Acoustically Induced Vibrations
Mitigate the Impact of AIV
Acoustically Induced Vibration (AIV) refers to structural vibration excited by intense pressure fluctuations in a compressible flow stream. Process plants have a number of requirements for abrupt pressure reductions, which invariably generate some amount of acoustic vibration. This is normally accomplished by a throttling valve or orifice such as:
- Blowdown valves and restriction orifices
- Relief valves
- Pressure reducing valves
- Compressor recycle valves
The pressure reduction process induces turbulent pressure fluctuations in the flowing medium, which in turn excites the downstream pipe wall, causing stresses and potentially fatigue failure. The intensity of vibration tends to increase with mass flow rate, velocity and pressure loss. The accompanying sound radiation is typically broadband in the range of 200Hz to 20 kHz with a peak somewhere above 1 kHz. AIV failures are known to occur preferentially at non-axisymmetric discontinuities in the downstream piping such as small bore branches and their welded supports.
Equity Engineering uses a rigorous methodology to predict AIV failures and provide remedial actions. This methodology starts with the identification of those processes requiring analysis (e.g., emergency venting, valves, compressor let-downs) and concludes with detailed recommendations to reduce dynamic stress levels where the potential for fatigue failures puts your facility at risk. If you are responsible for the design or operation of high-pressure blowdown systems on oil and gas facilities, flaring systems, compressor stations or power generation plants, we can mitigate the impacts of AIV and reduce costs associated with increased piping schedules.
Mr. Shipley is skilled in thermal and stress finite element analysis with emphasis on non-linear behavior such as buckling, contact, creep, plasticity and large deformation behavior. He has applied his FEA skills to pressure vessel nozzle designs, expansion joint designs, remaining life of high temperature components, hot-to-cold wall transitions, corroded equipment, hot spots, FCC equipment (orifice chamber, reactor, regenerator, expansion joints, slide valves, etc.) and specialty equipment.
Ms. Ward has 15 years of experience in the chemical industry where she has been responsible for pressure relief device system studies in chemical plant operations. She has also been involved in pipe stress and vibration analysis and has performed extensive Risk-Based Inspection studies on plant pressure vessels, heat exchangers and storage tanks.
