Mechanical seal, also called end face seal, is a shaft seal device of rotating machinery, which refers to a device for preventing fluid leakage, which consists of at least a pair of end faces perpendicular to the rotating axis, which are kept in contact and relatively slide under the action of liquid pressure, elastic force (or magnetic force) of compensation mechanism and auxiliary seal. Leakage is one of the frequent failures of mechanical equipment.
There are two main reasons for the leakage:
First, as a result of machining, there are inevitably various defects and shape and size deviations on the surface of mechanical products, so gaps will inevitably occur at the joints of mechanical parts;
Second, there is a pressure difference between the two sides of the seal, and the working medium will leak through the gap.
Reducing or eliminating the gap is the main way to prevent leakage. The function of sealing is to seal the gap between the joint surfaces, isolate or cut off the leakage channel, increase the resistance in the leakage channel, or add a small working element in the channel to cause pressure on the leakage, which partially offsets or completely balances the pressure difference that causes the leakage, so as to prevent the leakage. 37% of reducer failures are mechanical seal failures, 31% are bearing failures, and 32% are other reasons.
First, the principle and requirements of mechanical seal
Mechanical seal, also called end face seal, is a shaft seal device of rotating machinery, which refers to a device for preventing fluid leakage, which consists of at least a pair of end faces perpendicular to the rotating axis, which are kept in contact and relatively slide under the action of liquid pressure, elastic force (or magnetic force) of compensation mechanism and auxiliary seal.
Its main function is to change the easy-to-leak axial seal into the more difficult-to-leak end seal.
It is widely used to seal the rotating shaft of pumps, kettles, compressors and other similar equipment. Reducers are generally divided into two categories, which are unipolar transmission and multistage transmission. No matter what form the reducer is, the components of its internal structure are all composed of shaft, bearing, gear, coupling and casing and other related components.
Mechanical seal usually consists of moving ring, static ring, pressing element and sealing element. The moving ring rotates with the pump shaft, and the moving ring and the static ring are closely attached to form a sealing surface to prevent medium leakage. The end face of the moving ring is pressed against the end face of the stationary ring by the pressure of the liquid in the sealing chamber, and a proper specific pressure is generated on the end faces of the two rings and an extremely thin liquid film is maintained to achieve the purpose of sealing.
The compression element generates pressure, which can keep the end face of the pump in the non-operating state, ensure that the sealing medium does not leak out and prevent impurities from entering the sealing end face. The sealing element plays the role of sealing the gap between the moving ring and the shaft, and the gap between the static ring and the gland. At the same time, the elastic element plays a buffering role in the vibration and impact of the pump.
Mechanical seal is combined with other parts of the pump in actual operation, and the normal operation of mechanical seal has a great relationship with its own performance and external conditions. However, we must first ensure the performance of our own parts, the technical requirements of auxiliary sealing devices and installation, so that the mechanical seal can play its due role.