The Structure of the Vacuum System
The structure of the vacuum system is the key to affect the tightness of the vacuum system and the leak rate of the system. The structure of the vacuum system is reasonable or not, which will directly affect the sealing performance and the leak rate of the system.
1. Avoid the occurrence of dead angle with small curvature radius as much as possible. Ensure smooth transition to check the brakes in the polishing and cleaning.
2. The pipeline connected to the vacuum chamber, such as the evacuation pipeline and the air supply pipeline, adopts circular arc transition to make the gas passage unimpeded, but the convenience of cleaning should be considered.
3. Carefully design the structure of various connecting parts in the vacuum chamber to make the air passage clear and avoid blockage.
4. Grind and polish the inner surface of the vacuum system. The brighter the surface, the less gas is absorbed, and the easier it is to obtain vacuum.
5. Minimize the volume of the vacuum chamber and shorten the piping system.
The sealing form can be selected according to the required vacuum degree and the actual working needs.
Selection of sealing material: For vacuum system with vacuum degree below lO-3Pa, sealing material generally uses rubber sealing ring to meet the requirements. However, considering the actual working conditions (the vacuum chamber temperature can be up to 2300℃, the temperature of the sealing part is about 80℃ after water cooling, and the temperature of individual parts can reach more than 100℃). Therefore, choose the ideal sealing ring material is important.
For rubber materials that used for vacuum sealing, in addition to smooth surface, no scratches and no cracks, low permeability and gas output rate, good heat resistance and oil resistance, as well as certain strength, hardness and elasticity are required too.
Static Seal Structure Selection
In various vacuum systems, more than 80% of the seals are static seals, and the effect of static seal has a great influence on the vacuum degree and air leak rate. Therefore, the static seal structure should be carefully designed to achieve the desired results.
The design of the static seal structure mainly considers how to choose the main sealing surface, how to reduce the residual gas and how to fully exert the function of the rubber sealing ring.
Whether it is rectangular sealing groove, dovetail sealing groove or trapezoidal sealing groove, the roughness of the groove bottom is easily obtained as the main sealing surface, and the roughness on the side is often difficult to obtain. At the same time, in order to eliminate residual gas, a through hole is designed in the presence of residual gas, so that the interior of the system is unobstructed.