Posted, and a courtesy copy e-mailed to the OP, just in case.

On 11 Jul 2005 13:57:29 -0700, wrote:

Anyone have experience with this? Where I work we have alot of dust
collector fires. Our collectors are connected to shot peening
equipment. Occassionally, I am guessing a spark is sucked into the
collector and lighting the filters on fire.

We have sprinklers in the machine but we would like to stop it from
happenign all togther. (Every time the sprinkler goes off the fire
department is notified). needless to say the fire department is not
happy with us.

Is this happening when they're cleaning certain metal items in the
peening bays? Many packed powdered metals are highly reactive,
especially when mixed - Thermite is ideally ~75% powdered iron and
~25% powdered aluminum, and it burns /really/ good and *very* hot, and
it provides it's own oxygen for the reaction...

http://en.wikipedia.org/wiki/Thermite

You need to neutralize the conditions that would set the mixture
off, like reaching a critical mass, heat and static charges. I do NOT
work in that industry, but that's never stopped me from passing on a
decent idea before... ;-P

Silly Wild-ass Guess Idea #1: Try putting a few water misting heads
(like they use on outdoor patios) spraying into the inlet airflow?
Add just enough moisture to cool off hot bits going in (without making
mud) and the moisture should cut the static electricity levels. Link
the mist water solenoid to the fan motor contactor, so they run with
the fan motor.

Silly Wild-ass Guess Idea #2: A dispenser for metering some
powdered limestone or something else that would keep the powder from
igniting as easily, into the incoming airflow to the cyclone and bag
tower.

A simple screw augur feeder from a bulk hopper, and a variable-speed
drive motor on the feed worm to meter it in during the day.

I picked powdered limestone out of my (tuchis) because they spray it
around in coal mines to reduce the fire hazards there. One of the
chemistry wonks here can probably come up with something much better
suited for the purpose of breaking up the thermite reaction that your
factory can buy cheap in bulk.

Like bulk sodium bicarbonate (baking soda - Class BC extinguisher
powder) or a mix of ammonium phosphate and ammonium sulphate (Class
ABC extinguisher powder). Class D extinguisher powder is finely
ground sodium chloride - table salt - but that might create rust
problems.

Adding a moderator powder to the waste stream would add to the bulk
and slightly increase the disposal cost of hauling off what you
collect in the bag farm. But if you can stop the fires before they
ever start that's a *very* small price to pay.

-- Bruce --

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
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