Valve Vibrations: Examining the Complexities Associated with Control Valves – Part Two

In part two of this series, TK Arasu and Chris Vergos of Emerson continue with their report on Valve Vibrations from our December 2025 issue, identifying buffeting as another root cause of vibration. This low-frequency pattern is inaudible yet can have a significant impact on control valves and other equipment.

By TK Arasu and Chris Vergos, Emerson

As explored in the first part of this article, extreme vibrations around control valves can potentially lead to hazardous noise levels, impaired valve performance, and potential damage to valve internals and piping systems— even when the valve itself is not the root cause. This article continues to explore the sources of vibrations, risks, and strategies end users can utilize for effective mitigation.

Flow induced vibration (FIV) inside a valve can create a condition called buffeting. In this case, flow turbulence within the valve body creates localized low-pressure zones and pressure fluctuations.

Normally, buffeting is a low frequency phenomenon (< 20 hertz), so it cannot be heard, but the impact on the process can be significant. Figure 2 shows how incoming flow can set up a recirculation region, with high pressure fluctuations at the control valve cage inlet. The resulting recirculation obstructs flow and reduces valve flow capacity.

These pressure fluctuations also create low frequency shudders in the valve trim, creating erratic forces on the actuator, which impacts valve positioning and control. Buffeting can be mitigated in a number of ways. Adequate upstream and downstream straight pipe runs can settle the flow profile and reduce FIV enough to mitigate the condition. If piping modifications are not possible, the condition may be addressed by installing a grid seat ring on the inlet to smoothen the flow profile, and/or by stiffening the valve trim, stem, and/ or the actuator to dampen vibration and minimize valve damage (see figure 5).

A particularly troublesome example of buffeting occurred in an inlet pressure letdown valve feeding a large liquefied natural gas (LNG) facility. The upstream and downstream piping configuration was less than ideal and contributed to the condition, but it could not be easily altered. The high pressure drop across the valve was generating very high noise and vibration, which was limiting the throughput of the entire LNG train. It was also damaging the valve internals, shortening valve service life, and requiring more frequent maintenance.

After studying and modeling the application, the valve vendor identified the condition and suggested several changes to the existing control valve (see figure 6). A grid seat ring was installed on the trim inlet to eliminate the flow eddy and straighten flow through the valve. The valve stem and actuator were also strengthened to minimize resonance and damp any remaining vibrations.

The results were immediate and significant. Despite the slight obstruction it introduced, the grid ring actually increased valve capacity by eliminating the flow recirculation and smoothing fluid flow. Additionally, the reduced FIV and stiffer valve components dramatically improved valve positioning performance since the erratic pressure fluctuations and stem movement of the original valve were virtually eliminated (see figure 7).

The net result was a multi-million dollar cost savings for the customer by avoiding modifications to existing piping systems. Site production also increased and maintenance outages were limited.

Noise and vibration associated with a control valve installation can have a variety of causes. If left untreated, these conditions can create valve damage, and they can even crack pipe welds in extreme situations. The first step to address the problem is careful investigation of the valve installation and adjacent piping to fully understand the source of the vibration.

Often the frequency of the vibration can provide a clue, and advanced fluid dynamic modeling techniques can be utilized to fully identify the cause and investigate potential solutions. When faced with a vexing valve noise or vibration problem, it may be helpful to engage your control valve vendor.

With ready access to advanced modeling tools and laboratory fluid labs, which can be used to study and replicate the condition, the vendor can help end users understand the situation and identify the cause. Armed with that knowledge, the solution is usually straightforward, and it may involve simple piping modifications or changes to the control valve internal components. Extreme vibration and noise associated with control valves can be problematic, but mitigation or elimination is possible once the source is identified and the solution is implemented.