Several 
dust extractors

LESSMANN – THE GERMAN BRUSH COMPANY is one of the leading manufacturers of technical brushes in Europe. Due to an increase in capacity in the woodworking production area, a renewal of the extraction system was necessary.

Surface tools "Made in Germany" have been manufactured at the production site in Oettingen/Bavaria since 1948. As a medium-sized family business, Lessmann is a producer of surface treatment tools with a clear commitment to Germany as a manufacturing location. More than 240 qualified and motivated employees develop and manufacture technical brushes such as circular brushes or interior brushes for all areas of industry and trade. Only with the know-how and the good cooperation of all departments it is possible for Lessmann to supply "first-class products" to customers worldwide. The wide product range of wire brushes is distributed through trading companies or directly to industrial customers.

As part of the expansion of production capacity, the extraction system for woodworking also had to be renewed. The task submitted to SPÄNEX had several special features:

• The required extraction and filter system for an air volume capacity of approx. 40,000 m³/h should not be installed outside due to space problems.

• The chips produced should be briquetted and used as fuel in the company's own boiler plant. Excess briquettes should be disposed of.

The further requirements for the extraction system can be summarized as follows:

• connected working machines: 23,

• 100 % air return,

• silent operation,

• maximum energy efficiency.

In several site visits the responsible SPÄNEX regional sales manager, Mr. Rieder, discussed all details. The proposal was made to implement the extraction system by 4 dust collectors, which should be installed in the production hall. After the inspection of a plant already realized (picture 1) the customer agreed to this concept, so that a detailed offer could be made, which included the following main components:

• Extraction centre consisting of 4 dust collectors with integrated, speed-controlled extraction fans,

• Extraction piping system, divided into 4 groups,

• Briquetting press with a cacpacity of approx. 250 kg/h (material-dependent),

• Electrical circuit on PLC-basis with 4 frequency converters for the whole plant.

The advantages of the plant-technical solution convinced the customer, so that the order for the delivery of the suction and briquetting plant  was given to SPÄNEX in 2018.

The following aspects are the main advantages of this technical solution:

Interior installation of the extraction unit

The dust collectors, manufactured according to the European Standard EN 16770 and tested by the DGUV Test, Prüf- und Zertifizierungsstelle Holz (GS-sign and test certificate H3) meet all requirements in terms of workers´health and safety and are approved for installation in the working area. The compact dust collectors of SPÄNEX are complete dust extraction stations consisting of the flow-in/filter chamber, the fan cell and the container part. The fan is arranged on the clean air side and equipped with a high performance impeller so that high efficiencies are achieved. Energy-saving motors of efficiency class IE 3 are used as standard.

Energy efficiency

By dividing the piping system into 4 groups, the savings potential resulting from different requirements for extraction capacity can be fully used via speed control. Automatically opening and closing lock slides are installed in the connection lines to the woodworking machines (Fig. 2). The opening and closing of the slides is initiated by the control system and at the same time the need for the required extraction capacity is detected. The speed of the extraction fans is adjusted accordingly via the control system. At the same time, the control system ensures that the minimum conveying speeds for the chips and dust are maintained, so that no material deposits occur in the pipeline system.

Silent operation 

The fan cells of the compact dust collectors are lined with sound-absorbing mats, so that the noise emission is extremely low. Additional external silencers are not required.

Briquetting

The dust and chip material separated in the dust collectors is buffered in the containers of the dust collectors and transferred to the rotary valves (decoupling components) via the discharging unit. The rotary valves feed a screw conveyor which conveys the material into a container under that a briquetting press is arranged. The capacity of the briquetting press is approx. 250 kg/h. This corresponds to a chip throughput of about 2 m³/h. The octagonal briquettes produced are conveyed via a transport rail system into the silo for firing in the heating boiler plant. A changeover switch is installed in the transport rail (Fig. 3), so that alternatively, when the maximum filling level in the silo is reached, the briquettes can be conveyed into a big bag for disposal.

Intelligent control

The function package of the electric circuit automatically ensures the controlled and safe operation of the extraction and briquetting plant.

Resume of the Management Board

After almost one year of operation, the responsible managers at Lessmann are enthusiastic about the performance and functionality of this technical solution as well as the energy-saving and low-noise operation.