Type of oil diffusion pump
The diffusion pump is called diffusion-type steam flow pump, and it is one of the steam flow pumps. Although there are many kinds of pump fluid, most of them are low saturated vapor pressure oil. As working liquid said by an oil diffusion pump oil diffusion pump, with mercury diffusion pump fluid called mercury diffusion pumps, oil diffusion pump is most commonly used, diffusion pump ensures the former level in 10-2 ~ 10-3 of vacuum conditions to be able to do the work well. A mechanical pump is usually used as a fore - stage pump. Ordinary diffusion pump can get 10-4 ~ 10 9 ultimate pressure, if the baffle or liquid nitrogen frozen cold trap, and to bake to gas containers, can get 10-8 to 10-11 of the ultra high vacuum, if the pump is well designed, coupled with the removal of oil steam reflux and strict measures such as permanent gas pollution sources, and then took in more than 10-14 supporting high vacuum can be reached.
Diffusion pump's main advantage is: extraction capacity big, wide speed range, for various gases including inert gas (e.g., neon, helium, etc.) have the same pumping speed, this is unmatched by any other kind of pump; Moreover compared with other high vacuum or ultra high vacuum to obtain equipment, lower unit cost needed for pumping speed (no need to be very expensive, such as cryogenic pump condensing agent), simple structure, no mechanical rotation, easy to operate and can be recycled repeatedly, easy to maintain, long service life and is very easy to obtain high vacuum.
In our country, the diffusion pump has been included in the national standard series production, the use has been very extensive. Existing diffusion pumps can be classified into different categories.
1. The working fluid can be divided into oil diffusion pump and mercury diffusion pump.
2. The structural materials can be divided into metal diffusion pump and glass diffusion pump. Metal diffusion pumps can do a lot (pumping speeds can reach hundreds of thousands of liters per second), and glass diffusion pumps can only do a few hundred liters per second.
3. According to type and structure, it can be divided into vertical and horizontal type, single stage and multiple stage.
At present, the most commonly used is metal or glass vertical four-stage oil diffusion pump. Mercury diffusion pump is also gradually being paid attention to. The main structural components of diffusion pump include pump body, cooling cap, nozzle, steam pipe and heater.
Simple diffusion pump working principle is to use the high speed of steam flow, in a container and the diffusion pump set up is pumped gas partial pressure difference between, such is pumped gas molecules has been spread to the directional steam flow, level before it is compressed into the space, the final was siphoned off by backing pump.
The diffusion pump must operate under a certain prevacuum (10-2~10-3 supports). The current level of mechanical pump to diffusion pump after vacuum, can use the electric stove will work within the pump fluid is heated to boiling, it produces a large number of steam nozzle through the pump core distributed to all levels of the nozzle, steam at the nozzle cap change direction, from after the blast, there will be the orientation of high speed dense vapor flow.