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Failure analysis of the main shaft of stainless steel multis
Source:未知|Popularity:0|release date:2020-05-12 10:43:04
The stainless steel multistage centrifugal pump shaft is a rotating part. It’s mainly used to support rotating parts and transfer power or motion through rotation. The working conditions of the shaft are wide, such as corrosive environment, high temperature or low temperature environment. Reliability is an important part of product quality, marking the quality level of achieving product function indicators, and reliability is a sign of measuring reliability, and the reliability of the pump shaft is a measure of whether it is safe under specified conditions and within a specified time , an important indicator for the stable completion of prescribed functions.
1. Reliability design principle of the main shaft of stainless steel multistage centrifugal pump
At present, when pump manufacturers analyze and calculate the strength of pump parts, they still mainly use traditional mechanical design methods, that is, process variables such as stress and strength into deterministic single-value variables, and perform strength calibration according to the theory and methods of material mechanics The core uses the empirical safety factor as a standard to measure whether it meets the strength requirements. In the calculation, as long as the safety factor is greater than the value specified by a certain actual use experience, it is considered to be safe. This kind of calculation does not take into account the uncertain factors of things. It has greater empirical and blindness and cannot truly reflect the objective situation.
Process the variables involved into multi-valued random variables, these variables are subject to: multi-level pump shaft fracture analysis probability distribution, multi-value transformation can be performed between the variables through the probability function to obtain the probability distribution of stress and strength, and then the reliability Calculation, this non-deterministic variable processing takes into account the phenomena that may occur in the project and the uncertainty of its characterization parameters, which is in line with objective reality.
Therefore, while considering the load (rotor weight, centrifugal force, axial force, torque and other factors) acting on the pump shaft, and fully consider the situation of non-deterministic variable check in the operation of stainless steel multistage centrifugal pump, after that, the spindle can fully meet different working conditions.
2. The common cause of the failure of the main shaft of stainless steel multistage centrifugal pump
The design of the main shaft that meets the requirements of use is the first step to improve the reliability of the pump. Therefore, shaft breakage accidents other than design defects are relatively rare. The main shaft will still fail during production activities. the reasons are as follow:
1). Defects in shaft manufacturing
In the manufacturing stage, due to the uneven metallographic structure, the shaft is broken due to stress concentration; the shaft heat treatment process is not strictly controlled.
2). Failure of shaft due to insufficient assembly accuracy
Due to insufficient dynamic balance accuracy or frictional heating between the rotor and the casing during assembly, wear is stuck and causes violent vibration of the pump, and excessive radial friction causes shaft breakage.
3). Shaft broken due to improper use of stainless steel multistage centrifugal pump
The instability of the centrifugal pump system device, the pump flow rate and outlet pressure often fluctuate frequently, resulting in frequent fluctuations in the radial force and axial force of the pump main shaft, which causes mechanical fatigue and breaks;
The main shaft of the centrifugal pump is broken due to crevice corrosion between the impeller and the shaft sleeve;
The stainless steel multistage centrifugal pump suffers from water shortage and dry grinding, which causes the pump to lock up and the shaft is broken under the instantaneous driving force of the motor.
1. Reliability design principle of the main shaft of stainless steel multistage centrifugal pump
At present, when pump manufacturers analyze and calculate the strength of pump parts, they still mainly use traditional mechanical design methods, that is, process variables such as stress and strength into deterministic single-value variables, and perform strength calibration according to the theory and methods of material mechanics The core uses the empirical safety factor as a standard to measure whether it meets the strength requirements. In the calculation, as long as the safety factor is greater than the value specified by a certain actual use experience, it is considered to be safe. This kind of calculation does not take into account the uncertain factors of things. It has greater empirical and blindness and cannot truly reflect the objective situation.
Process the variables involved into multi-valued random variables, these variables are subject to: multi-level pump shaft fracture analysis probability distribution, multi-value transformation can be performed between the variables through the probability function to obtain the probability distribution of stress and strength, and then the reliability Calculation, this non-deterministic variable processing takes into account the phenomena that may occur in the project and the uncertainty of its characterization parameters, which is in line with objective reality.
Therefore, while considering the load (rotor weight, centrifugal force, axial force, torque and other factors) acting on the pump shaft, and fully consider the situation of non-deterministic variable check in the operation of stainless steel multistage centrifugal pump, after that, the spindle can fully meet different working conditions.
2. The common cause of the failure of the main shaft of stainless steel multistage centrifugal pump
The design of the main shaft that meets the requirements of use is the first step to improve the reliability of the pump. Therefore, shaft breakage accidents other than design defects are relatively rare. The main shaft will still fail during production activities. the reasons are as follow:
1). Defects in shaft manufacturing
In the manufacturing stage, due to the uneven metallographic structure, the shaft is broken due to stress concentration; the shaft heat treatment process is not strictly controlled.
2). Failure of shaft due to insufficient assembly accuracy
Due to insufficient dynamic balance accuracy or frictional heating between the rotor and the casing during assembly, wear is stuck and causes violent vibration of the pump, and excessive radial friction causes shaft breakage.
3). Shaft broken due to improper use of stainless steel multistage centrifugal pump
The instability of the centrifugal pump system device, the pump flow rate and outlet pressure often fluctuate frequently, resulting in frequent fluctuations in the radial force and axial force of the pump main shaft, which causes mechanical fatigue and breaks;
The main shaft of the centrifugal pump is broken due to crevice corrosion between the impeller and the shaft sleeve;
The stainless steel multistage centrifugal pump suffers from water shortage and dry grinding, which causes the pump to lock up and the shaft is broken under the instantaneous driving force of the motor.