Acoustically Induced Vibration (AIV) & Flow Induced Vibration (FIV) Studies

Acoustically Induced Vibration (AIV)

This refers to the phenomenon where mechanical structures or components experience vibration as a result of exposure to acoustic or sound waves. It occurs when high-intensity sound waves or pressure fluctuations in a fluid medium interact with the structure, causing it to vibrate.

AIV can occur in various industrial settings, including oil and gas facilities, power plants, chemical plants, and transportation systems. It is particularly relevant in environments where high-pressure fluid flows, such as pipelines, valves, compressors, and process equipment. AIV is caused by high-pressure drops and high flow rates in vapor/gas services.

The vibration induced by acoustic waves can lead to several issues, including:

It is important to note that the risk due to Acoustically Induced Vibration (AIV) can vary depending on the specific context and industry. However, here are some factors that could contribute to an increased risk of AIV:

To mitigate the increased risk of AIV, industries should employ appropriate engineering practices, conduct thorough risk assessments, implement noise control measures, and regularly inspect and maintain infrastructure. Additionally, adherence to relevant regulations and standards can help minimize the potential impact of AIV on structures and surrounding communities. The severity of AIV depends on various factors, including the sound frequency, sound pressure level, structural characteristics, fluid properties, and operational conditions.

Understanding the causes and effects of AIV is crucial for designing, operating, and maintaining industrial facilities to prevent potential safety hazards, reduce maintenance costs, and ensure reliable operation. Mitigation strategies, such as equipment design modifications, flow control measures, structural damping, and acoustic treatments, can be implemented to minimize or control AIV in affected systems.

Flow Induced Vibration (FIV)

This refers to the phenomenon where fluid flow passing through a structure or around an object induces vibrations in the system. It occurs when the fluid flow interacts with the structure, causing it to oscillate or vibrate.

FIV can occur in various industrial systems and components, including pipes, heat exchangers, valves, offshore structures, and other fluid-carrying equipment. It is particularly relevant in situations where the fluid flow is turbulent, high-velocity, or has irregular characteristics.

The vibration induced by fluid flow can have several effects and consequences, including:

The risk due to flow-induced vibration (FIV) in the oil and gas industry has increased for several reasons:

Given these factors, it is crucial for the oil and gas industry to employ advanced FIV assessment techniques, implement robust design practices, conduct regular inspections, and apply appropriate mitigation measures to ensure the safe and reliable operation of equipment and structures in the face of increased FIV risks. The severity of FIV depends on various factors, including fluid properties, flow velocity, structural characteristics, presence of flow-induced turbulence, and system design.

Understanding the causes and effects of FIV is crucial for designing and operating fluid-carrying systems to prevent potential safety hazards, reduce maintenance costs, and ensure reliable operation. Mitigation strategies, such as structural modifications, flow control measures, dampening techniques, or use of vibration-resistant materials, can be employed to minimize or control FIV in affected systems. Additionally computational fluid dynamics (CFD) simulations and experimental testing can be used to predict and analyze FIV behavior and evaluate the effectiveness of mitigation measures.

During the initial design phase of a new plant or when modifying an existing plant, we provide a two-step approach to preventing vibration problems.

This strategy entails a qualitative evaluation and prioritization followed by a qualitative evaluation that yields actionable recommendations.

Step 1 – Qualitative assessment & prioritization

Using a meticulous methodology, we conduct a qualitative evaluation of all the primary lines in a process system in order to determine the potential excitation mechanisms. Then, we produce a report that identifies and ranks the potential excitation mechanisms that require quantitative analysis.

 Step 2 – Quantitative measurement & Solutions

Main lines: For each identified potentially risky excitation mechanism, a quantitative analysis is performed to determine the likelihood of vibration-induced pipe failure.

The Methodology to carry out AIV & FIV Studies is as follows.

In the oil and gas industry, the study of AIV and FIV is essential for ensuring the integrity and reliability of equipment and structures. Here are some common methods used in AIV and FIV studies specifically tailored to the oil and gas industry:

  1. Field Measurements: Conducting field measurements is crucial to understanding AIV and FIV in the oil and gas industry. It involves installing sensors and instrumentation on equipment such as pipelines, risers, valves, and other components to measure vibrations, acoustic levels, fluid velocities, pressure fluctuations, and structural responses under operational conditions. These measurements help identify the severity of vibrations and assess the potential risks.
  2. Finite Element Analysis (FEA): Finite Element Analysis is widely used to simulate the behavior of oil and gas equipment subjected to AIV and FIV. FEA models can be created to represent the structures and components accurately. Acoustic loads, fluid flow conditions, and structural properties are considered to predict vibration levels, stress distribution, and potential failure modes. FEA can also help optimize the design of equipment to mitigate AIV and FIV.
  3. Computational Fluid Dynamics (CFD): Computational Fluid Dynamics is employed to simulate fluid flow behavior around oil and gas equipment. CFD models can predict fluid velocities, pressure fluctuations, and flow-induced forces that can lead to FIV. These simulations assist in identifying critical areas of flow separation, vortex shedding, and fluid-structure interaction, enabling the design of mitigation measures to reduce FIV risks.
  4. Experimental Testing: Experimental testing is conducted in laboratory or field settings to validate numerical models and investigate AIV and FIV phenomena specific to the oil and gas industry. It involves subjecting representative equipment or scaled-down models to controlled acoustic excitations or fluid flow conditions. Measurements of vibrations, acoustic levels, fluid velocities, and pressure fluctuations are collected to validate numerical simulations and provide insights into the behavior of the equipment.
  5. Risk Assessment and Mitigation: AIV and FIV risk assessments are performed to identify vulnerable equipment and potential consequences. This involves analyzing the equipment design, fluid flow characteristics, acoustic environments, and structural properties. Mitigation strategies can include modifications to the equipment design, implementing flow control devices, adding damping materials, or changing operational parameters to reduce the likelihood and severity of AIV and FIV.
  6. Standards and Guidelines: The oil and gas industry rely on industry-specific standards and guidelines to address AIV and FIV concerns. Organizations such as the American Petroleum Institute (API) provide recommended practices and design guidelines to mitigate AIV and FIV risks. Following these standards ensures that industry best practices are implemented during the design, operation, and maintenance of oil and gas equipment.
  7. Monitoring and Maintenance: Continuous monitoring of equipment performance and condition is crucial to detect and mitigate AIV and FIV risks in the oil and gas industry. Implementing a monitoring system with sensors and instrumentation allows for real-time monitoring of vibration levels, acoustic levels, fluid flow parameters, and structural responses. Regular maintenance activities such as inspection, cleaning, and repairing or replacing damaged components can help prevent or mitigate AIV and FIV issues.

AIV and FIV have the same potential failure points, and fortunately, many of the solutions are identical. Every portion of the pipe system, from the source to the affected pipelines further downstream, is mitigated. Reduced speeds, thicker pipelines, and bending are all methods for addressing both issues. With each form of vibration, various options are discussed.

In the table below, the differences between the two types of sound are shown.

High-frequency piping vibrationsLow-frequency piping vibrations
Flow is mostly gasFlow typically contains liquid
Produce sound waves within the range of human hearingLess sound waves
Source of vibration is pressure reduction devicesSource of vibration is turbulence at flow discontinuities
Vibration magnitude invisibleVibration magnitude visible
Vibration frequency is 500-2500 HzVibration frequency is 0-100 Hz
Location failure at branch fitting and welded supportLocation failure at welds and supports
Mitigation: Increase pipe wall thickness, Localized full wrap reinforcement, Split flows, Clamped supports, Apply low noise trim valvesMitigation: Increase pipe wall thickness, Add supports, Long radius bends, Flow straighteners, Increase pipe size, Viscous dampeners

The combination of these methods and practices tailored to the oil and gas industry enables a comprehensive understanding of AIV and FIV behavior, assists in designing robust equipment, and ensures the safe and reliable operation of oil and gas facilities.