Making an automatic fire suppression system?

Ben Delarre wrote 03/14/2014 at 18:245 points

I need a fire suppression system for my DIY CNC enclosure. I intend to run long unattended jobs and would like some piece of mind so I need some sort of automatic fail-safe fire suppression system inside the enclosure. There's a few commercial options out there but we're talking 500$+ so a DIY solution is required.

Anyone have any idea about how to go about this?

My current thinking is as follows.

* Buy a CO2 cannister (2lb)
* Hook it up to a braided hose that runs into the case, with a ballcock valve at the cylinder side for manual shutoff.
* Add a toggle valve to the end, something like this :
* Create a little box around the toggle valve that will hold a spring which is compressed by a fusible link.

Then when the temperature reaches the melting point of the fusible link (think 80 degrees celcius?) the link will melt, releasing the spring which toggles the valve to the open state, flooding the interior of the box with CO2 and suppressing any fire.

Obviously I'll need an additional fire alarm hooked up too. Would love to hear your thoughts on this proposed solution as I've never messed around with pressurized gasses before.


Eric Evenchick wrote 03/17/2014 at 22:07 point
I like the lack of electronics for this... it's not something you want under software control unless you're doing a lot of validation. Fail safe is a good thing!

I guess one of the big questions would be the reliability of the fusible link's melting point. Ensuring it will actually get hot enough to break within the required time could be tough, but I'm sure a blowtorch would help you test.

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Ben Delarre wrote 03/17/2014 at 23:16 point
Yeah it definitely needs to not involve any electronics. I will of course be wiring the fire alarm into my Raspberry Pi, but that will still be battery powered and hooked directly to an external speaker so even that is kept independent from the rest of the system. The Raspberry Pi will just monitor the level on the speaker lines so it can send automated alerts and shut off the vacuum system as well.

The fusible links I was thinking of using are these: they have a variety at different melt points, I think I could trust that these will melt. I'd have to be careful with the design of the holder so that the fusible link is exposed to the rest of the case but manages to constrain the spring that opens the valve properly.

Also not really sure if the valve I linked to above is sufficient for a pressurized CO2 cannister. Not many details on it there, and I haven't been able to find simple toggle valves anywhere else, and I know nothing about valves really, is there a difference between this sort of toggle valve and a 'flood valve' as has been suggested to me by others?

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