Duct Muffler Between Fan & Filter

[New Holland]

Hi Guys & Gals,

 

I have a 12" 550Litre/Sec fan with a duct muffler on the exhaust side of the fan. It's almost silent except you can still here the air rushing into the fan intake side. Would a short muffler between the filter and fan silence it?

[jimbojones5678]

Yes - highly likely.

I run it that way too and it is very quiet.

 

Jimbo

[Al B. Fuct]

To quiet the intake, attach a short length of duct and put a wide radius bend in it, just enough to interrupt the straight line path between impeller blades and your ear.

 

If that doesn't do it, you can make a baffle box.

 

 

Build a box with a couple of baffles in it to obtain a serpentine airflow. Can be cardboard, plywood, even a plastic storage tub might work. Line the box with foam rubber, pieces of old wooly blanket, even pink batt insulation.

 

Put a filter made out of an old piece of pantyhose over the intake to prevent dust from accumulating in the insulation.

 

The area of the intake and the serpentine duct should be at least the same area as the duct to the blower, larger if possible.

 

This will cut the vast majority of whoooooshing from air motion and high frequency whine from impeller blades.

 

The baffle box will also work on the outlet side of the blower but a durable insulation material should be used if the blower has any ballz.

 

The same serpentine box principles also work well for trapping light glow from inlets and exhausts.

[billos]

I like it

 

Would this system work adequately in reverse, for intake also?

 

Say with an axial? Seems an awful lot of work for a little old axial

 

 

nb: Al’s original has been edited by billos

 

[Al B. Fuct]

Yes, it will work in either direction.

 

The only caveat is that if you are blowing high velocity air into such a muffler box, make sure the insulating material is tough enough to stay together. Old wooly blanket slices are great, about 25-50mm deep.

 

A filter on the intake to keep dust out of it will make it work better longer. If it gets packed up with dust, it will not trap sound as efficiently.

[New Holland]

Hey Al.B,

 

Thanks for the advice. But can I be a lazy bastard and just buy one of those cylidrical duct silencers?. Alot of work building that box. And then theirs the cost of MDF etc?. This fan does have balls, it sucked the hair of my head like a dandy lion!. I'm worried that bits of blanket would get sucked into the fan. Plus I like to keep things neet and tidy!.

[Al B. Fuct]

Sure, if you can buy one cheaper than you can make one, have at it. I bet I could make one for under $20 out of a plastic storage tub and a cut-up wooly blanket from an opshop hotmelt glued to the interior surfaces (several layers, to make 25-50mm). Wooly blankets don't go to bits terribly easily. You'd need a wind tunnel to destroy one. If you have a 200hp exhaust blower, I'd consider other options, like putting wings on your growroom and flying it to Cuba.

[loylty gets u nothing]

pmsl

love it

bil