Tank Vibration Analysis Using CFD & FEA: Diagnosing Steam Condensation and Assessing Structural Integrity

The Challenge: Excessive Tank Vibration During Operation

A leading chemical process facility experienced persistent tank vibration during live operation, raising concerns around structural fatigue, shock loading, and long-term vessel integrity.

Although the tank remained operational, the client needed clarity on two critical questions:

• What is the root cause of the tank vibration?

• Is the vibration compromising structural integrity or reducing remaining service life?

Understanding whether the issue stemmed from fluid dynamics, process instability, or structural response was essential before implementing corrective measures.

SEAM’s Engineering Approach

SEAM conducted a comprehensive tank vibration analysis combining advanced Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA), integrating both disciplines through a Fluid Structure Interaction (FSI) methodology.

1. Root Cause Diagnosis: CFD Steam Condensation Analysis

A high-fidelity CFD model of the tank and steam injection system was developed to simulate internal process conditions during operation.

The CFD analysis revealed that the injected steam plume developed through a series of distinct transient stages:

• Growth

• Necking

• Detachment

• Collapse

These cyclical plume dynamics generated significant transient pressure waves within the vessel.

The colour contours in the CFD model highlighted the pressure fluctuations associated with the collapse phase of the steam plume. These pressure waves were transferred directly to the tank walls, resulting in structural stress and vibration.

This behaviour is characteristic of unsteady steam condensation shock loading, a phenomenon capable of producing cyclic forces that excite structural vibration modes.

The CFD modelling provided clear visualisation and quantification of:

• Pressure transients

• Localised condensation events

• Dynamic load generation mechanisms

• Frequency content of excitation forces

Computational Fluid Dynamics (CFD) Model Showing Steam Plume Growth, Necking, Detachment, and Collapse (Clockwise from Top Left)

2. Structural Integrity Assessment: FEA & Fluid Structure Interaction (FSI)

The transient pressure data from the CFD simulation was coupled with a structural FEA model using a Fluid Structure Interaction (FSI) approach.

This allowed SEAM to simulate the tank’s vibrational response under realistic operating loads and evaluate:

• Dynamic stress distribution

• Fatigue life under cyclic loading

• Fracture risk

• Structural safety factors

• Remaining lifetime assessment

By integrating CFD and FEA, SEAM provided a complete understanding of both fluid-driven excitation and structural response behaviour.

Structural Analysis of Tank

Results & Client Outcomes

The investigation delivered both technical clarity and strategic value as demonstrated in the video below .

Key outcomes included:

• Definitive identification of unsteady steam condensation as the root cause of tank vibration

• Quantified assessment of structural integrity margins

• Evaluation of fatigue and fracture risk under operational conditions

• Evidence-based recommendations for process mitigation

• Targeted structural modification strategy with defined implementation timeline

Rather than adopting costly blanket reinforcement or conservative shutdown measures, the client was able to implement risk-based engineering decisions supported by high-fidelity simulation data.

About the Author

Patrick Donnellan is a chartered engineer and a member of the Institution of Mechanical Engineers. He has extensive experience in Computational Fluid Dynamics (CFD), and Finite Element Analysis (FEA) for structural integrity assessments. Within SEAM, Patrick focusses on providing solutions to clients across a wide variety of industries through the use of CFD and Finite Element Analysis (FEA), including include medical device, pharmaceutical, manufacturing, civil and environmental engineering, and HVAC.

Contact Patrick at Patrick.Donnellan@setu.ie for further information about SEAM’s CFD and FEA capabilities .

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