Vacuum pump system pressure below 101 325 Pa is called vacuum. Generally, the pressure of 11325-1333 Pa is called rough vacuum. 1333-0.1333 Pa is called low vacuum, 0.1333-1.333 X10-5 Pa is called high vacuum, and the pressure below 1.333 X10-6 Pa is called ultra-high vacuum.
In order to obtain low vacuum, the most commonly used mechanical pump is the oil seal rotary pump, referred to as the vacuum pump. Because the limit vacuum of this kind of mechanical pump is high (0.133-0.0133Pa), and the pumping rate is not very low when the pressure is about 133.3Pa, so it is widely used.
The structure of the common vacuum pump system is mainly a circular and simple stator. There is a precisely machined solid circle inside as a rotor. The rotor is eccentrically installed above the stator chamber wall. It separates the intake and exhaust pipes and acts as air tightness. The two flaps S and S'are transversely embedded in the diameters of the rotor diagrams. A spring clamped between them is pressed. S and S'divide the space between the rotor and stator into three parts. When the sheet is mounted, air passes through the tube C to enter the space A. When S leaves with the rotation of the rotor, area 60b A increases. Gas is absorbed through the C tube. When it continues to rotate, S'separates space A from intake pipe C, and then the rotor continues to rotate. The volume of space A is gradually reduced. The gas is compressed. The exhaust valve opens and the gas is expelled until the pressure is greater than 101325P. In this way, when the rotor rotates, the space separated by the two vanes continuously sucks and exhausts, so that the vacuum of the evacuation container reaches a certain degree.
The compression ratio of this pump can be as high as 700:1. Therefore, if there is water or other condensable gas in the air to be pumped, when the gas is compressed, the swallow gas may condense into liquid and become numerous droplets mixed into the oil. With the circulation of the oil in the pump, on the one hand, it will swallow hair into the pumped container, which greatly reduces the vacuum of the system. On the other hand, it will destroy the quality of the oil, reduce the sealing and lubrication of the oil in the pump, and make the stator wall of the rotor rusty. In order to solve this problem, in addition to the air inlet in the pump to reduce the air-to-swallow compression ratio, cold traps or absorption towers need to be installed before the inlet.
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