Pressure buildup in the flow control valve
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May I ask, when the opening degree of the flow control valve is very small, a loud noise is produced – is this due to pressure buildup? What exactly is the reason? Will this cause damage to the valve? Here, the flow control valve on the circulation line has always been set at a very low opening degree, which causes a lot of noise; however, there is no leakage. Thank you for the answer!
When the opening degree of the control valve is very small, the valve’s characteristics become severely distorted, the pressure drop across the valve is high, and the flow becomes unstable. The flow noise can easily cause vibrations between the valve core and the seat, which in turn leads to vibrations in the valve stem. One possible reason for this is that the valve size chosen is too large.
When the pressure ahead of the control valve is high and its opening is small, the pressure of the fluid after passing through the control valve drops rapidly, causing it to vaporize; this leads to vibration in the pipeline and the generation of noise, a phenomenon known as cavitation. Cavitation has a significant impact on pipes and valves, and such situations should be avoided as much as possible.
When the valve opening is small, it acts as a throttle, which inevitably leads to vibration and whistling. The root cause is a design issue with the control valve; the flow rate must have been set too high. A solution that can be considered is to add a throttle orifice plate downstream of the control valve; a porous design is recommended to share the pressure drop across the valve, thereby creating a two-stage pressure reduction. Of course, since the valve is a flow control valve, the set value for the flow rate also needs to be adjusted accordingly.