Industrial Fan Silencers – Applications
“Attenuation of fan noise with custom-engineered silencers”
FRP scrubber discharge silencer
Heil FRP Scrubber Fan Silencers
Two Heil FRP scrubber fans were generating a low harmonic sound that was heard two miles from a client’s facility when the atmospheric conditions were wet and cool. An engineering study determined the harmonic sound was in the 125 Hz octave band. A stack silencer, constructed of fiberglass, was designed as a common exhaust stack for both scrubber fans, reducing the sound level by 15 dBA, and eliminating the noise issue.
Code Compliance With Fan Silencer Retrofit
The manufacturing facility were these fans were located was adjacent to a residential community that was a few hundred feet distant. Both the inlet and outlet industrial silencers shown were designed for 70 dBA at 5 feet based on the fan manufacturers sound data, and successfully met the requirement of 55 dBA at property line.
Fan inlet silencer
Fan outlet silencer
Industrial fan discharge silencer designed for a local strict noise code
Municipal Noise Ordinance Compliance
A food processing facility was having noise issues with an exhaust fan connected to a scrubber. The noisy exhaust discharge on the roof had become such a nuisance that neighbors started complaining and resulting in the municipality intervening. On the roof, six feet away from the discharge, the noise was 102 dBA and at the property line (100 feet away) the noise was 77 dBA. The municipality ordinance requires that noise levels need to be less than 70 dBA at the property line.
Silencer Options for Rooftop Location
Our solution was a 144” long galvanized discharge silencer. The silencer reduced the noise to 88 dBA (14% reduction) 6 feet away from the discharge and 65 dBA (15% reduction) at the property line which fulfilled the municipalities requirements. Since the silencer is on the roof, also provided was a weather hood to prevent any outdoor elements from entering the system.
Industrial fan silencer weather cowl
Radial Fan Wheels Require Extended Silencer Length
Shown is a 98-inch industrial fan silencer mounted on a radial-bladed exhaust fan. Fans with radial bladed wheels require extended silencer length to attenuate noise levels across all octave bands. More than what is expected in a backwardly inclined wheel. The additional silencer footprint is needed to house the increased amount of acoustic media and fiberglass cloth necessary to provide the required insertion loss. This silencer resulted in an attenuated noise level of 69 dBA at a distance of 5 feet.