Ventilation and Noise Control Resources

Everything You Wanted to Know about Air Filters

Posted by Gary Leseman, P.E. on Feb 18, 2016 3:10:57 PM

We’ve been designing ventilation systems with air filters for many, many decades. In this time, we’ve come to realize that sometimes a customer might expect air filters to actually filter out sound as well as particulates. It seems like a logical conclusion, but it’s actually pretty far from the truth. Here are some thorough answers to some of your most common questions.

Is it possible to use air filters instead of silencers? How can air filters be used as silencers?

This is a common misconception, but an air filter is not designed to filter out airborne noise.A Filter Silencer - Image from Universal Silencer

Air filters employ an air permeable media material that allows air to pass through the media but traps airborne dust and contaminated particles on the incoming air side of the media. Some air filters can also be coated or impregnated with a material  that eliminates odors such as a carbon filter.

For airborne noise you need what is commonly called a silencer.

Combination filter silencers are available that both filter air and silence airborne noise. However, this device consists of basically two components: an air filter plus a silencer. 

A Vent Silencer - Image from Universal SilencerHow does a noise-reducing vent silencer work?

A vent silencer is a device consisting of closely spaced sound absorbing baffles which allow air or gas to flow through the open area between the baffles while converting the noise energy into heat within the absorbing baffles. The air or gas is discharged to atmosphere at a more reduced noise level than the unsilenced air or gas stream would have without the silencer.

When a certain back pressure and release rate must be maintained on discharging air or gas (as in the case of a gas pipeline bleed valve), then a restrictive diffuser or flow orifice is added to the vent silencer. The backpressure to be maintained during the bleed off period can be upwards of a thousand psi. This special type of silencer is commonly referred to as a Blowdown Silencer.

Are there air filters I can use to meet DNV regulations?

We know of no DNV regulations that dictate air filter construction or performance.

How does a vacuum pump filter-silencer work?

There is actually no such thing as a vacuum pump filter-silencer. You can either have a stand-alone filter or a stand-alone silencer, but they are considered two separate pieces of equipment. There is a piece of equipment called a vacuum pump liquid separator silencer, but that is for eliminating liquids in a vacuum pump process application.

What other questions do you have about air filters and silencers? Feel free to post them in the comments or you can email us directly at [email protected]. This equipment is sometimes overlooked, but often times absolutely necessary to a well-functioning ventilation, process, engine, or gas turbine system. Images in this post come from Universal Silencer. You can buy their high quality equipment through us -- check out our offerings and send in a quote request

 

Topics: General Ventilation, Noise Control

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