Startseite / Retrofits

Manville, Wertheim

Here a silencer system in being used at a textile manufacturing facility. Since a lot of wet fibers and saturated process air are transported through the silencer, it can quickly become dirty and lose its function. Therefore, Nießing received the order to install a plate transducer that is insensitive to contamination and performs its noise damping work effectively under difficult conditions.

Also, Nießing has developed a special cleaning system which makes it possible to lower individual splitters to the bottom of the chimney by means of a lifting device and thus to clean them safely and sustainably. This eliminates the need for regular splitter replacement and saves the operator considerable maintenance costs.

Compo Krefeld

Retrofitting of a silencer on a 93 m high steel chimney. The requirement here was that the system should be insensitive to contamination, since cleaning would involve considerable effort due to the height of the outlet.

Thus, only the plate resonator was considered as a silencer concept. In addition to the insensitivity to contamination, the minimum pressure drop was a decisive factor in the selection of the system.

Both the edge lining of the silencer and the splitter cross were equipped with panel resonators. The neighborhood had previously complained about noise disturbances, which was verified during sound measurements. The identified noise frequency (200 Hz) was eliminated accordingly by the silencer retrofit to everyone’s satisfaction.

Units: 3 fans, total volume flow 245,000 m3/h

Silencer dimensions: Diameter 2,400 mm, length 8.5 m, insertion loss >30 dB at 200 Hz, pressure drop < 100 Pa.

Tucher Brewery, Fürth

Here, the steel chimney of a steam boiler plant is equipped with a splitter silencer.

The silencer splitter was specifically designed for the interference frequency of the boiler/burner (80 Hz). Minimum pressure loss with maximum attenuation to the desired frequency range were the specifications that were successfully met.

Power unit: Steam boiler

Baffle dimensions: Diameter 600 mm, length 7.0 m, insertion loss 25 dB at 80 Hz.


Here, 8 systems conveying exhaust air from painting/spray booths are equipped with plate resonator silencers.

On the one hand, the silencers were specifically designed for the interference frequency of the fans (315 Hz). On the other hand, a broadband insertion loss was to be realized with minimum pressure loss. For this purpose, a combined system of absorption silencers with integrated plate resonators was used, and the required sound values were met without compromising performance.

Units: 8 x exhaust fans, each with a volume flow of 30,000 m3/h

Silencer dimensions: Diameter 1,400 mm, length 4.0 m, insertion loss 20 dB

Getzner, Austria

This is a retrofit of plate resonator splitters installed in several chimney systems. Minimum installation effort with maximum effect.

The plate resonators were specifically designed for the disturbance frequencies of the fans (200 Hz). However, they also provide high insertion losses in the other frequency ranges. Thus, it was possible to achieve the goal of leaving a uniform residual spectrum with minimal pressure loss.

Units: two exhaust fans, each with a volume flow of 20,000 m3/h

Silencer splitters: combined absorption/resonator splitters, overall length 7.5 m, insertion loss >40 dB at 250 Hz

Ludwigshafen, mobile heating center

The mobile heating centre is equipped with a 9.5 MW boiler. Since the heating plant is located at an open site (close to residential buildings), the requirements for the permissible sound levels of the exhaust system were a decisive criterion for approval. Specifically, the frequencies < 100 Hz were the focus of attention. The successful implementation has resulted in further orders.

The combination silencer used was designed as a cantilevered chimney. The prescribed muzzle height benefited the silencer’s overall length. As an experienced steel chimney builder, Nießing was able to realize both the static/structural concept for the silencer chimney, as well as the acoustic performance.

Here, too, the silencer concept hardly shows any backpressure despite the high insertion losses, since the cross-section of the exhaust pipe is not reduced or disturbed by internals (splitters/cores).

Units: Boiler, 9,400 kW, with an exhaust gas mass flow of 15,320 kg/h

Silencer: combination silencer, overall length 10.0 m, insertion loss >35 dB at 125 Hz


Here is a retrofit of two resonance silencers which eliminates low-frequency noise from a 2 MW engine.

The hollow chamber resonators exhibit high attenuation at the disturnacnce frequency (100 Hz), but hardly cause any backpressure, since the nominal size of the exhaust pipe cross-section is not reduced. The delivery and installation of the exhaust silencers as well as the planning and modification of the exhaust system were realized by Nießing, on a “turnkey” basis.

Power unit: Gas engine, TCG 2020 V20, exhaust gas mass flow 11,423 kg/h

Silencer: Two resonance silencers, overall length of approximately 3.0m each, insertion loss >20 dB at 100 Hz