Dear experts, please discuss the principle of rotary vane vacuum pumps, precautions, issues that may arise during operation, and repair methods

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A roots-type pump is a vacuum pump without internal compression; it typically has a very low compression ratio, which is why high and medium vacuum pumps require a pre-pump. A vacuum pump that achieves pumping by using the thrust generated by the synchronous, opposite rotation of a pair of leaf-shaped rotors within the pump chamber to move gas. A Roots vacuum pump is a mechanical vacuum pump that features a pair of shoe-shaped rotors rotating at high speeds in synchronization; it cannot evacuate air on its own, and a pre-stage device equipped with an oil seal or water ring is required to allow direct discharge to the atmosphere. Its structure and working principle are similar to those of a Roots blower; during operation, its suction port is connected to the vessel being evacuated or to the main pump of the vacuum system. In this type of vacuum pump, the rotors do not come into contact with each other, nor do they come into contact with the pump casing; the clearance as shown in the schematic diagram is generally between 0.1 and 0.8 millimeters ； No oil lubrication is required. Rotor profiles include arc lines, involutes, and cycloids, among others. Gear-shaped rotor pumps have a high volumetric efficiency and it is easy to ensure their manufacturing precision; therefore, the rotor profile is often of the gear shape. The rotational speed of a Roots vacuum pump can range from 3450 to 4100 revolutions per minute; its pumping speed is between 30 and 10,000 liters per second (1 liter = 10-3 cubic meters) ； Ultimate vacuum: 6.5×10-2 Pa for single-stage, and 1×10-3 Pa for two-stage. The ultimate vacuum of a Roots pump depends not only on the pump’s own structure and manufacturing precision but also on the ultimate vacuum of the pre-pump. To improve the ultimate vacuum of the pump, Roots pumps can be used in series. The working principle of a Roots pump is similar to that of a Roots blower. Due to the continuous rotation of the rotor, the gas to be pumped is drawn in from the inlet into the space v0 between the rotor and the pump casing, and then discharged through the outlet. Since the v0 volume is completely sealed after inhalation, the gas inside the pump chamber does not compress or expand. But when the top of the rotor passes over the edge of the exhaust port and space v0 becomes connected to the exhaust side, the higher gas pressure on the exhaust side causes some gas to flow back into space v0, resulting in a sudden increase in gas pressure. As the rotor continues to rotate, the gas is discharged outside the pump. In a Roots pump, there are two rotor elements in an “8” shape that are mounted perpendicularly to each other on a pair of parallel shafts; they are driven by a pair of gears with a gear ratio of 1 to rotate synchronously in opposite directions. A certain gap is maintained between the rotors and between the rotors and the inner wall of the pump casing, which enables operation at high speeds.

Roths vacuum pumps generally do not fail, unless there is a lack of oil in the pump chamber which leads to damage to the bearings; additionally, problems can sometimes occur with the sealing piston rings. There’s nothing else to mention