Paint dust filters
Wet painting also results in overspray. Overspray is the solid portion of the paint that is not taken up by the workpiece. According to the purpose of use, the overspray is moist and sticky immediately after release. It is captured by the exhaust air stream in the spray booth and fed to a filter. This can be, for example, a baffle plate filter, paper filter, fleece filter, glass fibre filter or also combinations of these. The adhesive effect causes the paint particles to adhere to the contact surfaces of the respective filter medium, as a result of which a good degree of separation is achieved. However, all these filters are storage filters, i.e. the filters clog up more and more during operation and cannot be regenerated. A filter exchange becomes necessary if the exhaust air rate of the spray booth falls below the minimum. This can be very time-consuming under certain circumstances and the work process must be interrupted in order to do it. To make things worse, not only must the filtered and bound paint residues be disposed of, but also the actual filter materials.
Such tooling times are not justifiable for automatic, continuous or multi-layer painting processes. Continuous procedures such as automatically cleaned filters are likewise required for this. The humidity and the adhesiveness of the particles to be filtered are thereby the problem. In order to solve this problem, the paint particles should be relieved of their adhesive capability as far as possible whilst still inside the paint booth. Our patented ‘RTS-Rotation’ system is outstandingly well suited for this. The system is comprised of slowly rotating brush rollers, which take up the adhesive paint particles on the surface of the bristles and allow them to dry there. The bristles are automatically regenerated at pre-specified time intervals by combing devices that swing in at the rear of the brush rollers. The dislodged paint residues can then be removed and disposed of either manually during work breaks or automatically during operation.
The degree of separation of this system is, however, insufficient to satisfy the environmental protection requirements concerning residual dust content in the exhaust air. A further filter stage is necessary for that. It must be assumed that the paint particles arriving here are to a certain extent still damp and sticky. For this we use special paint dust filters with high-quality filter tubes with PTFE diaphragms. If necessary, precoating agents (auxiliary dust) are used in order to neutralise the adhesive capability of the particles and to keep the dust layer on the filter elements permeable to air. The precoating agent is injected into the raw air pipe by means of special dosing units. The filter tubes are cleaned by means of compressed air impulse cleaning.
The use of this technology requires special know-how. We have had the appropriate experience for almost ten years. The implemented plants have capacities ranging from 5,000 to 90,000 m³ /h.
Because of the large number of different paint systems, individual experiments are usually necessary in our pilot plant in order to find the correct solution for the individual case.
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