[2025 Valve Technology] Cavitation in control valves, causes of noise and blockage, and solutions
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I. Causes of cavitation in control valves: 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: Vaporous media such as high-temperature water and light hydrocarbons are more prone to cavitation. Valve structure: A standard single-stage valve core is prone to severe cavitation under high pressure differences.
II. Solutions to cavitation in control valves: Multi-stage pressure reduction design: The use of labyrinth-type valve cores and multi-stage throttle cages allows for gradual pressure reduction, thereby preventing sudden drops in local pressure differences. Material upgrade: The valve core and seat are made of cemented carbide (such as Stellite alloy, tungsten carbide) or ceramic coatings to enhance resistance to cavitation. Selection of anti-cavitation valves: Cavitation suppression valves should be used to reduce the impact caused by bubble collapse. 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.
III. Causes of noise in control valves: Mechanical vibration: Looseness of the valve core and valve stem, or high-speed flow of the medium, can cause the components to vibrate. 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.
IV. Solutions to valve noise: Reduce the flow velocity by increasing the valve diameter or using multi-stage pressure-reducing valve cores to lower the flow speed at the throttling point. Noise reduction measures: Install silencers or diffusers, or use porous noise-reducing valve cages. 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. Vibration damping design: Spring-loaded valve cores or guiding stabilization structures are used to reduce vibrations. Adjust operating conditions: Avoid keeping valves at a low opening degree for extended periods of time (
V. Causes of blockage in control valves: Deposition of solid particles: The fluid contains solid impurities (such as sediment and catalyst particles), which accumulate on the valve seat or valve core. Crystallization/polymerization: Certain media (such as urea, asphalt, high-viscosity fluids) crystallize or polymerize at low temperatures or when held in place for long periods. Accumulation of corrosion products: Rust and debris resulting from corrosion in valves or pipes block the flow channels. Valve structure issue: Straight-through single-seat valves are more prone to clogging than angle valves and ball valves.
VI. Solutions to clogged control valves: Optimization of valve selection – Choose valves with self-cleaning mechanisms such as angle valves, V-ball valves, and eccentric rotary valves. Avoid using straight-through single-seat valves (prone to clogging). Material optimization: The valve internals are made of wear-resistant materials (such as tungsten carbide and ceramics) to reduce particle adhesion. Flushing/purging design: Add flushing ports or perform regular back-purging (such as steam purging). For easily crystallizing media, a jacketed insulation valve is used to prevent solidification. Filter protection: Install a Y-type filter in front of the valve (the mesh size should be selected based on the medium), and clean it regularly. Operation management: Avoid keeping valves slightly open for extended periods (
VIII. Typical Application Case 1: Cavitation in control valves in oil refineries: The original single-seat valve failed after 3 months; by using a multi-stage pressure-reducing valve together with a Stellite alloy valve core, the service life was extended to 2 years.
IX. Typical Application Case 2: Clogging of chemical control valves – Urine as a medium causing crystallization on the valve seats → Switching to V-ball valves with steam tracing resulted in stable operation.
X. Typical Application Case 3: Noise from control valves in power plants – The noise level of steam valves was 110 dB; by installing labyrinth-type noise-reducing valve cages, this level was reduced to below 85 dB.
XI. Summary 1: Cavitation: Control the pressure difference and use cavitation-resistant valves and materials.