Setting up a fire extinguisher?

[jackssmirkingrevenge]

If your planing on using it for a bbmg, I would recommend a CO2 tank instead. They can easily hold 800psi (a good bit of air) and can be dialed into what ever psi your going to use in your gun with an inline regulator. The fire extinguisher tank might be better used in a different project.

Depends on the type of fire extinguisher really, if it's a black coded one then essentially it is a CO₂ tank... the ones I have in the lab are rated to 216 bar, that's just over 3,000 psi

The dry powder ones I have are rated to 35 bar, so they will happily take 500 psi if you are filling with a fridge compressor or similar.

[POLAND_SPUD]

the ones I have in the lab

Are they still in the lab or have you borrowed them ??

[jackssmirkingrevenge]

Are they still in the lab or have you borrowed them ??

Still there though when we used a 50Kg one on the day of the explosion (don't ask ) I did "borrow" the nitrogen propellant cylinder, it's rated to 300 bar still have to find a use for it though, maybe a full auto HPA golfball gun if I inheret a couple of acres of shooting area

[POLAND_SPUD]

I am pretty sure that you must have some refrigeration equipment/fridges
A fridge compressor would probably be more useful to you that to any one else since you can use it also as a vacuum pump for epoxy casting

[jackssmirkingrevenge]

The need isn't so pressing as I can decant from my scuba tank but I've been on the lookout for a fridgy for a while now, it would be good to have an HPA source I can refill at home.

[Ragnarok]

I've still got to find a use for several.

I'd point out that while they've been <s>rated</s> tested to 200 bar (although they are now long out of their test period), these ones are equipped with safety valves that burst at 190.
Not really a problem though - that's more than enough for most purposes!

[dewey-1]

You had better get busy!

Are these the specjifications for the ones you have?

http://www.firemarkext.co.uk/

CO2 product line tab.

[Ragnarok]

Are these the specifications for the ones you have?

Pretty much. As far as I know, all seven (one of them isn't shown in that picture) meet the typical 2kg CO2 extinguisher specs - in all except that they're black. These days, regulations demand they be red, which why these ones found their way into my hands.

[POLAND_SPUD]

These days, regulations demand they be red

Lol it's good they are civilising you...
when will you switch to metric units?

Anyway they would make a nice hybrid chamber or air reservoir for a fridge compressor. I know you think it is daft to use fridge compressors as air compressors but soon they might pass a law prohibiting excentric behaviour and opinions

[Ragnarok]

when will you switch to metric units?

We pretty much do. There are only three common uses of Imperial units in the UK - road signs (yards and miles), milk/cream (usually in pints, although increasingly less so), and beer (pints, of course).

The really daft one is road signs. As fuel is only bought in litres, it means either of the common fuel consumption figures (MPG or litres/100km) is easily used.

As far as "civilising us"... not really. These were originally from a stage, and the black ones were far more ideal - as they weren't quite so bleeding obvious.
The fact they were black also helped prevent an accident. Stopped a totally brain-dead actor finding and using an extinguisher they were completely untrained to use (CO2 extinguishers are pretty dangerous if misused). There's always going to be an idiot who doesn't listen to the "If there's an emergency, tell the stage crew" instruction.

Anyway they would make a nice hybrid chamber or air reservoir for a fridge compressor.

I've considered both.
The hybrid chamber idea can't really happen unless I can get the valves out of the neck - and they appear to have been mechanically tightened, so it's going to take some more ingenuity.

But the restriction of a valve is less of a problem for a high pressure reservoir - it's perhaps even desirable to be able to close it off.

[dewey-1]

The hybrid chamber idea can't really happen unless I can get the valves out of the neck - and they appear to have been mechanically tightened, so it's going to take some more ingenuity.

The brass valve may have a "permanent" type of thread lock sealant on it where it threads on to the neck.
A little heat applied at the neck may soften the sealant.

Can you post some close up views of the neck and valve for visual analysis?

[c11man]

with both my fire extinguishers i keeps the original valve. the nozzle that came with them was already npt so i didnt have to mod the tanks at all. i fill both to 350psi and reg it down to 200psi and under. i dont use the fire extinguishers now that i got my 8 gallon 400psi tank and my 20lb co2 tank.

[Ragnarok]

A little heat applied at the neck may soften the sealant.

If possible, I'm trying to keep heat applied to a minimum. I don't know what the alloy is or how much it's dependent on heat treating.

Can you post some close up views of the neck and valve for visual analysis?

I'm not sure how much they'll tell you, but here and here. (Sorry about the slightly sloppy picture quality - this camera is a bit funny about focusing under fluorescent lights.)
The neck is about 43mm across at the very top. Threads are known to be M25x2 (confirmed on bottle neck stamp).

I have been wondering about the possibility that they're reverse threads, but I've found little evidence on the internet that they might be.

[MrCrowley]

If you don't mind getting rid of the valve, one trick I've used in the past is to cut off the valve at the neck so you're just left with the threads in the bottle neck. Then, using a hacksaw blade, put it inside the bottle neck and cut about half way through the threads left over from valve. If possible, try and leverage the threads from the valve inwards and hopefully it will crack at where you cut through half way. Do that again 90 degrees further around the threads and then you'll have a chunk come off the threads, do it again and again until you have all the bits from the valve that were threaded in.

I've used this rather primitive and inexact method once before on something similar and it worked fine. I doubt it will work for your needs and I imagine you'd prefer to tackle it in a more precise manner but i'm just putting it out there

[dewey-1]

If possible, I'm trying to keep heat applied to a minimum. I don't know what the alloy is or how much it's dependent on heat treating.

I have been wondering about the possibility that they're reverse threads, but I've found little evidence on the internet that they might be.

Here is a possible OEM source for those cylinders.
Probably one of the first two on the spec sheet.

http://www.luxfercylinders.com/products ... rope.shtml

You may have to use one as a "sacrificial lamb" to remove valve.

Here are some valves for information;
http://www.alibaba.com/showroom/co2-valves.html

Temperature and torque specs.
http://www.firekwencher.com/default.asp?pages=servicing