Professional spraying in industrial wood machining, especially the production of boards, is gaining increasingly in importance. This is not just because of the increasing cost of energy and raw materials; it is also because increasingly high demands for quality in the manufacture of wooden boards encourage the demand for suitable processes and possibilities, in order to apply liquids as homogeneously as possible onto prepared base materials. A frustrating factor is that these materials vary depending on the type of board, such as medium density fibreboard (MDF), hard wood fibre building board, chipboard or oriented strand board (OSB), which in turn have an effect on the spraying.
Gluing, humidifying, coating ...
When manufacturing chipboard or MDF board, the gluing process is carried out differently. While the application of glue to the shavings for chipboard takes place in mixing drums, the fibres for MDF board are processed in a blowline (for wet gluing) or in a hopper (for dry gluing). The aim here is to distribute the glue in the blow pipe as homogeneously as possible, because an uneven application of glue leads to staining on the fibreboard and therefore a decrease in quality. As the shavings and fibres are transported along the conveyor lines to the presses, they are moistened with specially designed nozzles or various additives are applied. Here, the flat jet nozzles are used almost exclusively because of their spray features. These nozzles are used as pressure nozzles (single-substance nozzles) or two-substance nozzles. When twosubstance nozzles are used, a second substance (air or steam) is used as an auxiliary atomisation medium.
Pressure nozzles or two-substance nozzles?
Both nozzle systems offer different conditions, which must be considered during the production process: for example, the lower purchase price as well as the low operational costs of pressure nozzles prove to be a financial advantage, compared to those of two-substance nozzles. Other beneficial factors of the pressure nozzle system are the maximum attainable atomisation angle of 120° and the small atomisation momentum due to the low drop speed. With this atomisation system, the achievable drop size is directly proportionally to the current liquid pressure difference: the higher the pressure, the finer the spray. Experience shows that with pressure nozzles, drop sizes smaller than 100 micrometres (with flat jet nozzles) or 50 micrometres (with hollow cone nozzles) cannot be achieved. However, problems with atomisation, even at high pressures, emerge with more viscous media. With suspensions with a high solid content, pressure nozzles thus react sensitively in continuous operation. Furthermore, the control range is limited by the laws of physics. For example, to double the flow rate of a nozzle, the liquid pressure must be quadrupled.
In contrast to pressure nozzles, two-substance nozzles work with a second medium, such as air or steam, for example. In the externalmix nversions both mediums can be regulated independently from each other. The proportion of air or steam to liquid defines the drop size, and this makes sizes of even 10 – 15 micrometres feasible. The separate control of the two media allows for a liquid control range of 1:8. Even highly viscous media can be atomised homogeneously with this technology without being susceptible
to blockages.
Further Information about this Topic and professional publications available at: News und Facts: http://www.duesen-schlick.de/...
Publication free of charge. Please send a copy to Düsen Schlick GmbH, Mr. Christoph Pulkus, Author and contact for further information.
Düsen-Schlick is one of the worldwide leading nozzle manufacturers, offering the entire range of services relating to the use of nozzles starting from research and development through to production and service, all from one source. Providing solutions without delay. Trend-setting patents, such as ABC-Technology®, ensure the company's production success in the areas of pharmaceuticals, food as well as industry and plant construction.
Schlick precision nozzles meet the highest nozzle technology standards: Certified expertise in accordance with ISO 9001:2000, the exceptional vertical integration and the in-depth technical knowledge ensure that these standards are met. Düsen-Schlick is synonymous with cost-effectiveness in atomisation technology. The ongoing quality assurance, such as the guaranteed availability warranty, allows for long-term process reliability.
Gluing, humidifying, coating ...
When manufacturing chipboard or MDF board, the gluing process is carried out differently. While the application of glue to the shavings for chipboard takes place in mixing drums, the fibres for MDF board are processed in a blowline (for wet gluing) or in a hopper (for dry gluing). The aim here is to distribute the glue in the blow pipe as homogeneously as possible, because an uneven application of glue leads to staining on the fibreboard and therefore a decrease in quality. As the shavings and fibres are transported along the conveyor lines to the presses, they are moistened with specially designed nozzles or various additives are applied. Here, the flat jet nozzles are used almost exclusively because of their spray features. These nozzles are used as pressure nozzles (single-substance nozzles) or two-substance nozzles. When twosubstance nozzles are used, a second substance (air or steam) is used as an auxiliary atomisation medium.
Pressure nozzles or two-substance nozzles?
Both nozzle systems offer different conditions, which must be considered during the production process: for example, the lower purchase price as well as the low operational costs of pressure nozzles prove to be a financial advantage, compared to those of two-substance nozzles. Other beneficial factors of the pressure nozzle system are the maximum attainable atomisation angle of 120° and the small atomisation momentum due to the low drop speed. With this atomisation system, the achievable drop size is directly proportionally to the current liquid pressure difference: the higher the pressure, the finer the spray. Experience shows that with pressure nozzles, drop sizes smaller than 100 micrometres (with flat jet nozzles) or 50 micrometres (with hollow cone nozzles) cannot be achieved. However, problems with atomisation, even at high pressures, emerge with more viscous media. With suspensions with a high solid content, pressure nozzles thus react sensitively in continuous operation. Furthermore, the control range is limited by the laws of physics. For example, to double the flow rate of a nozzle, the liquid pressure must be quadrupled.
In contrast to pressure nozzles, two-substance nozzles work with a second medium, such as air or steam, for example. In the externalmix nversions both mediums can be regulated independently from each other. The proportion of air or steam to liquid defines the drop size, and this makes sizes of even 10 – 15 micrometres feasible. The separate control of the two media allows for a liquid control range of 1:8. Even highly viscous media can be atomised homogeneously with this technology without being susceptible
to blockages.
Further Information about this Topic and professional publications available at: News und Facts: http://www.duesen-schlick.de/...
Publication free of charge. Please send a copy to Düsen Schlick GmbH, Mr. Christoph Pulkus, Author and contact for further information.
Düsen-Schlick is one of the worldwide leading nozzle manufacturers, offering the entire range of services relating to the use of nozzles starting from research and development through to production and service, all from one source. Providing solutions without delay. Trend-setting patents, such as ABC-Technology®, ensure the company's production success in the areas of pharmaceuticals, food as well as industry and plant construction.
Schlick precision nozzles meet the highest nozzle technology standards: Certified expertise in accordance with ISO 9001:2000, the exceptional vertical integration and the in-depth technical knowledge ensure that these standards are met. Düsen-Schlick is synonymous with cost-effectiveness in atomisation technology. The ongoing quality assurance, such as the guaranteed availability warranty, allows for long-term process reliability.
