Fire Suppression

[jimpen]

I'm looking at re-building a metal-framed approx 12' x 20' shed to house my woodworking shop. I have other questions on that later. But my thinking on this is to build a fire suppression system into the shop from the beginning.

But with a shop this small and only a few feet clearance to the roof (8'-10') I'm thinking that a sprinkler head type system is not the way to go.

What crossed my mind:
Mount copper pipe (or 2 pipes depending on what ends up being my spray width) on the ceiling with small holes drilled along the length at about a 120 deg angles.
I would then have a solid state heat detector that can ring a bell and trigger a valve to allow the water to flow.
I would also have a main power cutoff and a manual water cutoff next to the main entrance of the shop.

Has anyone done this? Is it it a good idea? Is there a better cheaper way? Any other suggestions?

[doo_hicky]

I have not done anything like what you mention. I would have concern as to the water getting to the holes furthest from the source. I just have the standard fire extinguisher on the wall in my shop.

To be honest, I never really gave it that much thought, but with the advent of putting in a self suffeciant heat source(oil or lp) I to am curious to what other people have.

Mike

[jimpen]

I have a fire extinguisher in the shop already. I'm just thinking after hours. Rags spontaneously combusting, etc.

The water will actually start coming out at the far end first. The end of the pipe would be capped off.

What happens is that the water flows forward until it meets resistance, i.e. the end cap. When the pressure builds up at the end cap the water will start piling up and looking for the first availble spot to go out. So the hole that is closest to the end-cap will start squirting water. Then as the pressure builds the second one will start squirting and so on.

You can simulate this with a water hose you're willing to sacrifice. Hook it up to the water spicket and leave the far end open. put a small hole in the hose about 4" from the end. Turn the water on. No water should come out the small hole (unless you have really high water pressure, in that case back off the water pressure). Then cover the end of the hose. Very quickly you should see that hole squirting out.

I only have a ~7 Gal/Minute flow rate off my well. That is why I'm thinking this sytem would work better than a sprinkler head.

[Billy B]

Not knowing that much about fire supression, could you extinguish a chemical fire (rags,etc.) using water? I would rather have a few fire extinguishers to put out spot fires than a system that would most likely ruin everything. If the fire is large enough to require the need of a sprinkler system then really, the system is not to protect and preserve the shop but for rather to save your house right?

Billy B.

[jimpen]

The final distance from my house to the shop is going to be far enough that unless we are in a full-scale drought I shouldn't have a problem.

As far as a chemical fire (rags), the chemicals that fueled it will probably have burned off by by the time that the system activates. At that point it should have become a standard wood/structure fire.

I also intend to have a "chemical cabinet" for paints, varnishes, thinners, etc. If the fire starts in that then I might as well write it off anyway because the explosion will probably destroy the shop in one fell swoop. I'll stand back and watch it burn. :)

My thinking is that if a fire happens, I can always clean-up and de-rust, re-oil the equipment at a lot lower cost than trying to replace all the tools from the ground up. It will probably also be cheaper on my home insurance that I have something.

[TDHofstetter]

Jim, I have concerns - serious concerns. Over the course of my history, I have seen an awful lot of "high-reliability" electronic equipment fail. Sometimes it failed "safe", sometimes it failed "unsafe". In your case, a "safe" fail would be a false trigger. An "unsafe" fail would be no triggering at all.

False triggering could be caused by power glitches, by lightening, by the static spark cause by rubbing a cat's back too close to the sensor, by manufacturing inconsistency, by shelf age of any component in the system (solid-state devices DO have a shelf life). If it's battery-backed, it could false-trigger just as the battery fails, or just as the municipal power returns.

Sure, it would maybe be better than nothing... but it would NOT, in my opinion, be nearly as good as fusible-element sprinklers in a drypipe sprinkler system.

If you feel that you MUST go ahead with the solid-state sensor, please do me two favors. First, back it up with a grossly oversized battery backup that can handle the water solenoid (so the system can work despite power failures) and second, give yourself some extra insurance by using THREE sensors - any two of which must be in agreement before the system fires.

OK, three favors - third, do everything you can (within some modicum of reason) to prevent lightening, fluorescent lights, electric motors, and the cat's back from sending false signals to that system.

Oh, you might consider yet another add-on. As long as you're thinking about tossing water in there, you might also consider a gas solenoid that turns on a flood of CO2, too. That's enough to extinguish any fire except a magnesium fire or one involving oxidizers like saltpeter. You won't be tooling either in your shop, will you? :)

For those not familiar with the difference - CO2 (carbon dioxide) is the one that won't kill you except through simple oxygen starvation. It's the one found in your own breath. When you get too much CO2, you feel like you've been holding your breath too long. CO (carbon monoxide) is the evil heeba jeeba that can get you in your sleep. When you get to much CO, you don't feel much different except for a headache and a drowsy feeling that keeps getting worse.

-- Tim --


You can always take one more step against the wind.

[Frank]

I'm with Tim here, you'd be better off with a gaseous flooding system. Co2 works great, Halon works better, if you can still find it. Since it is a shop, you might consider a time delay with a warning so you can shut it down befor any "hot" work could set it off. You'd probably have to change your shorts if it went off while doing some brazing or soldering.x(

[Chagrin]

Before starting, I'd check to see what your anticipated savings in insurance would be.

Reasonably, for such a small space, if you have a fire major enough for you to want to turn on a sprinkler system you can pretty much expect some hearty rusting and a lot of your electrical equipment to be ruined. I doubt your insurance company would want to pay for anything other than replacement costs -- unless you specifically asked them to let you repair it free instead. That's nuts.

Also, if you tell your agent you're planning on a "home grown" system, well, I doubt they'll go for that either. I'd spend the money on fire extinguishers instead.

[daveferg]

Jim---I think you need to do some basic research on fire supression systems, because what you're describing won't work.

A typical sprinkler system (wet pipe) has water in the pipes, under pressure. When a fire starts, the lead fuse on the closest sprinkler head melts, opening the head and keeping the fire from spreading. The reason this type of system works is that it only takes one or two heads open to suppress a fire---

What you're describing is a dry pipe deluge system, when the whole thing opens up, but the way you want to cut the holes just won't work-

But with only 7 gpm on your pump, I'd be willing to be you wouldn't have enough to properly run any system---it would likely take a separate water tank and or a pond and fire pump.

I'd take your well flow and pressure readings and room size to a professional sprinkler company and they could tell you.

[jimpen]

Thank you for all the replies.

I was trying to come up with a system that would work and still be cheaper than the price of all the tools in the shop combined plus the building.

I'll do some more research and see what I can come up with. I'll let you all know.