Powder coating involves the coating of electrically conductive substances with a powder coating. This process is used for example in metal coating, the coating of household appliances (white goods), furniture coating or automotive coating. The field of sand blasting or compressed air blasting has precisely the opposite goal – namely to remove deposited substances such as paint, rust or contaminations. In both cases, valves are used to control the transport of powder or blasting agent and control the removal of excess powder and the sandblasting waste.
The paints or coatings used in powder coating primarily consist of dry powder with a grain size of less than 0.1 mm and are usually based on epoxy or polyester resin. Powder coating is not only carried out to change the visual appearance of the product but also to provide corrosion protection.
A number of steps are required in the pre-treatment stage in order to produce a uniform and stable coated surface. The products to be coated firstly need to be freed of any surface residues such as old paint or grease and multiple conversion layers (as the basis for the subsequent layers of paint) need to be applied. Imperfections, spalling and unevenness can occur if this preliminary work is not completed.
In the area of powder coating, valves are generally used to control and shut off all flows of powders or suspensions that are necessary during the process.
Sand blasting involves blasting very fine particles – so-called blasting agent – at the product with the aid of compressed air in order to remove undesired coatings, rust or other contaminations. Sand blasting may also be carried out for optical reasons to create matt surfaces from shiny ones. Two different processes are used for handling the blasting agent. If the blasting agent is disposable, it is simply disposed of after the blasting process, while reusable blasting agents are recycled and fed back into the blasting circuit.
Valves are also used in this sector in both the feed and outlet pipes to the blasting chamber for various different tasks related to controlling transport.
Pinch valves can be used in pre-treatment processes – as control valves for cleaning agents for the pre-washing stage – in powder coating plants. They control either the supply of cleaning agent mixed with water for cleaning or the removal of waste water.
However, they can also be used within the actual coating processes themselves as control or dosing valves for the transport of powder coatings or for the removal of the excess coating powder that is loose or combined with water or bulk goods.
In the area of sand blasting applications, pinch valves can also be used for multiple different applications. They can be part of the actual blasting process, where they act as control valves for the stream of blasting agent. In addition, pinch valves can be used in the processing of waste blasting agent. In this case, they control the removal of the contaminated blasting agent that collects underneath the blasting chamber.
No matter whether the pinch valves are used in powder coating or sand blasting, they often need to control the transport of highly abrasive media. Therefore, it is essential to use abrasion-resistant components or corresponding valve configurations.
The focus is clearly placed here on the sleeve inside the valve that comes into contact with the medium because it occupies almost the complete width of the valve and thus is practically the only thing that blocks the medium being transported. This is why AKO Armaturen developed special anti-abrasive rubber compounds many decades ago to satisfy the requirements mentioned above.
A glass blowing workshop uses pinch valves as control valves for blasting agents.
The manufacturer of window frames uses pinch valves to remove the coating powder during the coating process
The paint shop uses pinch valves in the pre-washing of the metal parts to be coated.
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