DIY sound muffler for outdoors dust collector exhaust

[John K Jordan]

...flex 8" ducting with the pink insulation. I unhooked the 17' of metal 7" exhaust that I recently installed and replaced it with 20' of the flex. I shaped the flex into a few (S) shapes just for fun. This has completely eliminated 100% of the jet turbine noise going outside. I only hear the swoop of the air , no noise Period.

Mike,

Have you had this running for a while and if so, is it holding up ok? The reason I ask is while I was researching my own installation a few years ago I remember some discussion on the ClearVue forum about using insulated HVAC flexible duct for exhaust duct. There was some speculation that a powerful airflow might cause some tearing or degrade after extended use. I didn't follow the discussion long enough to hear any resolution.

Do you have experience with long life? When in operation, does the flex duct show any movement, rippling, etc?

JKJ

[James Biddle]

Changing the direction of the air creates a restriction in the form of turbulence, and a loss of air flow. That is, you're slowing down the air by bouncing it around so much. No different than adding a restriction to the ductwork that's hooked to the machine producing the dust (ever notice how the sound changes when you choke off a blast gate?). Similarly, Mike B's solution is to restrict the air flow by using flexible pipe in a serpentine fashion. Have you ever read the manuals for dryer duct installation and seen that they tell you to add x number of feet for 45 degree fittings, y number of feet for 90 degree fittings and z number of feet for every door of flex pipe? That is to account for the air flow loss.

Now, this loss of air flow may not have any affect the ability to remove the dust from your machine because your DC is oversized enough to overcome that flow loss. We used a similar baffle in a previous shop to accomplish that same effect. The DC was oversized because we never ran enough machines at the same time to challenge the capacity of the DC. Building the baffle was easier than adding a VFD to slow down the DC or fine-tuning the blast gates real time as you change the machine usage pattern.

The key is to absorb as much sound as possible with the least amount of performance loss. This is what the product Oneida sells attempts to do, as well as the product Mike K references. It creates a controlled turbulence and minimal flow loss. I have no idea how effective the Oneida offering is (we never used it) and Mike K's product was combined with other measures so we don't know that product's actual contribution as well.

One thing the Staffan H's solution does accomplish, in addition to and in spite of the flow loss from the baffle, is to redirect the noise from the direction of his neighbors towards the ground where additional sound attenuation in realized. As long as the DC performance remains acceptable, he's accomplished his goal.

[andy bessette]

Changing the direction of the air creates a restriction in the form of turbulence, and a loss of air flow...

This is inevitable.

[Chris Parks]

I have the solution and it worked for me. I search every where online and couldn't find what I was looking for, than I had an IDEA!
I recently installed a full diy dust collection system...I installed a large dust collector venting outside. My exhaust pipe was solid 7" metal pipe. It also sounded like a screaming jet turbine engine, Ouch, I have neighbors. Had to do something, I was ready to make a baffle, had the design & materials but had an idea that I just had to try. I purchased a 25' roll of flex 8" ducting with the pink insulation. I unhooked the 17' of metal 7" exhaust that I recently installed and replaced it with 20' of the flex. I shaped the flex into a few (S) shapes just for fun. This has completely eliminated 100% of the jet turbine noise going outside. I only hear the swoop of the air , no noise Period. Hope this helps the op AND FUTURE lurkers. I can once again work all night long with out disturbing the peace.
The third-fourth image is the wall vent I used, Has a magnetized flapper door.
Not sure if Im the originator of this idea but you heard it from me first.

That method is quite common in Australia, some find it good and some find it less than successful for some reason.

[Mike Bigfoot]

I have the flexible exhaust strapped to the rafters near the ridge of the attic. does not flex. Super quiet. Regardless, if for whatever reason I need to replace it after say 10 years so be it, it was so cheap and would take just 10 minutes. Having said that the sound before was unacceptable, Now its nonexistent - ZERO Noise! My advice is keep the exhaust as short as possible and make it oversized, don't be afraid to experiment.
My set up is 6" solid Metal pipe FROM the tool through a cyclone through the collector than the 6" exhaust becomes 8" flex to reduce restriction than right before it exits the building its reduced to the 7" exhaust wall vent. I suppose an 8" exhaust vent would of been ideal but it took a week to get the 7" and after swapping out the original 7" solid piping to 8" flex I just left the 7" installed.
Its a fairly newer set up so no experience with longevity. No worries either. It saved me a lot of stress . It's as efficient as I could of ever hoped for. Its not a hokey set up.

[John K Jordan]

I have the flexible exhaust strapped to the rafters near the ridge of the attic. does not flex. Super quiet. Regardless, if for whatever reason I need to replace it after say 10 years so be it, it was so cheap and would take just 10 minutes. Having said that the sound before was unacceptable, Now its nonexistent - ZERO Noise! My advice is keep the exhaust as short as possible and make it oversized, don't be afraid to experiment.
My set up is 6" solid Metal pipe FROM the tool through a cyclone through the collector than the 6" exhaust becomes 8" flex to reduce restriction than right before it exits the building its reduced to the 7" exhaust wall vent. I suppose an 8" exhaust vent would of been ideal but it took a week to get the 7" and after swapping out the original 7" solid piping to 8" flex I just left the 7" installed.
Its a fairly newer set up so no experience with longevity. No worries either. It saved me a lot of stress . It's as efficient as I could of ever hoped for. Its not a hokey set up.

My DC (5hp ClearVue) was also deafening, painfully loud. I knew from my reading it would be so I included a sound-insulated closet in my shop plans for the DC and the big air compressor . I tried it yesterday - I can hear a whisper just outside the DC closet. I can't go in the closet without hearing protection.

For HVAC efficiency I decided to vent mine through Wynn nano filters and return the air to the shop through a duct. Since the closet is air-tight, I was concerned about both restricting the exit air flow and passing sound back into the shop through the return duct. I solved this by making building a return duct from plywood with a cross-sectional well over that needed. The duct has multiple turns for sound baffling and is sprayed inside with a rubber coating. I can hear no sound through the return duct.

My duct is snaked up through the roof trusses which further insulates the sound. This is my design sketch:

Dust_collector_baffle_small.jpg

Some day I'd like to build a diversion valve to switch the exhaust and dump it outside on occasion. If I do that I'll probably try the insulated flex and continue it in a housing down the outside of the building to vent near the ground (with something to keep birds, snakes, and rodents out!)

JKJ

[mark mcfarlane]

I recently installed a full diy dust collection system.... I purchased a 25' roll of flex 8" ducting with the pink insulation. I unhooked the 17' of metal 7" exhaust that I recently installed and replaced it with 20' of the flex. I shaped the flex into a few (S) shapes just for fun. This has completely eliminated 100% of the jet turbine noise going outside. I only hear the swoop of the air , no noise Period. ...

I'm glad this is working for you. I did a similar design for returning air from my DC closet back into the shop. It's not operational yet (another month or two) but it seemed like a reasonable solution. I bought some good flex duct from an HVAC supplier. Not fiberglass, looks more like like rock wool.

[matthew lippel]

For those of you venting outside and have the cyclone in an airtight shed how do you provide the motor with cool air/vent the hot air all the while maintaining adequate noise abatement?

[Peter Aeschliman]

Matthew, if it's a TEFC (totally enclosed, fan-cooled) motor, the motor will cool itself for the most part. I would recommend running your DC for a while and putting a remote temp sensor near it to see how hot it gets with extended use. I would be surprised if it gets hot enough to cause issues with the motor.

[John K Jordan]

Matthew, if it's a TEFC (totally enclosed, fan-cooled) motor, the motor will cool itself for the most part. I would recommend running your DC for a while and putting a remote temp sensor near it to see how hot it gets with extended use. I would be surprised if it gets hot enough to cause issues with the motor.

For those looking a good tool for measuring temperatures like this, consider a dual-channel thermocouple thermometer. I bought this one a few years ago and have already used it enough to make it worth the cost:
https://www.amazon.com/gp/product/B001EUB6BM
71DQegHRGrL._SL1500_.jpg

I got a couple of inexpensive inserting probes that I use the most. I used it recently to address a question about any elevated temperature of the spindle bearings of one of my lathes after extended running. I taped one probe to the bearing housing and the other to the tool rest to measure the ambient temperature. (After 1/2 hour, the housing was just 4-degrees F higher than ambient). I've also used the insertion probes to measure the temperature deep inside of suspected damp bales of hay! (One reached 160F, yikes)

The nice thing about measuring temperature with a thermocouple instead of standard thermometer is you can tape the probe in contact of something remote (like a cyclone motor!) and don't have to stand on a step stool to try to read it. I think the dual-channel models are worth getting simply for differential readings.

JKJ