The general centrifugal pump shutdown is mainly caused by the failure of the mechanical seal. The failure performance is mostly leaks. Minquan now tells you the reasons for the leakage. It is divided into the following categories: 1 The leakage of the static sealing surface of the static ring, the main reasons are: the flatness of the end face, the roughness does not meet the requirements, or the surface is scratched. There are particulate matter between the end faces, which causes the two end faces to not operate in the same way; the installation is not in place and the method is not correct.
2 compensation ring seal leakage, the main reasons are: gland deformation, pre-tightening force is uneven; installation is not correct; the quality of the seal ring does not meet the standard; the seal ring selection is wrong.
Detailed explanation of failure of mechanical seal of centrifugal pump
The actual use results show that the most ineffective part of the sealing element is the end face of the moving and stationary ring, the centrifugal pump is sealed, and the crack on the end face of the static ring is a common failure phenomenon. The main reasons are as follows: 1 The sealing surface clearance is too large during installation. The rinsing liquid is too late to take away the heat generated by the friction pair; the rinsing liquid leaks away from the gap of the sealing surface, causing the end surface to overheat and be damaged. 2 The liquid medium vaporizes and expands, so that the two end faces are separated by the vaporization expansion force. When the two sealing faces are pressed together, the lubricating film is broken and the surface of the end face is overheated. 3 The liquid medium has poor lubricity, and the operating pressure is overloaded, and the tracking surfaces of the two sealing surfaces are not synchronized. For example, the high speed pump speed is 20445r/min, the center of the sealing surface is 7cm, and the line speed is up to 75 m/s after the pump is running. When there is a sealing surface lag, the rotation cannot be tracked, and the sealing surface is damaged by the instantaneous high temperature. 4 The seal flushing liquid orifice plate or filter is clogged, resulting in insufficient water and invalidation of the machine seal.
In addition, the surface of the sealing surface is slipped, and the gap is caused by the gap at the end surface. The main reasons are: 1 The liquid medium is not clean, there are tiny hard particles, and the sealing surface is swept at a high speed, and the surface of the end surface is drawn. Injury and failure. The pumping parts of the 2 pump are poor in coaxiality. After the pump is turned on, the end face is shaken once every revolution, and 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 hydraulic characteristics of the liquid medium causes the pump unit to vibrate, causing the sealing surface to be misaligned and fail.
The liquid medium corrodes the sealing element, stress concentration, soft and hard material coordination, erosion, auxiliary sealing 0-ring, V-ring, concave ring is incompatible with liquid medium, deformation, etc. will cause mechanical seal surface damage failure, so The damage form should be comprehensively analyzed to find out the root cause and ensure that the mechanical seal runs for a long time.