Introduction

Pressure vessels are critical components in industries such as oil and gas, chemical processing, and power generation. Their design, analysis, and optimization require precise engineering to ensure safety, durability, and compliance with industry standards. Finite Element Analysis (FEA) has become an indispensable tool for engineers, offering accurate insights into the behaviour of pressure vessels under various operating conditions.

This blog takes you through key FEA applications for pressure vessels, showcasing how advanced simulations solve real-world challenges. From understanding stress concentration at nozzle-to-shell junctions to ensuring structural stability through buckling and fatigue analysis, FEA helps engineers design pressure vessels that meet stringent safety and performance requirements.

In this blog, we’ll explore:

• Fundamental analyses like complete pressure vessel evaluation and lifting studies.
• Junction-specific evaluations, including nozzle-to-shell and Y-forging connections.
• Advanced assessments like thermal analysis, elastic-plastic stress studies, and buckling stability.

Every case study demonstrates how FEA is used to optimize pressure vessel designs so they can endure harsh environments and continue to function safely for the duration of their lives.

Join us as we delve into these applications, arranged from simpler to more complex analyses, and uncover how FEA revolutionizes the design and performance of pressure vessels.

1. FEA of Nozzle-to-Shell Junction

Introduction

Multiple nozzle holes are included in pressure vessels to accommodate different needs; some of these nozzles are small and utilized for process control, while others are used for monitoring.

 Usually, Nozzles which are tangential or on critical locations like the knuckle needs to be qualified using FEA. Analyzer CAE has done 1500+ nozzle analysis for clients in India and Abroad. The nozzles are subjected to internal pressure and design nozzle loads.

Solution / methodology

If a nozzle does not get qualified as per WRC calculations, then FEA becomes mandatory to qualify the nozzle. The Nozzle to Shell junction was analysed using finite element method to determine the structural strength against the various applicable loading like internal pressure, nozzle loads & combination.

To assess strength for the structure, guidelines from ASME BPVC (Boilers & Pressure Vessels Code) Section VIII Div. 2, Part 5 were utilized. For evaluating various stresses across nozzle & shell thickness.

The nozzle-to-shell junction is a critical area in pressure vessels, often experiencing high stress due to pressure loads and thermal gradients.

How FEA Helps:

• Accurately evaluates stress intensities and deformation at the junction.
• Assesses the impact of internal pressure, temperature, and external forces.
• Optimizes geometry to minimize stress concentrations.

This analysis ensures that the junction can withstand extreme conditions without compromising the vessel’s structural integrity.

2. FEA of Skirt (Y-Forging) Junction

Introduction

Pressure vessels have different types of supports depending upon their service & location of installation. Supports are of great importance in a pressure vessel assembly as their failure will be failure of complete pressure vessel unlike other localized failures. Skirt supports involves Y-Forging, which is a connecting element between shell, dished end & Skirt support. As this element is a major player in load transfer to support so it needs to verify for its strength against applied loadings.

Process equipment manufacturer from India & Abroad approached ANALYZER to seek assistance in evaluating the design of their newly developed vessels to multiple loading conditions using simulation techniques & provide the solution in case of any observed failure.

Solution / methodology

The Skirt (Y-Forging) junction geometry was analysed using Finite Element Method to determine the induced stresses due to various loading conditions. To assess strength of the geometry, guidelines from ASME BPVC (Boilers & Pressure Vessels Code) Section VIII Div. 2 Ed. 2013 were utilized.

Stress Linearization has been carried out at various cross sections of the Forging & its connection with shell & Skirt. The results showed that the induced stresses were well within the acceptable limits as per guidelines. Hence, the structure’s design was predicted to behave safe during operation without premature failure.

The skirt provides structural support to the vessel, making its junction with the main body a critical area for analysis.

How FEA Helps:

• Evaluates thermal and mechanical stresses at the Y-forging junction.
• Simulates operating conditions to predict crack propagation risks.
• Enhances stability by identifying weak points and suggesting reinforcements.

Accurate modelling of this junction helps prevent structural instability during operations.

3. FEA of Complete Pressure Vessel

Introduction

Pressure vessels are subjected to various loadings depending upon their applications. Due to asymmetric nature of this loadings sometimes the vessel assembly experiences sudden failure. Most of the times it is observed that these failures are localized. So, to avoid such a catastrophic failure.

Process equipment manufacturer from India & Abroad approached Analyzer CAE Solutions Pvt Ltd to seek assistance in evaluating the design of their newly developed vessels to multiple loading conditions using simulation techniques & provide the solution in case of any observed stress failure

Solution / methodology

The pressure vessel was analysed using Finite Element Method to determine the induced stresses due to various loading conditions. To assess strength of complete pressure vessel, guidelines from ASME BPVC (Boilers & Pressure Vessels Code) Section VIII Div. 2 Ed. 2013 were utilized. Stress Linearization has been carried out at various locations.

The results showed that the induced stresses were well within the acceptable limits as per guidelines. Hence, the structure’s design was predicted to behave safe during operation without premature failure.

A comprehensive analysis of the entire pressure vessel is essential to ensure overall safety and performance.

How FEA Helps:

• Combines thermal, structural, and fatigue analyses for a comprehensive view.
• Identifies weak zones under operational loads and suggests design improvements.
• Ensures the vessel meets industry standards and safety regulations.

By analysing the complete vessel, engineers can optimize designs to handle extreme operational conditions effectively.

4. Lifting Analysis of Pressure Vessels

Introduction

At the time of transportation, the pressure vessels need to be lifted. For lifting, a lug arrangement is provided on the vessel. At the time of lifting, due to self-weight of structure & various angle of inclination, some stresses got induced in the vessel geometry. This stresses sometimes leads to permanent sets in pressure vessel. Analytical calculations do not provide the actual stress pattern & hence FEA is an important tool in such cases.

Process equipment manufacturer from India & Abroad approached Analyzer CAE Solutions Pvt Ltd to seek assistance in evaluating the design of their newly developed vessels for lifting condition & provide the solution in case of any observed failure.

Solution / methodology

The pressure vessel was analysed using Finite Element Method to determine the induced stresses at the time of lifting for different angle of inclinations. The vessel is evaluated for the stress & deformation pattern.

The results showed that the induced stresses were well within the allowable stress limits. Hence, the structure’s design was predicted to behave safe during lifting without inducing any permanent set.

Transporting and installing pressure vessels involves lifting them, which can induce significant stress.

How FEA Helps:

• Simulates lifting operations to identify stress and deformation.
• Ensures lifting lugs and attachment points are robust enough to handle loads.
• Prevents damage during handling by optimizing lifting procedures.

Proper lifting analysis minimizes risks during transportation and installation, ensuring compliance with safety standards.

5. FEA of Quick Opening Closure

Introduction

Quick Opening Closure (QOC) is door in pressure vessel & boilers, which also serves as a head. It is locked at its position by locking mechanism. QOC’s always comes under the influence of mechanical static & fatigue loadings.

FEA gives better understanding of actual behaviour of assembly due to various static & fatigue loadings. Main door structure, hub, locking ring are critical components of QOC assembly, which can be analysed by FEA. Due to asymmetric nature of static loadings, structure may result in higher localized stresses; while fatigue loading is dangerous than other loadings as the structure will experience sudden failure without any prior indication. 

Process equipment manufacturer from India & Abroad approached Analyzer CAE Solutions Pvt Ltd to seek assistance in evaluating the design of their newly developed QOC’s to multiple loading conditions using simulation techniques & provide the solution in case of any observed stress failure.

Solution / methodology

The QOC was analysed using Finite Element Method to determine the induced stresses due to various cyclic loadings. To assess fatigue strength for the QOC, guidelines from ASME Section VIII Div. 2 part 5 & Annexure 3.F were utilized.

The fatigue calculations were performed & fatigue damage factor is found much below unit value. Hence, the structure’s design was predicted to behave safe during operation without premature failure.

Quick opening closures (QOCs) are essential for ease of access but must withstand high internal pressures.

How FEA Helps:

• Analyses stress concentrations during opening and closing operations.
• Evaluates the sealing mechanism under internal pressure.
• Ensures safety without compromising operational efficiency.

Properly designed QOCs enhance operational flexibility and safety in pressure vessels

6. Thermal Analysis of Heat Exchanger

Introduction

Process equipment is subjected to higher temperatures during their service life. This higher temperature causes thermal stresses in various parts of the equipment.

Excessive differential expansion of the equipment sometimes leads to its failure. Hence such severe conditions need to be analysed to ensure safety of the equipment. 

Solution / methodology

The equipment (Pressure vessel/Heat exchanger) was analysed using Finite Element Method to determine the induced stresses due to differential thermal loading. To assess structural strength of the equipment, guidelines from ASME BPVC (Boilers & Pressure Vessels Code) Section VIII Div. 2 part 5 were utilized.

For Thermal analysis, as secondary stresses are induced in the geometry hence membrane stresses are not evaluated. The induced stresses are observed to be within the allowable limit. Hence, the structure’s design was predicted to behave safe during operation without premature failure.

Thermal gradients can cause stress and deformation in process equipment, leading to operational inefficiencies.

How FEA Helps:

• Simulates temperature distribution and resulting thermal stresses.
• Identifies areas prone to expansion or contraction.
• Guides material selection and design improvements.

7. Elastic-Plastic Stress Analysis

Introduction

FEA of most of the components is performed to study the actual behaviour of the structure. It is generally performed by elastic stress analysis approach which is quick & reliable. But in some cases, more accurate evaluation against plastic collapse is required.

This requirement is satisfied by elastic plastic analysis of the structure. This approach of analysis considers material as well as structural non-linearity into consideration for FEA resulting a more accurate approximation of actual structure.

Process equipment manufacturer from India & Abroad approached Analyzer CAE Solutions Pvt Ltd to seek assistance in evaluating the design of their newly developed equipment to multiple loading conditions using simulation techniques & provide the solution in case of any observed failure.

Solution / methodology

The structure was analysed using FEM for elastic plastic stress analysis. The loading combinations are used from table 5.5 of ASME Sec. VIII Div.2. To consider material non-linearity, stress-strain curve is provided as an input to the MoC/s & for structural non-linearity, large deflection is considered in FEA .

The solution shows that the structure is capable of designed loadings also the induced strain is within the allowable limit. Hence, the design was predicted to behave safe during operation without premature failure.

Elastic-plastic stress analysis is essential for understanding material behaviour beyond the elastic limit.

How FEA Helps:

• Predicts permanent deformation in structural components under heavy loads.
• Evaluates failure mechanisms to ensure safety margins are maintained.
• Guides material selection and design improvements.

8. Fatigue Analysis of Pressure Vessels

Introduction

Pressure vessels are subjected to fluctuating loads either mechanical or thermal depending on their service subject. This loading is dangerous than other loadings as the structure will experience sudden failure without any prior indication. Hence fatigue calculations need to be part of design of a vessel.

Process equipment manufacturer from India & Abroad approached Analyzer CAE Solutions Pvt Ltd to seek assistance in evaluating the design of their newly developed vessels to multiple fatigue loadings using simulation techniques & provide the solution in case of any observed fatigue failure.

Solution / methodology

The pressure vessel was analysed using Finite Element Method to determine the induced stresses due to various cyclic loadings. To assess fatigue strength for the vessel, guidelines from ASME BPVC (Boilers & Pressure Vessels Code) Section VIII Div. 2 part 5 & Annexure 3.F was utilized.

 The fatigue calculations were performed & fatigue damage factor is found much below unit value. Hence, the structure’s design was predicted to behave safe during operation without premature failure.

Fatigue is a major concern for pressure vessels operating under cyclic loading. Over time, repeated stress cycles can lead to crack initiation and eventual failure.

How FEA Helps:

• FEA simulates cyclic loading conditions to predict fatigue life.
• Identifies high-stress concentration zones where cracks are likely to form.
• Assists in improving material selection and design modifications to enhance durability.

By addressing fatigue early in the design process, engineers can extend the operational life of pressure vessels and prevent catastrophic failures.

9. Buckling Analysis

Introduction

Most of the process equipment are subjected to compressive loadings during their operation (e.g., Pressure vessel/ heat exchanger sub. to full vacuum). Sometimes this type of loading results into buckling of the component causing buckle failure of the structure.

 Hence a process equipment needs to be evaluated for any possible buckling failure. This type of failure is mainly observed in long vessels, vessels with larger diameter, vessels with improperly spaced stiffeners.

Process equipment manufacturer from India & Abroad approached Analyzer CAE Solutions to seek assistance in evaluating the design of their newly developed equipment against buckling failure using simulation techniques & provide the solution in case of any observed failure.

Solution / methodology

The structure was analysed using Finite Element Method for elastic buckling analysis. The loading used for this analysis is unit loading. The structure is solved for bifurcation analysis & design factor calculations were performed.

The results showed that the structure is the calculated design factor for the structure is greater than the min. design factor as defined in clause 5.4 of ASME BPVC Sec. VIII Div. 2. Hence, the structure’s design was predicted to safe against buckle failure during its service life.

Buckling is a critical failure mode for slender structures subjected to compressive forces.

How FEA Helps:

• Identifies critical buckling loads and deformation patterns.
• Suggests design modifications to prevent instability.
• Ensures compliance with industry safety standards.

Fig: Centre Pipe of Heat Exchanger is Evaluated for Buckling Failure against shell side pressure

By addressing buckling risks, engineers ensure the stability and safety of structures.

 Benefits of FEA in Pressure Vessel Design

• Enhanced Safety: Prevents structural failures and accidents.
• Cost Savings: Identifies design flaws early, reducing manufacturing and repair costs.
• Improved Durability: Extends operational life by addressing fatigue and other critical issues.
• Insight from Thermal Engineering Case Studies: FEA-driven case studies have demonstrated significant improvements in pressure vessel performance and reliability across industries.

Conclusion

Pressure vessels are vital across industries, serving as critical components under challenging conditions. Ensuring their safety, durability, and efficiency is non-negotiable. Finite Element Analysis (FEA) has proven to be an invaluable tool in achieving these objectives, enabling engineers to address complex design challenges with precision and confidence.

From fundamental evaluations, such as complete vessel analysis and junction studies, to advanced techniques like thermal assessments, elastic-plastic stress analysis, and buckling simulations, FEA offers a holistic approach to pressure vessel design and optimization. It helps predict potential failures, refine designs, and enhance performance while meeting the strictest industry standards.

By leveraging FEA, engineers and manufacturers can not only improve the reliability and safety of pressure vessels but also reduce material costs, extend operational lifespans, and boost overall productivity. As industries continue to innovate, the integration of FEA into pressure vessel engineering remains essential for driving advancements and maintaining a competitive edge.

Whether you’re designing new pressure vessels or improving existing ones, embracing FEA is no longer just an option—it’s the future of pressure vessel engineering. With its ability to simulate real-world conditions and provide actionable insights, FEA continues to revolutionize the way pressure vessels are designed, analysed, and optimized.