Diffuser Silencers
 IAC designs D-Duct Diffuser Silencers (DDS) for installation at the outlet of vane axial fans. The combined interior diffuser cone and exterior square jacket casing make these units into aerodynamic regain devices as well as silencers. The DDS is an effective inlet cone and silencer.
The D-Duct Diffuser Silencer offers the following benefits:
- Combined silencer and diffuser – all in one
- Excellent acoustic performance characteristics
- Permits silencing where it is most effective
- Reduces pressure drop
- Easy to handle and install
- Certified performance
- Available in sizes to match directly a manufacturer’s fan sizes
IAC designs and manufactures D-Duct Diffuser Silencers to order in our own state of the art manufacturing facility based at our European Headquarters in Winchester, Hampshire, UK. At IAC, we use the best laser cutting technology and also in-house painting and finishing facilities.
Typical uses of IAC Diffuser Silencers
Diffuser silencers are suitable for many different types of applications and markets that include:
- Shopping Centres
- Schools
- Sports Facilities
- Hospitals and many more
To find out more about our D-Duct Diffuser Silencers, please contact our Building Services Team or download our Duct Silencers catalogue.
Diffuser Silencer Range of Products
IAC offers the following range of diffuser silencers:
- FLAKT for variable vane axial fan discharges
- JOY for controllable pitch vane axial fans
- BUFFALO for controllable pitch vane axial fans
- WOODS for varofoil variable pitch vane axial fans
Materials and Construction
The rectangular jacket outer casing of the Diffuser silencer is from lock former quality type G-90 galvanised steel in the following minimum gauges based on the smallest diameter of the internal diffuser cone. The internal diffuser cone is from lock former quality type G-90 galvanised perforated steel in the following minimum gauges based on the smallest diameter of the diffuser cone.
| OUTER CASING |
INTERNAL CONE |
| Dia (mm) |
Min. Shell Gauge |
Dia (mm) |
Min Shell Gauge |
| Up to 904 |
0.71mm |
Up to 904 |
0.71mm |
| 914-1143 |
1.2mm |
914-1397 |
1.2mm |
| >1143 |
1.2mm |
>1397 |
1.2mm |
Diffuser silencers include an internal cone of consistent diameter along the entire length in the direction of the airflow. The core diameter is selected based on the adjacent hub diameter or, in the case of C-frame mounted motors, the motor frame size for the respective fan system on which the diffuser silencer is installed. The core is from lock former type G-90 galvanised perforated steel in the same gauge as the internal diffuser cone. The core is supported by a minimum of three welded radial attachment brackets installed on 120-degree angles to each other to provide uniform support.
100mm long, 3mm thick-sleeved end connections are standard. When noted, rolled angle flanges are welded to the sleeve by the manufacturer.
For units where the minimum diffuser cone diameter is 914mm or greater, an additional support rod is welded between the radial bracket and the sleeve to prevent from being exerted on the internal core by the airflow of the fan.
All welds are touched-up with zinc-rich paint after fabrication by the manufacturer. The internal core and the rectangular outer jacket of the diffuser silencers are filled with inorganic mineral or glass fibre of a density sufficient to obtain the specified acoustic performance. The fill is packed under not less than 5% compression to eliminate voids due to vibration or settling. The fill material is inert, vermin and moisture proof. Combustion ratings for the silencer acoustic fill when tested in accordance with ASTM E84, NFPA Standard 255 or UL No. 723 are not greater than the following:
- Flame spread classification 20
- Smoke development rating 20
Download our Duct Silencers catalogue to learn more about the many sizes and standard types of silencers that are available from IAC.
Ducted Discharge |
 |
 |
 |
Fan plus DDS Silencer |
Fan plus 45 degree (or greater) Transition, No Diffuser |
|
Discharge Into Low Velocity Plenums |
 |
 |
 |
Fan plus DDS Silencer at Plenum Entrance |
Direct Discharge into Plenum, No Diffuser |
|
Free Discharge |
 |
 |
 |
Fan Discharge, No Diffuser |
Fan plus DDS Silencer |
|
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