The mechanical seal itself is a kind of high-precision precision parts, and it has high requirements for design, machining, and assembly. In the use of mechanical seals
, the use of various types of mechanical seals should be analyzed, so that mechanical seals apply to the technical requirements of a variety of pumps and the use of media requirements and allow lubrication conditions, so as to ensure long-term reliable operation of the seal.
1. Periodic leakage
(1) The axial movement of the pump rotor is large, the amount of interference between the auxiliary seal and the shaft is large, and the moving ring cannot be flexibly moved on the shaft. After the pump turns over and the static and dynamic rings are worn, no compensation displacement can be obtained.
Solution: When assembling the mechanical seal, the shaft axial check amount should be less than 0.lmm. The amount of interference between the auxiliary seal and the shaft should be moderate. While ensuring the radial seal, the ring can be flexibly moved on the shaft after assembly (Pressing the ring against the spring will bounce back freely).
(2) The amount of lubricating oil on the sealing surface is insufficient to cause a thousand friction or napped seal faces.
Solution: The oil level in the oil chamber cavity should be higher than the sealing surface of the static and dynamic rings.
(3) Rotor periodic vibration. The reason is that the stator is not aligned with the upper and lower end caps or the impeller and spindle are not balanced, cavitation or bearing damage (wear). This situation will shorten the seal life and produce leakage.
Solution: The above problem can be corrected according to the maintenance standards.
2. Abrasion phenomenon caused by leakage of small pump seals
(1) The failure of small pump seals often produces grinding shafts. The main positions of the grinding shafts are the following: Auxiliary sealing ring at the moving ring, static ring position, and a few springs have grinding shafts.
(2) Main reasons for grinding axis:
a.BIA type double-end mechanical seal, back pressure condition is bad working condition. Particles and impurities in the medium can easily enter the sealing surface and cause the seal to fail.
b. The main part of the grinding shaft is a rubber bellows. H is due to the poor lubrication condition of the upper sealing surface. The friction torque between the dynamic and stationary rings is greater than the transmission torque between the rubber bellows and the shaft, and relative rotation occurs.
c. The auxiliary seals of the moving and static rings are corroded by the weak acid and weak alkali in the sewage, and the rubber parts have no elasticity. Some have rotted, lost their proper function, and created a grinding axis.
a. Ensure the cleanliness of the lower cover and the oil chamber, and prohibit the assembly of unclean lubricants.
b. The oil line in the chamber of the machine oil chamber should be higher than the sealing surface of the moving and stationary ring.
c. According to different use of media choose different structure of the machine seal. For the high lift pump, the mechanical seal structure should be redesigned. The corrosive medium rubber should be made of gas rubber resistant to weak acid and weak alkali. Machine seal static ring should be added to prevent re-sale.
3. Leakage due to pressure
Leakage of mechanical seals caused by high pressure and pressure waves. Because the specific pressure of the spring and the total specific pressure design are too large and the pressure in the sealed chamber exceeds 3 MPa, the pressure of the sealed end face is too large, the liquid film is difficult to form, the sealed end face is seriously worn, the heat generation increases, and the cover is thermally deformed.
Solution: When assembling the machine seal, the amount of spring compression must be carried out according to regulations. No excessive or too small phenomenon is allowed. Mechanical seals under high pressure should take measures. In addition, in order to make the end of the force and reasonable, minimize deformation, can be used carbide, ceramics and other materials with high compressive strength, and strengthen the cooling lubrication measures, use reliable transmission methods, such as keys, pins and so on.