How to prevent leakage of mechanical seal of water

  • Detail

How to prevent the leakage of the mechanical seal of the water pump

the mechanical seal is also called the end seal. It has a pair of end faces perpendicular to the rotation axis. Under the action of fluid pressure and compensating the external elastic force of the machine, the end faces rely on the cooperation of the auxiliary seal to keep fit with the other end and slide relatively, so as to prevent fluid leakage

I. common periodic leakage

1. The axial displacement of the pump rotor is large, the interference between the auxiliary seal and the shaft is large, and the moving ring cannot move flexibly on the shaft. When the pump is overturned, the dynamic and static rings are worn and cannot be compensated for displacement

countermeasures: when assembling the mechanical seal, the shaft software of the shaft questions the solution: the axial displacement should be less than 0.1 mm, the interference between the auxiliary seal and the shaft is moderate, while ensuring the radial seal, the movable ring can move flexibly on the shaft after assembly (press the movable ring towards the spring and spring back freely)

2 Insufficient lubricating oil on the sealing surface causes dry friction or roughening of the sealing face

countermeasures: the height of the lubricating oil level in the oil cavity should be higher than that of the dynamic and static ring sealing surfaces

3. The rotor vibrates periodically because the stator is not aligned with the upper and lower covers, or the impeller and the main shaft are unbalanced, cavitation or bearing damage

II. Leakage due to pressure

1 Mechanical seal leakage caused by high pressure and pressure wave

due to the design of excessive spring specific pressure and total specific pressure, when the pressure in the seal cavity exceeds 3Mpa, the specific pressure of the seal end face will be too large, the liquid film will be difficult to form, the seal end face will be seriously worn, the heat will increase, and the seal face will be thermally deformed

countermeasures: when assembling the mechanical seal, the compression amount of the spring must be carried out according to the regulations, and it is not allowed to be too large or too small. Measures should be taken for mechanical seals under high pressure. In order to make the end face stress reasonable, materials with high pressure resistance such as cemented carbide and ceramics can be used, and cooling lubrication measures can be strengthened

2. Mechanical seal leakage caused by vacuum operation

during the starting and stopping of the pump, due to the blockage of the pump inlet and the gas contained in the pumping medium, it is possible to cause negative pressure in the sealing cavity, thereby causing dry friction on the sealing surface

countermeasures: adopt double face mechanical seal, which will help improve lubrication conditions and seal performance

III. leakage caused by medium

particles and impurities in the medium enter the sealing surface, making the seal invalid; Due to the corrosion of weak acid and alkali in the medium, the dynamic and static ring auxiliary seals lose their functions

countermeasures: ensure the cleanliness of the lower cover and oil chamber, and prohibit the assembly of unclean lubricating oil; The oil level line in the mechanical seal oil chamber should be higher than the sealing surface; Mechanical seals with different structures shall be selected according to different media. For example, for corrosive media, fluororubber with high temperature resistance, weak acid resistance and weak alkali resistance shall be selected for rubber parts, and tungsten carbide mechanical seal for tungsten carbide friction pair shall be selected at the position where solid particles are easy to enter

The recovery of the international market

IV. mechanical seal leakage caused by other problems

mechanical seals are installed with portable, safe and reliable safety components, and there are unreasonable places in the design, selection and installation of mechanical seals

countermeasures: the error of spring compression should be between -2 mm and 2 mm. If it is too large, the specific pressure of the end face will be increased, and the friction heat is too much, which is easy to cause thermal deformation of the sealing face and accelerate the wear of the end face. If it is too small, it will move The specific pressure on the end face of the stationary ring is insufficient and cannot be sealed; The end face of the sealing gland (or shell) on which the dynamic ring seal ring is installed should be chamfered and polished to avoid damaging the dynamic and static ring seal rings during assembly

the common leakage causes and Countermeasures of mechanical seals are summarized above. Mechanical seal itself is a precision component with high requirements. When using 8. Filter: for the filter without infarct inducer, various factors should be analyzed to make the mechanical seal suitable for the technical requirements of various pumps and the requirements of using media, so as to ensure long-term reliable operation. (end)

Copyright © 2011 JIN SHI