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Complete Pipe Stress Analysis using Caesar II Online Course

Piping systems are the veins of industrial plants, carrying fluids and gases critical for various processes. Ensuring the reliability and safety of these piping systems is paramount, and this is where Advanced Pipe Stress Analysis comes into play. Advanced Pipe Stress Analysis goes beyond basic analysis, offering a comprehensive understanding of how pipes behave under various conditions.

Pipe Stress Analysis is a critical aspect of piping design that evaluates the effects of loads, pressures, and thermal gradients on a piping system. Basic Pipe Stress Analysis typically considers factors like pressure, temperature, and weight to ensure the system’s integrity. However, as systems become more complex and industries demand higher efficiency, Advanced Pipe Stress Analysis becomes essential.

Various sophisticated software tools are essential for Advanced Pipe Stress Analysis. One such powerhouse in the field is Caesar II. Developed by Hexagon PPM, Caesar II is a widely used software application that plays a pivotal role in ensuring the integrity and reliability of piping systems. Caesar II allows engineers and designers to model, analyze, and optimize piping systems. Known for its robust capabilities, the software enables a comprehensive evaluation of various factors influencing pipe behavior, providing a detailed understanding of stress, deformation, and stability under different operating conditions. Throughout the course, the explanations and case studies are provided using Caesar II software.

The complete online pipe stress analysis course is divided into several modules. Each module will explain some aspects of Pipe Stress Analysis that are required for every pipe stress engineer. New modules will be added as and when prepared. You can enroll in the module that you require.

Module 1: Basics of Pipe Stress Analysis (Duration: 5 hours)

  • Click here to join the course. You will learn the following:
    • How to Use Caesar II Software
    • Creating a 3D model of the piping system adding piping, components, fittings, supports, etc
    • Modeling equipment connection in Caesar II
    • Basics Theory of Pipe Stress Analysis
    • Load Case Preparation
    • Analyzing the system and reviewing the Results

Module 2: Pipe Support Engineering (Duration: 2 hours)

  • Join the module by clicking here. The support engineering module will cover the following details:
    • Role of Pipe Supports in Piping Design
    • Types of Pipe Supports
    • Pipe Support Spacing or Span
    • How to Support a Pipe
    • Pipe Support Optimization Rules
    • Pipe Support Standard and Special Pipe Support
    • Pipe Support Engineering Considerations

Module 3: ASME B31.3 Basics for Pipe Stress Engineer (Duration: 1.5 hrs)

  • To enroll in this module click here. You will learn the following:
    • Learn the basics from ASME B31.3 required for a pipe stress engineer
    • Learn Code equations that stress analysis software use
    • Learn the allowable values for different types of code stresses
    • Learn Material allowable stresses
    • Learn to calculate pipe thickness as per ASME B31.3

Module 4: Stress Analysis of PSV/PRV Piping System in Caesar II (Duration: 1 hr)

  • Enroll in this module by clicking here. This module covers
    • Brief about Pressure Safety Valve Systems
    • PSV Reaction Force Calculation
    • Application of PRV Reaction Force in Stress System
    • Case Study of Stress Analysis of PSV System using Caesar II Software
    • Best Practices for PSV Piping Stress Analysis

Module 5: Flange Leakage Analysis in Caesar II (Duration: 1 hr)

  • Click here to enroll in this module. It covers
    • Reasons for Flange Leakage
    • Basics of Flange Leakage Analysis
    • Types of Flange Leakage Analysis
    • Case Study of Flange Leakage Analysis using Caesar II (Case Studies of Pressure Equivalent Method, NC 3658.3 method, ASME Sec VIII method)

Module 6: Spring Hanger Design and Selection (Duration: 1.5 hours)

  • Here is your module for registering. Spring hanger module covers:
    • What is a Spring Hanger?
    • Types of Spring Hangers
    • Differences between Variable and Constant Spring Hangers
    • Design and Selection of Spring Hangers
    • Case Study of Spring Hanger Design and Selection Using Caesar II

Module 7: WRC 537/WRC 297 Calculation in Caesar II (Duration: 1 hr)

  • To join the module click here. It will cover the following:
    • What is WRC 537 and WRC 297
    • When to Perform WRC Calculation
    • Steps for WRC Calculation
    • Practical Case Study of WRC Calculation

Module 8: Buried Pipe Stress Analysis (Duration: 1.5 hr)

  • Click here to enroll for this course. It covers
    • Learn how to model buried piping and pipeline systems in Caesar II software
    • Additional Inputs required for buried pipe stress analysis
    • Create load cases based on ASME B31.3/B31.4/B31.8 codes
    • Perform the underground/buried pipe stress analysis
    • Review the results calculated by the software and understand their meanings

Module 9: Pump Piping Stress Analysis Using Caesar II (Duration: 2.5 hrs)

  • To enroll in this course proceed by clicking here. The course briefly covers
    • Learn the basics of pump piping stress analysis.
    • Learn to create load cases for pump piping analysis in Caesar II software.
    • Learn to read data from pump GA to model and analyze using Caesar II.
    • Practical Case Study of a Pump Piping Stress Analysis

Module 10: Static and Dynamic Analysis of Slug Flow in Caesar II (Duration: 1.5 hrs)

  • To learn from this course click here. It covers
    • Basics of Slug Flow Analysis
    • Calculation of Slug Forces
    • Application of Slug Forces
    • Static Analysis of Slug Flow
    • Dynamic Analysis of Slug Flow

Module 11: FRP-GRP-GRE Piping/Pipeline Stress Analysis Using Caesar II (Duration: 1.5 hrs)

  • Proceed here to enroll in this module of the course. It briefly explains
    • Basics of FRP/GRE/GRP Piping
    • Inputs to ask from the vendor for FRP/GRP/GRE Pipe Stress Analysis
    • Modeling and Analyzing GRP/FRP/GRE Piping system in Caesar II
    • Flange Leakage Checking for FRP Piping Systems
    • FRP Pipe Supporting Guidelines

Module 12: Pipeline Stress Analysis using Caesar II (Duration: 1.5 hrs)

  • Click here for enrolling in this module. This module covers
    • Liquid and Gas Pipeline Stress Analysis using ASME B31.4 and ASME B31.8
    • Difference between Piping and Pipeline
    • Differences between ASME B314 and ASME B31.8
    • Use Caesar II software for pipeline stress analysis with a practical case study

Module 13: Dynamic Analysis of Piping Systems in Caesar II Software (Duration: 1.5 hrs)

  • Join this module by clicking here. This module covers
    • Dynamic Analysis Basics
    • Static Analysis vs Dynamic Analysis
    • Types of Dynamic Analysis
    • Modal Analysis Case Study
    • Response Spectrum Analysis Case Study

Module 14: Guide to Reviewing a Pipe Stress Analysis Report (Duration: 1 hr)

  • Click here for joining this module. It covers
    • Learn How to Review a Pipe Stress Analysis Report
    • Requirements of Pipe Stress Analysis Report
    • What to Review in a Pipe Stress Analysis Report
    • Practical Sample Review Process
    • Steps for Reviewing Pipe Stress Analysis Report

Module 15: Flow-Induced Vibration Analysis of Piping System (Duration: 1 hr)

  • Enroll in the FIV analysis module by clicking here. It covers:
    • Common causes of piping vibration and their effects.
    • Definition of Flow-Induced Vibration.
    • Reasons for FIV in a piping system.
    • FIV Study/Analysis Steps Based on Energy Institute Guidelines
    • Mitigation Options of FIV Study Results.

Module 16: Acoustic Induced Vibration Basics for Piping Systems (Duration: 45 Mins)

  • Click here to enroll in this module. This module covers:
    • What is Acoustic-Induced Vibration or AIV?
    • Causes and Effects Of Piping Vibration
    • Acoustic-Induced Vibration Analysis Steps
    • Mitigation of AIV

Module 17: Storage Tank Piping Stress Analysis (Duration: 1 hr)

  • Click here to enroll in this module. Storage tank piping stress analysis module covers the following
    • Differences between a storage tank and a pressure vessel?
    • Types of storage tanks used in oil and gas industries
    • Why is storage tank piping critical?
    • What is Tank settlement?
    • What is Tank bulging?
    • Storage Tank Nozzle Load Qualification
    • Practical case study of storage tank piping analysis

Module 18: Stress Analysis of Tower/Vertical Column Piping System (Duration: 1.5 hrs)

  • To join Module 18, Click here. This module Covers:
    • Application of Vertical Columns/Towers
    • Inputs Required for Column Piping Stress Analysis
    • Creating temperature profiles for Column/Tower Piping systems
    • Modeling of the Equipment
    • Clip/Cleat Support Modeling from Towers
    • Skirt Temperature Calculation
    • Nozzle Load Qualification
    • Practical Case Study

Module 19: Stress Analysis of Heat Exchanger Piping System (Duration: 1.5 hrs)

As mentioned earlier, new modules will be added frequently. So, keep visiting this post. Also, you can request any specific module by mentioning it in the comment section.

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

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

What’s New in Caesar II-Version 14?

Some of you must be aware that Hexagon has released their new version of stress analysis software, Caesar II Version 14 recently. The latest software version has truly extended its capabilities by incorporating many changes based on user feedback from the Caesar II user community. The much-awaited Hydrogen piping and pipeline code (ASME B31.12) is included in Version 14 of Caesar II software. In this article, we will highlight some of the new capabilities that you will find when you install Caesar II Version 14 on your PC/laptop. So, let’s start with the changes in codes and standards.

Caesar II Version 14

Newly Added Codes and Standards

As already mentioned, support for ASME B31.12-2019 has already been added to the new software. Additionally, most of the codes are updated to have their latest available editions. Let’s have a look at all the code changes below:

ASME B31.12 – 2019 Hydrogen Piping and Pipelines, including Part IP Industrial Piping and Part PL Pipelines. The allowable stress auxiliary data tab has been updated to support this new code addition. The configuration editor is updated to use alternative rules for stress range evaluation for supporting ASME B31.12 Appendix-B.

ASME B31.3: Process Piping– 2022 edition: This means they must have included the stress range reduction factor calculation based on the recent changes in ASME B31.3-2022. Click here to learn all the major changes in ASME B31.3-2022 as compared to its earlier edition.

  • ASME B31.1: Power Piping – 2022 edition.
  • ASME B31.4: Pipeline Transportation Systems for Liquids and Slurries- 2022 edition.
  • ASME B31.8: Gas Transmission and Distribution Piping Systems- 2022 edition
  • ASME B31.5: Refrigeration Piping and Heat Transfer Components- 2022 edition

API 617: Centrifugal Compressors- 2022 edition (9th edition) for equipment analysis. Now users can use an allowable load multiplier greater than 2.0 with manufacturer approval.

ASCE 7 – 2022 edition for wind and seismic loads. The Seismic Wizard in piping input has been updated to support ASCE 7-22 and IBC 2021. Additionally, the Wind Loads Tab (Static Analysis – Load Case Editor Dialog) and the DLF/Spectrum Generator are also updated to support ASCE 7-22 and IBC 2021.

  • EN-13480-3:2017/A5:2022 (Metallic industrial piping – Part 3: Design and calculation).
  • IBC – 2021 edition for wind and seismic loads.

Updates in Material and Content Database

As the major code changes in Caesar II Version 14 are already stated, let’s learn the other changes that the software release in 2024 will provide:

  • Caesar II Version 14 is further enriched with the following additions:
  • Added 119 material records for B31.12-2019 into the material database. The physical property data is taken from ASME B31.3-2018 and ASME BPVC Section II Part D-2021. While the allowable stress data is taken from ASME B31.12-2019
  • Added fifth working range quadruple springs to the ANVIL hanger tables. Also added spring sizes 000 and 00 for the B-268 springs.
  • Added the fourth and fifth size springs to the PSSI Group hanger tables.
  • Added hanger tables for Rilco Manufacturing pipe supports.

Improvements in Static and Dynamic Analysis

The software version 14 has enhanced its capabilities to consider the thermal bowing load when defining a Thermal Bowing Delta Temperature and define an operating temperature that is the same as or close to the Ambient Temperature. A new technical discussion for thermal bowing is also added to help explain the condition thoroughly.

The program has updated the Dynamic Analysis calculations for the B31.4, B31.8, B31.4 Chapter IX & Chapter XI, and B31.8 Chapter VIII piping codes with multiple offshore and transportation code stresses. The changes have a significant impact on the time history and spectrum analysis.

Caesar II Version 14 now supports the MDMT calculations devised in the ASME B31.3-2022 edition.

Other Improvements

Other significant changes to Caesar II Version 14 as compared to Caesar II Version 13 are:

  • The SIF Multiplier for Sustained Stress Index option in the Configuration Editor is added for Piping codes that use ASME B31J.
  • The equipment analysis using NEMA SM23 for Steam turbines has been updated to allow the Allowable Load Multiplier to be greater than 2.0 with manufacturer approval.
  • The output report for for primary stress types (example: SUS, OCC, and HYD) now displays sustained intensification factors (SSI) for metallic piping codes.
  • The option for creating a combined PDF output report has been activated in the Output Viewer Wizard of the Static Output Processor.
  • The length for displaying your company name on output reports has been increased by 30 more characters.
  • A new offline version of help has been added for installations that do not have internet access to the online help. Offline help now opens in your default web browser.

So, from the above discussion, you can easily understand that Version 14 of Caesar II software comes with many advancements to help users perform their analysis with more accuracy following all the latest developments in codes and standards. It also fixed most of the issues that users have faced in Caesar II version 13. Some of the notable fixes made in Caesar II version 14 are:

  • The implementation of ISO 14692-2005 when a stress type has no envelope has been changed. The stress reports in the latest Caesar II software program will now display the maximum between hoop stress and longitudinal stress instead of always displaying the hoop stress.
  • Fixed the issue of requiring all flange yield strength field inputs (SY1 through SY9 when temperatures T1 through T9 were not defined) in the NC-3558.3 flange leakage checking.
  • The incorrect EN 10269:1999 material number for X2CrNiMo17-12-2 has been fixed.
  • The incorrect gasket diameters for the ASME-2009 and ASME-2009M – Class 900 databases have been updated with correct values.
  • Fixed the error of the Type list for B31J SIFs & Tees sometimes that did not display correctly.
  • Fixed the issue of B31J surface nodes not renumbering when renumbering all nodes.
  • Fixed Caesar ii import issues from Smart 3D/ SmartPlant Review .vue files, CADWorx .dwg file.

References and Further Studies:

https://docs.hexagonali.com/r/en-US/CAESAR-II-Quick-Reference/Version-14/328888

Pipeline Engineering Interview Questions

The following section will list some interview questions asked in the different interviews for a Pipeline Engineer Position. Readers are requested to provide the answers in the comment section which I will add in the main section in due course.

  1. Explain the basis of pipeline hydraulics and how will differentiate the gas and crude oil pipeline that is which method will perform to do the calculation.
  2. What are all the softwares available in the market to perform pipeline hydraulics and how will you check the input and output?
  3. What are the criteria for route selection of gas and crude oil pipelines?
  4. For the sloped pipeline, how to fill the water during the hydrostatic test and why?
  5. Explain the hydrostatic test pressure with respect to ASME B 31.8/31.4. How do they arrive the 90% of SMYS and what is the basis?
  6. Explain about one pipeline project lifecycle, starting from concept, FEED, Detail Design, and construction (Sequence).
  7. What is the difference between PSL-1 and PSL-2, what are all the tests involved during manufacturing?
  8. What is the procedure/sequence of linepipe manufacturing?
  9. What % of line pipe is radiographically tested during manufacturing?
  10. Spiral welding can be used in oil and gas, if No, why?
  11. Wadi crossing types and construction methods.
  12. Isolation joints internal and external coating requirements and temperature ranges.
  13. Draw and explain the pig launcher and receiver sequence.
  14. Pipeline Hydrotest procedure.
  15. What are the steps involved in pre-commissioning of the pipeline?
  16. Steps involved in pipeline construction.
  17. Distance between pipelines in the same trench and separate trench.
  18. What are the disadvantages of the pipelines in the same trench?
  19. Distance between the OHL line and the pipeline.
  20. GRE pipelines – explain the advantages and disadvantages compared to carbon steel pipelines.
  1. Specify Internal and external coating types with temperature limitations.
  2. What is the reason for choosing the DSS pipeline with respect to fluid properties?
  3. What are all the testing requirements for SOUR service pipeline items?
  4. What is PWHT and what is the limitation of thickness with respect to international codes?
  5. What is the philosophy of Pipeline supporting and anchor points for looped lines?
  6. What is Cathodic Protection? What are the Anodic materials used in the pipeline CP systems?
  7. What are the calculations performed during Hot tap design?
  8. Draw a Block Valve Station for gas and crude oil pipelines separately.
  9. What is the MPT requirement for Golden Joints?
  10. Explain the GRE wall thickness calculation basis and steps.
  11. Explain DPE and SPE on the ball valve.
  12. For high sour service, how you will provide grease point and sealant injection?
  13. During PE lining Wall Thickness calculation, what are the important factors you considered?
  14. During PE lining pulling how many bends are allowed?
  15. 3LPE /3LPP temperature minimum and maximum.
  16. Explain uni-directional and bi-directional pig traps.
  17. How you will consider corrosion allowance in pipeline systems?
  18. Explain upheaval bucking and how to avoid it.
  19. Briefly explain the pipeline routing considerations for Greenfield and Brownfield: Start with design and end with commissioning.
  20. Briefly explain the gauging.
  1. What is the double piston effect on pipeline ball valves?
  2. Explain upheaval buckling and its calculation methodology.
  3. What are Location classes with respect to ASME B 31.8 and ASME B31.4?
  4. Explain road crossing calculation methodology.
  5. Explain the Isolation Joint working principle.
  6. Specify the Types of pigs and their applications.
  7. What HIPPS valves? Explain about SIL level.
  8. Difference between transition and pup piece.
  9. What are all the required parameters for hydraulic analysis? As a pipeline engineer, what are the inputs needed to perform hydraulic analysis?
  10. What is your understanding of Environmental Impact Assessment (EIA)?
  11. What are the different types of tests involved in GRE pipes?
  12. Types of pigs and usage. Length of the intelligent pigs and MFL tools.
  13. Explain cathodic protection and Types of cathodic protection – in general.
  14. As a pipeline engineer, what do you know about line sizing?
  15. What is pipeline equivalent stress? What are all the stresses generated in a pipeline?
  16. How bending radius will affect the Pipeline Wall Thickness Calculation?
  17. What are the proximity distances and no. of buildings according to the location class?
  18. Where are Isolation joints to be installed and why? In IJ above 50 bar, what is the precaution?
  19. Draw the pig trap and explain pigging the procedure.
  20. Explain about CMA fittings and location, why?
  1. Compare a BVS requirement with EIA.
  2. What are the differences between restrained and un-restrained pipelines?
  3. What are the criteria for expansion loops for un-restrained pipelines? During A/G pipeline design how expansion loops will be fixed?
  4. What are the types of supports used for pig traps and why?
  5. Tell about allowable displacement values and if exceed the limit what are the other considerations to be taken care of to have a flexible pipeline system during design.
  6. What is Carbon Equivalent (CE) for line pipe and split tees? If two different CE pipes are needed to weld, which CE value has to be considered for qualification?
  7. DWTT and CVN tests – Explain.
  8. Explain the minimum branch sizes on pipelines.
  9. Golden weld joints – explain what tests need to be performed for golden joints.
  10. External coating types and temperature range.
  11. Velocity accepted during the design for liquids and gas?
  12. During End closure design what are the safety devices we have to consider?
  13. During the design of pipeline design life, what are the factors to be considered?
  14. PWHT requirement on the pipelines.
  15. How you will protect your pipeline and flowline: explain from the well to manifold and manifold to the station.
  16. Explain the pipeline design of the high temperature and pressure.
  17. What are the major differences between ASME B31.4 and ASME B31.8?
  18. A pipeline carries a fluid having a temperature of 250 Degrees C. Which ASME code will be used to design that pipeline?

Reciprocating Compressor Sizing

A reciprocating compressor is a kind of positive displacement compressor that compresses and delivers air or gas at high pressure using a reciprocating component, such as a piston or plunger. The piston of the reciprocating compressor moves forward and backward, compressing the gas or air. For this reason, another name for it is a piston compressor.  The gas or air in this compressor is drawn into the chamber and compressed by a reciprocating piston. The working fluid volume is moved by this piston to function. Applications requiring both high gas pressure and low flow rate are often served by reciprocating air compressors. Fig. 1 below shows the working of a reciprocating compressor.

Working of a Reciprocating Compressor
Fig. 1: Working of a Reciprocating Compressor

Codes and Standards for Reciprocating Compressor:

Various codes and standards govern the design and manufacture of reciprocating compressors:

  • API Standards: API-11P (Packaged Reciprocating Compressors) and API-618 (Reciprocating Compressors for Petroleum, Chemical, and Gas Industry Services)
  • ISO Standards: ISO-13707 and ISO-13631
  • Shell DEP: DEP 31.29.40.31
  • API RP 688 for Pulsation and Vibration Control

Reciprocating Compressor Sizing:

Reciprocal compressor sizing has been a task for many decades.  Engineers, packagers, and end users can benefit from the robust sizing software offered by the majority of reciprocating compressor OEMs nowadays.  However, these sizing tools might produce inappropriate and deceptive hardware suggestions if not used carefully and with attention to detail.

A typical compressor sizing methodology proceeds as follows:

  • Inlet and discharge pressures and a desired flow rate are specified by the Client.
  • A gas analysis or equivalent is specified by the Client.

Steps for selecting the proper compressor:

  1. Calculate the compression ratio.
  2. Choose the number of stages of the compressor.
  3. Calculate Estimated BHP.
  4. Calculate estimated Discharge Pressure.
  5. Calculate the discharge temperature.
  6. Determine the suction volumetric efficiency.
  7. Calculate the required piston displacement.
  8. Determine the Velocity of Valves
  9. Determine the Gas rod loads.
  10. Selecting of Reciprocating Compressor cylinder and Frame by using the OEM Design Data

OEMs typically carry out steps 1 through 10 using sophisticated software, however hand calculations are frequently sufficient.

Step 1: Calculate the Compression Ratio (CR):

A single-stage compressor has only a single R-value. Whereas a typical two-stage compressor has three R values.

  • CR (or) R = total compression ratio for the compressor
  • R1 = compression ratio for the first stage
  • R2 = compression ratio for the second stage

R = Pd/Ps, R1 = Pi/Ps, R2 = Pd/Pi

Here,

  • Ps=Suction pressure,
  • Pd=Discharge pressure,
  • Pi=Interstage pressure – the pressure between the 1st and 2nd stages of the compressor.

Step 2: Calculate / Choose no. of stages of the compressor:

The number of stages can also be determined using the thumb rule, which is shown in Fig. 2, however, it depends on the OEMs.

R-value vs Number of Stages
Fig. 2: R-value vs Number of Stages

Step 3: Calculate Estimated Power (BHP):

Where, Ƹad = Volumetric adiabatic Efficiency (From Figure 3); k = specific heat of the gas.  Compression Ratio R= (P2/P1); Flow Rate (MMSCFD)

Compression Ratio vs Estimated Efficiency
Fig. 3: Compression Ratio vs Estimated Efficiency

Step 4: Calculate estimated Discharge Pressure (Psia)

It is crucial to estimate the number of stages, power required, and interstage pressures.  Every OEM has a set number of frames and a family of standard cylinders that are predesigned to fit those frames.  As a result, the number of possible frame/cylinder combinations is limited.  The best option any specific OEM can offer is at least one of the potential combinations.

Step 5: Calculate the discharge temperature (oR)

The life of the valves and piston rings is directly impacted by the compressor’s discharge temperature. The discharge temperature of an air-cooled single-stage compressor can be determined using the following formula:

  • Ts Suction temperature °R (°K)
  • Ps Suction pressure PSIA (Bar-a)
  • Pd Discharge pressure PSIA (Bar-a)
  • R Compression Ratio (Pd/Ps)
  • n specific heat ratio of the gas.

Step 6: Determine the suction volumetric efficiency

Volumetric efficiency includes many factors that help explain the differences between ideal gas behavior and real gas behavior. In general, volumetric efficiency depends upon compression ratio, cylinder clearances, gas compressibility values, and the ratio of specific heats (k or N value) (Z1, Z2, and k values are specified in Gas properties). CL might be 15% (CL = 0.15) for normal cylinders and 65% (CL = 0.65) for pipeline cylinders.

*Where L is taken from Figure 4.

Ratio of Compression vs Loss Correction
Fig. 4: Ratio of Compression vs Loss Correction

Step 7: Calculate the required piston displacement

Piston displacement is the actual volume displaced by the piston as it travels the length of its stroke from Position 1, bottom dead center, to Position 3, top dead center.  Piston displacement is normally expressed as the volume displaced per minute or cubic feet per minute. 

Step 8: Determine the Velocity for Valves

Compressor valves are the most critical part of a reciprocating compressor.  Generally, they require the most maintenance of any part.  They are sensitive both to liquids and solids in the gas stream, causing plate and spring damage and breakage.  When the valve lifts, it can strike the guard and rebound to the seat several times in one stroke.  This is called valve flutter and leads to breakage of valve plates.

Where,

  • V = average velocity in feet/minute.
  • D = cylinder displacement in cubic feet/minute.
  • A = total inlet valve area per cylinder, calculated by valve lift times valve opening periphery, times the number of suction valves per cylinder, in square inches.

Step 9: Determine the Gas rod loads

Gas rod loads are calculated based on internal cylinder pressures. The equations below are based on pressures in gauge units. If absolute units are applied, then additional terms for Patm being applied on the piston rod diameter must be included.

Thumb Rules for good Compressor sizing:

  1. Rod loads < 100%
  2. Rod reversal Degree (Xhd pin degree / % Rvrsl Lbf) > 30% & Force > 25%.
  3. Cylinder Discharge Temperature < 300oF (Some OEMs allow < 350 oF)
  4. Volumetric Efficiency >15%
  5. Discharge Events > 4.5ms; >2.5ms (With Speed Reversal).
  6. Ideal BHP load is 75-100%
  7. Pressure Ratio F/F ideally should be < 3:1

Step 10: Selecting of Reciprocating Compressor cylinder and Frame by using the OEM Design Data

Once the above steps are calculated, use the calculated Volumetric Efficiency, Maximum HP, Displacement, Discharge Temperature, and Gas Rod Loads and check with respective OEMs design data to determine the number of Strokes and speed (RPM). Using these Strokes and speed calculate the Cylinder Area as per below.

By this, the Cylinder area is determined which helps in finding out the right Cylinder bore and Cylinder model. It also helps us in deciding the number of Cylinders used in the multistage compressor. Attached below is the Performance chart for reference where it satisfies all the user criteria and with cost cost-effective selection of the reciprocating compressor and its frames and cylinder Models.

A Typical OEM software compressor Sizing outputs for Reference
Fig. 5: A Typical OEM software compressor Sizing outputs for Reference

Is Pipe Stress Analysis Required for Cold Water Piping Systems from Pump Stations?

Is Pipe Stress Analysis Required for Cold Water Piping Systems from Pump Stations? This is perhaps one of the most frequently asked questions in the water piping industry. Engineers often argue over this question which results in a dual answer. Some engineers say stress analysis is not required and others say it is required. In this article, we will explore the answer to the above question.

The answer to the above question is not straightforward. In general, as for water piping systems with pump stations, the difference between the maximum working temperature and installed temperature (generally 10 to 20 Degrees) is less, hence it is believed that pipe stress analysis of such water piping systems is not required. This could be valid up to a certain point if good engineering judgments are followed and the piping system is provided with sufficient flexibility.

But before we can conclude, a high level of assessment must be conducted to understand if pipe stress analysis is required. The parameters that substantiate the need for pipe stress analysis are:

How an increase in pipe temperature affects the system:

Even though it is believed that the water piping system will be near to installed temperature. Still, there could be variation due to the following reasons:

  • Seasonal variation of temperature from winter to summer.
  • Empty pipe exposed to sunlight.
  • Full pipe exposed to sunlight.
  • Temperature variation between day and night.

How external forces and displacements affect the water piping and Pump system:

Forces and displacements due to seismic, wind, and structural settlements may impose unacceptable levels of stress on the system. These stresses can not be estimated without proper pipe stress analysis.

Limitation of Pump Nozzle Loadings:

It’s difficult to estimate the nozzle loads without performing pipe stress analysis.

Support optimization:

Cold water piping systems usually have very large sizes along with large valves that result in huge structural loading. Without proper stress analysis, those loads can be overestimated and support optimization may not be possible.

Design of Expansion Bellows or Expansion Joints:

The use of rubber bellows or steel expansion joints at pump stations for water piping systems is quite common. In general pump stations are routed quite straight without much flexibility. So, these expansion joints are used to absorb thermal expansion which in turn reduces pump nozzle loads.

However, there is a concern as the subject of expansion joints is one of the most misunderstood components in the piping industry. In the usual case, simple untied bellows are used which is simply a flexible element between two flanges. It is true that they easily absorb the thermal expansion by compressing the bellow elements in all axial, lateral, angular, and torsional directions. However, a pressure thrust force is generated in untied expansion joints which must be calculated and considered in pipe stress analysis to get the actual effect. This pressure thrust force will be transferred to the pumps. In some situations, the pressure thrust force, itself, will be more than the allowable pump nozzle loads.

Another option is to use a tied expansion bellows. However, even though the tie rods will take care of the pressure thrust load, they will not compress to absorb axial movement and the thermal effect will be transferred to the nozzles. So, their position has to be such that the thermal movement is lateral.

A common misconception is to use tied bellows to a pump line with a gap in the tie nut and believe that the tie rods will take care of the pressure thrust force and the gap between the tie rod nuts will help in absorbing the thermal force by compressing. But as soon as any thermal expansion occurs, the tension in the tie-rods reduces and the pressure thrust load is transferred to the nozzle. So, this has to be carefully considered.

Typical Example of a Pump Station Cold Water Piping System

Fig. 1 below shows a typical example of a water piping system pump station.

Cold Water Piping from Pump Station
Fig. 1: Cold Water Piping from Pump Station

From the image, you can easily understand that the configuration does not have sufficient flexibility, and nozzle loads may increase the allowable.

From the above discussion, we can understand that pipe stress analysis for cold water lines from pump stations needs to be performed

  • To compute nozzle loads.
  • To study the effect of seismic and other displacements
  • To design the pipe expansion joints.
  • To optimize the supports.
  • To study the thermal effects.
  • To assure owners that the design is properly engineered.

References and further Studies

More details about the subject can be found here.

What is a Golden Joint? Meaning, Application, and Code Requirements

We all know that a hydrostatic test is performed in all piping systems to ensure the integrity of all the joints. It is a code requirement before the commissioning of the piping/pipeline system. However, in certain situations, hydrostatic testing may not be technically feasible or may be hugely cost-intensive. For example, When a new piping component is connected to an already existing pipe. The situation may not always be favorable for hydro tests. In such a situation, the golden joint comes as a savior to construction professionals. In this article, we will learn the meaning and applications of golden joints in piping.

What is a Golden Joint?

Golden Joint is a pipe/pipeline joining procedure where hydro testing is not performed after the joining. Extensive NDT methods like radiographic test/ultrasonic testing methods are used to ensure that the joint is defect-free, design is in line with codes and standards, and fit for intended service. A golden joint is also known as a golden weld or closure weld.

Examples of Golden Joints

Some typical examples of golden joints are:

  1. Golden joints in tie-ins from existing pipe parts.
  2. During Hot tapping from running/working/operating pipelines.
  3. When only a little repair work is performed on the system at one or two locations, and hydro-testing of the complete system is difficult, costly, and time-intensive.

Golden Joint Procedure

The requirements of golden weld joints are identified by the construction contractor. Then they mark up the isometric/alignment drawings and get permission from the client. Next following a proper golden joint fabrication method statement, the welding is performed. Next NDE and final inspection clearance is taken and the golden joint is approved. The golded weld or closure weld must be performed by a highly skilled welder.

NDE requirements for Golden Joints

Non-destructive examination or NDE is performed after the PWHT if required by the piping class, thickness, and service limitation. In general, the following NDT tests are performed for golden piping joints.

  • Radiographic Testing: Radiographic testing can be performed as per the guidelines provided in Article 2 of ASME BPVC Code section V.
  • Ultrasonic Testing: Ultrasonic testing can be performed as per the guidelines provided in Article 5 of ASME BPVC Code section V.
  • Magnetic Particle Testing: Magnetic Particle Testing is performed as per the guidelines provided in Article 7 of ASME BPVC Code section V.
  • Dye Penetration Test: Dye Penetrant testing is performed as per the guidelines provided in Article 6 of ASME BPVC Code section V.

Code requirements for Golden Joints

ASME B31.3 Requirements for Golden Joint

As per clause 345.2.3 (c) of ASME B31.3, The final weld connecting piping systems or components need not be leak tested (golden weld) provided the weld is examined and passes with 100% radiographic examination or 100% ultrasonic examination.

ASME B31.4 and ASME B31.8 codes also permit the use of golden pipeline welds for tie-in joints.

API 570 Requirements for Golden Weld Joints of Piping

As per API 570, when performing a pressure test of a final closure weld that joins a new or replacement section of piping to an existing system is not practical, all of the following four requirements need to be satisfied.

  • a) The new or replacement piping section is pressure tested and examined by the applicable code governing the design of the piping system, or if not practical, welds are examined with appropriate NDE, as specified by the authorized piping inspector.
  • b) The closure weld is a weld between any pipe or standard piping component of equal diameter and thickness, axially aligned (not miter cut), and of equivalent materials.
  • c) Any final closure butt weld shall be of 100 % RT; or angle beam ultrasonic flaw detection may be used, provided the appropriate acceptance criteria have been established.
  • d) MT or PT shall be performed on the root pass and the completed weld for butt welds and on the completed weld for fillet welds.

The owner/user shall specify industry-qualified UT angle beam examiners for closure welds that have not been pressure tested and for weld repairs identified by the piping engineer or authorized piping inspector.

API RP 14-E Requirements for Golden Joint

API RP 14E recommends that when hydrostatic or pneumatic tests create any adverse effect on the piping or operating fluid, a golden joint can be used.