Sources of Vibration in Control Valves

Compressible fluid flow through control valves will inevitably cause some form of flow induced vibration in the fluid system. Identifying the type and cause of the vibration requires detective work.


Control valve vibration may be caused by many factors, some generated internally by the process stream and others generated externally. Some of the different forms of flow induced vibration are enumerated as follows :

1. Process Stream Energy Release - a flowing process stream contains considerable energy, a portion of which is released during its journey through a valve. The released energy takes the form of fluid turbulence, viscous drag, generated noise flow instabilities, and other forms of released energy. This energy will also interact with the valve trim and may cause noticeable vibration.
2. Upstream Equipment Pulsations - Compressors, pumps and other upstream equipment generate mechanical vibrations and pressure pulsations that interact with other process equipment and piping in the system. The vibration energy is efficiently carried downstream by the piping system. In addition, pipe configurations such as elbows and tees upstream of the valve can create swirling flows and introduce turbulence, which may affect the valve.
3. Pipeline Resonance - Pipelines with long runs between supports can resonate at the first or second bending mode of the system, vibrating up and down in a "U" or "S" shape. Higher order pipe natural modes (radial and circumferential) may also be excited. These natural modes can be excited by other vibration levels to build up and affect process equipment and the supporting structure.
4. Support Structure Vibration - Some form of vibration is always present in a running plant, but normally, it is not severe enough to be problematic. However, if the support floor resonates in tune with this vibration, the amplitude can increase to the point where it may become destructive.
5. Acoustic Noise Creation - Very high sound power levels can release enough energy to create serious valve vibration and in extreme cases, cause metal fatigue.

Excerpted from "Control Valve Design" by Asher Glaun