Notes on taking apart a Dust Collector & a question

Notes on taking apart a Dust Collector & a question · 08-08-2009, 08:11 PM

I have been wanting a good dust collector and usually save the big purchases for the summer, having already spent my allowance on a Table saw and a jointer. But then this Tempest, 3.5HP, 1700 cubic feet of flow, 0.5 micron 9' tall filter, with a collection canister, new is $1125, and is listed for $300. Well, I make the call. The gent is moving and has to sell everything. The DC is less than a year old. All of his PSI metal ducting and gates is also for sale for $300. He will throw in the remote switch (worth $125). He also has some wood and other items for sale. First come first serve, but he will hold the DC for 2 days if I commit to buy, so I do. A little more DC than I had intended, but how can that be wrong.

After 6 hours of driving, I arrive to find that the DC is in good shape and the ducting is all in place.

I was hoping that this might be little less work intensive. Well, after two hours we have it all down and loaded in my van and trailer. I also throw in (4) 4' foot Bessey clamps for $25 each, a solid maple rolling cabinet for $50, a Freud Super Dado for $50, a Jet ceiling mount Air Filter system, and a DeWalt jig saw for $25. Well, when the wife learned a couple of days later that I did not spend $300 as expected, I was in trouble for a few hours. I tried to explain that it was all worth over $3K. Oh well.

Got it all home. Then the figuring out the system and solving some problems began.

1-Putting up the plywood and hanging brackets went well.
2-Took apart the bottom of the collector, to rotate the filter port and the collector port to opposite sides, as they are on the same side now. Well, there are the bolts that hold the motor blow assembly. One of the bolts is blocked by the neutral vane cylinder. I see if it will budge. I cut away a little of the silicone holding it in. No way it is moving. It is held in by 8 inches of tubing inside of tubing and layer with silicone. Well, looks like a new plan for the port placement.
3-Down comes the plywood and hanging brackets and relocated.
4-Up goes the cyclone on the brackets. No problem, just a little top heavy, but not to much problem for 3 gents.
4-Start taking apart all of the ducting joints and cleaning them up for my own installation. Also, take off the many metal strapping strips that he had riveted to almost every piece. Each joint had been siliconed, some also have caulk, are riveted with at least 3 rivots, and then metal taped.
5-Taking the tape off and drilling out the rivets is no problem, just tedious.
6-I notice that although the silicone was heavily applied it is not uniform around each joint. There are big gaps in the joints where the silicone is not sealing. It also looks like more had been applied
more than one. Some of of the silicone is clear and some is silver. Some joints are still difficult to pull apart, but do come apart. Once I have each joint apart, I notice that the silicone peels right off of the inside of the PSI metal spiral tubing. The good news is that there seems to be about 2 to 3 times more ducting than I will need.
7-I notice that when I take one shutoff gate in the main line, that it is loose. The pipe is shoved right up to the gate, where the tape can not seal it. With all of the silicone and tape, I am beginning to think this gent had a leakage problem.
8-I just about have it all ready to begin installing the ducting in my own shop, but I want to avoid the apparent leaks.

So, here are the questions. What is the best sealer for the ducting? The silicone or the metal tape? What is the easiest way to support the ducting without all of the riveting? I have open stud work in my shop, if that helps.

Thanks in advance,
Guy

McRabbet · 08-08-2009, 10:30 PM

I'm a PVC guy, so this is my best suggestion based on other successful applications I've seen. You mentioned that the style of the metal ducting is spiral. The key to good joints is the fit into each elbow or wye. You may need to buy a crimping tool if you cut some of your straight lengths. Once you have determined your best layout, I would make a series of plywood yokes to screw to the walls every 2nd stud and then use 3/4" metal hanger strapping from open ceiling to support runs across the room. Always align the crimped ends of the pipe toward the DC to minimize the internal obstruction at joints. You can pop rivet key joints and a small bead of clear silicone will seal most joints. A layer of metallic tape can be used to seal it if applied tightly. Part of the reason I prefer PVC is that it is perfectly round and leaks are almost non-existent because of the good fit. And it is cheaper.

froglips · 08-09-2009, 01:59 PM

There is a product I've seen called Duct Mastic. Its a brush on sealent. Somewhat flexable.

I see it on shows like This Old House etc.

I don't know about specific products, but this write up seemed helpful.
http://www.oikos.com/library/ducts/index.html

I also can't comment on if this stuff works with woodworking dust collection.

Hmmm, other than the fact I know something related to the word duct, I'm pretty useless

Jim

Travis Porter · 08-09-2009, 10:01 PM

I use the silicon on 90's, and crevices like in Wye joints. I use the foil tape (NOT DUCT TAPE) everywhere else. I find I have been able to remove the foil tape as well when necessary.

Congrats on the haul!!!

Dusty Sawyer · 08-09-2009, 11:30 PM

I've seen the duct mastic used in HVAC applications and it seems to have a good workability while applying as well as long term reliability. The tapes eventually seem to develop leaks no matter how good they are. Silicone is great too, but your cure time can be excessive if you are applying any great thickness.

Hope this helps

David

Guy in Paradise · 08-11-2009, 10:26 PM

I have all of the metal system taken apart. The previous owner must have many leaks, but I am fairly sure he caused most of his own problems. Even though he siliconed, riveted and taped every joint, I found evidence that he did repeated applications. The biggest failure seemed to be at the shutoff gates. the pipe was run right up to the end, so the silicone and tape didn't have a good surface to seal. Sealing a corner is far harder than sealing a flat connection. The metal tape pealed off very easily at any joint that was not very flat, the tape was loose at every rough or irregular joint.

Actually, I am glad to have gotten this used system and taken it apart, as I have learned more about how to make a better sealed system. I know that silicone itself does not seal the system. Rivets provide strength, but they also provide more holes in the system. Metal tape must be applied on flat surfaces to seal.

I am actually wondering if "duct tape" would work better.

McRabbet · 08-12-2009, 07:24 PM

Guy,

Duct tape works and is more pliable, but it leaves lots of residue and can be a PITA to remove. I would use metal tape where possible on pipe-to-pipe joints and then duct tape where it is the only option. The most important sealing is below the cyclone for the entry into the bin and the bin cover itself is it will impact separation efficiency if leaky (more bypass into your filters is bad news).

Guy in Paradise · 08-16-2009, 05:40 AM

McRabbet,

The more I think about it, the more I like the idea of using some, if not all, PVC for the ducting. Getting good tight joints in this metal pipe seems like a problem. I found quite a few unsealed joints even the though previous owner had used a ton of silicone, rivets and tape. The silicone seal just wasn't uniform around each joint and there was quite a bit of silicone on the inside of each pipe joint that was obstructing the flow. Several of the final 4" joints I took apart, had a bunch of sawdust in them.

I am not very knowledgeable about PVC. Is it easy to adapt to PVC? The outlet pipe from the collector is 7", which is currently adapted down to 5" for the main lines, with 4" for the final connectors to the tools. In the manual, PSI recommends running 6" for the main lines. All of the gates are the PSI aluminum ones, or are there better gates to use? How are the gates best connected to PVC?

Thanks, Guy

McRabbet · 08-16-2009, 11:24 AM

Guy,

Your first challenge is to get an adapter to go from 7" to six inch diameter. Ideally, the adapter will actually neck down to the outside diameter of S&D PVC pipe, which is 6.275", so the PVC will fit inside the adapter (you may want to make your own, using some ingenuity and 6" couplings as used below). I don't know the specifics for your blastgates, but I would suggest that you make your own because it is really easy. I've made several from standard PVC couplings cut in half that are then glued into 1/2" Baltic Birch plates with Gorilla Glue (I score the exterior of the coupling to help the glue joint) and then use a piece of laminate and some shim pieces to complete the sliding gate -- here is a picture borrowed from Alan in Little Washington's Photo Gallery showing his blast gate production line -- the one in the center front is a perfect example of a well-made manual gate with a block of wood on each end of the laminate to form a handle. (Of course if you want to go upscale, you'll want to make the autogate pneumatic versions that Alan has on his system).

Here is a picture of ones I made with 1/4" Baltic Birch gates and 3/4" plywood. Frankly, the through gate slider is a better design because it won't clog.

If you don't want to make your own, but want ones that fit perfectly, you can buy these from the folks at ClearVue Cyclones.

PVC pipe fits into these readily and they won't cause the leak problems you've encountered with the metal pipe. I made 6" ports for my table saw and jointer the same way, but used 3/4" plywood. I cut a hole in the back of my tablesaw cabinet using a metal blade on my jigsaw. Here is the port I made for my tablesaw before it was painted Grizzly Green and connected up.

Hope all of this helps -- I know from experience that PVC works very well and it won't leak. And it does not need to be glued or screwed together because the joints are slightly tapered and fit very well. If you want, you can add a small bead of clear silicone sealant around each joint where the pipe enters the bell end of a fitting or another length of pipe.

Guy in Paradise · 08-18-2009, 11:02 PM

McRabbet,
Thank-you for the PVC information, and the pictures are invaluable. I will begin planning.
Guy

Guy in Paradise · 08-18-2009, 11:15 PM

McRabbet and others knowing about dust collection,

Does a Dust Collection system using PVC ducting need to be grounded? I noticed on the Oneida system in the classifieds that it is not grounded. And of course, there are those proponents that will wrap all of the pipes in wire and at certain distances drive in a screw. Never been to sure all of that was needed.

Thanks, Guy

McRabbet · 08-19-2009, 05:18 PM

I have never grounded my systems because it really is not practical and IMHO, it is not dangerous. Please review this link from our Link Library, which I think is a fairly good analysis of the issue. Static discharges will occur externally with PVC and you may experience a small shock here and there, but I've learned not to put one hand on my table saw and another on a piece of PVC in my system. I use wire-style hose clamps on my flexible duct and may link the coil wire to the machine to which it is attached to dissipate the static charge.