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I'm trying to minimize noise in a lampwork shop exhaust system. The system consists of a 1/2 hp squirrel cage type blower connected to the shop space with 8" round ducting.

I am installing a manually-adjustable damper on the suction side of the blower to regulate exhaust flow depending on how many stations are in use, and to reduce power consumption when the blower's full capacity is not needed, while minimizing acoustic noise created by the addition of the damper.

Is there a difference in the level of noise created by a butterfly damper versus a gate (guillotine) style damper? Are there other important concerns regarding the use of the two types?

I do not need to create a full air seal with this damper, so this advantage of gate style dampers is not relevant.

Brian Ford
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  • radial or tangential blower? It is possible to control the speed that the blower runs at. ? – Jasen May 08 '21 at 11:52
  • That is a big motor for 8” duct I would probably control it electronically. If you close the damper in the intake the motor will actually speed up as you are removing the load (air). – Ed Beal May 09 '21 at 16:50

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Adding a damper to a squirrel cage blower either to the inlet or outlet may sometimes increase the noise due to the flow of air past that damper. Other ideas which may work better but will cost more would be to purchase a 2 speed motor. You would get 2 fan speeds which could be selected by switch mounted where you choose. Another idea would be to install a variable speed ECM motor. This motor would yield an infinite number of speeds. You could even have a motorized damper installed that would yield complete control of the amount of air flow. These last 3 ideas, although more costly, would give you an easy adjustment of the air flow as opposed to a manual type damper.

d.george
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  • Fully agree with the noise and electronic control – Ed Beal May 09 '21 at 16:51
  • While I agree in principle with the advantages of a dc drive and motor or 3-phase ac motor and vfd, the extremely low profit margins associated with this shop make the payback period for costly upgrades too long to make economic sense. Reducing the power by swapping in a smaller ac motor that we have on hand, or reducing the speed by changing the drive ratio (the blower is belt-driven) are viable options, but in the short term the air flow control for this system will most definitely be via suction-side damper. Is there a significant difference in noise produced by the two damper types? – Brian Ford May 11 '21 at 02:23