Views: 4709 Author: Site Editor Publish Time: 2020-06-24 Origin: Site
The mechanical seal refers to a device for preventing fluid leakage, which is composed of at least a pair of end faces perpendicular to the rotation axis under the action of the fluid pressure and the elastic force or magnetic force of the compensation mechanism and the cooperation of the auxiliary seal to maintain adhesion and relative sliding.
When the mechanical seal is working, the axial force caused by the pressure of the sealing fluid and the elastic force of the elastic element cause the moving ring and the static ring to adhere to each other and move relative to each other. Due to the close cooperation of the two sealing end faces, a tiny gap is formed the between boundary of the sealing end faces. When pressurized medium passes through this gap, an extremely thin liquid film is formed, which generates resistance and prevents the medium from leaking. At the same time, the liquid film makes the end face lubricated and obtains a long-term sealing effect.
In order to obtain a better sealing effect when poisonous and harmful media are used, double mechanical seals are used. According to the pressure of the sealing liquid system, they can be divided into double seals with pressure and double seals without pressure. The pressure of the double-sealed sealing fluid system is generally 0.01-0.03MPa higher than the pressure before the first-level sealing. In this way, when the primary seal leaks, the sealing liquid will enter the pump, ensuring that the medium in the pump will not leak to the outside. Since the sealing liquid enters the pump, the pressure and liquid level of the sealing liquid system are reduced, and the sealing leakage monitoring and early warning can be realized. The pressure in the pressureless double-sealing sealing system is generally normal pressure or slight pressure, which is lower than the pressure of the sealing cavity before the primary seal. When the primary seal leaks, the medium in the pump will enter the sealing liquid system, causing the pressure and liquid level of the sealing liquid system to rise. The leakage monitoring and early warning can be achieved through the pressure switch or the liquid level switch.
1. Pressure Double Mechanical seal
The double mechanical seal with pressure is also called double end mechanical seal. Its principle is basically the same as that of the single end mechanical seal. The double-end mechanical seal is not only a repetition of the single-end mechanical seal. It can effectively prevent the leakage of dangerous, toxic, flammable, and explosive substances in some key chemical industries, and has a high-performance insurance effect. When sealing high-pressure media, the pressure difference between the two ends of each seal can be reasonably distributed to improve the working pressure range of the seal. For some media with poor self-lubricity, easy to condense and vaporize, the sealing condition is improved by injecting sealing liquid into the sealing cavity, which greatly improves the efficiency and service life of the sealing.
2. Pressureless Double Mechanical seal
Pressureless double seals, also called tandem mechanical seals, are two sets of single-end mechanical seals that form a tandem double-end mechanical seals. The two sets of seals are arranged in the same direction, and the pressure in the seal chamber is gradually reduced, and the medium does not leak. Due to its compact structure, the tandem double-end seal can be applied to medium load occasions where the shaft diameter is not large, the axial size is small, and the rotation speed is large. The inner end is a balanced mechanical seal, and the outer end is an unbalanced mechanical seal with pump effect ring. The sealing liquid provides cooling and lubrication of the sealing surface and circulates through the built-in pump effect ring.
The double mechanical seal is to obtain a better sealing effect and improve the safety of the device. You can choose the mechanical seal method according to your needs.