COMPOSITION OF THE DIFFUSION PUMPING SYSTEM

COMPOSITION OF THE DIFFUSION PUMPING SYSTEM :

The diffusion pump system mainly consists of diffusion pump, cold trap, gate valve and mechanical pump. For example, in a vacuum system with low oil return rate, there is no need to configure a liquid nitrogen cold trap, only a water-cooled baffle plate is needed. In applications where the oil return rate is strictly required, a liquid nitrogen cold trap should be installed in the system, and a local water cooling baffle may be used. The liquid nitrogen cold trap is mainly used to capture the water vapor and the light fraction reflux in the pump working fluid. The net pumping rate of air at the entrance of vacuum chamber for a 150 mm diffusion pump set is about 1000L/s, and the pumping rate of water vapor by the liquid nitrogen cold trap is as high as 4000L/s. A well designed and manufactured diffusion pump system can reduce the oil return rate from the working fluid of the pump in the vacuum chamber to a very low level, even smaller than that from other sources of organic matter.

DIFFUSION PUMP SYSTEM:

In a smaller vacuum system, a mechanical pump can be used alternately for the coarse vacuum chamber and as the front-stage pump of the diffusion pump. When roughing, the pressure in the partitioned preceding pipeline will increase. If the roughing time is less than 15 minutes, the pressure increase is usually not obvious. For large vacuum systems, such as diffusion pump pumping systems with a diameter of 400 mm or larger, a Roots pump unit with a mechanical pump as the front pump is often used for rough pumping of the vacuum chamber. In the rough extraction process, a smaller maintenance pump can be used as the front pump of the diffusion pump. When the vacuum chamber is pumped to a high vacuum (after the inlet pressure of the diffusion pump is reached), the Roots pump is switched to the front stage of the diffusion pump to ensure that the pumping system has the maximum exhaust capacity.