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Industrial, Power, and Process Silencers
Industrial Fan Silencers
A fan radiates noise equally through its inlet and its discharge. Usually either the fan’s inlet or outlet is connected to some sort of equipment that contains and/or absorbs the noise from that side of the fan. Normally, only the inlet or the discharge side has to be silenced. One exception is that type of air conditioning system in which both the fan inlet and discharge are ducted into occupied spaces. In these installations, silencers are often required on both the inlet and discharge sides of the fan.
Flextech Fan/Blower silencers are available in a wide variety of sizes and capacities. They are compatible with popular-size airfoil blade and other type fans to reduce fan noise to required or legal levels. Also available are rainhoods, flow-measuring piezometer tubes, and filter assemblies.
A discussion of the methods for computing fan silencing requirements and listings of standard centrifugal fan inlet and discharge silencers is available in our literature
In addition, fans are sometimes encased in either acoustical or concrete enclosures with splitter silencers quieting the air inlet ducts to the enclosures. If the fan discharges into a stack, a stack stuffer may be used. Large axial fans are silenced by means of splitter silencers.
For Large Fans, A Special FTIB Fan Silencer Should Be Used
Since the cost of even a few decibels of noise reduction is high with large fans, it pays to tailor the silencer to the fan’s exact requirements. This advice particularly holds true when the flow per silencer exceeds about 200,000 CFM. We are prepared to accomplish this aim.
Fan size, make, RPM, wheel diameter, number of blades, and BHP:
- Inlet box for fan inlet size
- CFM and density of air
- Pressure drop allowance for silencer
- Acoustic criterion required
- Fan noise generation by octave band (from fan manufacturer); if not available, we can estimate the same from fan RPM, number of blades, and wheel diameter
MODEL FTIB For Fans with Inlet Boxes
The internal configuration of this model silencer is designed so that the silencer exit matches the fan inlet box. As a result, the need for a separate transition piece is eliminated.
Each silencer has a pressure drop of 1.00" of water at its rated flow. The silencer includes a 3/4" mesh galvanized inlet screen, a silencer section, and a flanged discharge, which is sized and drilled to match your inlet box.
MODEL FTDF Fan Discharge Silencers
Flextech has designed a series of fan discharge silencers for use when the fan inlet is connected to the process and the discharge is linked to the atmosphere.
The required silencers are generally larger than the fan discharge connection, and transitions from the fan discharge to the silencer are not included. However, both inlet and discharge transitions are available on request.
The pressure drop at the rated flow is 1.00 inch of water. This pressure decline has been corrected for the pressure recovery from the fan discharge velocity. A 50% diffusion efficiency is assumed for the transition from the fan to the silencer.
Model FTDF silencers can be supplied at extra cost with internals removable for cleaning. This approach is recommended when the silencer is used with dirty gases.
Note that transitions from the fan discharge to the silencer inlet must expand at an angle not exceeding 15° on the fastest expanding side. Also note that "B" dimension must be parallel to the fan shaft for good aerodynamic performance.
MODEL FTCI For Single Inlet Fans Without Inlet Boxes
Model FTCI Fan Silencers are designed to bolt directly onto the fan inlet flange. The Silencer includes a silencing element, followed by a plenum section, with one or two removable plates to allow access to the bolts, and 3/4" mesh inlet screen. Each Silencer has a resistance of 1.00" of water at its rated flow.
MODEL FTSI for Single Inlet Fans without Inlet Boxes – 90° Inlet
Flextech’s Model FTSI fan inlet silencer is designed to bolt directly to the fan inlet flange. This silencer includes the silencing section, followed by a plenum section that is large enough to accommodate the fan inlet opening. A removable plate is incorporated to allow access to the plenum for installation. A 3/4" mesh galvanized inlet screen is standard. Model SI has a built-in, all-metal inlet box.
MODEL FTCIF FILTER ASSEMBLIES
Flextech’s Model FTCI fan inlet silencers can be supplied with a matching inlet filter. When clean, these filters will add 0.15" of H2O to the silencer at the silencer-rated flow. Filter elements are removable and can be reused after cleaning. Filter is a cleanable viscous type of all-galvanized construction and has a filtering efficiency of 93% at rated flow on 10 micron particles. CIF model numbers correspond to CI silencer model numbers.
RAINHOODS For Vertical FTIB, FTSI and FTDF Fan Silencers
Flextech rainhoods provide uniform flow at the silencer face. As such, a minimum increase in pressure drop results when they are used with a Blower inlet silencer. Rainhoods for vertical down installation will add 0.25" of H2O at silencer rated flow.