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Comprehensive Piping Stress Analysis (Caesar II) Online Course (35+ hours)

Written by Anup Kumar Dey in Piping Stress Analysis

Whatispiping Team, in association with Everyeng, is conducting an online pre-recorded Comprehensive Piping Stress Analysis Certificate course to help mechanical and piping engineers. Along with the regular content that the participants will be learning, there will be a dedicated 2-hour doubt-clearing session (/question-answer session) with the mentor.

Contents of Online Piping Stress Analysis with Caesar II Course

The program will be delivered using the most widely used pipe stress analysis software program, Caesar II. The full course is divided into 4 parts.

  • Part A will describe the basic requirements of pipe stress analysis and will help the participants to be prepared for the application of the software package.
  • Part B will describe all the basic static analysis methods that every pipe stress stress engineer must know.
  • Part C will give some understanding of dynamic analysis modules available in Caesar II; and
  • Part D will explain all other relevant details that will prepare a basic pipe stress engineer to become an advanced user. Additional modules will be added in this section as and when ready.
Comprehensive Piping Stress Analysis Online Course

In its present form, the full course will roughly cover the following details:

Part A: Basics of Pipe Stress Analysis

  • What is Pipe Stress Analysis?
  • Stress Critical Line List Preparation with Practical Case Study
  • Inputs Required for Pipe Stress Analysis
  • Basics of ASME B31 3 for a Piping Stress Engineer
    • ASME B31.3 Scopes and Exclusions
    • Why stress is generated in a piping system
    • Types of Pipe Stresses
    • Pipe Thickness Calculation
    • Reinforcement Requirements
    • ASME B31.3 Code Equations and Allowable
  • Introduction to Pipe Supports
    • Role of Pipe Supports in Piping Design
    • Types of Pipe Supports
    • List of Pipe Supports
    • Pipe Support Span
    • How to Support a Pipe?
    • Pipe Support Optimization Rules
    • Pipe Support Standard
    • Support Engineering Considerations
  • What is a Piping Isometric?
  • What is an Expansion Loop?
  • Bonus Lecture: Introduction to Pipe Stress
  • Bonus Lecture: Pressure Stresses in Piping

Part-B: Static Analysis in Caesar II

  • Introduction to Caesar II
  • Getting Started in Caesar II
  • Stress Analysis of Pump Piping System
  • Creating Load Cases
  • Wind and Seismic Analysis
  • Generating Stress Analysis Reports
  • Editing Stress Analysis Model
  • Spring Hanger Selection and Design in Caesar II
    • Introduction
    • Types of Spring Hangers
    • Components of a Spring Hanger
    • Selection of Variable and Constant Spring hangers
    • Case Study of Spring Hanger Design and Selection
    • Certain Salient Points
  • Flange Leakage Analysis in Caesar II
    • Introduction
    • Types of Flange Leakage Analysis and Background Theory
    • Case Study-Pressure Equivalent Analysis
    • Case Study-NC Method
    • Case Study-ASME Sec VIII method
  • Stress Analysis of PSV Piping System
    • Introduction
    • PSV Reaction Force Calculation
    • Applying PSV Reaction force
    • Practical Case Study
    • Certain best practices
  • Heat Exchanger Pipe Stress Analysis
    • Introduction
    • Creating Temperature Profile
    • Modeling the Heat Exchanger
    • Nozzle Load Qualification
    • Practical Case Study
    • Methodology for shell and tube inlet nozzle stress analysis
  • Vertical Tower Piping Stress Analysis
    • Introduction
    • Creating Temperature Profile
    • Equipment Modeling
    • Modeling Cleat Supports
    • Skirt temperature Calculation
    • Nozzle Load Qualification
    • Practical Example
  • Storage Tank Piping Stress Analysis
    • Introduction
    • Reason for Criticality of storage tank piping
    • Tank Settlement
    • Tank Bulging
    • Practical example of tank piping stress analysis
    • Nozzle Loading
  • Pump Piping Stress Analysis
    • API610 Pump nozzle evaluation using Caesar II

Part C: Dynamic Analysis is Caesar II

  • Introduction-Dynamic Analysis in Caesar II
  • Types of Dynamic Analysis
  • Static vs Dynamic Analysis
  • Dynamic Modal Analysis
  • Equivalent Static Slug Flow Analysis
  • Dynamic Response Spectrum Analysis

Part D: Miscellaneous other details

  • WRC 297/537 Calculation
    • What are WRC 537 and WRC 297?
    • Inputs for WRC Calculation
    • WRC Calculation with Practical Example
  • Underground Pipe Stress Analysis
  • Jacketed Piping Stress Analysis
  • Create Unit and configuration file in CAESAR II
  • ASME B31J for improved Method for i, k Calculation in Caesar II
  • Discussion about certain Questions and Answers
  • GRE/FRP Pipe stress analysis
    • GRE Pipe Stress Analysis using Caesar II
    • GRE Stress Analysis-Basics
    • FRP Pipe Stress Analysis Case Study
    • GRE Flange Leakage Analysis
    • Meaning of Stress Envelope; Understand it
  • Reviewing A Piping Stress System
    • Introduction
    • What to Review
    • Reviewing Steps
    • Case Study of Reviewing Pipe Stress Analysis Report
    • Reviewing Best Practices
  • FIV Study
    • Flow Induced Vibrations-Introduction
    • What is Flow-Induced Vibration (FIV)?
    • Flow-Induced Vibration Analysis
    • Corrective-Mitigation Options
  • AIV Study
    • Introduction
    • What is Acoustic-Induced Vibration (AIV)?
    • Acoustic-Induced Vibration Analysis
    • Corrective-Mitigation Options

How to Enroll for this Course

To join this course, simply click here and click on Buy Now. It will ask you to create your profile, complete the profile, and make the payment. As soon as the payment is complete, you will get full access to the course. If you face any difficulty, contact the Everyeng team using the Contact Us button on their website.

Detailed Online Course on Pipe Stress Analysis (25 hours of Content) with Certificate + Free Trial Version of Pipe Stress Analysis Software

Written by Alex Matveev in Engineering Courses,Pipeline,Piping Design Basics,Piping Stress Analysis,Piping Stress Basics,Start-Prof

This course is created by an experienced pipe stress analysis software developer (15+ years experience), Ph.D. and covers all features of onshore above ground and underground piping and pipeline analysis. This course is based on the PASS/START-PROF software application, though it will be interesting for users of any other pipe stress analysis software tools as it contains a lot of theoretical information.

The course consists of video lectures, quizzes, examples, and handout materials.

Type: an on-demand online course.

Duration: 25 hours.

Course price: 200 USD 30 USD.

Instructor: Alex Matveev, head of PASS/START-PROF Pipe Stress Analysis Software development team. Always available for your questions at Udemy, LinkedIn, Facebook

Alex Matveev

Who should attend

All process, piping, and mechanical engineers specialized in design and piping stress analysis for the specified industries:

  • Oil & Gas (Offshore/Onshore)
  • Chemical & Petrochemical
  • Power (Nuclear/ Non-Nuclear)
  • District Heating/Cooling
  • Water treatment
  • Metal industry

Training software

All trainees are provided with a free 30-day pipe stress analysis software license (PASS/START-PROF). How to get a free license

Certificate

After finishing the course, you will receive Certificates from both the Udemy and from PASS Team.

Detailed Training Agenda: Download the detailed training agenda in PDF.

Brief Summary of the Course

Introduction
Section 1. Working with PASS/START-PROF User Interface339 min
Section 2. Piping Supports138 min
Section 3. Stress Analysis Theory and Results Evaluation237 min
Section 4. Underground Pipe Modeling249 min
Section 5. Static and Rotating Equipment Modeling and Evaluation244 min
Section 6. Expansion Joints, Flexible Hoses, Couplings106 min
Section 7. Non-Metallic Piping Stress Analysis99 min
Section 8. External Interfaces65 min
Brief Course Summary

How to Enroll for the Course

Visit the Pipe Stress Analysis course page on Udemy

Then click Add to Cart or Buy Now and follow the instructions

What you will learn in this Course

  • Pipe stress analysis theory. Load types. Stress types. Bourdon effect. Creep effect in high-temperature piping, creep rupture usage factor (Appendix V B31.3)
  • ASME B31.1, ASME B31.3, ASME B31.4, ASME B31.5, ASME B31.8, ASME B31.9, ASME B31.12 code requirements for pipe stress analysis
  • How to use PASS/START-PROF software for pipe stress analysis
  • How to work with different load cases
  • How to model different types of piping supports, the spring selection
  • What are stress intensification and flexibility factors and how to calculate them using FEA and code requirements
  • How to model trunnion and lateral tees
  • How to model pressure vessels and columns connection: modeling local and global flexibility, WRC 297, WRC 537, FEA
  • How to model storage tank connection (API 650)
  • How to model connection to air-cooled heat exchanger API 661, fired heater API 560, API 530
  • How to model connection to Pump, Compressor, Turbine (API 610, API 617, NEMA SM23)
  • How to model buried pipelines: Submerged Pipelines, Long Radius Bends Modeling of Laying, Lifting, Subsidence, Frost Heaving, Fault Crossing, Landslide
  • Underground pipelines Seismic Wave Propagation, Pipe Buckling, Upheaval Buckling, Modeling of Pipe in Chamber, in Casing with Spacers. Electrical Insulation kit
  • Minimum design metal temperature calculation MDMT calculation, impact test
  • Modeling of Expansion Joints, Flexible Hoses, Couplings
  • Import and export to various software: CAESAR II, AVEVA, REVIT, PCF format, etc.
  • How to do Normal Modes Analysis and how to interpret results
  • ASME B31G Remaining Strength of Corroded Pipeline Calculation

Interview Questions on Dynamic Pipe Stress Analysis

Written by Anup Kumar Dey in Caesar II,Piping Stress Analysis,Piping Stress Basics

Dynamic Pipe Stress Analysis is a specialized engineering evaluation used to assess how piping systems respond to time-dependent (dynamic) loads, such as:

  • Seismic activity (earthquakes)
  • Water hammer (fluid transients)
  • Wind or vibration loads
  • Pulsating pressure or flow
  • Equipment vibrations (e.g., pumps, compressors, turbines)

Key Characteristics of Dynamic Analysis:

  • Time-dependent: Unlike static stress analysis, dynamic analysis considers forces that vary with time.
  • Transient and steady-state effects: It may account for one-time events (e.g., seismic shock) or repeated, cyclical loads (e.g., harmonic vibration).
  • Modal behavior: Often involves calculating natural frequencies and mode shapes of the pipe system to see if it could resonate under certain conditions.

Types of Dynamic Analysis:

  1. Modal Analysis: Determines the natural frequencies and mode shapes of the system.
  2. Response Spectrum Analysis: Used for seismic analysis; calculates maximum response using a predefined spectrum.
  3. Time History Analysis: Simulates the time-varying nature of loads (e.g., a recorded earthquake waveform).
  4. Harmonic Analysis: Evaluates the system’s behavior under sinusoidal (vibrating) forces.
  5. Force Spectrum Analysis: Used for flow-induced or acoustic-induced vibrations.

Purpose of Dynamic Analysis:

The goal is to ensure:

  • The integrity of the piping system under dynamic events.
  • Compliance with codes and standards (e.g., ASME B31.1, B31.3, ISO 14692).
  • Prevention of fatigue failure, excessive deflection, or joint failure.

Tools used for Dynamic Pipe Stress Analysis:

Dynamic pipe stress analysis is typically performed using specialized software like:

  • CAESAR II
  • AutoPIPE
  • ROHR2
  • Start-PROF
  • PIPESTRESS
  • Caepipe, etc

Interview Questions on Dynamic Pipe Stress Analysis

All advanced pipe stress analysts are expected to learn dynamic pipe stress analysis to study the behaviour of piping systems under dynamic loading conditions. Various questions related to dynamic analysis are asked during interviews to decide the capability of piping stress engineers. The following section lists some of the frequently asked interview questions related to dynamic pipe stress analysis.

  1. Explain the term degree of freedom with an example. Why is the word “independent” used in the definition?
  2. Explain the terms mass matrix and stiffness matrix.
  3. What is meant by mode shape?
  4. Explain the meaning of each column of a matrix of mode shapes (the PHI matrix).
  5. What is modal orthogonality, and what is its use?
  6. Explain how the phase angle changes with the damping ratio.
  7. Explain the key differences between overdamped, underdamped, and critically damped systems.
  8. How does damping affect response?
  9. What is the key difference between lumped and consistent mass matrices?
  10. Explain the calculation and significance of the term mode participation factor (also referred to as mass participation factor)
  11. Explain how the mass% report is generated in Caesar II and what should be the target % of mass in the X, Y, and Z directions.
  12. Can an X-direction excitement result in the Z mass getting excited?
  13. Explain the term “response spectrum.”
  14. Explain what is meant by DLF (first define DLF) spectrum, pseudo velocity spectrum and pseudo acceleration spectrum.
  15. Time history analysis is required to generate the response spectrum – is this true? Support or challenge these using arguments.
  16. What is meant by modal, spatial, and directional combination methods?
  17. Explain the strengths and weaknesses of various combination methods.
  18. What is meant by the 100-40-40 rule?
  19. Explain the meaning of the terms force set and time history definition.
  20. Explain how a DLF spectrum is generated from a time history
  21. Explain the possible outputs from harmonic analysis.
  22. Explain when you should use and not use harmonic analysis
  23. Explain the meaning of the term frequency-phase pairs.
  24. Make a planar model of a piping system (say X, Y plane).
  25. Explain the difference in time history input between a force spectrum analysis and a time history analysis.
  26. Can you perform response spectrum and time history analysis for slug flow?
  27. What are the limitations of time history analysis in Caesar II?
  28. Explain why imaginary numbers are used in dynamic analysis when a physical problem is in real space
  29. Explain how you need to arrive at the input for the time step and load duration in time history analysis.
  30. Explain how to decide whether the modal combination should precede spatial or vice versa.
  31. Explain the terms missing mass and ZPA. How is the missing mass concept used in seismic response spectrum analysis?
  32. Explain the possible outputs from a time history analysis in Caesar II.

Online Course on Dynamic Analysis

Are you looking for the answers to the above questions? Then you can enroll in the following online course that explains all the concepts to help you answer all the above interview questions.

Interview Questions on FIV, AIV, and Random Vibrations

Written by Anup Kumar Dey in Piping Stress Basics

In the piping engineering industry, the terms FIV, AIV, and Random-Vibrations refer to different types of vibration phenomena that can affect the integrity and safety of piping systems. In recent times, due to various piping vibration-related failures in the oil and gas industries, the study of FIV, AIV, and random vibrations has become compulsory in different engineering organizations. Before we list down all interview questions related to FIV, AIV, and random vibrations, here’s a concise explanation of each term:

1. FIV – Flow-Induced Vibration

Flow-Induced Vibration (FIV) occurs when the flow of fluid inside the pipe causes vibrations due to turbulence, vortex shedding, or fluid-structure interaction.

Key Features of Flow-Induced Vibrations:

  • Common in high-velocity systems or multiphase flows.
  • Often results from turbulent eddies, pressure pulsations, or sudden changes in flow direction.
  • It can lead to fatigue failure, loosening of supports, or noise if not controlled.

Example Causes of FIV:

2. AIV – Acoustic-Induced Vibration

Acoustic-Induced Vibration (AIV) is caused by high-frequency pressure waves (acoustic energy) typically generated by pressure-reducing devices, like control valves or relief valves.

Key Features of Acoustic-Induced Vibrations:

  • Typically occurs in gas or vapor systems.
  • Frequencies involved are much higher (often in the ultrasonic range).
  • It can cause high-cycle fatigue failures, especially in small-bore connections or branch welds.

Example Causes of AIV:

3. Random Vibrations

Random vibration refers to vibrations with no definite or predictable pattern, caused by stochastic (random) loads or forces acting on the piping system.

Key Features of Random Vibrations:

  • May be due to multiple overlapping sources like rotating equipment, flow turbulence, or external environmental loads.
  • Requires statistical analysis for assessment (e.g., Power Spectral Density – PSD).
  • Often analyzed when multiple vibration sources are present or when the exact input is unknown.

Example Causes of Random Vibrations:

  • Vibration transmitted from rotating machinery.
  • External environmental factors, like seismic activity or wind.

The above concise details can be summarized in a tabular format as follows:

TermFull FormCaused ByFrequency RangeRisk
FIVFlow-Induced VibrationTurbulence, flow separationLow to MediumFatigue, noise
AIVAcoustic-Induced VibrationHigh-pressure drops, shock wavesHighWeld failure, fatigue
Random Vibrations—Mixed/random sourcesVariesDepends on amplitude and duration
Table 1: FIV, AIV & Random Vibrations

Interview Questions Related to FIV, AIV, and Random Vibrations

Piping stress engineers are asked various questions related to FIV, AIV, and random vibrations. Here are the top 25 frequently asked interview questions concerning FIV, AIV, and random vibrations that you should prepare for before facing any interview.

  1. Define sound power and sound pressure level. State the relation between them.
  2. Why does flow separation take place at pipe bends and piping valves?
  3. Explain the terms monopole, dipole, and quadrupole with respect to sources of fluid force-related vibrations. Give one example of each of the situations.
  4. Explain the terms random vibration, probability distribution function, autocorrelation function, broadband, and white noise. Explain using the Fourier transformation where required.
  5. Explain the key characteristics of AIV and its causes.
  6. Explain the different available methods in the industry to address AIV. Explain their strengths and weaknesses.
  7. Is the velocity of vibration related to D/T or D/T2?
  8. What is the upper bound for D/T recommended in Eisinger’s work? Explain the M.(Delta)P approach of Eisinger.
  9. Explain the development of the Energy Institute guideline requirements for AIV.
  10. What is a joint acceptance function?
  11. Explain the significance of the term FVF. Why is its value 1.0 for liquid or multiphase systems?
  12. What is the typical frequency range and time scale of failure due to AIV? Contrast this with FIV.
  13. Explain the significance of the term likelihood of failure as used in the Energy Institute guideline.
  14. Why is a (rho*v2) value of 5000 very conservative for filtering lines with FIV? Can you refer to another industry standard that has more relaxed requirements?
  15. Is AIV significant for an open PSV system? Explain with reasons.
  16. Is AIV a concern on a straight pipe? If not, why not?
  17. Briefly describe recommended corrective actions for AIV, including the use of low-noise trims.
  18. Explain a method to quantify forces due to FIV. How will you use this calculation? What are the risks of using this approach (and similar approaches)?
  19. Explain methods to solve FIV issues.
  20. In the design stage, what can be done to address AIV and FIV concerns?
  21. What is the key concern with the energy institute guideline check for RMS velocity vs. frequency?
  22. What is the significance of the term RMS? What could be done better?
  23. Explain the use of viscous dampers, stating the challenges and gains. How will you select a viscous damper for your application?
  24. Should the LOF cutoff be different for continuous vs. non-continuous systems with respect to AIV?
  25. Explain the potential changes behind the upcoming edition of the EI guideline and explain the rationale behind the same.

Online Course on Acoustic and Flow-Induced Vibrations (FIV and AIV) with an Introduction to Random Vibrations

Are you looking for the answers to the above questions? Then I can suggest that you enroll in the following online course that provides a detailed explanation of each of the questions mentioned above. Further, you can ask additional questions to the mentor to clarify your doubts. Click here to enroll and access the course.

Differences in Thermal Elongation & Load Between FRP and CS Pipes

Written by Kourosh Mashayekh in Caesar II,Piping Stress Analysis

Fiberglass Reinforced Plastics (FRP) pipes, also known as Glass Reinforced Plastic (GRP) pipes, are widely used across various industries, including petrochemical and desalination plants, and can be installed as either above-ground (AG) or underground (UG) piping systems.

When FRP pipes are utilized in AG piping systems, the piping designer must be aware of the inherent differences between FRP and carbon steel (CS) pipes.

This document outlines the differences in thermal elongation between FRP and CS pipes. It examines how these differences influence the design and behavior of the support system in above-ground piping systems. Furthermore, a simple example is presented to demonstrate the impact of these differences. The example is validated through a software-based analysis using CAESAR II.

FRP vs CS Pipe

Coefficient of Axial Thermal Expansion (α)

Thermal elongation is directly proportional to the coefficient of thermal expansion (α). The greater the value of α, the greater the resulting elongation.

∆L = α.L.∆T

This coefficient for FRP pipes is higher than that of CS pipes.

For FRP pipes, α typically ranges between 18×10-6 to 22×10-6 mm/mm/°C, while for CS pipes (e.g., A106 Gr. B), it is approximately 11.5×10-6 mm/mm/°C.

As a result, FRP pipes exhibit nearly twice the thermal elongation of CS pipes under the same conditions of temperature change and pipe length.

Axial Elastic Modulus (Ea)

Ea for FRP materials is significantly lower than that of steel, typically ranging from 1.5% to 10% of steel’s value, as stated in AWWA M45. Moreover, the thermal load induced in a pipe is directly proportional to both α and Ea.

F = Ea.α.∆T.Ac

Thus, the thermal load transferred to supports due to thermal expansion depends on both the α and the Ea.

Although the α value for FRP pipes is approximately twice that of CS pipes, the Ea of FRP pipes is typically less than 1/10th that of CS pipes. As a result, the thermal loads transferred to supports in an FRP piping system are much lower than those in a CS piping system under similar conditions.

Explanation Example

Note: The values of α and Ea for the FRP pipe used in this example are taken from the datasheet of a biaxial GRP pipe.

  • OD=219.075 mm, THK.=8.1788 mm, ∆T=60°C
  • Ea(A106 Gr.B)=203.46 GPa, Ea(FRP)=12 GPa
  • αFRP=22*10-6mm/mm/°C, αA106 Gr.B=11.95*10-6 mm/mm/°C,
  • L=50,000 mm
  • Ac=(π/4)(219.0752-(219.075-28.1788)2)=5419.5 mm2

FRP Pipe:

A106 Gr.B Pipe:

Conclusion

The thermal expansion of a 50-meter FRP pipe is approximately 66 mm, which is nearly twice the thermal expansion of a CS pipe of the same length, calculated at 35.85 mm.

This results in a ratio of 66/35.85≈1.84, confirming that FRP pipes elongate nearly twice as much as CS pipes under identical temperature changes.

However, the thermal load transferred to supports from the FRP pipe is significantly lower, approximately 85.84 kN, compared to 790.6 kN for the CS pipe.

This means the FRP pipe approximately transfers only 10% of the thermal load transferred by the CS pipe, indicating a reduction of nearly 90%.

The Importance of Y Factor in ASME B31.3

Written by Kourosh Mashayekh in Piping Stress Analysis,Piping Stress Basics

The Y factor is a dimensionless coefficient used for calculating the required wall thickness (t) for thin-walled pipes under internal pressure. According to Equation 3a of ASME B31.3, for determining the design pipe thickness, the application of the Y factor results in a reduction in the calculated wall thickness. In this article, we will examine the significance of factor Y in pipe wall thickness calculations.

The equation for pipe wall thickness calculation as per ASME B31.3 is given as

ASME B31.3-(3a): t = P.D/[2.(SEW+PY)]

Where:

  • t = minimum required pipe wall thickness (excluding corrosion allowance)
  • P = internal design pressure
  • D = outside diameter of the pipe
  • S = allowable stress of the pipe material at design temperature
  • E = quality factor (depending on pipe manufacturing method)
  • Y = coefficient from B31.3
  • W = Weld Joint Strength Reduction Factor

Significance of Y-Factor in Pipe Thickness Calculation Formula

From the above equation, we can understand and interpret the reasons for using the Y factor as follows:

Simplification of thickness calculation: Instead of applying the equation for thick-walled pressure vessels, a simplified approach with a correction factor is used.

Design optimization: Prevents overestimation of the required wall thickness, thereby reducing project costs while maintaining compliance with safety requirements.

The pipe thickness is calculated based on the Lame’s hoop stress equation:

Lame’s hoop stress equation
Lame’s Equation

According to this equation, the stress across the pipe wall is not uniformly distributed. Therefore, to simplify the calculation and compensate for the non-uniform stress distribution, the Y factor is introduced.

Typical Values of Y-Factor in ASME B31.3

The value of Y is determined based on empirical data, allowing for some initial yielding at elevated temperature ranges.

Coefficient Y Values as per ASME B31.3
Coefficient Y Values as per ASME B31.3

According to the provided table, an increase in temperature leads to an increase in the Y factor for certain materials. This implies that the code allows greater flexibility in thickness calculations at elevated temperatures, which is attributed to the material behavior under such conditions. A detailed explanation is provided below:

Based on Lame’s equation, the hoop stress is higher at the inner wall of the pipe compared to the outer wall, resulting in a non-uniform stress distribution. If wall thickness were calculated solely based on this equation, no Y factor would be applied, and the design would be based on the maximum hoop stress.

However, experimental observations have shown that localized yielding initially occurs at the inner wall of the pipe. This yielding does not lead to failure but instead allows for stress redistribution to other regions (e.g., the middle and outer wall). This process leads to a more uniform stress distribution across the pipe wall. As a result, the actual stress experienced by the pipe is lower than the peak value predicted by Lamé’s equation.

At higher temperatures, materials become softer, localized yielding occurs earlier, and the material naturally redistributes stress more effectively. Therefore, the code allows for a higher Y factor at elevated temperatures, acknowledging that the risk of stress concentration decreases due to improved stress distribution in softer material conditions.

It is important to note that for gray iron, the Y factor is specified as zero. This is because gray iron is brittle, has low tensile strength, and tends to fail suddenly without significant deformation. Due to its poor ability to absorb and redistribute localized stresses, the code adopts a conservative approach, not allowing any reduction in thickness through the Y factor.

For other ductile non-ferrous metals, the Y factor is constant across all temperatures. This is because such materials are already softer and more ductile than ferrous metals even at low temperatures. Therefore, localized yielding and stress redistribution occur early, and temperature increase does not significantly improve stress distribution. So, the code assigns a fixed Y value for all temperature ranges.

If the Y factor is not applied and the wall thickness is calculated based solely on the maximum hoop stress, the following consequences may occur:

  • Increased material costs
  • Greater complexity in welding and fabrication
  • More challenging inspection and maintenance
  • In most practical cases, economic efficiency is compromised without providing a meaningful increase in safety

References

  • ASME B31.3 – Process Piping Code
  • Pipe Stress Engineering – L.C. Peng and T.L. Peng

Piping Material Engineer Interview Questions

Written by Anup Kumar Dey in Engineering Materials

Piping Materials Engineers work quietly to ensure the reliability, safety, and integrity of critical piping systems in the oil and gas, petrochemical, power generation, and other industrial sectors. They play a crucial part in the selection, specification, and management of piping materials, ensuring that every pipe, fitting, flange, valve, and gasket stands up to the operational demands and environmental challenges it faces.

A piping materials engineer is a mechanical, metallurgical, or chemical engineer specialized in selecting and specifying materials for piping systems used in industrial facilities such as refineries, offshore platforms, chemical plants, and power plants. Their decisions directly affect the safety, cost-efficiency, and longevity of piping networks, making their expertise essential during the engineering design phase of a project.

Good piping material engineers are always in demand, and frequently they face interviews for various engineering positions. In this article, I will list some of the most frequently asked questions to help them prepare for any upcoming interview.

Piping Material Engineer Interview Questions

Here is a list of some of the most common interview questions for a piping material engineer. If you know some more questions that need to be added to this list, please specify those in the comments section, and I will add them to the main list from time to time.

  1. As a piping materials engineer, what roles have you performed in your previous company?
  2. Have you performed pipe thickness calculation? Can you specify the pipe thickness calculation formula as per the ASME B31.3 code?
  3. What is the significance of the E factor and W factor in the pipe thickness calculation formula?
  4. What are the parameters on which the E factor and W factor depend?
  5. What is the meaning of mill tolerance? What do you understand when it is said that mill tolerance is 12.5%? Does mill tolerance always remain at 12.5% or does it vary?
  6. From where to get the values of mill tolerance for pipe thickness calculation?
  7. Do E, W, and Y factors change or remain constant? If changes, can you specify how?
  8. What is corrosion allowance, and from where to get the value of corrosion allowance? Who will decide the corrosion allowance value?
  9. What do you consider when there is a vacuum condition in a piping system?
  10. What is the branch thickness calculation philosophy?
  11. When and why do we perform branch thickness calculation?
  12. What is Piping Material Specification and Piping Class? Have you ever generated any PMS or Piping class? What are the considerations?
  13. What are the differences between a PMS and a piping class?
  14. What information is typically included in a piping material specification? What are the input documents to a PMS? What information does a PMS give?
  15. What do branch tables specify?
  16. What is the difference between a stub-in and stub-on connection? Which one is stronger?
  17. ASME B31.3 specifies two pipe thickness calculation formulas. How do you decide which one to follow?
  18. What are the assumptions for pipe thickness calculation based on ASME B31.3?
  19. Have you worked in power piping (B31.1)? For the same piping with the same temperature and pressure conditions, which code will provide thicker material, and why?
  20. What are the common pipe fittings, and what are their governing design codes/standards?
  21. What are the differences between a code, a standard, and a specification?
  22. Valves are designed based on which standard?
  23. What are the different types of valves, and how do you decide the materials forthe valve body?
  24. What is the meaning of valve trims? In general, valve trim is of which materials?
  25. What is the meaning of VMS?
  26. Explain the terms: MTO, BOQ, BOM
  27. What are the stages of MTO?
  28. For a design temperature of -46° C, which piping material is generally used?
  29. For a piping material of A-106 Gr B, what is the common fitting material?
  30. What is the impact of temperature on material selection?
  31. What are the major differences between A106 Gr B and Gr C?
  32. What is TBE, and what is the role of a piping material engineer in TBE?
  33. Have you heard the term, Piping Specialty Item? Can you please provide 5 examples of piping specialty items?
  34. What is the equation for Line Blank Thickness Calculation?
  35. Have you prepared any datasheets for piping specialty items? If yes, what are the contents of a datasheet?
  36. As a piping materials engineer, do you use any software?
  37. Are you aware of the term “SMAT” or “SPM”, AVEVA ERM, and PUMA?
  38. What are the different types of ferrous materials you know?
  39. What are the differences between low alloy steel, high alloy steel, and LTCS?
  40. How do you decide when to use seamless vs welded pipe?
  41. What is CE value? Have you heard the term PREN?
  42. What are the differences between SS and DSS, and when are they chosen?
  43. What is the meaning of dual-certified material?
  44. What are the piping flange standards for a 16-inch and 32-inch pipe?
  45. Can you specify some differences between ASME B16.47 series A and series B flanges?
  46. What is the meaning of galvanized steel? When do you choose galvanized steel?
  47. What is the major difference between ASTM A312 TP 304, TP 304L, and TP304H?
  48. What is the difference between different stainless steel grades?
  49. How do you select materials for sour service (H₂S environments)?
  50. What is the importance of NACE MR0175?
  51. What are the typical materials used for cryogenic services?
  52. What factors influence your selection of piping material for a high-temperature, high-pressure service?
  53. What is PWHT, and when is it required?
  54. Describe how you handle corrosion allowance in piping design.
  55. What is galvanic corrosion and how do you prevent it in piping systems?
  56. Can you describe the difference between duplex and super duplex stainless steels?
  57. What are typical issues encountered with DSS and SDSS in fabrication?
  58. Have you heard the term, MTC? What do you check in a Material Test Certificate (MTC)?
  59. Describe how you develop a piping material class from scratch.
  60. How do you link a piping material specification to 3D modeling software?
  61. How do you assign valve materials in piping classes?
  62. What is the meaning of LLI? How do you handle long lead items or material shortages?
  63. How do you track and control revisions in piping material specs?
  64. What is the importance of PMI (Positive Material Identification)? How do you ensure material traceability throughout a project?
  65. How do you manage piping material delivery for a brownfield revamp?
  66. What is the difference between CS and LTCS piping materials?
  67. Explain the difference between ASTM and ASME material specifications.
  68. What are your responsibilities during FAT (Factory Acceptance Testing)?
  69. What is the difference between DSS and CRA piping materials?
  70. Describe the selection criteria for cladding vs. solid alloy piping.
  71. How does hardness testing relate to material selection for sour service?
  72. What’s the significance of impact testing in low-temperature services?
  73. How do you manage material compatibility in dissimilar joints?
  74. How do you select gasket materials for high-pressure and high-temperature service?
  75. What’s the difference between NACE MR0175 and MR0103?
  76. What is HIC and how do you mitigate it?
  77. How do you deal with ambiguous specifications or missing information?
  78. How do you evaluate suppliers for piping materials?
  79. Describe your experience with VDRL (Vendor Document Requirement List).
  80. What are the metallurgical differences between forged and cast components?
  81. How do you coordinate with process and mechanical teams on material selection?
  82. What lessons have you learned from site execution involving piping materials?
  83. How do you handle conflict with vendors or procurement over specs?
  84. Have you ever challenged a design or spec due to material concerns?
  85. How do you ensure integration of MTO data across disciplines?
  86. How to decide the Hydrotest Pressure for oil and gas piping? What are the criteria for Hydrostatic testing and pneumatic testing?
  87. Have you used A106-Gr B material for (-)45 Deg C temperature? Can it be used? Under What condition?
  88. What is the type of corrosion allowance selected for a pipe subjected to internal pressure?
  89. Explain in detail the procedure to check whether the pipe is suitable when subjected to external pressure.
  90. What is the basic concept behind the Rpad calculation?
  91. How is the impact test considered for the ASTM 516 plates?
  92. What are the design requirements of a valve subjected to cryogenic service?
  93. Why is a spectacle blind generally not preferred or used in cryogenic service?
  94. What are the important points/clauses to be considered while preparing the Technical or Purchase or Supply specification?
  95. What is the procedure from MTO preparation to the issuance of Inquiry MR to TBE to Issuance of Purchase order?
  96. What are the documents required to be attached while issuing MR?
  97. What are the generally used design standards for gate, globe, check, ball valve, and plug valves?
  98. What is the standard to specify a valve as fire-safe? What is the fire-safe requirement in a valve?
  99. What are the general temperature limits for BUNA-lined, EPDM, PTFE, and metal seats used in valves?
  100. What is the difference between API 600 and ASME B16.34?
  101. What are the requirements to select a suitable trap size?
  102. What are the different types of strainers?
  103. For a 16” Tee type strainer, end connection with Flanges or Buttwelded which is more beneficial and why?
  104. What is the total amount of man-hours you worked on a single project, and the number of MR/POs handled?
  105. What were the earlier and present exemption thicknesses for carbon steel material subjected to PWHT as per ASME B31.3?
  106. What do you include in a component datasheet?

If you are aware of any additional questions that you have faced in any interview, kindly mention those in the comments section.

Extractive Distillation for Aromatics Separation

Written by Sujoy Maity in Process

What is Extractive Distillation?

Aromatics, such as benzene, toluene, xylene, and ethylbenzene, are crucial raw materials in the petrochemical industry. These compounds are used extensively in the production of plastics, synthetic fibers, pharmaceuticals, and a wide range of industrial chemicals. However, the separation of aromatics from complex hydrocarbon mixtures, such as naphtha or reformate, can be challenging due to their close boiling points and the presence of azeotropes.

Extractive distillation is a highly effective technique for separating aromatics from non-aromatic hydrocarbons. This process involves the use of a selective solvent that alters the relative volatility of the components in the mixture, thereby enabling their separation.

This report provides a detailed analysis of the principles of extractive distillation, its importance in aromatics separation, the solvent selection criteria, and the effect of molecular weight on solubility. It also examines the key challenges and benefits associated with the process, providing insight into its practical applications and future potential in the petrochemical industry.

Principles of Extractive Distillation

Extractive distillation is a variation of conventional distillation, where a selective solvent is added to the mixture to modify the relative volatilities of the components. This solvent interacts more strongly with the desired component (e.g., an aromatic compound) than with the other components (e.g., alkanes or cycloalkanes), thus making the desired compound less volatile compared to the remaining components. The solvent forms strong intermolecular bonds (e.g., hydrogen bonding, dipole-dipole interactions) with one of the components in the mixture. This strong interaction reduces the partial pressure of that component in the vapor phase, effectively decreasing its volatility. By selectively decreasing the volatility of one component, the relative volatility between the components is enhanced, making their separation easier in a distillation column. As a result, the aromatic compounds can be separated more efficiently from non-aromatic hydrocarbons.

Unlike simple distillation, which relies on differences in boiling points, extractive distillation works by altering the relative volatility between the components, making it possible to separate compounds with very close boiling points or those that form azeotropes.

Why is Extractive Distillation Needed for Aromatics Separation?

The separation of aromatics from other hydrocarbons, especially in complex mixtures such as naphtha or reformate, is often a challenge due to the following reasons:

Close Boiling Points:

Many aromatic compounds share similar boiling points with non-aromatic hydrocarbons. For example, benzene (80.1°C) and cyclohexane (80.7°C) are difficult to separate using conventional distillation due to their very close boiling points. It would require ~ 750-1000 separation stages or even more numbers of stages for a fractional distillation column, making it non-feasible.

Azeotrope Formation:

In some cases, azeotropes are formed between aromatic and non-aromatic hydrocarbons, making their separation impossible by standard distillation methods.

High Purity Requirements:

Aromatic compounds must often be separated with high purity, especially for downstream applications such as polymerization or pharmaceutical synthesis. Conventional distillation may not achieve the required purity levels.

Economic and Environmental Considerations:

Extractive distillation offers a more energy-efficient and sustainable alternative compared to other separation technologies. Using selective solvents reduces the energy required for separation, and the solvent can be regenerated and reused, minimizing waste.

Solvent Selection for Extractive Distillation

The selection of an appropriate solvent is critical in extractive distillation, as it directly influences the efficiency and economics of the separation process. The key criteria for selecting solvents include

  • Selectivity: The solvent should selectively interact with the desired aromatic compound and enhance its volatility. For example, N-Methyl-2-pyrrolidone (NMP) is a commonly used solvent due to its high selectivity for aromatic compounds.
  • Capacity: The solvent should have a high capacity to dissolve a large amount of the aromatic compound. The capacity of a solvent refers to its ability to absorb or extract the target compound from the mixture without excessive consumption of solvent.
  • Boiling Point and Volatility: The solvent should have a boiling point that is higher than that of the aromatic compounds to ensure efficient separation and easy solvent recovery after the process.
  • Solvent Regeneration: The solvent must be regenerable and reusable to minimize costs and environmental impact. Common solvents such as water, NMP, and ethylene glycol can be regenerated for repeated use in the process.
  • Solvent-Mixture Compatibility: The solvent should be compatible with the entire distillation system and should not react with other components in the mixture.

The Effect of Molecular Weight on Aromatic Solubility

The solubility of aromatics in solvents is significantly influenced by the molecular weight of the aromatic compounds. Generally, as the molecular weight of an aromatic compound increases, its solubility in most solvents tends to decrease. This is due to the increased hydrophobicity and larger molecular size, which makes it harder for solvents to interact with the aromatic molecules.

For example, xylene and ethylbenzene, which have higher molecular weights than benzene and toluene, show lower solubility in many common solvents. This means that solvent selection must also consider the molecular size of the aromatics to achieve effective separation.

Increasing the molecular weight of aromatics tends to reduce their solubility in many solvents, which requires careful consideration when designing extractive distillation processes for mixtures containing large aromatic compounds.

Solvent Capacity and Selectivity Balancing Efficiency

In extractive distillation, the balance between selectivity and capacity of the solvent is critical for achieving optimal separation efficiency. Selectivity refers to the solvent’s ability to preferentially extract the aromatic compounds over other hydrocarbons, while capacity refers to the solvent’s ability to dissolve or extract the desired compound.

By adjusting the solvent mix (e.g., a combination of NMP and water), it is possible to achieve a balance that maximizes both capacity and selectivity. NMP has high selectivity for aromatics like benzene, but its capacity can be limited by its relatively low solvent concentration. Combining NMP with water or another solvent can enhance the overall capacity of the solvent mix while maintaining high selectivity for aromatics. The same is true for BD extraction process-related technologies, e.g., the BASF NMP process.

Benefits of Extractive Distillation in Aromatics Separation

  • High-Purity Separation: Extractive distillation enables the separation of aromatics with high purity, which is crucial for downstream chemical processes.
  • Energy Efficiency: Extractive distillation requires less energy compared to traditional distillation methods, making it a cost-effective option for large-scale separation.
  • Sustainability: The use of regenerable solvents reduces waste and minimizes the environmental impact of the separation process.
  • Flexibility: Extractive distillation can be tailored to specific feedstocks and separation requirements, making it adaptable to a wide range of industrial applications.

Conclusion

Extractive distillation is an essential technology for the separation of aromatics from complex hydrocarbon mixtures, particularly when traditional distillation methods fail due to close boiling points or azeotrope formation. By using selective solvents, extractive distillation enhances the purity of the desired aromatic compounds and provides a cost-effective, energy-efficient, and sustainable solution for large-scale industrial applications.

The selectivity and capacity of the solvent, along with the influence of molecular weight on solubility, play critical roles in achieving optimal separation. As the demand for high-purity aromatics continues to grow, extractive distillation will remain a cornerstone technology in the petrochemical industry.

References

  • BASF Research Journal, 2019. “Solvent Selection and Efficiency in Aromatics Separation by Extractive Distillation.”
  • Schneider, T., et al., 2018. “Effect of Solvent Properties on the Separation of Aromatic Compounds in Extractive Distillation.” Journal of Chemical Engineering.
  • Park, S. et al., 2020. “Advancements in Extractive Distillation: Solvent Effects and Efficiency.” Chemical Engineering Science, 204: 233-245.
  • Chung, D., et al., 2021. “Molecular Weight and Solubility in Aromatic Separation.” Journal of Applied Polymer Science, 138: 41350.