# How many Cyclones?



## blktoptrvl2 (Jul 18, 2016)

Hello again, it's been a while. I have been merrily making sawdust for a few years now, but I am tired of cleaning it all up.

In my shop, I have a planer, table saw, mitre saw, drill, press and sander as my main tools. For the past two+ years, I have also been using a shop vacuum with a two inch hose - about 20' long. The vacuum draws enough air that I can keep the dust off the floor and most of it out of the air - as long as I use the hose. Sometimes when I move from one tool to another I forget to disconnect the hose from tool (a) and move it to tool (b).

Over the past week or two, I have been trying to fix this problem by installing PVC piping. I am only using 2" pvc because the 20' vacuum hose I have been using for these years is only 2".

My shop vac hose runs into a t-joint in the pvc, the upper branch goes a foot or so up the wall to a y-pipe. After the "y", the two pipes each go through a ball valve, up to the ceiling, then left or right along the ceiling around corners, to the tool station, and then drop down to where flex vacuum hose is used again to connect to the tool. The lower branch of the "t" travels to another ball valve that then goes to another flex hose to my table saw. Depending on the tool I want to use, I will open and close the associated valves.

Of course I have been reading about dust explosions/sparks and such. I figured that since I didn't have trouble with the 20' of hose, then the same length or shorter pipes on the wall shouldn't be an issue either... but then, they are different materials, so I decided to go ahead and ground the pipes using both metal tape and bare copper wire on the outside.

In all the past two years, I never used a cyclone separator. But upon finishing the main construction I had these thoughts...



Doesn't the spark danger come from the dust traveling inside the pipe at high speed?
I was worried about chunks or longer pieces of cast off wood being caught in one or more of the elbows, but won't a cyclone trap those pieces before they can travel into the pvc?
Isn't pipe clogging a problem related to dust in the pipe clogging at a corner or at a internal protrusion?
If I put cyclones between each of the tools and the pvc piping - in theory very little of the dust should go into the pvc so won't that help protect from both clogs and spark?
Is there any reason the cyclone needs to be close to the shop vac, or can it be at the tool as I plan?

Any thoughts would be appreciated.


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## HoytC (Dec 30, 2019)

blktoptrvl2 said:


> ....
> 
> 
> 
> Doesn't the spark danger come from the dust traveling inside the pipe at high speed?


First, read this.

Static charges are generated by the wood dust rubbing against the inner wall of the PVC pipe, like rubbing a balloon on your hair or against a wool sweater. PVC is an excellent insulator so the charges are stuck there until they leak away, the leakage rate highly dependent on humidity and other stuff in the air. Discharges between insulators are tiny arcs, like the ones you get separating polyester and cotton clothes pulled out of the dryer. They're not going to ignite anything.


Since you read this you know that the shocks you get are from induced charges, but are not discharging the inside of the pipe. It's an insulator. Your tape acts as a shield, making you more comfortable.





> I was worried about chunks or longer pieces of cast off wood being caught in one or more of the elbows, but won't a cyclone trap those pieces before they can travel into the pvc?
> Isn't pipe clogging a problem related to dust in the pipe clogging at a corner or at a internal protrusion?
> If I put cyclones between each of the tools and the pvc piping - in theory very little of the dust should go into the pvc so won't that help protect from both clogs and spark?
> Is there any reason the cyclone needs to be close to the shop vac, or can it be at the tool as I plan?


I too would be worried about the tight elbows available for plumbing PVC. Not only are they a clog hazard but they also reduce airflow. I hope you're using the long turn 90s.


You can put the cyclone(s) anywhere you like, but preferably no more than one inline at a time.


Also, I've seen some forum threads about getting nasty shocks when emptying the bucket under a dust deputy. IIRC, one of them was on this forum. When the dust moves through the pipe and charges the inside surface the dust also acquires an equal and opposite charge. Filling a clean insulating bucket leaves you with a lot of charged dust in the bucket. Worse is that wood is a conductor and can transfer all of that charge in a large, painful arc. That arc is possibly big enough to cause dust to ignite although I've never heard of a dust deputy explosion.:surprise2: Some of your metal tape inside the bucket on the bottom and then connected to a ground on the outside will fix this problem if you run into it.


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## DrRobert (Apr 27, 2015)

You really need a dust collector, at least 1 1/2HP.

Shocks are definitely real with PVC ducts. Fires are a myth with any kind of duct.

If you enough blower and your layout is done right, dust accumulation is not an issue.

A cyclone will degrade CFM's a little you need at least 1000CFM to use one. It is attached directly to the blower. The can goes directly under the cyclone and must be sealed tightly.


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## blktoptrvl2 (Jul 18, 2016)

Well, 

Thanks Dr. Robert, but a dust collector is nowhere near my future - for a variety of reasons.
And thank you HoytC for the feedback.

Now I will post my results...

I tried my system for the first time today. I couldn't be happier right now. My shop vac is providing all the suction power I need and the pipes are doing their jobs very well. There is no resonance sound or anything like that. In fact, the whole thing has a muffled sound to it.

The valves are easy to turn and the whole assembly is held together with friction - I taped the joints where the couplings are joined so I can easily disassemble it later if I need to. Even though it is only 2" I still am getting the suction I need, there are no static sparks to be found (yet - I've only cut a few things today.)

Now that I am sure it is working I will go ahead and close the panels so the pipes are no longer exposed. As you can see at the bottom, the honey colored and black trimmed panel will extend to the ceiling. Across the ceiling I'd like to drywall in the PVC framing, but I still want it to be removable if I have to get into the pipes for some reason later. So I will have to figure out how I want to do that. Maybe instead of drywall, I will just use thin plywood screwed to the framing.

About the dust, the problem I was having with dust flying was because I sometimes did not drag my vacuum hose from machine to machine when they were being used. Do that just a few times and the dust is everwhere. This I consider solved! The PITA of positioning the shop vac and running the hose is gone. But that is only step one.

Next I have to tackle the problem of dust that spits forward and to the sides when cutting. The hose port handled most of the dust, but the "spattering of dust" still is unacceptable. To solve this I will install a floating blade guard over the table saw with it's own vacuum port if needed. I already have a hose attachment for one of the jig/sleds I built and with that in operation, I see no noticable dust at all. For the other machines, I plan to make tent like surroundings that will corral the "splattering" dust being ejected to the front. It too will have a vacuum draw.

Next, I will order a timed on/off switch for all the tools so that when one is started, it will also automatically start the shop vac. I was happy to see that such a switch is very inexpensive at about $45 bucks. I will also have to get long heavy duty wiring to handle the distance and the amperage.

https://www.woodworkingtalk.com/mem...s/my-small-shop/55445-shop-vac-pvc-piping.jpg


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