Working Principle, Advantages and Disadvantages of Direct-coupled Pumps

    The high-speed direct-coupled rotary vane vacuum pump, referred to as direct-coupled pump for short, is a new branch product of rotary vane pumps. Traditional rotary vane pumps emerged early and are products with simple structures and extensive applications. However, such pumps with the old structure feature low rotational speeds, mostly around 400 r/min. They adopt belt drive for speed reduction, resulting in large size and heavy weight.

To achieve a compact and lightweight pump body, according to the calculation theory of the geometric pumping speed of pumps, when the pumping speed is fixed, the main method is to increase the pump speed. The key to increasing the rotational speed of a vacuum pump is to ensure that the components directly bearing the high-speed load can adapt to such working conditions. In other words, the materials of the pump body and rotary vanes, as well as the rotor structure, should be suitable for the working conditions after the speed increase.

In 1965, Germany's Leybold-Heraeus Company made significant improvements to the pump structure, materials and processes on the basis of the original rotary vane pumps, and successfully developed the high-speed direct-coupled rotary vane vacuum pump, opening up a new path for the miniaturization and instrumentalization of rotary vane pumps.

The direct-coupled rotary vane pump adopts a motor to directly drive the pump rotor, increasing the rotational speed to over 1400 r/min. This design can make the pump structure compact, significantly reduce its size and weight, improve the pumping performance of the pump, and greatly lower vibration and noise.

It is characterized by high efficiency and energy saving, convenient installation and maintenance, stable operation, safety and reliability. The motor shaft and the pump shaft are directly coaxial coupled with high concentricity, ensuring stable operation, safety and reliability.

The mechanical seal position of the shaft is prone to corrosion. Once the shaft of a direct-coupled pump is corroded, it will easily lead to the failure of the mechanical seal. Therefore, it is advisable to adopt an inset stainless steel shaft sleeve to avoid corrosion, extend the service life of the shaft, and reduce operation and maintenance costs.

The base component of the mechanical seal generally adopts a rubber bellows structure, which changes the shaft sealing in the traditional mechanical seal from the line seal of an O-ring to the double-face seal of a rubber part, improving the sealing effect when conveying clean water medium.

Advantages

The shaft of the direct-coupled pump has a short overhang, resulting in small radial runout during rotation, low noise during pump operation, and a long service life of the mechanical seal.

It uses fewer materials and has a low cost.

It has low transmission loss and high efficiency.

Disadvantages

Some structures cause disassembly troubles and affect maintenance time.

If the seal fails, the conveyed medium will directly affect the motor bearings.