Posted on 10/04/2003 8:03:18 PM PDT by Old Professer
We had a nursing home fire here in Nashville a week ago and 11 old people died; no fire sprinklers in the building and now there is a hue and cry to require retrofitting of all the "grandfathered" buildings.
I've tried to do some on-line research to see if there was a room-sized, pre-charged unit that could be installed to protect the occupants while permanent fixtures were installed.
So far, I've come up empty, but I have a great idea using a system that could be made from off-the-shelf components.
What I envision is a 75 gallon water heater tank connected to an 80Cubic Foot gas bottle charged to ~2300PSI and fitted with a double-regulated valve set at 75PSI connected to the cold water inlet line; the hot water outlet would in turn be piped across the ceiling to a conventional fire-sprinkler head that would "burn-out" at 155 degrees F.
This design would flood a 10X10X8 foot ceiling room with a bit over 1 inch of water in just over 2 minutes.
The two tanks would be clamped together with a bracket made in a figure-eight shape about the mid point from the floor.
The clamp would be equipped with flanges to bolt to the wall for earthquake protection and accidental jarring or bumping.
The whole thing could be hand-trucked into the room and filled from a garden hose and a temporary outflow pipe; the ideal location would be in a corner adjacent to the door.
I think I misstated the volume of the room; it is, of course 800 cubic feet.
What he's referring to as the "dip tube" I think is the cold water pipe. You need to take water from the bottom of the tank, since gas will accumulate at the top. If you remove the pipe that goes to the bottom, you'll get nothing but gas out.
This is basically an oversized version of the old-fashioned water-filled hand-held fire extinguishers Class A.
Have you considered other substances besides water? An 80 cubic foot room measures 10 feet on a side and 8 feet high; an inch of water on the floor is about 63.5 gallons.
How effectively can you make sure that water will get to or stay at places other than the floor? Would detergent or some other such substance help?
That requires a 120CUFT N2 bottle? Why not use a pilot-valve arrangement like that used in electropneumatic pipe organs (in a pipe organ, a small valve allows pressurized air into a bellows which then operates the main valve; for water, I'd sugget having a small valve let water into a piston to do likewise).
Actually, I started with the idea of using a bladder-fitted tank with the bladder enclosed inside the tank and chargeable from an outside source with air at normal ASME air tank pressures of 120-200PSI but this would require a special construction and would cost more but would be far simpler.
In any case, I figure the device would need to dump (rain) at least one inch of water in less than 5 minutes to be effective, which is why I said it would take at least 63 gallons for a 10 foot by 10 foot floor area.
This whole thing relies on a single fire sprinkler head of an industry standard design that is capable of delivering 25 GPM and will cover the entire enclosed area, floor-to-ceiling thereby smothering the fire.
If the fire has a secondary source of fuel and air, all is lost.
I wasn't intending the CO2 as a primary fire suppression agent; I was suggesting its use as a propellent (though having large quantities of it dissolved in water may not be too good, limitting the time that water is exposed to CO2 under pressure would keep that down). The quantity of gas needed as a propellent is small enough that asphyxiation should not be a problem.
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