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subject: How To Prevent Pump Cavitation Phenomenon [print this page]

Heat Pump Network HC First, the phenomenon of cavitation

Liquid at a certain temperature, reduce the pressure to the pressure of vaporization temperature, the liquid will produce bubbles. This produces the phenomenon known as cavitation bubbles. When cavitation bubbles, flow to the high-pressure office, the volume decrease resulting in burst. Such as increased pressure in the liquid bubble away the phenomenon known as cavitation bubble collapse.

Pump In operation, if the over-current part of the local area (usually the impeller blade inlet somewhere later) for some reason, the absolute pressure of pumping the liquid at temperatures down to liquid vaporization pressure, the liquid will be in the area Start vaporized, producing a lot of steam, the formation of bubbles, the bubble when the liquid contains a lot of forward pressure by the impeller zone, bubble bubble around the high pressure liquid resulted in dramatically reduced and even rupture. Condensation in the bubble burst at the same time, liquid filled particles at high speed holes, in this moment has a very strong effect of water hammer, and to a very high impact frequency against the metal surface, the impact of stress up to several hundred to several thousand atmospheric pressure, impact frequency up to tens of thousands of times per second, severe wall thickness will be the breakdown.

In the water Pump Bubble burst in a bubble and suffered damage to over-current components in the process is the water pump cavitation process. Pump Cavitation after the addition to the over-current components other than the destructive implications, but also create noise and vibration, and lead to decreased pump performance, serious interruption of liquid pump will not work properly.

Second, the basic relationship pump cavitation

Pump cavitation condition that the pump suction device itself and the two decisions. Therefore, studying the conditions of cavitation, the pump itself and the inhalation device from both sides to consider, pump cavitation is the basic relationship

NPSHc NPSHr [NPSH] NPSHa NPSHa = NPSHr (NPSHc)?? Pump cavitation started

NPSHaNPSHa> NPSHr (NPSHc)?? Pump without cavitation

Type of NPSHa?? Device known as the effective NPSH NPSH, the more difficult the greater the cavitation;

NPSHr?? Pump NPSH, also known as the necessary NPSH or pump inlet dynamic pressure drop, the smaller the better resistance to cavitation;

NPSHc?? Critical NPSH, is the decline in the corresponding certain value Pump NPSH;

[NPSH]?? Permissible NPSH, is used to determine conditions of use the pump NPSH is usually taken [NPSH] = (1.1 ~ 1.5) NPSHc.

3, the device calculated NPSH NPSHa = Ps / g + Vs/2g-Pc/ g = Pc / g hg-hc-Ps/ g

Fourth, measures to prevent the occurrence of cavitation

To prevent the occurrence of cavitation must improve NPSHa, so NPSHa> NPSHr prevent the occurrence of cavitation as follows:

1. Reduce the suction on the geometric height hg (or increase the geometric intrusion height);

2. Reduce the inhalation of loss hc, this can be done to increase the diameter, to minimize the pipe length, elbows and attachments;

3. Prevent the long run in the high flow;

4. At the same speed and flow rate, double suction pump, the flow rate due to reduced imports, pump less prone to cavitation;

5. Pump cavitation occurs when the flow should be run down or spin-down;

6. Pumping pool pump cavitation situation on the important influence;

7. Operation in harsh conditions for the pump to avoid cavitation damage, cavitation-resistant materials can be used.

How To Prevent Pump Cavitation Phenomenon

By: yoyo

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