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Ducts and blast gates

Gerald

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Now this may be getting the cart before the horse but lets call it collecting supplies you will need to connect your DC to machines. Thin wall PVC will work just fine . For the best you can order metal ducts any size you want but you will also have to buy expensive connections .

 

A consideration many people talk about is grounding the dust collector and duct. To my knowledge and every forum I have been on and every article and book "there has never been a explosion in a home workshop due to dust collector" . Now , yes a dust collector will create static electricity which causes dust to adhere to outside of ducts. If you do want to ground you can use bare copper wire wrapped around the outside of the pipe and ground to machine and the DC.

 

Using thin wall PVC is easier to work with and connectors are readily available. When you put all these together you can use PVC cement but I guarantee you will rearrange the system and your shop so go with something reversible such as caulk.  You can also use screws to hold the connections together but use as short a screw as will do the job to limit disruption inside duct. You do not have to seal these joints inside as you can do that on the outside of the pipe . This is not to keep the pipe together but to seal leaks. Every little air leak reduces the air flow you will get  from your system and that includes all connections.

 

When using PVC try to keep the long runs as one solid piece of pipe, and after that the fewer joints the better. When I use 45 elbows to create a 90 I grind off that little shelf inside the fitting. Reason: you want the walls as smooth as possible because any bumps or restriction cause disruptions in airflow and reduce suction. This is why you want to reduce the use of flex hose to a minimum. Dust collectors work on a volume of air not the suction power. Dust is suspended in the air flow and disruptions can cause it to drop out and start a clog.

 

Now as to the size of duct " the bigger the better" is not a rule but it is better close to the DC to have larger and go to smaller closer to the machine. My Dc only starts at 5 inch so the 6 I used is overkill but not a killer as it is only 8 foot. Dust collectors do not work well on shop vac hose but that can work for small areas such as drill press or small sanders. Planners, bandsaws, tablesaws, and other large machines are bet to use 4 inch or larger connections.

 

Hanging the duct in the ceiling is simple and easy with several methods. Large plastic twist ties work well. Perforated metal strap will also do the job . I have made several of mine from galvanized wire. Or you can make nice hangers from wood.

 

I started out with what I would call a traditional blast gate made of plastic with short tapers on each end to connect flex. Note that 4 inch PVC connectors do fit 4 inch flex but take a piece with you when you buy. You can buy wire clamps made to seal the flex to connectors or buy a kit at Harbor Freight to make your own hose clamps. Recently I found a new blast gate with a spiral on one end and a shape on the other end which will fit PVC. There are many many designs of blast gate out there from plastic to metal and even some that automatically open when you turn on the machine. When you install the blast gate you will want in convenient and as close to the machine as you can get it. When you do branches off the main gates are a good way to shift the air down different runs. I have one at the top of a run and when open air goes to CMS and wide belt sander (each also with a gate) on the other side the gates at the lathes need to be closed.

 

More pictures next time and how to make your own gates ,

 



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When I use 45 elbows to create a 90 I grind off that little shelf inside the fitting. Reason: you want the walls as smooth as possible because any bumps or restriction cause disruptions in airflow and reduce suction.

 

Interesting little tidbit here.  I have used PVC a lot over the years for many different things other than plumbing and never thought about the inside of it much.

Edited by Woodbutcherbynight

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Gerald - This is exactly the kind of information I need.  

 

I'll start with a few more specific questions...

 

Any thoughts on running the main pipe to the DC on the floor at the base of the wall?

Do you use flex to connect a mobile machine to the blast gate?

Would duct tape make an effective seal at the joints?

 

Thank you, Jim

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3 hours ago, RedMGB said:

Would duct tape make an effective seal at the joints?

It will do sufficiently.  Gerald wrote:  When you put all these together you can use PVC cement but I guarantee you will rearrange the system and your shop so go with something reversible such as caulk.  You can also use screws to hold the connections together but use as short a screw as will do the job to limit disruption inside duct.

 

Screws are okay, especially for joints that prove difficult to keep together.  For caulk I use the cheapest clear caulk I can find.  Easier to take back apart later.

 

 

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6 hours ago, RedMGB said:

Gerald - This is exactly the kind of information I need.  

 

I'll start with a few more specific questions...

 

Any thoughts on running the main pipe to the DC on the floor at the base of the wall?

Do you use flex to connect a mobile machine to the blast gate?

Would duct tape make an effective seal at the joints?

 

Thank you, Jim

1. Floor or ceiling does not matter if you have the room. By using ceiling I have decreased my efficiency because dust goes up to main then down to cyclone and then up to DC.  For the "best" system the dust goes in as near as possible to a straight line at the same level all the way to DC, that is in a perfect world. Any ups and downs causes dust to drop out of the stream of air. But again we do not live in a perfect world so just get as close as you reasonably can or buy DC oversized.

2. I use flex at all machines just limit the use as much as you can. There are commercial adapters you can use to avoid flex such as RV waste connections, and some others that are friction fit.

3. Already covered by others but I will add when you break down the duct to move there will be a mess. The foil tape used on HVAC may work better as it is designed to seal cracks and is easy to work with.

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4 hours ago, Fred W. Hargis Jr said:

I've never had much luck with fabric duct tape, seems to me like it always started peeling off after a year or 2 (on PVC). The foil tape seems to stay on forever. Another ereason to seal the joints (IMHO) is to eliminate the annoying whistle that they sometimes make when they leak.

I also rely on foil tape for sealing joints and patching the odd hole in my collection bag. A friend of mine does HVAC and gave me a huge roll a couple years ago. Great stuff! 

This blog just reminds how much I need to revamp my system. :PullingHair: Hopefully this winter when/if things slow down a bit. 

 

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10 hours ago, RedMGB said:

Considering this as a pre-filter...any comments, opinions, experiences?

 

Thank you,

Jim

image.png.9857580989551ce805eb4ea31e4d8421.png

 

 

image.png.9857580989551ce805eb4ea31e4d8421.png

 

Not with this one. Built my own from an adapter from woodcraft-

143290.0.jpg.665ed573bb1783550abd7a3683036840.jpg

https://www.woodcraft.com/products/trash-can-cyclone-lid?via=573621bd69702d0676000002%2C576455d369702d2f2f0013a2

 

Then added a Thein baffle from this idea-

http://www.jpthien.com/cy.htm

cypro2.jpg.187accc3f9f08008a8d2e3cdf851bb19.jpg

 

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23 hours ago, RedMGB said:

Considering this as a pre-filter...any comments, opinions, experiences?

Next upgrade for me.  Just finished up rebuilding the DC last year and getting some extra ducts run to several machines.  One of many things to do in the shop.

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On 9/3/2019 at 8:29 PM, RedMGB said:

Considering this as a pre-filter...any comments, opinions, experiences?

 

Thank you,

Jim

image.png.9857580989551ce805eb4ea31e4d8421.png

 

 

 

 

This is the one I have in my current setup and do not have a longterm result as yet. I did check the bag on DC upstairs after emptying the barrel on the Dust Deputy had very little in the bag. So my evualation is that it not only collects well it also increased my airflow mainly due to having larger hose down to the branching.

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Jack, you may have to measure it to see the difference, but it exists. I could actually see the amperage draw on mine drop as I sealed the joints. Another reason is to eliminate the annoying "whistle" that sometimes happen when a joint leaks. All this depends, to some degree on the system. Larger ducting, longer runs, and huge airflow, benefit more from the sealing.

Edited by Fred W. Hargis Jr

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I won't say it's not there, just not enough to make it a priority. In big shops cfm lose is a big deal with many users and pieces of equipment being used..

 

I agree with measuring but at the same time I've never felt it was necessary...

 

Metal tends to have the worst air leaks were  I've never really seen it too bad with  pvc...

 

Most have too small of a DC to cover way too many tools with planers at the ends of a run...

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