Cavitation is an undesirable and harmful phenomenon, but unfortunately often ignored. It should be counted, because it can lead, among others for the erosion of the pump components, and in extreme cases to irreversible damage.
What is the phenomenon of cavitation?
Cavitation is a process involving the formation, accumulation and sudden disappearance of gas follicles in the liquid around the pump rotor. The phenomenon is accompanied by rapid pressure changes.
Cavitation occurs when in the central part of the rotor there is a decrease in liquid pressure, which in turn results in the inflow of liquid through the suction. When a pressure drop below the saturation level at conditions corresponding to room temperature, the liquid begins to evaporate. That's when small bubbles are formed, which falling apart, creating a shock wave with quite high energy. Cracks of a large amount of bubbles cause micro impacts that contribute to the development of corrosion of structural materials and serious damage.
What are the main symptoms of cavitation in the pump?
submersible pump, which is covered by the phenomenon of cavitation, can give some characteristic symptoms. First of all, there is a clear decrease in the parameters of her work and performance. There is also increased electricity consumption. The pump works loudly and vibrations appear, which cause pressure pulsation. After dismantling, visible damage to structural elements caused by corrosion, including above all the rotor, can be seen. These damage can cause leaks during operation.
How to counteract cavitation phenomenon?
The better the anti -acvitative properties of the pump, the higher the level of cavitation resistance. The basis may therefore be construction counteracting this phenomenon, i.e. Appropriate construction of rotors, proper profiling of the shoulder blades, the use of a limited number of blades or prefers (preliminary turmoil in the direction consistent with engine speed). Such actions are taken by device manufacturers, and the role of the consumer is the selection of high quality pumps, which is characterized by all these features. This property is determined by the NPSHA parameter.
NPSHA parameter can be increased in several ways. One of them is the use of a small length in the installation of a pipeline and a large diameter. It is also necessary to plan the installation with the smallest possible number of elements contributing to pressure losses. The liquid speed above 2 m/s should also be counted and the pump sucking is happy. Pumping the liquid should take place at the lowest possible temperature. The use of a smooth internal surface (e.g. PVC) may also be helpful.
