Common sealing devices for centrifugal pumps
The commonly used sealing devices of centrifugal pumps mainly include the following:
1. Packing seal
Composition: It is mainly composed of a packing box, a packing plate, a water seal ring, a packing gland, etc., also known as a packing seal.
Principle: The sealing effect of the shaft seal is adjusted by loosening and tightening the packing gland. After tightening the gland, the packing is squeezed tightly to reduce the amount of air leakage, but it may increase friction. In severe cases, it will cause heat, smoke, and even burn the gasket or sleeve. Loosening the gland will increase the leakage.
Features:
Simple structure, easy to install and repair.
The sealing effect is good when the pressure is not high.
The packing has a short service life and needs to be replaced and maintained frequently.
The leakage is relatively large and the power consumption loss is large.
It is suitable for medium and low pressure pumps with a pump shaft circumferential speed of less than 25m/s, and is often used to transport general media such as water.
2. Mechanical seal
Composition: Including dynamic ring, static ring, gland, spring, transmission seat, fixing pin, O-ring, etc.
Principle: A shaft seal device that relies on one or several pairs of end faces that slide relative to the shaft, and maintains contact under the action of fluid pressure and the elastic force (or magnetic force) of the compensation mechanism, and is equipped with auxiliary seals to prevent leakage.
Features:
Good sealing performance and small leakage.
Long service life, generally up to 1~2 years or longer in oil and water media, and usually more than half a year in chemical media.
The shaft and sleeve are not easy to wear.
Low power consumption and low friction power consumption, only 10%~15% of the power consumption of packing seals.
Long maintenance cycle, automatic compensation after end face wear, generally no regular maintenance is required.
Good vibration resistance, insensitive to vibration, deflection of the rotating shaft and deflection of the shaft to the sealing chamber.
Complex structure, expensive price, high installation and processing accuracy requirements.
Suitable for high temperature, high pressure, high speed water pumps, as well as the transportation of petroleum and chemical media.
3. Floating ring seal
Composition: Multiple single ring sleeves are arranged in sequence on the shaft, and each circle consists of a floating ring, a support ring and three springs.
Principle: A good sealing effect is obtained by controlling the radial clearance and sealing length.
Features:
Simple structure and reliable operation.
The axial length is long, and the cavity formed by the support ring must contain liquid when working.
It is not suitable for thick, short, and large-capacity water pumps, nor can it work under dry running or evaporation conditions.
4. Labyrinth seal
Principle: By designing a complex channel structure, the leakage fluid generates resistance when passing through, thereby achieving the sealing effect.
Features:
The structure is relatively complex, but the sealing effect is stable.
Applicable to occasions with high sealing requirements.
5. Spiral seal
Principle: A spiral groove opposite to the oil leakage direction is opened on the surface of the sleeve, which acts as a seal when the pump shaft rotates.
Features:
Applicable to specific occasions, such as reducing air leakage in high-pressure pumps.
