Mechanical seal itself is a kind of fine parts with high requirements, which has high requirements for planning, machining and device quality. In the application of mechanical seals, various factors of mechanical seals should be analyzed, so that mechanical seals can be used in all kinds of pumps. The skills of mechanical seals need to be begged for and lubricated with abundant medium. Only in this way can the seals work reliably for a long time.

Mechanical seals, also known as end seals, have a pair of ends perpendicular to the axis of rotation. Under the effect of fluid pressure and compensating mechanical external elasticity, the end depends on the cooperation of auxiliary seals to adhere to the other end and slide relatively to prevent fluid leakage.

Leakage Phenomenon of Water Pump

The leakage of mechanical seals accounts for more than 50% of all repaired pumps. The operation of mechanical seals directly affects the normal operation of pumps.

1. Periodic leakage of pumps

(1) The axial channeling momentum of the pump rotor is large, the interference between the auxiliary seal and the shaft is large, and the moving ring can not move agilely on the shaft. When the pump is turned over and the dynamic and static rings are worn out, the displacement can not be compensated.

Countermeasure: When the mechanical seal is installed, the axial movement of the shaft should be less than 0.1mm, the interference between the auxiliary seal and the shaft should be moderate. When the radial seal is ensured, the moving ring device can ensure agile movement on the shaft (the pressure of the moving ring can be bounced back freely from the spring).

(2) The lack of smooth oil on the sealing surface results in dry conflict or grooming of the sealing face.

Water pump seal leakage countermeasures: the smooth oil surface height in the oil chamber should be higher than the dynamic and static ring seal surface.

(3) Periodic oscillation of the rotor. The factors are that the stator is not aligned with the upper and lower end caps or the impeller and spindle are unbalanced, cavitation or bearing damage (wear), which will shorten the sealing life and cause ignition leakage.

Pump seal leakage countermeasures: according to repair specifications to correct the above problems.

(3) In order to deal with the above problems, the following measures are adopted: (1) Ensure the cleanliness of the lower cover and oil chamber, and prohibit the non-clean lubricating oil device. (2) The oil surface of the oil chamber should be higher than that of the dynamic ring seal. (3) Seals with different structures are selected according to different application media. The sealing structure of high lift pump should be planned from scratch, and the fluorine rubber with weak acid and alkali resistance should be selected for the rubber of corrosive medium. The static ring of machine seal should be prevented from being resold.

2. Leakage due to pressure ignition

(1) The leakage of mechanical seals consisting of high pressure and pressure wave will result in excessive specific pressure of the seal face, difficult formation of liquid film, severe wear of the seal face, increased fever and thermal deformation of the seal face when the specific pressure and total specific pressure of the tension spring are too large and the pressure in the sealing chamber exceeds 3 MPa.

Leakage countermeasure of water pump seal: When installing machine seal, tension spring tightening must be carried out according to the rules, and it is not allowed to have too large or too small scenes. Mechanical seal under high pressure should adopt measures. In order to make the end face stress fair and minimize the deformation, high compressive strength materials such as cemented carbide and ceramics can be selected, smooth cooling method can be strengthened, and transmission methods such as keys and pins can be selected.

(2) During the start-up and shutdown of the mechanical seal leakage pump consisting of vacuum operation, due to the obstruction of the inlet of the pump and the presence of gases in the pumping medium, it is possible to make the sealing chamber show negative pressure. If negative pressure is applied in the sealing chamber, dry conflict will occur at the sealing end. The internal mechanical seal will have the phenomenon of fire and leakage (water). The difference between the vacuum seal and the positive pressure seal lies in the difference between the vacuum seal and the positive pressure seal. The directivity of the sealing target is different, and the mechanical seal also has its adaptability in one direction.

Leakage Countermeasures of pump seal: double-end mechanical seal is selected, which is helpful to improve the smooth premise and improve the sealing function.