ATEX approved

Filter specialist Leiblein with new dosing station for cellulose

P‌owdered cellulose may only be introduced into liquid for the deposition of a filter bed for high filtering quality in compliance with all regulations for hazard prevention in order to avert possible ignition and explosion events. The filter specialist Leiblein has launched onto the market a new equipment product, an ATEX-approved dosing station for cellulose. This accessory equipment is an important addition to the precoat and pressure belt filters manufactured by Leiblein. In this system module, components with their own ATEX approvals and new elements of the Leiblein dosing station are combined, for which ATEX approval has also been obtained. In the entirety of the module, therefore, all necessary areas are covered to meet the guidelines for hazard prevention in accordance with the ignition hazard assessment in DIN EN ISO 80 079-36 dated 18.01.2019. With the TGD 500 and TGD 900 models, different quantities of cellulose can be processed depending on requirements.


Safety and efficiency thanks to high equipment quality

The dosing process starts with placing and cutting open of a cellulose bag. At the same time, following activation by means of inductive sensors, the resulting mix of powder, dust and air is suctioned into the receiver unit. As the valve is closed, the dosed material slides in, collects above the discharge screw and is loosened up by the upstream rotating bridge breaker to avoid any damming up of the material. After the material has reached the screw outlet, a vacuum conveyor suctions up the material and fills the precoat tank. Here the liquid immediately absorbs the cellulose, an agitator effectively supporting the mixing process. A built-in sensor monitors the mixing process to prevent overfilling while ensuring maximum filling level.


Approved technical standard for hazard prevention

In its entirety, the dosing unit ensures all measures are ­effected for protection against explosion and ignition hazards in compliance with ATEX requirements during the processing of cellulose. The assemblies are divided into different zones which are indicated with EX-zone 22 (green), 21 (yellow) and 20 (red), and with reduction of the indicator, these zones are assigned a higher hazard assessment. In the diagram, this is made extra clear with the colours green through yellow to red. So with proper use with filling in the dosing station (green) in normal operation, an explosive atmosphere at the filling valve and in its direct vicinity cannot be expected. The estimation of hazards by whirling up of dust in the following zones (yellow) of buffer tank, bridge breaker, screw conveyor and precoating tank is higher. In the vacuum conveyor ­component, with the EX zone 20 (red) the highest hazard assessment is assigned. The adapted high-quality design, the materials used and safety fixtures, based on the ATEX approvals of all modules, guard against all hazards in the respective EX zones. The new ­Leiblein dosing station is therefore a safe unit for precoating celluloses and achieve special filtering quality.


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