FIV ASSESSMENT
Flow-Induced Vibration Assessment
Vortex shedding. Dead leg excitation. Turbulence-induced fatigue. Assessed with authority.
The Problem
Flow-induced vibration is the failure mode that kills quietly. Unlike acoustic-induced vibration — which is audible and dramatic — FIV accumulates fatigue damage at dead legs, thermowells, small bore connections, and instrument tappings over months and years. By the time cracking is visible, fatigue life is already exhausted.
The risk is highest in centrifugal compressor systems, high-velocity gas headers, and any dead leg branch where flow velocity creates vortex shedding frequencies that approach the mechanical natural frequency of the connected piping or instrumentation. A frequency coincidence of this kind is not a design deficiency. It is an integrity event waiting for operating conditions to align.
Our Approach
Emveedo's FIV assessment follows the Energy Institute Guidelines for the Avoidance of Vibration Induced Fatigue Failure in Process Pipework (EI AVIFF, 2nd Edition) as the primary screening framework. This is the industry standard accepted by UKCS operators, North Sea regulators, and international NOCs. Our assessments are not limited to the screening phase — where elevated risk is identified, we proceed directly to detailed fatigue analysis using our proprietary analytical workflows, removing the need for a second engagement and a second mobilisation.
For dead leg branches, assessment includes geometry evaluation, flow regime classification, acoustic mode analysis, and vortex shedding frequency calculation. For thermowells and probes, the calculated shedding frequency is checked against mechanical natural frequency with appropriate separation margins. For centrifugal compressor piping, FIV assessment is conducted in parallel with AIV screening — the two mechanisms are never assessed in isolation on high-energy gas systems.
What You Get
A fully documented FIV assessment report: line-by-line screening results, risk classification per EI AVIFF methodology, detailed analysis for elevated-risk locations, and a clear engineering recommendation for each identified concern. Where modifications are required, we provide the engineering basis — not a requirement to appoint another consultant.
Deliverables are suitable for regulatory submission, FEED gate review, and brownfield management of change.
When You Need This
COMMON QUESTIONS
Frequently Asked Questions
What is flow-induced vibration (FIV)?
Flow-induced vibration (FIV) occurs when turbulence, vortex shedding, or unstable flow excites the piping system. Unlike acoustic-induced vibration, FIV often develops gradually and rarely produces obvious warning signs. If left unmanaged, repeated cyclic loading can lead to fatigue cracking at supports, dead legs, thermowells, and small bore connections.
How is FIV different from acoustic-induced vibration (AIV)?
FIV is driven by turbulence and flow instability within liquid or gas flow. Acoustic-induced vibration (AIV) results from high acoustic energy generated by pressure-reducing devices such as control valves, restriction orifices, and relief systems. The two mechanisms require different assessment methodologies, although both may exist within the same facility and are often assessed together on high-energy process systems.
When should an FIV assessment be carried out?
FIV assessments are valuable during FEED, detailed design, brownfield modifications, and life-extension studies. They are also recommended following significant process changes, debottlenecking, equipment replacement, or whenever operating conditions differ from the original design assumptions.
Does an FIV assessment require shutting down the plant?
No. Most FIV screening studies are completed using existing design documentation, piping data, process conditions, and operating information. Detailed engineering assessment can usually be carried out without interrupting normal plant operation.
Which standards are used for FIV assessment?
Our assessments are primarily based on Energy Institute EI 3160 guidance, supported by relevant international engineering standards and good industry practice. Where project-specific requirements apply, these are incorporated into the assessment methodology to provide a clear and defensible integrity position.
What happens if screening identifies a high-risk location?
Screening is only the first step. Where elevated risk is identified, we determine the underlying excitation mechanism, assess fatigue susceptibility, and provide practical engineering recommendations. These may include support modifications, geometry changes, operating adjustments, or detailed dynamic analysis, depending on the governing failure mechanism.
Related Expertise
Piping Stress Analysis
Independent stress analysis for new design, brownfield modifications, and life extension assessments.
Learn more →Acoustic-Induced Vibration Assessment
Acoustic vibration analysis for high-velocity gas and two-phase flow systems.
Learn more →Small Bore Connection Screening
Rapid assessment of small bore connections for vibration and fatigue risk.
Learn more →The EI AVIFF Guideline
Energy Institute Guidelines for the Avoidance of Vibration Induced Fatigue Failure in Process Pipework.
Learn more →