The cavitation of pump and its cause


The cavitation of pump and its cause


1. The cavitation

Cavitation is when a flow channel(it could be a pump, turbine, rivers, valves, propeller, and even human and animal blood vessels, etc.) of the liquid (water, oil, etc.) the partial pressure drops to critical pressure (typically near the vaporization pressure), liquid gas nuclei grow into bubble, bubble accumulate,flow, splitting and breaking.

2. Cavitation collapse

The bubble that occurs when cavitation occurs, when it flows to a high pressure area, its volume is reduced to the point of collapse. The phenomenon known as cavitation erosion is caused by the loss of air bubbles in the liquid.

3. Causes and hazards of cavitation

Pump in operation, if the flow of local area (usually the impeller inlet somewhere later) for some reason, reduced to the absolute pressure of pumping liquid temperature of liquid pressure, liquid at the begin to boil, to produce a large amount of steam, bubble formation, when the liquid containing a large number of bubbles within the impeller forward high, bubble around the high pressure liquid bubble dramatically narrow and fracture. In bubble burst at the same time, the liquid particle filling holes at high speeds, in this moment of strong water hammer effect, and with the impact of the high frequency on metal surface impact stress can amount to several hundred to several thousand atmospheric pressure, impact frequency up to tens of thousands of times per second, serious when wall thickness breakdown.

4. Cavitation process

The process of producing bubbles and bubbles in the water pump that causes the flow components to be damaged is the cavitation process in the pump. In addition to the right after produce cavitation flow pump parts will produce damage outside, still can produce noise and vibration, and resulting in a decline in the performance of the pump, serious interruption of liquid in the pump, when not working.


What is the characteristic curve of the pump?

Usually called said the curve of the relationship between the main performance parameters of the centrifugal pump performance curve or characteristic curve, in essence, a centrifugal pump performance curve is the law of motion of the liquid in the pump in the external form, by the measured. Characteristic curve include: flow (Q - H) - the head curve, traffic - efficiency curve (Q - eta), flow rate (Q - N) - power curve, traffic - NPSH curve - (NPSH) r (Q), action is the pump performance curve of the flow of arbitrary point, can find a set of the curve and its relative lift, power, efficiency and cavitation surplus value, this set of parameters called work status, referred to as "condition or conditions, the highest efficiency point centrifugal pump condition known as the best conditions of points, the best point as design point in general. The rated parameters of the general centrifugal pump are the same or very close to the optimal operating point. It is very important to understand the performance parameters of the pump in the practical selection of efficiency interval, namely energy saving and the normal operation of the pump.

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