Cavitation, noise, and blockage in control valves: causes and solutions

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I. Causes of cavitation in control valves and solutions. Causes: Excessive pressure difference: When the pressure at the valve outlet is lower than the saturated vapor pressure of the fluid, the liquid vaporizes to form bubbles; these bubbles collapse in areas of high pressure, generating shock forces that damage the internal components of the valve. Fluid properties: Mediums that are easy to vaporize, such as high-temperature water and light hydrocarbons, are more prone to cavitation. Valve structure: A conventional single-stage valve core is prone to severe cavitation under high pressure differences. Solution: 1. Multi-stage pressure reduction design: Use a labyrinth-shaped valve core and multi-stage throttle cages to gradually reduce pressure, thereby avoiding sudden drops in local pressure differences. 2. Material upgrade: The valve core and seat are made of cemented carbide (such as Stellite alloy, tungsten carbide) or ceramic coatings to improve resistance to cavitation. 3. Selection of cavitation-resistant valves: Cavitation suppression valves should be used to reduce the impact caused by bubble collapse. 4. System optimization: Increase the downstream back pressure (e.g., by adding flow control orifice plates) to ensure that the outlet pressure is higher than the saturated steam pressure. Reduce the fluid temperature (e.g., by using a cooler) to minimize the risk of vaporization. II. Causes of noise in control valves and solutions Causes: Mechanical vibration: Looseness of the valve core or valve stem, or high-speed flow of the medium causing vibration of the components. Fluid turbulence: High-speed fluids passing through a throttle under high pressure differences generate vortices and turbulent noise. Cavitation noise: High-frequency popping sounds generated when bubbles collapse (associated with the cavitation phenomenon). Resonance: The natural frequency of a valve or pipe coincides with the frequency of fluid pulsations, amplifying noise. Solution: 1. Reduce the flow rate, increase the valve diameter, or use a multi-stage pressure-reducing valve element to lower the flow velocity at the throttling point. 2. Noise reduction measures: Install silencers or diffusers, or use porous noise-reducing valve cages. 3. Pipeline optimization: Increase the straight section downstream (≥10 times the pipe diameter) to prevent valves from being located near elbows. Use thick-walled pipes or wrap them with sound-insulating materials such as glass fiber. 4. Vibration reduction design: Spring-loaded valve cores or guiding stabilization structures are used to reduce vibrations. 5. Adjust operating conditions to avoid keeping the valve at a low opening degree for extended periods (