How to prevent cavitation pump?

First, the pump cavitation phenomenon:
Liquid at a certain temperature, reduce the pressure to the temperature of the vaporization pressure, the liquid will produce bubbles. The phenomenon of bubble generation is called cavitation. Cavitation bubble generated when flowing to high pressure Department, its volume decreases so that burst. This phenomenon of bubble disappearing in liquid due to pressure increase is called cavitation collapse.
In operation, if the pump is in operation, the fluid will be lost if the localized pressure of the overcurrent portion (usually somewhere later in the impeller vane inlet) is lowered for some reason to the absolute vapor pressure of the aspirated fluid to the vaporization pressure of the fluid at that temperature Vaporization, resulting in a large number of steam, the formation of bubbles, when the liquid containing a large number of bubbles forward through the high-pressure zone within the impeller, the bubbles around the high-pressure liquid bubbles so sharply reduced to rupture. Bubble condensation rupture at the same time, the liquid particles fill holes at a very high speed, in this moment has a very strong water hammer, and a high stamping frequency of the metal surface, the impact stress of up to hundreds to thousands Atmospheric pressure, severe wall breakdown will be.
Cavitation in a pump is the process by which bubbles and bubbles burst in the pump and the overcurrent portion is destroyed. Pump cavitation in addition to damaging the overcurrent components, it will also produce vibration and noise, and lead to the original pump performance degradation, serious pump will interrupt the liquid, can not work properly.

Second, the basic relationship between pump cavitation Pump cavitation conditions are caused by the pump itself and the inhalation device determined in two ways. Therefore, the conditions for studying cavitation should be considered from both the pump itself and the inhalation device. The basic relationship of the pump is:
NPSHc≤NPSHr≤ [NPSH] ≤NPSHa
NPSHa = NPSH (NPSHc) -------- pump start cavitation NPSHa> NPSHr (NPSHc) ------ pump without cavitation NPSHa --- device NPSH is also called effective cavitation Margin, the greater the more difficult to cavitation;
NPSHr ---- pump NPSH, also known as required NPSH or pump inlet pressure drop, the smaller the better anti-cavitation performance;
NPSHc ----- Critical NPSH is the NPSH corresponding to the decrease in pump performance.
[NPSH] ----- Permissible NPSH, is to determine the pump operating conditions with NPSH, usually take [NPSH] = (1.1 ~ 1.5) NPSHc.

Third, to prevent cavitation measures:
To prevent cavitation must increase NPSHa, so NPSHa> NPSHr, to prevent the occurrence of cavitation as follows:
1, reduce the geometric suction height hg (or increase geometric inversion height);
2, to reduce the loss of suction hc, this can try to increase the diameter, minimize pipe length, elbows and accessories;
3, to prevent a long time under the work flow;
4, in the same speed and flow, the use of double suction pump, due to reduce the import flow rate, the pump is not prone to cavitation;
5, the pump cavitation occurs, the flow should be reduced to speed reducer work;
6, pump suction pump cavitation has an important impact;
7, for the pump running under harsh conditions, to avoid cavitation damage, use of cavitation-resistant materials.