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What is the impact of the fire pump cavitation, how to advance?

2019-08-26
 During the daily use of the fire pump, cavitation will inevitably occur for a long time. What is cavitation? How should we deal with this phenomenon?

During the operation of the fire pump, due to factors such as pressure and temperature, the liquid vaporizes and generates steam. When the bubble is formed at a high pressure, the bubble shrinks rapidly and ruptures (condensation), and the liquid particle will fill the hole at a high speed. The impact creates a water hammer, which causes corrosion and damage to the solid wall, which is the cavitation process in the fire hydrant pump.

What effect does cavitation have on the fire pump?
First, the cavitation of the fire pump produces noise and vibration.

Secondly, if the fire pump is operated under cavitation conditions for a long time, the components of the fire pump are corroded and destroyed, causing pitting of the metal surface to cause perforation. In severe cases, the metal grains are loose and peeled off to form a honeycomb shape. In addition to mechanical forces, cavitation damage is accompanied by many complicated functions such as electrolysis and chemical corrosion.

Moreover, the energy exchange of the liquid in the impeller during the cavitation of the fire pump is disturbed and destroyed, and in severe cases, the liquid flow in the fire pump is interrupted and cannot work.

So, how should we reduce the probability of cavitation and reduce the damage caused by cavitation? In fact, it can be improved at the time of production, that is to say, when purchasing a fire pump, the following points can be purchased.

1. Whether to use the front induction wheel. The front induction wheel causes the liquid flow to work in advance in the front induction wheel to increase the flow pressure.
2. Consider the size of the positive angle. Increase the inlet angle of the blade, reduce the bending at the inlet of the blade, reduce the blockage of the blade, and increase the inlet area to reduce the flow loss. However, the positive angle should be appropriate, and the conference will affect the efficiency of work.
3. The double suction impeller is used to allow the liquid flow to enter the impeller from both sides of the impeller at the same time. The inlet cross section is doubled and the inlet flow rate can be doubled.
4. Use anti-cavitation materials. Practice has shown that the higher the strength, hardness and toughness of the material, the better the chemical stability and the stronger the resistance to cavitation.
5. Improve the structural design of the suction port of the pump to the vicinity of the impeller. Increase the flow area; increase the radius of curvature of the inlet section of the impeller cover plate to reduce the rapid acceleration and depressurization of the liquid flow; appropriately reduce the thickness of the blade inlet, and round the blade inlet to make it close to the streamline shape, or Reduce the acceleration and depressurization of the head of the flow vane; improve the surface finish of the impeller and the inlet part of the blade to reduce the resistance loss; extend the inlet edge of the blade to the inlet of the impeller, so that the liquid flow receives work in advance and increases the pressure.