1. Thermal crack of sealing ring
When the mechanical seal is disassembled, it can be found that the surface of the hard ring has an overheated tempering color, the surface of the graphite ring has annular grooves, and the rubber ring is aging.
The main reasons are: 1. Due to the high temperature of the medium, cavitation is formed in the pump body. After the cavitation occurs, the hydraulic impact drives the seal to make rapid axial oscillation, which causes serious wear of the dynamic and static rings and auxiliary seal rings, and damages the mechanical seal device. . ②The lubrication is not good, the liquid lubricating film is not formed on the end face of the sealing ring or the liquid film between the end faces of the sealing ring is vaporized, resulting in dry friction; ③The cooling and solidification system does not dissipate heat well.

2. Vibration of centrifugal pump
All centrifugal pumps are subject to vibration due to manufacturing and installation accuracy. The main reasons for the vibration are the unbalanced rotor, the non-concentricity of the machine and the pump, and the failure of the rolling bearing. The maximum amplitude measured from the surface of the bearing box cannot be greater than 0.06mm, and the pump should be stopped if it exceeds this value. Vibration can be dispersed in three directions: vertical, horizontal and axial, among which axial vibration is more harmful to the seal. When the pump vibration intensifies, separation occurs between the dynamic and static rings. The instantaneous separation causes the sealing surface to open under the action of the liquid film pressure, resulting in a large amount of leakage. If the solid particle content in the medium exceeds 5% at this time, the end face is separated due to vibration, and the particles are embedded in the soft graphite ring end face, resulting in hard Excessive wear on the seal faces of the mass ring. During disassembly and inspection, it can be found that there are clear friction marks on the hard sealing surface, and there are scratches when solid particles enter.

3. The elastic element fails to bounce
The main feature is that when the elastic element is disassembled and inspected, the elastic element is insufficiently elastic, deformed and the height is obviously reduced. The probability of this happening is relatively small.
The main reasons are: 1. Most of the materials used to make springs and bellows will have the disadvantage of falling elastic force under high temperature for a long time, so that the closing force of the sealing end face is insufficient, resulting in serious leakage of the sealing end face. The high-temperature loss of elasticity of the metal bellows is a common and typical failure form of this type of mechanical seal; ② the spring has creep and fatigue failure after long-term work at high temperature; ③ the spring has corrosion failure after long-term work at high temperature.