Analysis of the reasons for the shutdown caused by the failure of the mechanical seal of the desalination pump
The stoppage of the desalination pump is mainly caused by the failure of the mechanical seal. The most common manifestations of failure are leaks. The causes of leaks are as follows:
① The leakage of the sealing surface of the dynamic and static rings is mainly due to: the flatness of the end surface, the roughness does not meet the requirements, or the surface is scratched; there is particulate material between the end surfaces, which causes the two ends to not operate the same;
② The leakage of the seal ring of the compensation ring is mainly due to: the deformation of the gland, the uneven preload force; the incorrect installation; the quality of the seal ring does not meet the standards; the type of the seal ring is not correct.
The actual use effect shows that the most failure part of the sealing element is the end face of the dynamic and static ring. Cracking on the end face of the dynamic and static ring of the centrifugal pump is the common failure phenomenon. The main reasons are:
① The gap of the sealing surface is too large during installation, and the flushing liquid is too late to take away the heat generated by the friction pair; the flushing liquid leaks from the gap of the sealing surface, causing overheating of the end surface and damage.
②The liquid medium is vaporized and expanded, so that the two end surfaces are separated by the vaporization and expansion force. When the two sealing surfaces are pressed together, the lubricating film is destroyed and the end surface surface is overheated.
③ Poor lubricity of the liquid medium, coupled with the overload of the operating pressure, the tracking and rotation 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 linear speed of the pump after operation is as high as 75 m / s. When there is a sealing surface lag, it cannot track the rotation, and the instantaneous high temperature causes damage to the sealing surface.
④ The sealing flushing liquid orifice plate or filter is blocked, resulting in insufficient water volume and invalidating the mechanical seal.
In addition, the groove on the surface of the sealing surface and the gap on the end surface cause the failure of the sealing element. The main reasons are:
① The liquid medium is not clean, and there are tiny hard particles, which slip on the sealing surface at a high speed, scratching the end surface and failing.
② The coaxiality of the transmission parts of the pump is poor. After the pump is turned on, the end face is shaken and rubbed once every revolution. The running track of the moving ring is not concentric, causing the end face to vaporize and overheat and wear.
③ The frequent occurrence of the hydraulic characteristics of the liquid medium causes the vibration of the pump unit, causing the sealing surface to be misaligned and fail.
The corrosion, stress concentration, soft and hard material cooperation of the liquid medium on the sealing element, erosion, auxiliary seal 0-ring, V-ring, concave ring are incompatible with the liquid medium, deformation, etc. will cause mechanical seal surface damage and failure, so Comprehensive analysis of its damage forms to find out the root cause and ensure that the mechanical seal runs for a long time
