Are you experiencing frequent pitting and erosion of valve trim and pipe walls? Or loud gravely noises coming from your valves?
Control valve cavitation could be the problem. Over time, cavitation can result in reduced control, performance issues, or even catastrophic failure.
Cavitation is a common occurrence in high-pressure-drop applications, particularly in liquid systems such as water or volatile chemicals used in refining, chemical processing, and power generation industries.
Cavitation occurs when fluid pressure temporarily drops below its vapor pressure, causing bubbles to form that collapse violently, often resulting in material pitting and damage to valve trim.
Here’s the science behind it:
When fluid passes through a conventional single-seated, globe-style control valve, changes in velocity and pressure can cause a vena contracta — the point of narrowest flow restriction — to form just downstream of the throttling point.
As a result, the fluid velocity increases while static pressure drops.
This activity is consistent with Bernoulli’s Principle. Bernoulli’s Principle states that faster-moving fluid has lower pressure, while slower-moving fluid has higher pressure.
If local pressure drops below the fluid’s vapor pressure, vapor bubbles form within the liquid. As the flow expands downstream and pressure recovers above the vapor pressure, the bubbles collapse violently.
This implosion generates high-energy micro-jets capable of causing severe material damage, including pitting, erosion, and eventual failure of valve trim and adjacent piping. This is called cavitation.
Alternatively, when liquid pressure drops below its vapor pressure and does not recover, the condition is known as flashing.
In flashing, the vapor bubbles do not collapse. Once the fluid pressure drops below its vapor pressure at the vena contracta, the liquid partially vaporizes and remains in the vapor phase downstream.
This creates a permanent two-phase flow (liquid and vapor) that takes up more volume, increasing velocity.
The impact of flashing is different from cavitation; it doesn’t create microjets that cause pitting and damage. But over time, it creates continuous high-velocity erosion where the vapor-liquid mixture scours internal surfaces. This causes thinning of valve trim, loss of sealing capability, and contamination from eroded material.
But flashing is a conversation for another day.
From an operational standpoint, the characteristics of valve cavitation are pretty recognizable. At low levels of cavitation, popping, ticking, or gravel-like noises can be heard coming from the site. As cavitation becomes more severe, you may hear a steady hiss or rattle that increases in volume.
Bubble collapse from cavitation causes:
Even if you’re lucky enough not to have catastrophic damage, low levels of cavitation can cause cumulative damage, eventually eroding parts until they fail.
The effects of repeated, violent vapor bubble collapse create shockwaves and micro-jets that can destroy valve components, piping, and downstream equipment. At this point, the effects are irreversible. You’ll start experiencing structural material erosion and failure in pumps, engines, and other adjacent equipment.
When cavitation is prolonged, the consequences are:
To address cavitation issues and avoid damage is to prevent vapor bubble formation or control its implosion with anti-cavitation valve trim and severe service valves.
Engineered valve trims such as multi-hole, multi-stage, or axial flow designs reduce the severity of pressure drops and distribute pressure across multiple smaller flow paths. This helps minimize bubble collapse and direct it away from critical surfaces.
MCE offers severe service control valve products from multiple brands. Here are some of our solutions:
Flowserve’s CavControl trim mitigates cavitation damage by directing vapor bubble formation and collapse away from critical metal surfaces. Using arrays of small, opposed flow passages, the design controls the location and intensity of bubble implosion rather than preventing cavitation, significantly reducing trim erosion and extending service life in low to moderate cavitation conditions.
Flowserve’s ChannelStream trim eliminates cavitation damage through multi-stage pressure reduction using a cartridge of engineered flow channels. Each stage incrementally reduces pressure while maintaining it above the fluid vapor pressure, preventing bubble formation. The design is optimized for high-pressure-drop liquid applications and offers easy maintenance.
Flowserve’s DiamondBack trim is a multi-stage cavitation elimination technology that combines several pressure-drop mechanisms, including impingement, turbulent mixing, directional changes, and controlled expansion/contraction within a compact geometry. By maintaining fluid pressure above vapor pressure throughout the flow path, it prevents cavitation and delivers high-capacity, solids handling capability, and broad rangeability.
The Multi-Z valve from Flowserve uses a partitioned, multi-stage letdown design tailored for extreme pressure-drop applications. Its staged flow path distributes energy dissipation across multiple zones, preventing cavitation formation and accommodating entrained solids in liquid media. The design offers durability, low noise, and a noticeable reduction in wear, even in severe industrial environments.
Learn more about Flowserve valve options.
Experiencing noise, wear, or unstable flow? Need a replacement valve? Contact MCE today.
Choosing the right valves from the start can mitigate these issues before they become major problems.
Swanson Flo, an MCE company, helps customers address cavitation challenges by combining application-level diagnostics with targeted severe-service valve solutions.
We’ll evaluate your system conditions to identify underlying issues before applying the right strategy to solve them. Through material evaluation, proper valve and trim selection, retrofit support, and system-level optimization, we can help you reduce erosion, extend your equipment life, and maintain reliable process performance in your demanding flow applications.
Our team of factory-certified technicians provide in-house and in-field support to keep your processes safe, reliable, and efficient. Our instrumentation and calibration services cover the lifecycle of your critical assets, including valves, actuators, and sensors.
We offer comprehensive evaluation, repair, and replacement services on your industrial flow equipment, including: