The VPI process ensures all pores as well as the surface of the component under impregnation to be wetted with impregnating agent in a uniform and complete manner, and that there are no blowholes.
Potential impregnants are varnish, oil, resin or wax. After drying and degassing of the components under vacuum the impregnating agent is taken off the storage vessel and fed into the impregnating tank either by means of pressure difference or a pump. Under pressure, the impregnant penetrates into the components, ensuring a uniform impregnation. Unused impregnating agent is pumped back into the storage vessel for later use.
In order to safe their electrical and mechanical properties, electric components are often treated by impregnation. This is when the vacuum-pressure impregnation process (VPI) comes to show its significant advantages compared with the impregnation at atmospheric pressure (dip coating process).
The optimum equipment configuration is drafted based on the type of component and impregnating agent.
Advantages of this process:
- Avoiding blowholes in the component pores
- Uniform and complete wetting
- Compact construction with short transport distances
- Adaptation of the equipment to the components and impregnating agent
- Reduced costs for energy