Spark Bong question/WIP/construction

In the old days when most folks used a dry spark trap and a shop vac many of us had a few vacuum fires. They are often more alarming then dangerous ... if you catch them . Most of the time the whole shop filled with smoke and yoiu carted the shop vac outside where it revealed a smouldering filter and tank. If one stars as a tiny smoulder in the tank or on the filter and you go inside for the night, you may have been awakened by sirens. The creation of the spark bong and an additional dust deputy has eliminated that issue. I don't know of anyone who has had a vac fire who was using a spark bong/deputy combo. A few folks who grind wood and metal into the bong have had it get dry enough to smoulder, but that isn't a big deal. Just pour some water down the bong and clean it out.
 
Okay, spark bong, dust deputy make sense. Last part, I have a good sized dust collector and do lots of woodwork. Should I be using a dust collector that is dedicated to metal and another for wood dust? Or does the spark bong/dust deputy do the job and I can use one dust collector for both?
Oh ... one other comment Randy ... I have known from my education / training that cyclonic dust collectors are used in industry for particulate separation . But that was “theory”, and the designs are MUCH bigger than our little dust deputies. That said, I have a second dust deputy that takes the exhaust from my bandsaw. Wood only, so I run it dry - and virtually nothing Of that wood dust makes it to the vacuum (only very very small stuff .. which is why I have a HEPA in the vacuum) . I have been absolutely amazed at how effective these little units are at collectIng particles.
 
Cushing brings up a good point.
Air flow is important in a cyclone separator . It has to make the low speed/high pressure area in the center of the cyclone much greater than the high speed/low pressure zone of the cyclonic flow so the particles fall out of the center zone and drop into the bin. You want a BIG shop vac or a 1HP or larger dust collector blower. In woodshops the blowers are as big as 10 HP. Air volume (Cubic Feet per Minute) is how they create the air speed through the ductwork. The more air that goes through the better. Restriction of the air flow reduces CFM that can pass through. Ductwork size and smoothness affects the flow rate. Metal or PVC duct work of 2.5" to 3" or smooth flex hoses are best for all air passage up to the cyclone. 4" hose or duct is good after the cyclone. The duct from the cyclone should be the same or slightly larger than the entry port of the blower or shop vac. Have as few elbows or tees as possible. Elbows should be the radiused type, not 90° bend type. Tees should have a radiused side port. Elbows and tees can reduce air flow as much as 50% in some cases. Also, don't fight gravity. Ductwork runs should be horizontal or slightly downhill. The whole system should be roughly on the same plane. Don't run a vac line up a wall and across the shop unless it is absolutely necessary. Run it under the bench and along the baseboard. The best system has the ductwork at the same height as the blower port. Finally, keep all ductwork and hoses as short as possible. Distance resistance is the same for the air flow/pressure in a duct as it is in electrical wiring with voltage. The longer the run, the more the loss. Just like in wiring, larger gauge (duct size) and more power (bigger blower) is the answer for longer runs.
 
I have a pretty reasonable dust collector that I plan to set up outside my shop in the place we are building now. I hate the noise of vaccums and to a lesser degree my dust collector. But I also fear a shop fire too. It sounds like a spark bong/dust deputy combo is relatively safe. I'm still thinking I may repurpose my shop vac if I can have it outside my shop and use it to run my bong/dust deputy set up, and the dust collector to run the rest of my machines.

Funny story, Late one night I was working on a large slab table and mixed up a very large batch of rotfix epoxy wood hardener (really thin epoxy) to harden a punky part of the burl. Poured 3/4 of the bucket of rotfix onto the soft area and what I thought was steam started to rise out of the table. Got my nose down there and discovered it was smoke! Sh**!!!!!!! It's burning in there somewhere. Being really smart I poured the rest of the epoxy into that area to put it out. Smoke stopped and then started again. Smoke was increasing, about the amount off a starting campfire. Racing mind, I got a 5 gallon pail of water and dumped it on my 10% moisture content slab to put whatever was burning out. That almost brought me to tears because I had waited a long time for it to get to that point. I figured it was out, but the garage was pretty smokey now and I was worried it might start again. It's surprising how little information there is in google about burning epoxy in slab tables. No smoke alarm in the garage. So I went and got the smoke detector from the basement, my sleeping bag and pillow. Opened the garage door for a few minutes to clear the smoke and then put the smoke alarm on the top shelf, put my respirator on, and slept in the garage for the night.
 
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