The stoppage of the centrifugal pump is mainly caused by the failure of the mechanical seal. The performance of failure is mostly leakage. The reasons for the leakage are as follows:
1 Leakage of the static and dynamic ring sealing surface, mainly due to: flatness of the end face, roughness does not meet the requirements, or scratches on the surface; there is particulate matter between the end faces, resulting in both ends can not be the same operation; installation is not in place, the method is not correct.
2 The leakage of the compensation ring seal ring is mainly caused by: deformation of the gland, uneven preload; incorrect installation; quality of the seal ring does not conform to the standard; incorrect selection of the seal ring.
The actual application results show that the most failure parts of the sealing elements are the end surfaces of the moving and stationary rings, and the centrifugal pump is sealed. The cracking of the static ring end surface is a common failure phenomenon. The main reasons are:
1 When the sealing surface gap is too large during installation, the flushing fluid is too late to take away the heat generated by the friction pair; the flushing fluid leaks from the gap of the sealing surface, causing the end surface to overheat and damage.
2 The liquid medium evaporates and swells, and the two ends are separated by the vaporization expansion force. When the two sealing surfaces are forcedly attached, the lubricating film is destroyed and the surface of the end surface is overheated.
3 Lubricity of the liquid medium is poor, and the operating pressure is overloaded. The tracking surfaces of the two sealing surfaces are not synchronized. For example, the high speed pump speed is 20445r/min, the center diameter of the sealing surface is 7cm, and the line speed of the pump is up to 75m/s. When there is a sealing surface, the lag cannot follow the rotation, and the instantaneous high temperature causes damage to the sealing surface.
4 Sealed rinsing liquid orifice plate or filter clogging, resulting in insufficient water, so that the mechanical seal failure.
In addition, the surface of the sealing surface glide, when the end surface of the gap when the sealing element caused failure, mainly due to:
1 The liquid medium is not clean, has tiny hard particles, slides the sealing surface at a very high speed, and scratches the surface of the end surface and fails.
2 The concentricity of the pump transmission components is poor. After one revolution of the pump, the end surface is shaken and rubbed once, and the running trajectory of the moving ring is not concentric, resulting in vaporization of the end surface and overheating and wear.
3 The frequent occurrence of hydraulic characteristics of the liquid medium causes the pump group to vibrate, resulting in misalignment of the sealing surface and failure.
Corrosion of the sealing element by the liquid medium, stress concentration, cooperation of soft and hard materials, erosion, auxiliary sealing O-ring, V-ring, concave ring and liquid medium are incompatible, deformation, etc. will cause mechanical seal surface damage and failure, so Comprehensive analysis of the damage to its form, to find the root cause, to ensure long-term operation of the mechanical seal.