There are generally two sealing methods for vacuum pump.
Packing seal refers to the sealing method with packing, which can be used for dynamic and static coordination. Generally, a small amount of leakage is allowed in the dynamic fit room.
Mechanical seal is used in the occasion of high requirement of dynamic fit seal. It is not necessary and not suitable for static fit.
Packing seal and mechanical seal have their own advantages. Packing seal has simple structure, low price and convenient maintenance. Mechanical seal, good sealing, little leakage and long service life. Next, we will make an analysis from their structural performance and explain their advantages and differences.
1. Packing seal: simple structure, low price, convenient maintenance, but large leakage and power loss. Therefore, packing seal is used to transport general media, such as water, which is not suitable for petroleum and chemical media, especially in expensive, explosive and toxic media.
2. Mechanical Seal: good seal, little leakage, long life, but expensive, processing, installation and maintenance requirements are higher than general seal. It can be used in all kinds of corrosive media and chemical media.
Packing seal is a traditional contact seal, which is widely used. The utility model has the advantages of simple structure, convenient replacement, low cost, wide application range (it can be used for the sealing of rotary, reciprocating and spiral motion), and the axial movement of the rotating shaft is allowed. Its disadvantage is that the sealing performance is slightly poor, the shaft is not allowed to have large radial runout, large power consumption, wear shaft, short service life. The packing seal fits with the packing part through the shaft surface, forming labyrinth effect to achieve the sealing. Since it is a sliding seal, there should be enough liquid for lubrication to ensure that the seal has a certain life, that is, the so-called bearing effect.
Material requirements for fillers:
A certain Elastoplasticity
2. Chemical stability
4. Good self lubrication, low friction coefficient and wear resistance
5. Temperature resistance
6. It is convenient to assemble and disassemble.
Mechanical seal, also known as end face seal, has at least one pair of end faces perpendicular to the rotating axis. Under the action of fluid pressure and compensating mechanical external elastic force (or magnetic force), and with the cooperation of auxiliary seal, it keeps close to the other end face and is opposite to East China, so as to prevent leakage. Because the two sealing faces are closely connected, a tiny gap is formed at the junction between the seal faces. When the pressure medium passes through the gap, a thin liquid film is formed, which causes resistance, prevents the leakage of medium and makes the end face lubricated, thus obtaining long-term sealing effect.
The mechanical seal for vacuum pump is one of the basic mechanical components with precision and complex structure, and is the key component of pump machinery. Its sealing performance and service life depend on many factors, such as type selection, accuracy of the machine, correct installation and use, etc. There are many kinds of mechanical seals for pumps. Different models make it difficult to distinguish and judge the maintenance. Generally speaking, it is easy to find and solve the leakage between the extended shaft sleeve and the sealing end cover and the pump body, but it needs careful observation, especially when the working medium is liquefied gas or high pressure, toxic and harmful gas, it is relatively difficult. It is difficult to distinguish and judge the remaining leakage intuitively. Only by observing, analyzing and judging the leakage symptoms on the basis of long-term management and maintenance practice can the correct conclusion be drawn.