needed to be hydro tested and proceed to dance around in it's vapor like a man possesed. I think the chanting may have caused some to think I was off my rocker.


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## cvairwerks (Jun 5, 2016)

I've used medical oxygen tanks that wouldn't pass hydro as low pressure accumulators. I used to get them free from the guys that supplied my mother-in-law's oxygen. I've probably got a dozen of varying sizes and materials in storage.


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## RJSakowski (Jun 5, 2016)

I was under the impression that hydrostatic pressure testing of gas cylinders involved filling the cylinder with water so that any rupture would not have explosive consequences.  

That said, you can satisfy your safety concerns, by hydrostatically testing the cylinder at twice the working pressure.  If it passes the test, it should be safe to use at the lower working pressure.


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## Andre (Jun 5, 2016)

I believe hydro testing is done with water inside the tank, with the entire thing submerged in water.

The tank is sheet metal, and the top nozzle is already off and the powder has been washed out. I can look for any rust.


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## TOOLMASTER (Jun 5, 2016)

I use paintball co2 tanks and breathing oxygen tanks a lot for some of my projects..scored 20 tanks last year for 20 bucks at a g sale ;-)


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## TOOLMASTER (Jun 5, 2016)

what do you want to make out of it?


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## rgray (Jun 5, 2016)

I'd suggest a propane tank instead. Don't see any sheet metal air compressor tanks.


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## fixit (Jun 5, 2016)

RJSakowski said:


> I was under the impression that hydrostatic pressure testing of gas cylinders involved filling the cylinder with water so that any rupture would not have explosive consequences.
> 
> That said, you can satisfy your safety concerns, by hydrostatically testing the cylinder at twice the working pressure.  If it passes the test, it should be safe to use at the lower working pressure.


You are correct


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## kd4gij (Jun 5, 2016)

Tony did a write up on hydro testing on here. The thread should be around some where.


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## f350ca (Jun 5, 2016)

Our oilfield wellhead equipment was pressure tested every three months to twice working pressure. Ends were blanked off and the equipment filled with water then stand behind a concrete wall and take some of it to 20,000 psi. 
A large styrofoam coffee cup reduces to about the size of a shot glass at 20K psi. Interestingly a clean one deformed nearly perfect, if it had coffee in it it would distort from the film not letting the air out evenly.

Greg


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## Andre (Jun 5, 2016)

rgray said:


> I'd suggest a propane tank instead. Don't see any sheet metal air compressor tanks.


Every air compressor tank starts out as sheet metal 

But I understand your thought, get something thicker and more robust. I have two other extinguisher tanks that are much thicker!


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## TOOLMASTER (Jun 5, 2016)

are they 20 pound co2 tanks?

luxfer aluminum?


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## dlane (Jun 6, 2016)

I have a couple water extinguishers , the top unscrews and I put water, or what ever in it and pressurize to 120 psi, ( heck of a squirt gun)  they are stainless steel sheet metal welded seems.
I put a air Chuck on one to fill tires , they are light waight, aprox 2-1/2 ft tall 9" Dia., I like them.


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