Piping Vibration Analysis
Vibrations in piping systems can arise from interactions between the transported medium and the mechanical properties of the system. These vibrations are problematic because they waste energy, produce unwanted noise, and can cause mechanical failures due to fatigue.
At Dynaflow Research Group, we specialize in diagnosing and mitigating these issues through vibration measurements, modal analyses, and mechanical response analyses. Our extensive experience allows us to identify the root cause by combining detailed structural and transient flow analyses.
Vibration issues stemming from varying flows in pumps, compressors, or process conditions, can lead to harmful pulsations and fatigue failures. Effective system design is crucial to prevent these issues, and that's where our expertise makes us the ideal partner to ensure the reliability and efficiency of your piping systems.
Challenges We Help You Solve
- Pulsations from reciprocating or rotating compressors
- Flow-induced turbulence (FIT) or vibrations (FIV)
- Flow-induced pulsations
- Acoustic-induced vibration (AIV)
- Vortex shedding and vortex-induced vibrations
- Slug flow and multi-phase flows
- Machine vibrations
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Vibration Analysis Process
1. Screening of the system during the design phase
All lines in the systems are screened for potential FIV, AIV, and flow-induced pulsation issues. Inputs to this study include line sizes, geometry, and a review of all operating conditions the system will experience. The study’s outcome will indicate a Likelihood of Failure (LOF) value that portrays the necessity of mitigation measures to prevent vibration issues. The screening method is conducted with reference to the Energy Institute Guideline methodology.
2. Re-design of the system
Based on the screening of the system, re-designs can be proposed by DRG to reduce the LOF of the system to non-problematic levels. Redesigns can be targeted at mitigating against the source of vibrations, or against the pipework response to the vibrations. The re-designs are always proposed in close consultation with the client to deliver a design that is optimal from both a technical and cost perspective.
3. Detailed analysis and mitigation of existing systems
For some systems, initial screening methods might prove overly conservative, or simple redesigns are not possible. For these systems, DRG offers a detailed analysis of the specific location of concern. Through this analysis, DRG can eliminate conservatism made in earlier simplified analyses possibly eliminating the need for changes to the system or creating problem-specific re-designs.
4. Piping vibrational assessment and mitigation
Dynaflow can conduct vibration measurements and assessments. This is recommended for critical systems or for systems that are susceptible to vibrational issues and that have not been analyzed during the design phase of the system.
Vibration measurements may be required for a good match between the digital model and the physical system. The applied load amplitude is then fine-tuned to match the displacements in the model to the calculated displacements from the measurements of the actual system. In this case, the source of the vibrations must be known.
Advanced techniques like motion amplification of high-speed video data are used by Dynaflow to obtain an even better match between model and reality.
Vibration Analysis Case Studies
For the assessment of vibration problems in piping often vibration measurements are required. For the initial measurements, Dynaflow uses its vibration sensors to be able to inspect and efficiently capture important data quickly.
The dynamic analysis required for the assessment of piping vibrations is set up from a static piping model that is constructed with extra care for the correct stiffness and mass distribution.
The forced vibration is applied so that it corresponds to the vibration source of the actual model. The vibrations of the model are matched to the measurement results. From the replicated vibrations in the digital model, the dynamic stresses in the system are determined.
The vibration analysis can be performed using the time history profile of the vibration or, when the vibrations are more random, using a spectrum profile of the vibration. In this case, the time history profile from the measurements is converted into the frequency spectrum. The dynamic forcing amplitude is then scaled to match the maximum displacement of the displacement time history obtained from the measurements.
In case the time history profile can be used for the analysis directly, the mechanical response is fine-tuned and tuned to the measurement data.
Process equipment like pulsation dampeners or reactor vessels are often checked for vibrations in the design phase. In this case, the primary objective of the study is to make sure that the Eigenfrequencies in the shell of the vessel do not coincide with the loading frequencies related to the process properties.
An FEA (Finite Element Analysis) model of the vessel is developed. In the case where the assessment is performed for a vessel in operation, the wall thickness of the partly corroded shell needs to be used in the analysis for accurate results.
With a modal analysis, the Eigenfrequencies and Eigenmodes of the vessel are calculated. If the Eigenfrequency of the vessel matches the process-related loading frequency, the Eigenfrequency of the system is raised by e.g. adding stiffener rings to the vessel’s shell. This will move the Eigenfrequency of the vessel away from the loading frequency and subsequently limit the vibration amplitudes.
When there is enough clearance between the vessel’s Eigenfrequency and the loading frequency, a forced mechanical response analysis may be performed to verify that the vibrational stresses are within allowable limits and conform to the applicable design codes.
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Software Solutions For Piping Vibrations
CAESAR II
DRG conducts piping flexibility assessments using the software Caesar II from Hexagon. Caesar II is used for both static and dynamic piping analyses. We have a thorough understanding of the software and are also an official Caesar II training provider for Hexagon. Caesar II is considered the industry standard for pipe stress analysis.
