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Centrifugal pump shutdown is mainly caused by the failure of machine seal. Failure is mostly manifested by leakage. The reasons for leakage are as follows:

The reasons for leakage of sealing surface of message ring are as follows: flatness of end face, roughness not up to the requirement, or scratch of appearance; particulate matter between ends, which makes both sides unable to operate equally; inadequate placement and absolute prohibition of methods.

(2) The reasons for leakage of the sealing ring of the compensation ring are as follows: deformation of the cover, uneven pre-tightening force, precise placement prohibition, improper quality of the sealing ring and improper selection of the sealing ring.

According to the results of practical application, the most frequently invalidated parts of sealing elements are dynamic, static ring end face, centrifugal pump seal and static ring end face cracking, which are common failure signs. The main reasons are as follows: (1) the clearance of sealing surface is too large when installed, and the heat generated by friction pairs can not be taken away by flushing fluid; the flushing fluid leaks from the clearance of sealing surface, causing the end surface to be overheated and destroyed.

(2) The vaporization expansion of liquid medium causes the two ends to be separated by the vaporization expansion force. When the two sealing faces are pressed together properly, the lubrication film is destroyed and the appearance of the ends is overheated.

(3) The lubricity of liquid medium is poor, and the operating pressure is overloaded. The two sealing surfaces track the differential rotation step. For example, the speed of high-speed pump is 20445r/min, the central diameter of sealing surface is 7cm, and the linear speed of the pump is up to 75 m/s after operation. When a sealing surface lags behind, it can not track the rotation, instantaneous high temperature causes damage to the sealing surface.

(4) Blockage of the orifice plate or filter of the sealing flushing fluid results in insufficient water and failure of the machine seal.

In addition, the appearance of the sealing surface sliding groove, the timely appearance of the gap in the end face paste lead to the failure of sealing elements, the important reasons are as follows:

(1) The liquid medium is not clean, and there are small hard particles, which slide the sealing surface at a high speed, and scratch the appearance of the end surface and fail.

(2) The coaxiality of the transmission parts of the pump is poor, and the end face of the pump is swing and frictioned once every turn after opening, and the trajectory of the moving ring is different, which causes the end surface to vaporize and overheat and wear.

(3) Frequency of hydraulic characteristics of liquid medium still causes vibration of pump set, which results in misalignment of sealing surface and failure.

The decay, stress convergence, the erosion of hard and soft materials together, help to seal 0-ring, V-ring, concave ring and liquid medium incompatible, deformation and other cities cause the failure of machine seal appearance, so as to comprehensively analyze its failure situation, find out the basic reason, and guarantee the machine seal to run permanently.