On Fri, 30 Jan 2009 22:13:30 -0000, "ian field"
wrote:
wrote in message
...
On Jan 30, 4:37 pm, "ian field"
wrote:

An application that requires compressed gas - a CO2 fire extinguisher is
known to be a suitable source.

Does anyone know how I can obtain a couple of fire extinguishers that have
been taken out of service (but are more or less full)?

Obviously scrap prices would be preferable.

You *might* be able to get some from an extinguisher servicing
company, but for liability reasons they might not let old ones out the
door.

They will NOT let them out the door as-is, I've tried. The usual
reasons they get scrapped as fire extinguishers is that the
instructions band with the maker name and model numbers is damaged and
unreadable, or the horn and hose or head/handle are unserviceable and
no spares are available, or the seals in the head have died and the
company is gone so they are no longer available. (Sounds stupid, but
to be rated they have to buy the O-rings from the original maker.)

I have a local FE shop that will gladly do the needed Hydrotest,
install a standard CGA200 (?) valve (without the syphon) and refill
it. Then you can use it for american-style beer or soda, or as
welding shielding gas, or to blow out HVAC drain lines.

Maybe you could watch auctions for when a building/business closes?

Would soda cylinders work as well?

Its for blowing tubeless tyres onto their rims - using a fire extinguisher
the right way up pumps liquid CO2 into the tyre, resulting in alarming
creaking and pinging noises, using the fire extinguisher upside down only
lets evaporated gas into the tyre and works perfectly.

I have a tubeless repair kit with "mushroom patches" and insertion tool,
these come complete with a soda siphon style CO2 bottle - the instructions
state clearly this is not adequate to reseat dislodged tyre beads.

You do NOT want to use liquid CO2 for this! Not good to freeze the
rubber by injecting Liquid CO2 that is going to flash into Dry Ice
inside the tire, chilling it to way below zero (C or F) - and then
expect the tire to flex easily into position... Not to mention that
when the Dry Ice evaporates into gaseous CO2 you could overinflate the
tire to the bursting point REALLY easily - long before you could vent
it out the valve stem.

Build a copy of the "Cheetah" bead blast bottle instead, uses
compressed air. (Could use gaseous CO2 to fill the tank too, but
that's a technicality - many non-flammable compressed gases would work
if you don't have an air compressor handy.)

You can fabricate one using an old 5 gallon/20 Lb/10KG LPG bottle
and a ball valve and a piece of pipe flattened into the oval blast
fitting (with a little hook/tab on the end to hold in position on the
rim flange) - but you need a certified welder to install a large bore
pipe flange on the bottle. You need a 2" (~ 50MM) pipe and ball valve
to move a lot of air out of the bottle in a hurry.

You basically aim the blast output tube at the gap between the tire
and rim and slam open the valve, and try to play the tire like a flute
- the air blast goes inside and bounces, then the bead is blown up
onto the rim when the air bounces back. Noisy, but it is safe and
works like a charm.

-- Bruce --