Acoustic induced vibration (AIV) is the high frequency acoustic excitation of a piping system as a result of gas flowing through a pressure reducing device such as a relief valve, control valve or orifice plate resulting in high noise levels being generated. These high noise levels are a function of the pressure drop across the pressure reducing device and the gas mass flow rate. These high frequencies can result in acoustic fatigue at circumferential discontinuities on the pipe wall, such as small bore connections and fabricated Tees. Acoustic Fatigue is of particular concern as it primarily effects safety related systems, such as relief and blowdown lines.
At WKC we have developed a tool that enables engineers and consultants to screen valves for AIV against the Energy Institute Guidelines (2008).
Energy Institute Guidelines
In January 2008 the Energy Institute (EI) published the ‘Guidelines for the Avoidance of Vibration Induced Fatigue in Process Pipework’.
The EI Guidelines were published to help minimise the risk of vibration induced fatigue of process piping, intended to be used by engineers with no prerequisite vibration knowledge.
The EI method generates a Likelihood of Failure (LOF) score. The LOF is a form of scoring to be used for screening purposes. It should be noted the LOF is not an absolute probability of failure nor an absolute measure of failure.
Acoustic Induced Vibration dB Screening Calculator
This tool can be used for AIV screening to determine the resulting noise level in dB due to a pressure reducing device, this is value is based on process parameters. Pressure reducing devices with a noise level below 155dB can be screened out of an AIV assessment, however If the resulting noise level is calculated to be above 155dB a further detailed analysis of this device and the downstream piping to its termination point needs to be conducted. At the stage WKC and its team of consultants should be contacted to conduct this specialist assessment.
Please note that this or any other calculators on the wkcgroup.com tools room are for information only. WKC Group has endeavoured to ensure that the information presented here is accurate and that the calculations are correct, but will not accept responsibility for any consequential damages, faults or human errors that may arise from the use of formulas, inventories and values