KRUGER Type KRA rectangular splitter attenuators have been tested in accordance with ISO 7235 – Measurement Procedures for Ducted Silencers. Test results are determined in a “duct-to-reverberation room” laboratory facility. Performance data shown include static and dynamic insertion loss, self-generated airflow noise, and pressure loss in the direction of airflow.

KRA series was tested in accordance with BS EN 12101-3 and satisfies the performance criteria for Class F250, F300, F400.

Elbow attenuator is available, for more information, please contact your nearest Kruger office for details.

Insertion Loss

The static insertion (Airway velocity = 0m/s) was measured without airflow through the attenuators, while dynamic insertion (Airway velocity > 0m/s) was measured with airflow travelling in the direction of noise travel. Insertion loss is a measure of the noise reduction characteristics of an attenuator. Insertion loss test data is obtained from substitution method where the attenuator is being replaced by an exactly matching ductwork.

Regenerated Noise

Additional noise occurs when air passes over fixed duct elements such as splitters in attenuators. These noises are due to the changing cross sections in the attenuators. It is normally severe at high air velocities.

Pressure Drop

Pressure loss across the attenuator increases with attenuator’s length and insertion loss. Attenuators with reduced airway area have higher insertion loss, however the higher flow restriction will induce a larger pressure drop.

Quick Facts

 •  Module 400-150 to 600-600

 •  Insertion Loss Up to 50 dB

 •  Performance Tested as per ISO 7235

 •  High Temperature Test as per EN 12101

Casings

The casings are constructed of high quality pre-galvanised steel sheets. The modular system allows KRA attenuators to be manufactured in an unlimited size to handle any specified airflow. The larger attenuators would normally be supplied in sections for ease of handling on site.

Flange Connections

Type KRA rectangular attenuators are complete with metal flanges as standard on all single units and multi-section units with mounting hole at each of the corners.

Acoustic Splitters

The acoustic splitters consist of a pre-galvanised steel framework into which is packed acoustic media. The media is consistently packed so as to negate voids. The splitter frames are fixed firmly into the attenuator casing. The method of splitter construction used on KRA attenuators provides an extremely stable and robust assembly.

The acoustic media in-fill is covered in a glass fibre facing to prevent the erosion of particles into the air-stream. As standard, the in-fill is then covered with pre-galvanised perforated sheet steel. Both ends of the splitter sections are fitted with bull-nose fairings in order to reduce pressure loss and give better re-entry conditions for the attenuated air.

Acoustic Media In-fill

The in-fill is mineral fibre which has Class 1 rating for surface spread of flame, as measured to BS476 and a non-combustible rating when exposed to BS476 Part 4. The splitters are suitable for air velocities up to 30 m/s.