Control valves
Not so good valve vibrations
This article explains the sources of the extreme vibrations and sound that can occur around control valves, as well as the damage that can result. The discussion then turns to different solutions for mitigation once the cause has been identified.
TK Arasu and Chris Vergos, Emerson
Figure 1. This chart explains how the energy of flow turbulence creates fluid and acoustic vibrations that impact valve performance, damage pipe and radiate sound. Courtesy of Emerson.
Extreme vibrations are often attributed to control valves. These conditions can create hazardous levels of sound, affect control valve performance, damage valve internals and even crack the piping systems to which the valves are affixed. Interestingly, the valve may not even be the cause of the condition.
Vibration sources
Most plants have a screaming control valve, maybe more than one. It may be a high pressure drop application that howls like a banshee, or perhaps it is a valve that sounds like gravel is passing through it. Other valves shriek only during certain process conditions and are quiet otherwise. Sometimes the sound seems to emanate from the area around the valve in such a way that it is difficult to identify the actual source. The first step to addressing a vibration and / or noise issue is to understand what is causing the situation. There are many potential sources of noise and vibration that could be involved with a particular application. Reciprocating compressors, water hammer, pump pulses and slug flow are all possible causes. However, this article will focus on the three main sources associated with control valves: flow induced vibration( FIV), acoustic induced vibration( AIV), and buffeting. All these conditions usually result from flow turbulence( Figure 1). The energy of that turbulence may ultimately be propagated through FIV that resonates in the piping, or it may create extreme buffeting within the valve itself. In other situations, the flow turbulence creates acoustic waves that vibrate the downstream piping via AIV.
Flow induced vibration
One of the more common causes of vibration and noise around a control valve is FIV. In liquid applications, FIV can be created by cavitation, flashing or outgassing. With these conditions, the liquid undergoes a phase change due to reduced pressure, either in the throat of the valve or downstream. In the case of cavitation, the liquid turns to vapour as it moves through the restricted valve port, and it then collapses back to a liquid as pressure is recovered. Flashing occurs when the downstream pressure is below the fluid’ s vapour pressure, permanently vapourising some or all the liquid. Outgassing is a phenomenon where dissolved gas within a liquid mixture is released when there is a pressure drop. All these conditions can damage the valve internals and downstream piping, but all are well understood, so they will not be discussed in further detail in this article. Mitigation for these conditions usually involves specialised anti-cavitation trims that utilize pressure staging, hardened valve internals, and / or carefully designed valve bodies and downstream piping to minimise the damage. With compressible process media like gas, FIV typically arises from rapid gas expansion, caused by a significant pressure drop or drastic velocity changes. This situation can occur when one flow stream merges with another, or as the fluid navigates the complex flow path of a control valve( Figure 2). FIV excitation of pipe resonances is typically a low frequency(< 500 hertz) phenomenon and can be exacerbated by inadequately sized piping— which increases velocity— or by convoluted piping configurations, such as close coupled expanders,
26 Valve World February 2026 www. valve-world. net