Fire extinguisher dismantling query.

[rileytoolworks]

Evening all.
Do any of you folks out there in Cyberville know of a SAFE procedure for dismantling a fire extinguisher, and what type of thread are they likely to have?
TIA
Adam.

 

[Shadowfax]

Hi Adam,
What type of extinguisher and why do you want to dismantle it?
Threads could be anything. There is no standard as such, as far as I know.
Cheers,

SF

 

[rileytoolworks]

Hi Shadowfax. Probably water extinguishers. I want to use two as reservoirs for a vacuum press I'm building.
I'm guessing there's still some pressure in them even when fully discharged?

 

[Shadowfax]

Adam,
Make sure they are fully discharged and you will have no problems with pressure.
Just take the tops off and make sure the insides are not rusty. If they are clean you can be pretty sure they will be safe to use for storage at small overpressure but remember water extinguishers are not pressure vessels as such.
If you had CO2 extinguishers that would be a slightly different matter.
Does that help at all?

SF

 

[rileytoolworks]

Spot on mate.
Thanks. Will look out for C02 extinguishers.

 

[9fingers]

Other possible vessels are calor gas cylinders or vacuum tanks from trucks with 'air' brakes from your local truck agents of breakers. These (tanks!) tend to have BSP threads so easy to get fittings from plumbers merchants.

hth

Bob

 

[TheTiddles]

You really don't need a reservoir for a vacuum press, you can only store 1 bar of "pressure" which isn't very much energy storage. If you want rapid evacuation, look into using a low vacuum, high flow pump to evacuate then a second to run to the higher vacuum. That said, you don't need much vacuum at all to slam veneers down onto a substrate or bend ply around formers, even half an atmosphere is around 7psi which when you multiply it up over the area is a huge clamping force

Aidan

 

[Oldman]

All the water extinguishers I have seen taken apart for yearly inspection have had a bulb like a soda syphon one screwed into the top and when you hit the button it sets off the bulb to pressurise the water vessel.

Just unscrew the top without hitting the plunger and then unscrew the bulb. Once thats done just drain the water and its all yours.

 

[laird]

If the extinguisher is pre-pressurised (most dry powder, all CO2, all hyperbaric) there will be a pressure guage on it. If not (water, foam) it can be unscrewed without setting off(assuming the gas cylinder hasn't burst or leaked). Always safest to discharge first (WARNING CO2 will kill you in a confined space, and DP makes an awfu'big mess). Remember the cylinder will re-pressure slightly as it warms up to room temperature.

 

[ivan]

The main purpose for a vac tank is to prevent pump cycling on and off too frequently. If you're going to let the pump run contiuously no need for tank (but not very kind to pump) You don't need a very big tank, if you're using one. See here:

http://www.joewoodworker.com/veneering/welcome.htm

UPVC pressure pipe looks similar to what's suggested here, and as posted here a while ago, is available from Koi carp / aquatics dealers as used in big fishponds.