Influencing Factors and Solutions of Cavitation Allowance in Axial Flow Pump

Category: Water pump knowledge

2024-08-12

Axial flow pump in the operation process, cavitation is a common and key problem, it will affect the performance and service life of the pump, cavitation margin is the quantitative evaluation of this phenomenon index, the following is the impact of axial flow pump cavitation margin of the main factors and the corresponding solutions.

1. influencing factors

1. Fluid properties: the viscosity, density and surface tension of the liquid will affect the occurrence of cavitation. High viscosity or low surface tension liquids are more likely to initiate cavitation.

2. Operating conditions: the working speed, flow rate and suction pressure of the pump directly affect the cavitation margin. The risk of cavitation increases with high flow velocity, high head or low suction pressure.

3. The design parameters of the pump: the structural design of the pump, the shape of the blade and the geometry of the inlet will also affect the cavitation allowance. An unreasonable pump design may increase the risk of cavitation.

Calculation Method of 2. NPSH

The NPSH of the submersible axial flow pump refers to the difference between the maximum allowable steam pressure and the liquid saturated steam pressure during the operation of the axial flow pump. The common calculation formula of NPSH is:

Npsha = HS-HVP-HF-HC-HSS

Among them, NPSHA is the net positive suction margin, Hs is the liquid level on the central axis of the suction inlet, Hvp is the steam saturation pressure head, Hf is the friction head loss, Hc is the outlet valve loss, and Hss is the additional loss of the pipeline.

3. Solution

1. Optimize the design of the pump: reasonably design the blade shape and inlet geometry of the pump to reduce the pressure fluctuation in the fluid and reduce the risk of cavitation.

2. Select the appropriate material: the use of good anti-cavitation performance of the pump body, such as stainless steel or special alloy, in order to improve the pump cavitation resistance.

3. Adjust the operating parameters: reasonably adjust the operating parameters such as the working speed, flow and suction pressure of the pump to avoid operation under adverse conditions to reduce the risk of cavitation.

4. Use additives: add anti-cavitation agents or inhibitors to the liquid to improve the performance of the liquid and reduce the occurrence of cavitation.

5. Improve installation and maintenance: Ensure that the pump is installed in a reasonable position to avoid inhaling air or other pollutants. Regularly check and maintain the running status of the pump, and find and deal with potential problems in time.

6. Increase the cavitation margin: In the design stage or during operation, increasing the cavitation margin can more effectively prevent the occurrence of cavitation. By adjusting the design or operating parameters of the pump, the pressure head in the fluid is increased to improve the cavitation resistance of the pump.

NPSH is an important parameter to evaluate the durability and reliability of axial flow pump, which is affected by fluid properties, axial flow pump structure, operating conditions and other factors. By increasing the net positive suction margin NPSHA, changing the liquid properties, and changing the structure of the axial flow pump, the NPSH can be effectively improved, thereby improving the durability and reliability of the axial flow pump.

In short, the cavitation problem of axial flow pump needs to consider a variety of factors and take corresponding measures to solve. By optimizing the design, selecting appropriate materials, adjusting operating parameters and using additives, the cavitation risk of axial flow pump can be effectively reduced, and its operating efficiency and life can be improved.

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