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Thread: 8" dwv fitting

  1. #1
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    8" dwv fitting

    Right angle exhaust fittings are said to reduce DC noise. Would this coupling be better at reducing sound or would it create too much head?
    https://www.pvcfittingsonline.com/8-...-p700-080.html
    Last edited by John K Jordan; 11-09-2019 at 1:02 PM. Reason: Bill: Could not figure out how to edit title. Should read 8" dwv fitting

  2. #2
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    Quote Originally Posted by Bill Jobe View Post
    Right angle exhaust fittings are said to reduce DC noise
    New one for me. Where is a reference for this? Insulation/muffler are recommended to reduce exhaust noise in a cyclone.

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    By noise do you mean decibels or how the dust moves in the pipe?

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    There will be very little noise reduction without some sort of thick sound absorbing material lining the inside of the duct. The thickness needed can be calculate & depends on the frequencies the are to be damped, but that's beyond my pay grade. I just used 3/4" fiberglass duct liner in my return air duct from the collector closet. It has a 90* bend and a dog's leg in it & damps the sound very well.

  5. #5
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    If you are direct venting outside, a 90º turn toward the ground can help with "direct" noise transmission. It doesn't eliminate it but it can help a little with radiated noise. If you heading to a filter setup indoors, only isolating the system is going to have major impact on noise and that still requires an indirect air return path to the shop.
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  6. #6
    I have seen piping used to quiet equipment. The best example perhaps was while visiting a boiler manuf. in the lab they were testing Wayne gas conversion burners. It was very noisy. The engineer said, “watch this.” He took a 12” piece of 4” pipe and put it on the inlet. The system quieted right down. It was amazing. That small section of pipe just smoothed out the air feed reducing the turbulence on that in feed. Every system has a personality. I would be surprised if a short radius return bend would work and the air would be rolling as it come out of the bend. I think you would want 3-5 pipe diameters of straight pipe to smooth the air flow some, but back to that personality thing.

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    I just thought it was an unusual fitting, but I recall reading (on SMC perhaps) that 90° bends in the exhaust can reduce sound. Just curious if others think this might work, as well.
    My number 1 priority has to be sound reduction. Otherwise, I will have to give up turning. Just using an orbital sander for an hour or so while wearing good sound protection is enough to cause my ears to roar the rest of the day.
    Ok, priority 2. Number 1 is as much dust removal as possible, as I have developed a serious sensitivity to sawdust.

    This is a bit off topic, but I do not believe 2 45s are better than a long-sweep 90.
    With every fitting there is turbulence created at both ends. As a former koi ponder, I'm fairly certain that's how it works when dealing with water, anyway.

  8. #8
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    Quote Originally Posted by Bill Jobe View Post
    ...
    My number 1 priority has to be sound reduction. Otherwise, I will have to give up turning. Just using an orbital sander for an hour or so while wearing good sound protection is enough to cause my ears to roar the rest of the day.....
    If you haven't, consider putting the DC in a well designed sound insulated cabinet. My cyclone is a screamer but with the closet I can hear a whisper in the shop. If my ears were that sensitive I would also wear good in-the-ear plugs covered with earmuff protectors. I use that combination sometimes on my bobcat which is pretty loud.

    JKJ

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    Quote Originally Posted by John K Jordan View Post
    If you haven't, consider putting the DC in a well designed sound insulated cabinet. My cyclone is a screamer but with the closet I can hear a whisper in the shop. If my ears were that sensitive I would also wear good in-the-ear plugs covered with earmuff protectors. I use that combination sometimes on my bobcat which is pretty loud.

    JKJ
    I'm building a new home for my CV 1800. A shed 6' away from the shop. I have a number of soundproofing on their way. Both of Green Glues in the tubes, as well as some Mass loaded vinyl.

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    Quote Originally Posted by John K Jordan View Post
    If you haven't, consider putting the DC in a well designed sound insulated cabinet. My cyclone is a screamer but with the closet I can hear a whisper in the shop. If my ears were that sensitive I would also wear good in-the-ear plugs covered with earmuff protectors. I use that combination sometimes on my bobcat which is pretty loud.

    JKJ
    I'm building a new home for my CV 1800. A shed 6' away from the shop. I have a number of soundproofing on their way. Both of Green Glues in the tubes, as well as some Mass loaded vinyl.
    Pricy, yes. But what's left of my hearing is worth a little extra.

    On a lighter note, I just thought of an idea to make headwear that covers the ears out of MLV.
    It would have the additional benefit of protecting your head from flying objects.

  11. #11
    If you are that sensitive to the noise you have a few simple options. There are more complicated options for sure but the easiest ones would be to either build an isolation closet for your dust collector, or put it outside the shop and pipe your trunk line through the wall. This would do wonders for sound reduction.

    For the first option I would just frame up some 4ft x 3ft walls in the corner that the dust collector is located in. Line the inside with Roxul or Owens Corning 703 or both and install a fairly good sized return air vent with a filter attached. Then you could either line the outside with plywood or you could take it a step further and cover the outside in two layers of basic 5/8” drywall with Green Goo and sound isolation clips in between the two layers. This might also work with two layers of plywood instead of drywall.

    For the second option you could frame up a small lean to on your outside wall in the back where it’s not visible from the road. Doesn’t need to be that complicated. Just take some 2x6’s about 3ft in length has attach them roughly 8ft up and cover in either sheet metal or matching roof material if you want to make it look better. Don’t need any walls just to cover the top. Cut a hole in your wall for your trunk line (preferably at least a 6” trunk line) and run an electrical line from your breaker box with an outlet on the end. Depending on the size of your dust collector you will probably want to use 12/2 sized wire and I would get the 12/2 MC that comes already installed in conduit. It’s not that much more and would be highly recommended since it’s going outside.

  12. #12
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    Quote Originally Posted by Bill Jobe View Post
    I'm building a new home for my CV 1800. A shed 6' away from the shop. I have a number of soundproofing on their way. Both of Green Glues in the tubes, as well as some Mass loaded vinyl.
    Don't know if we discussed this earlier, but if you build with staggered stud walls you get enhanced sound dampening since no can transmit sound by contact from the inner walls to the outer walls. And even insulated doors will transmit more sound than the walls. I mounted my doors away from my wood shop area into a back room in the building which helped a lot.

  13. #13
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    Bill, with the unit in a separate building, the noise level in your shop is going to be substantially less...almost ambient. I don't believe you need to compromise the air flow from your duct network to the shed with any turns in hope that it will further reduce noise. The air in the duct isn't causing most of that...the motor/impeller is and with it completely out of your shop and in a different building, then that's pretty much solved, especially if you are putting additional insulation in the shed for sound containment. I do feel that having a long sweep 90º on the exhaust to the open air so it's pointing down will help mitigate ambient sound "to the neighborhood" including when you have doors and windows open. Be sure you also screen that so critters cannot enter your system.

    BTW, I agree that a long-sweep 90º is preferable to a couple of 45º joined, but the latter is often used because the cost of the former can be high for some folks and the part is sometimes hard to source in some materials and sizes. The majority of my bends are long-sweep provided by Oneida a long time ago; a few installed over the years were made from readily available adjustable from the 'borg, but sometimes using two to "stretch" out the change in direction.
    Last edited by Jim Becker; 11-14-2019 at 10:28 AM.
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  14. #14
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    Also I would think blowing into a big bush or group of trees would help soak up the sound. Something like a mature redwood grove with bark 2' thick is very quiet. Of course that may take a few thousand years to mature and give you the full effect. Maybe Monterey pines for quick growth with redwoods to replace them in 50 years or so when they die.
    Bil lD

  15. #15
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    Vegetation can and does help with reducing sound transmission. Probably not a great idea to blow directly onto that vegetation, however.
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