1. Improper assembly of mechanical seal
When replacing the mechanical seal at the non power end, the O-ring on the moving ring was not assembled properly during the assembly process. The O-ring should have been installed on the surface of the seal groove on the moving ring seat, but the assembly inspection found that the O-ring was not so assembled, but was wrongly installed on the surface of the spring spacer, and even the spring was deformed, which could not play the role of axial static seal staining, and even leakage.
2. Excessive cooling water pressure of mechanical seal
The adhesive force of the sealing surface of the static ring is exerted by the spring on the moving ring. When the cooling water pressure is too high, the water pressure will soak in the static ring, because the static ring is solid, so the water pressure will push the dynamic ring and compress the spring in the same direction as the static ring, so as to weaken or offset the adhesion force of the static ring, resulting in the leakage of the sealing surface. After the inspection, the mechanical seal at the power end is filled with cooling water for leakage test. When the inlet valve is opened less than 2 / 3, the mechanical seal is intact without leakage. When the water valve is opened more than 2 / 3, the mechanical seal leaks. At first, it was determined that it was caused by excessive water pressure. It is suggested that the motor should be started and used after maintenance, and the real cause of leakage should be further traced and found out.
3. Split mechanical seal surface of static ring
This is an important cause of leakage of mechanical seal of the pump which was replaced several times before. The mechanical seal of power end and non power end is assembled on the same shaft, the impeller is assembled in the middle of the shaft, and the bearing support at both ends of the shaft is firm. When the power end or non power end machine seal is replaced separately, the bearing (bearing seat) at the corresponding end must be assembled before the old machine seal can be taken out and new mechanical seal is installed. At this time, due to the gravity of the shaft and impeller, the impeller and shaft supported by one end of the bearing must collapse and the shaft inclines to the bearing free end. Because the static ring at the end of the uncoupled end is firmly fixed on the pump end cover with bolts, while the moving ring is firm on the shaft and rotates with the shaft. The rest is because the clearance between the inner ring and the shaft is very small. When the shaft falls and tilts, it will be composed of:
a. The static ring at the end of the device is relatively displaced, which makes the sealing surface of the static ring squeeze each other and causes the split;
b. The shaft is directly pressed on the inner ring of the static ring at the end of the unsealed end, which forms the sealing surface of the static ring broken or split.