Oil diffusion vacuum pump for high vacuum pump

Oil diffusion pump (abbreviated as oil diffusion pump) is a momentum transfer vacuum pump with low pressure and high speed oil vapor as working medium. The pump works in high vacuum area. The oil diffusion pump has the advantages of simple structure, convenient operation and low cost per unit pumping speed. The oil diffusion pump has no mechanical moving parts, long service life, high reliability and convenient maintenance. The oil diffusion pump is especially suitable for the process that requires rapid evacuation of large working vessels and rapid removal of large amounts of gases from treated materials during treatment. For example, vacuum metallurgy and vacuum heat treatment equipment.

When working, the oil diffusion pump and the system are pumped into a preparatory vacuum by the front-stage pump, and the boiler at the lower part of the pump is equipped with pump oil, which is heated by an electric heater to make it boil and evaporate to produce oil vapor. Due to pre-vacuum in the pump, the pressure is low, so the pump oil can be evaporated at a lower temperature (related to the type of working media, generally 370-420K). The diffusion pump oil evaporates rapidly into vapor in vacuum, and the vapor rises along the diversion pipe and is ejected from the umbrella nozzles at all levels. Umbrella shaped nozzles can be set at level 1, two, three and four. The oil vapor from the high-speed jet strikes the water wall and condenses into a liquid to flow back to the bottom of the pump. It is reheated and gasified, thus circulating continuously. The gas molecules in the pumped system diffuse into the vapor jet through the inlet and are carried to the next stage by the collision of a large number of high-speed directional oil molecules. The gas molecules are carried and compressed by the step-by-step diffusion, and are pumped out by the front stage pump through the outlet nozzle and the exhaust port.

KT Series Oil Diffusion Pump

There are two harmful reverse diffusion processes in the diffusion pumping process:

(1) When the pumped gas molecules are compressed to the outlet of the pump, the density difference between the outlet and the population exists, and the pumped gas molecules at the outlet will diffuse back to the inlet side.

(2) When oil molecules in directional motion collide with the pumped gas molecules, some of them will change the direction of motion and enter the pumped system. Additionally, the molecular density of oil vapor in the nozzle is higher than that in the pumped system, and the oil molecules will diffuse to the pumped system in reverse direction. These two harmful backdiffusion is one of the reasons that affect the increase of the limit vacuum degree of oil diffusion pump, and also produce oil vapor pollution to the vacuum system. Improving the nozzle design and improving the quality of diffuse pump oil, and installing liquid nitrogen cold trap at the inlet of the pump can improve the limit vacuum of the pump to a certain extent and reduce the oil pollution of the system. The limit vacuum of the conventional oil diffusion pump can reach 10-5Pa, and the ultra high vacuum oil diffusion pump can reach 5 X 10-8Pa.

The oil diffusion pump must pump the system pressure to lower than the initial working pressure of the diffusion pump before it can work normally, and the oil diffusion pump must heat the pump oil before it can work normally. The oil diffusion pump must be cleaned before installation and sufficient working fluid is loaded. The s body cooling water jacket must have enough cooling water. Do not heat diffusion pump oil when the cooling water is not connected. Stop heating and stop cooling when the oil is cooled.

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