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Suction Loss at and through Blast Gates?

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Forum topic by Rayne posted 05-31-2015 11:32 PM 978 views 0 times favorited 12 replies Add to Favorites Watch
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Rayne

470 posts in 1001 days


05-31-2015 11:32 PM

Topic tags/keywords: question tablesaw planer

Good Evening LJ’s, I was finalizing my dust collection and noticed one part of my table saw collection to not have as much suction as i thought it should, so I started to check for suction loss and air gaps. I know some (if not all) of the 90 / 45 degree elbows have some loss, so I’ll be sealing those up, BUT when I open up my blast gate at the table saw, I felt a lot of air AT the blast gate itself. Is this normal for everyone? And that’s not the only problem. For the heck of it, I checked a hose at the longest end of my piping, which was at the jointer / planer and with the Blast Gates CLOSED, I felt minute suction at the tool itself (end of flex hose to the tool). I’m not even sure how that is happening as the gate itself doesn’t have holes and should be creating a seal once the DC is on, but somehow the air is going Around the gate? It just boggles my mind how it’s creating suction. Can anyone input their thoughts? I’d like to create as air tight system as I can get, even if it means replacing all the blast gates. They are 4” metal gates; no plastic. I’d appreciate the feedback.


12 replies so far

View Kazooman's profile

Kazooman

624 posts in 1414 days


#1 posted 06-01-2015 12:19 AM

Blast gates leak. I am certain that the leakage varies between manufacturers, but, in my experience, the plastic gates are actually tighter. I consult for a chemistry company and I am a part owner of the building. On average we move about 25,000 CFM of air through the facility. We have several “elephant trunks” that come down to service individual pieces of equipment. That would be the equivalent of a section of hose running to an individual machine. That all have a metal blast gate with a retaining thumb screw to hold it I place. They will all whistle with an air leak until you cut a chunk of cardboard and let the suction hold it in place. Not a faulty design, and not junk components. Just reality. I am certain that there are leakproof blast gates available, but you would not want to pay the price to buy them.

I have plastic blast gates in my central dust collection system, and I am happy with the levels of air flow at each of the stations when the other gates are closed.

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Rayne

470 posts in 1001 days


#2 posted 06-01-2015 01:12 AM

Thanks for the confirmation Kazooman. I’ll seal up all the 45’s and 90’s and see what happens then. Worst case scenario is that I buy plastic blast gates and see what happens at each tool when left closed (of course opening one somewhere else to test). I’ll respond back after I taped up all the elbows.

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Roger

19867 posts in 2266 days


#3 posted 06-01-2015 12:52 PM

I think those metal gates are screwed together. Maybe take them apart and run a thin bead of silicon around the edge creating a gasket, of sorts. Now I might even try that. Good luck. I’ll keep watching.

-- Roger from KY. Work/Play/Travel Safe. Keep your dust collector fed. Kentuk55@yahoo.com

View mramseyISU's profile

mramseyISU

419 posts in 1007 days


#4 posted 06-01-2015 01:56 PM

The biggest issue I have with blast gates is crap getting in the corners of them not allowing them to shut all the way. I ended up nipping the corners so I could clean them out. I leaks a little but way less than having the gates part way open.

-- Trust me I'm an engineer.

View WoodNSawdust's profile

WoodNSawdust

1417 posts in 638 days


#5 posted 06-01-2015 02:19 PM

I found that plastic leaks less than metal gates due to the way the plastic is extruded. I switched to metal to prevent the clogging issue. My metal gates always keep metal in the track so that they never have space for dust to accumulate. Here is a link gate&searchmode=2 to the ones I use.

-- "I love it when a plan comes together" John "Hannibal" Smith

View Rayne's profile

Rayne

470 posts in 1001 days


#6 posted 06-04-2015 12:08 AM

I just finished sealing up all the 45’s and 90’s. That really helped the suction at the table saw and am not having any issues so far after a few quick tests. I’ll have to test my jointer and planer later to see how much better the suction is at those tools. Looking forward to more project shop time rather than maintenance shop time.

View Roger's profile

Roger

19867 posts in 2266 days


#7 posted 06-05-2015 12:20 PM

I agree w/u there about shop time is much better than maintenance time. I’ve had lots of maintenance time here lately it seems, and I’m a bit of a stickler when it comes to “preventative maintenance”. Work/Play safe. Keep that dust collector fed. :)

-- Roger from KY. Work/Play/Travel Safe. Keep your dust collector fed. Kentuk55@yahoo.com

View MrRon's profile

MrRon

3926 posts in 2705 days


#8 posted 06-05-2015 05:26 PM

“Airtight” is not easy to accomplish on a DC system. It may even be impossible to attain. To put the term “airtight” into perspective, I will tell you what is required to attain air-tightness on a ship. There are compartments on board a ship that need to be airtight. To do this, all joints and seams on steel have to be welded 100%; doors have to have rubber gaskets on them and the whole thing is tested using 2psi air pressure to detect for leaks. The manometer has to show zero leakage after 15 minutes. A soap solution is sprayed on seams and door gaskets to check for bubbles which would indicate a leak. If found, it must be made airtight and tested again. A DC system obviously is not going to be put together as stringently as a ship. The best you can do is to tape up all your pipe joints and accept the little leakage you will still have.

View Rayne's profile

Rayne

470 posts in 1001 days


#9 posted 06-07-2015 12:14 AM

Yeah, all the pipes are taped up, which helped increase the performance. I still get leaks at the blast gates, but I may experiment with something that could seal it perfectly without having to modify the gates much. If it works, I’ll post it as a new project.

View Blackie_'s profile

Blackie_

4531 posts in 1974 days


#10 posted 06-07-2015 10:46 AM

When I plumbed my shop with 4” I didn’t glue the joints I just pushed them all together and used duct tape to seal the joints around the fittings, just this past week and after my addition onto my shop I had to re plumb for the new addition and repositioning of the equipment, I tore the whole thing down and started over this time going back priming and gluing each joint and I can sure tell the difference, I figure if I add a new machine or make changes I can always cut and resplice using couplings.

-- Randy - If I'm not on LJ's then I'm making Saw Dust. Please feel free to visit my store location at http://www.facebook.com/randy.blackstock.custom.wood.designs

View MrRon's profile

MrRon

3926 posts in 2705 days


#11 posted 06-07-2015 04:14 PM


Yeah, all the pipes are taped up, which helped increase the performance. I still get leaks at the blast gates, but I may experiment with something that could seal it perfectly without having to modify the gates much. If it works, I ll post it as a new project.

- Rayne


If you can take the blast gates apart, you may be able to wrap some thin plastic tape around the edges of the blade. Plastic electrical tape might work; if too thick, you can get a slippery UHMW tape that has a pressure sensitive adhesive on one side . It is only around .005” thick. You can find it at McMaster-Carr under tapes. http://www.mcmaster.com/#76445a722/=xis9gh.

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Rayne

470 posts in 1001 days


#12 posted 06-07-2015 05:10 PM


Yeah, all the pipes are taped up, which helped increase the performance. I still get leaks at the blast gates, but I may experiment with something that could seal it perfectly without having to modify the gates much. If it works, I ll post it as a new project.

- Rayne

If you can take the blast gates apart, you may be able to wrap some thin plastic tape around the edges of the blade. Plastic electrical tape might work; if too thick, you can get a slippery UHMW tape that has a pressure sensitive adhesive on one side . It is only around .005” thick. You can find it at McMaster-Carr under tapes. http://www.mcmaster.com/#76445a722/=xis9gh.

- MrRon

Considering I couldn’t find much info about blast gate leaks, this is the same idea I came up with, except I didn’t think of electrical tape. I was thinking along the lines of hobby craft sticker sheets i could custom cut to create a continuous border around the blast gate blade. That “should” end the issue with all the closed blast gates leaking. The only thing that will leak after that is the opened blast gate, which should be o.k. to deal with. Thanks for the suggestion. I’ll use electrical tape first since that is plentiful before I cut up these sheets I just bought.

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