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Application technology of oil diffusion pump
01-07-2020, 04:00 PM,
Application technology of oil diffusion pump
Application technology of oil diffusion pump

Because the partial pressure of the extracted gas above the steam stream is greater than that of the gas in the steam flow, the gas molecules are continuously diffused from the higher pressure area to the lower partial pressure area, and are collided by the supersonic steam molecules. Thus, the gas molecules get a velocity component pointing to the front stage of the pump. From a macroscopic point of view, it seems that the gas molecules are gradually transferred by the steam flow Push down. After several stages of compression, the gas with larger volume and lower pressure has become a gas gap with smaller volume and higher pressure (more than 10-3 Torr) when it reaches the front stage space, and is then pumped away by the front stage mechanical pump. The steam from the nozzle flows to the wall of water-cooled pump, condensed into liquid, flows back to the fractionator, and then heated into steam. In this way, a low pressure area is gradually formed at the upper end and near the nozzle, and the pressure in the container is continuously reduced.

The high-speed steam flow acts as a barrier to the high-pressure and strong gas in the front vacuum chamber, preventing it from returning to the high vacuum end. The high vacuum end pressure of this kind of pump can be generally as low as 10-8 Torr, while the front stage pressure can be higher than the first 10-1 Torr. Therefore, the gas compression ratio is as high as 100 million times, which is also an incomparable advantage of other pumps. However, due to various reasons, the vapor molecules in the pump liquid will inevitably flow back into the high vacuum end and pollute the vacuum system and the evacuated vessels or devices, which must be eliminated.

The efficiency of the pump is more than 50% under the conditions of different pump structure and diffusion mechanism, The maximum working capacity per kW is higher than 1 Torr · L / s, the back pressure of the front stage is better than 0.5 Torr, the limit pressure of direct pumping without cold trap can reach 1 x10-9 Torr, the pumping rate has been increased by two times compared with the old pump, the maximum allowable discharge pressure and durability have been enhanced. Generally speaking, the key problem is that it is possible to obtain ultra-high or extremely high vacuum and "clean" vacuum by oil diffusion pump due to the development of low vapor pressure pump liquid and backflow control. As long as the influence of dissolved hydrogen in materials can be completely prevented, thoroughly baking and degassing, and penetration can be prevented, the pollution caused by the outgassing of materials and pump walls can be reduced as far as possible. It seems possible to obtain the ultimate ultimate pressure of 10-16 Torr with diffusion pump.

Oil Diffusion Vacuum Pump

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