Additional Authors: Freeman Self and Yuqing Liu

Understanding the Different Effects of AIV and FIV can Help Prevent Piping System Failures

In the chemical and hydrocarbon processing industries, piping accounts for approximately 20 to 30 percent of total installed costs. The typical process piping system consists of components such as valves, tees, bends, and pipe supports. Due to the energy of the fluid flow, systems are naturally subjected to vibration, which can result in fatigue failures and additional repair costs. However, fatigue failures can be prevented through proper design and engineering methods. 

Vibrations are generally categorized by frequency, which is how often the pipe moves back and forth over time. Another characteristic is the amount of movement or vibration amplitude.

High-frequency piping vibrations are called acoustic-induced vibration (AIV), because the flow is mostly gas and the vibrations typically produce sound waves within the range of human hearing. Low-frequency vibrations are called flow-induced vibration (FIV), as the flow typically contains liquid and less sound waves. Both frequencies cause fatigue failures – the weakening of a material caused by repetitive motion that results in cracks.

These are two separate phenomena, whose terms have been used interchangeably, despite their differences. To prevent failures, the design approaches to address acoustic-induced and flow-induced vibrations should differ and are discussed in the following paper.

Read more about fatigue failure mitigation strategies by clicking the link below.