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Shenyang Leete Machinery Co., Ltd.

Structure of a Roots Pump

2024-02-28 16:02:45

The arrangement of the two rotors in the pump body determines the overall structure of a Roots vacuum pump. There are generally three types of overall structural arrangements for Roots vacuum pumps used domestically and internationally:

1.Vertical: The axis of the two rotors is horizontally installed, but the plane formed by the axis of the two rotors is perpendicular to the horizontal plane. In this structure, the inlet and outlet of the pump are horizontally arranged, making assembly and connection of pipelines more convenient. However, the disadvantage is that the pump has a high center of gravity and poor stability during high-speed operation. Therefore, this structure is not widely used except for small-sized pumps.

2.Horizontal: The axis of the two rotors is horizontally installed, and the plane formed by the axis of the two rotors is in a horizontal direction. In this structure, the inlet of the pump is located above the pump, and the outlet is located below the pump (or vice versa). The outlet is generally horizontally connected, resulting in perpendicular directions for the inlet and outlet. The outlet is connected to a three-way pipe that opens in two directions, with one end connected to the exhaust pipeline and the other end either closed or connected to a bypass valve. This structure is characterized by a low center of gravity and good stability during high-speed operation. Large and medium-sized pumps both domestically and internationally often adopt this structural type.

3.Vertical-axis: In some foreign Roots pumps, the axes of the two rotors are installed perpendicular to the horizontal plane. This structure allows for easy control of assembly clearances, convenient rotor assembly, and occupies a small footprint. However, the disassembly and assembly of gear and other transmission mechanisms are inconvenient, and the lubrication system is more complex.

Once the overall structure is determined, the structure and shape of the pump body itself are correspondingly determined.

4.Roots Pump with Relief Valve: To prevent accidents caused by overload, a reliable safety device, namely a relief valve, is installed in the bypass pipe of the Roots pump. When the pressure at the exhaust outlet is within the specified range, the relief valve remains closed. However, when the exhaust pressure exceeds the specified limit, the valve of the relief valve automatically opens, causing the excess gas to be discharged. Once the exhaust pressure returns to normal, the relief valve closes by itself. It can automatically adjust and serves as a device that allows pressure differential in the pump. Therefore, the main advantage of the relief valve is that it allows the Roots pump to operate continuously within various pressure ranges, together with the preceding pumps. By using this design, the pumping downtime in a rough vacuum state of the vacuum chamber can be reduced by 30-50%. For larger pumps, the relief valve is installed in the bypass pipe outside the pump body, while for smaller pumps, the relief valve is installed inside the pump casing.

5.Roots Pump with Steam Condenser: When steam suction is required, the vacuum pumping system must be designed with a condenser to condense the steam. This condenser can be installed before or after the pump, rather than on the pump body of the Roots pump itself. In certain cases, the heat absorption by condensation can reduce the heat generated by the Roots pump. If a compound condenser is used, appropriate solvents can be used to remove dirt during maintenance, allowing steam to flow smoothly in the conduits.