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fire extinguisher

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fire extinguisher

Unread postAuthor: ilovefire » Tue Jun 21, 2011 7:10 am

i have a steel fire extinguisher that has written on it that is has been tested to 2.5mpa (362psi), would it be safe to take it to that or similar pressure on a regular basis? how much would be a safe pressure to use it at? i had a look inside and it only has surface rust and very little at that so its still in pretty good condition
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Unread postAuthor: ramses » Tue Jun 21, 2011 7:48 am

the safe pressure to take it to on a regular basis is 362 psi, but only if you prevent the inside from rusting by painting it or something. You also need to be careful about converting the treads to something usable. Epoxy may or may not hold, but I would be wary of drilling, tapping, or brazing the fire extinguisher.

May I ask what "type" of fire extingusher this is (dry foam, etc), and where you found it?
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Unread postAuthor: ilovefire » Tue Jun 21, 2011 7:56 am

i was thinking of epoxying the inside, and its a powder type that i found at an old motel that is destined for destruction, and yes i will only use it if i am satisfied that i can connect it properly, not sure if i will be able to or not
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Unread postAuthor: ramses » Wed Jun 22, 2011 7:43 am

If you don't need fast flow, you might be able tap new threads somewhere in the original valve. I'd consider that safe, as long as you have safe wall thickness.
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Unread postAuthor: saefroch » Wed Jun 22, 2011 5:59 pm

I think you have a little bit of a problem with your metric prefixes... I don't pretend to be able to convert Pa to psi in my head, but I'm pretty sure 2.5mPa isn't 362psi, but 2.5MPa is.

You could try finding the wall thickness with a caliper, and calculating a pressure rating for a common steel alloy of that thickness, then pressure-testing it to that. It's likely that the fire extinguisher is tested to a pressure that still has a significant safety factor, it may not be too unsafe to push it a little farther, but I'd just be concerned about rusting.
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Unread postAuthor: ilovefire » Wed Jun 22, 2011 7:27 pm

ah ok yea i didn't know the capitals mattered, but yes is it MPa not mPa, as for sittings i have cut down the old valve a bit and there is a thread where the pressure gauge was and it fits the nosily from a blow gun so maybe i could use that to attach a hose to like you do with a fridge compressor. flow isnt much of a concern to me because i am only thinking of making a semi in ether 5 or 8mm, anyways here are some pics
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Unread postAuthor: warhead052 » Wed Jun 22, 2011 8:06 pm

Wow, your lucky to have found a FE with pre made threads like that. I would be lucky to find one with a metal valve, even though I have one I would like some more....
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Unread postAuthor: saefroch » Wed Jun 22, 2011 9:17 pm

If I recall correctly, M stands for Mega, which is 10<sup>6</sup>, as opposed to m which stands for mili, or 10<sup>-3</sup>. DYI's old sig before I made it in was a quote from somebody who also confused the two. Something about only needing a 3-5MW laser to do star pointing. I'm not even sure if a 5MW laser exists. :p

If you can attach something to those fittings, that would be amazing.
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Unread postAuthor: ilovefire » Wed Jun 22, 2011 9:31 pm

do you mean amazing as in really really hard?
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Unread postAuthor: Gippeto » Thu Jun 23, 2011 12:20 am

2.5MPa is the listed as the "periodic test pressure"... this is a proof pressure, not a working pressure.

The label also states the working pressure to be 1036KPa @ 23C +/- 2C.


Where's the confusion?
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Unread postAuthor: ilovefire » Thu Jun 23, 2011 1:28 am

Gippeto wrote:2.5MPa is the listed as the "periodic test pressure"... this is a proof pressure, not a working pressure.

The label also states the working pressure to be 1036KPa @ 23C +/- 2C.


Where's the confusion?


that is all clear, the main question was if it would be safe to take it to the periodic test pressure regularly, or would i have to keep it to the working pressure?
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Unread postAuthor: ramses » Thu Jun 23, 2011 7:50 am

I didn't realize that was proof pressure. I would recommend against measuring the wall thickness and calculating the failure pressure, then testing to that because the walls at the neck are generally much thicker than further down the bottle.

as to the 5MW laser, they are actually quite common. You can actually make one quite easily.
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Unread postAuthor: saefroch » Thu Jun 23, 2011 10:50 am

Whoa that's a lot of laser information I wish I had a while ago. Still mulling over the article and trying to wrap my brain equipped with only pre-university science knowledge around it.

It would be amazing if you could use the connections already on the extinguisher.
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Unread postAuthor: K8TOW » Fri Aug 19, 2011 11:23 pm

i used a 1 inch pipe thread nipple to go from the opening of the extinguisher,to the nipple.i use pipe dope with jb weld on the top of the opening
it works so far
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