Help, could this cause cavitation? ? There are pictures

Only the inlet piping was drawn; the outlet was not drawn

Vortex pump, flow rate 2 m3/h, head 60 m

As a technical expert in this field, it’s best to back up claims with data; P

Use it with confidence; there’s no problem, but you need to be patient regarding the self-priming time

This post was last edited by liaifeng on 2020-9-6 at 12:17. At a certain temperature, when the pressure is reduced to the vaporization pressure at that temperature, bubbles form in the liquid. This phenomenon of bubble formation is called cavitation. The bubbles formed during cavitation shrink in volume as they flow to higher-pressure areas, resulting in their collapse. This phenomenon of bubbles disappearing in the liquid due to rising pressure is called cavitation collapse. While the pump is in operation, if the absolute pressure of the liquid being pumped in a certain local area of its flow path – usually somewhere slightly downstream of the inlet to the impeller blades – drops to the vaporization pressure of the liquid at that temperature for some reason, the liquid begins to vaporize there, generating large amounts of steam and forming bubbles. When this liquid containing many bubbles moves forward through the high-pressure areas inside the impeller, the high-pressure liquid surrounding the bubbles causes them to shrink rapidly until they burst. As the bubbles condense and burst, liquid particles fill the voids at high speeds; this creates a very strong water hammer effect, which strikes the metal surface at a high frequency. The impact stress can reach several hundred to several thousand atmospheres, while the impact frequency can be in the tens of thousands of times per second. In severe cases, this can cause the wall thickness to be damaged. The process in which bubbles are formed and burst in a water pump, causing damage to the flow-through components, is known as cavitation in water pumps. After cavitation occurs in a water pump, in addition to causing damage to the flow-through components, it also generates noise and vibration, leading to a decline in the pump’s performance; in severe cases, it can even disrupt the flow of liquid within the pump, preventing it from functioning properly. To fill the pump with liquid, a bottom valve equipped with a filter is usually installed at the bottom of the suction pipe. This bottom valve serves as a check valve, and the filter prevents solid substances from entering the pump and damaging the impeller or interfering with its normal operation. II. How to solve the cavitation problem in centrifugal pumps: Measures to improve the cavitation resistance of the centrifugal pump itself (1) Improve the structural design from the suction inlet of the centrifugal pump to the vicinity of the impeller. Increase the overcurrent area ； Increase the radius of curvature at the inlet section of the impeller cover to reduce sudden acceleration of the fluid flow and pressure drop ； Appropriately reducing the thickness at the blade inlet and rounding it to make it more streamlined can also reduce the acceleration and pressure drop around the blade tip ； Improve the surface finish of the impeller and the inlet section of the blades to reduce drag losses ； Extending the blade inlet edge toward the impeller inlet allows the fluid flow to be worked on earlier, thereby increasing pressure. (2) A pre-induction wheel is used to enable the liquid flow to do work in advance within the pre-induction wheel, thereby increasing the pressure of the liquid flow. (3) A double-suction impeller is used, allowing the fluid to enter the impeller from both sides; as a result, the inlet area doubles, and the inlet flow velocity can be reduced by half. (4) A slightly larger positive attack angle is adopted in the design conditions to increase the blade inlet angle, reduce bending at the blade inlet, minimize blade blockage, and thereby increase the inlet area ； Improve working conditions under high flow rates to reduce flow losses. However, the impact angle should not be too large, otherwise it will affect efficiency. (5) Use materials resistant to cavitation. Practice has shown that the higher the strength, hardness, and toughness of a material, as well as its chemical stability, the better its resistance to cavitation. Measures to increase the effective NPSH of the liquid inlet device: (1) Increase the pressure of the liquid level in the storage tank ahead of the centrifugal pump to raise the effective NPSH. (2) Reduce the installation height of the pump in the suction device. (3) Replace the upward suction device with a backflow device. 　(4) Reduce the flow losses in the pipeline ahead of the centrifugal pump. For example, minimize the length of the pipelines within the required range, reduce the flow velocity in the pipelines, decrease the number of bends and valves, and maximize the opening degree of the valves. The above measures can be appropriately applied after comprehensive analysis based on factors such as the centrifugal pump model, materials used, and the installation site of the pump.

……Just add a small priming tank in front of the pump; there’s no need to worry about cavitation:)

Two points need to be noted in order to determine whether cavitation will occur: 1. The composition of the liquid in the tank, as well as its temperature and pressure； 2. Pressure drop of the pipeline ；