There are many kinds of vacuum furnaces, and the requirements for vacuum system are different. In terms of vacuum degree, there are low vacuum, medium vacuum and high vacuum systems. Here are some common vacuum systems.
1. Low vacuum system
It is suitable for vacuum heat treatment furnace with vacuum degree in the range of 1333-2pa, such as pre pumping low vacuum well furnace. Most of them are oil sealed rotary mechanical pump systems.
2. Medium vacuum system
It is suitable for vacuum heat treatment furnace with vacuum degree in the range of 1.333-3 × 10Pa. Medium vacuum system is widely used in vacuum heat treatment furnace, which is usually composed of two-stage vacuum pump unit. The primary pump mostly adopts rotary mechanical pump or slide valve type mechanical pump, and the main pump is mechanical booster pump (roots pump) or oil booster pump.
3. High vacuum system
It is suitable for vacuum heat treatment furnace with vacuum degree in the range of 1.333 × 10 ~ 6.6 × 10 Pa, such as vacuum annealing furnace and vacuum brazing furnace. It is usually composed of three-stage vacuum pump unit, the main pump is usually oil diffusion pump and ion pump, the primary pump is mostly rotary mechanical pump or slide valve mechanical pump, and the front pump is mechanical booster pump (roots pump) or oil booster pump.
Basic parameters of vacuum system
The main parameters of vacuum system of vacuum heat treatment furnace include limit vacuum degree, working vacuum degree, air extraction time, air extraction rate and air leakage rate (pressure rise rate).
The maximum vacuum degree that the vacuum furnace can achieve in the empty and cold state is called the limit vacuum degree. The limit vacuum degree is an important index to evaluate the processing and assembly quality of various parts of the vacuum furnace, the pumping capacity and limit vacuum of the vacuum unit, the sealing and air leakage of the furnace body and the vacuum sanitation. Generally, the limit vacuum degree of vacuum furnace should be about one order of magnitude lower than that of main pump.