Basics of pipe stress analysis

acoustics-vibration
youngs-modulus
#1

SOURCE https://www.eng-tips.com/viewthread.cfm?qid=189629

QUESTION

tarunstress
Can somene please recommend a good book on basics of pipestress analysis and materials for starters in Pipe stress analysis in refinery, oil and gas, LNG , GTL etc industries?

REPLIES

JohnBreen
Within “piping engineering” there are many subcategories. To name a few there are flow of fluids, heat transfer, control, construction methodologies (fabrication and erection), etc., and structural design and analysis – I will address structural design and analysis here.

First, generally speaking, I would caution the reader to understand you cannot get everything you need to become a competent piping engineer from a book. Everything you need is not in print. You need to gain experience by working under a under a knowledgeable senior piping engineer to get where you want to be professionally. The “body of knowledge” required for competence in this field is huge and you should be prepared to devote the rest of your professional career in continuing to learn. The “student of piping engineering” (and I hope that includes all of us in this field) is “shooting at a moving target” – it is a dynamic discipline and it will continue to evolve – we must try to “keep up”. That needs to be understood before I get into books.

Next, I would point out that you must decide what it is you want to read first. I would very strongly recommend to the beginner that some time should be invested in reading (or perhaps reading again) some good books on piping drafting and understanding piping drawings. No student of piping engineering should think he/she already knows all that is needed in this regard. Also, there are some “general” or “overview” types of books that can get you started, but if you want to master this discipline you will eventually want to get into the books that present the fundamental theory and those that present more developed theories and methodologies. Walk before you run. The better books that present the “overview” approach will have solid bibliographies that will point you toward the underlying theory.

Next, be aware that in virtually every part of the world the structural analysis of piping systems is tied to various sets of Codes and Standards. You have to determine what Codes and Standards are mandated by the jurisdiction in which the piping system you are to design will be located. Then you must simply sit down and read the Codes and Standards mandated by that jurisdiction. So, these “books” must be on your “required reading” list (do not look for “free” copies of these but your company “technical library” MUST have them). DO NOT trivialize this aspect of piping engineering as it is a mandatory exercise. Another VERY IMPORTANT aspect of piping engineering is learning to use your tools. Recognize that the providers of piping structural analysis software have developed EXCELLENT product specific documentation and also recognize that these documents build a bridge between theory and practical application. You will need to understand the software and the best methods for using it to model your piping systems for structural analysis. These documents are often overlooked but you will find they are rich in the information that you NEED to know to become competent.

There have been many good books on piping design and stress analysis published in the last 50+ years. Some of the older books have become “classics” that we often refer to for insights into theory and methodology. Some of these “classics” have been around since before computers became generally available and they include lengthy descriptions of “approximate methods” for structural analyses of piping systems (perhaps one half of the pages in these books will be devoted to this topic). This is good background and it might be a good investment of your time to eventually read and understand these methods but structural analysis of piping is no longer performed this way as it is time consuming and economics dictates that we use computers. Just be aware that you will find that some of the most highly touted (and mo$t expen$ive) “classics” will be fifty percent “obsolete”.

In general engineering books are very expensive. Perhaps you will be surprised to find how much really good information (data and design methodology) is on the internet and available at no cost (the development generally underwritten by federal taxes). You will find that a little “looking around” on the Internet can be rewarding – valuable publications that you can download without charge. Some examples (not an exhaustive list):

There are two good books CURRENTLY available (but they too will be “Classics) to give you a very good head start in learning the artful science of piping structural analysis:

Process Piping: The Complete Guide to ASME B31.3, Second Edition, by Dr. Charles Becht IV,

CASTI Guidebook to ASME B31.3 Process Piping (Fourth edition), ISBN: 0071364714, by Glynn E. Woods, and Roy B. Baguley
http://www.casti.ca/ (click on books and ebooks)

The cited books will help by providing some of the background for the rules you see in the ASME B31 Codes and Standards that you MUST read. One of the most important things that must be understood about the ASME B31 Pressure Piping Codes is that the structural analysis methodologies presented there are based upon beam theory (albeit they do not preclude other valid methodologies) and the software for piping structural analyses are based upon beam theory. Learn about the beam theory method of analysis of structural SYSTEMS. Focus upon the distribution of forces and moments over the SYSTEM. Review the loadings on the system (weight (dead weight and live weight), wind, thermal expansion thrusts, seismic excitation, etc.) and the load paths that take these loadings to the boundary fixtures (anchors, hangers, supports, rotating equipment and non-rotating equipment (vessels, heat exchangers, etc)). You must focus upon following the load path all the way to the ground (the point where the Civil Engineer takes over responsibility).

When working with pressure technology (i.e., piping) Codes and Standards, it is useful to be comfortable with the various methods used by the various Codes to combine stresses (Rankine, Tresca and Von Mises failure criteria). Review the fundamentals of beam theory structural analysis. Go back into your introduction to mechanics and strength of materials books and look at Mohr’s circles of stress and review the concept of unit cubes and how stresses are combined.

Again, remember that the Codes and the software are based upon beam theory and in some cases beam theory will not predict the highest stresses that will be developed in some pipe system components. So you must understand the limits of beam theory and learn about methods (typically finite element method) for modeling individual components and applying forces and moments from your beam theory analysis to your FEA model.

Learn about the strain sensitivity of the equipment to which piping systems are frequently attached (rotating equipment and non-rotating equipment). Study the Standards that set the limits for the amount of loading (forces and moments) that may be safely transferred to this equipment by the piping.

Some of these topics are addressed in the “classics” mentioned above. My simplistic definition of “a classic” is a book that must be read (and preferably on your book shelf) but which might be out of print (there are exceptions). If you perform an Internet search (or a search of the engineering discussion forums) you will find previously compile lists of “classics”. It should be kept in mind that many of the “classics” contain information (e.g., pressure temperature rating of piping components) that is based upon Code allowable stresses that MAY HAVE CHANGED after the book was written – be aware of this and check the Codes.

A (necessarily) very incomplete list of “classics” would include:

Design of Piping Systems, Kellogg, John Wiley & Sons Inc; 2nd edition (June 1964), 385 pages, ISBN-10: 0471467952, ISBN-13: 978-0471467953, out of print. Often referred to in discussion boards. This is a “classic among classics”. The book is grossly overpriced on the used book market and is now rumored to be available on the Internet as an electronic file.

The Piping Handbook, Updated and available. Editor: Mohinder L. Nayyar,
Publisher: McGraw-Hill, ISBN: 0-07-047106-1 (paperback or hardbound)

The Piping Guide, Syentek: 2nd edition (March 1991)Authors: David R. Sherwood, Dennis J. Whistance, ISBN-10: 0914082191, ISBN-13: 978-091408219

Process Piping Design, Gulf Pub Co (January 1973), Author: Rip Weaver, 218 pages, Two Volumes, ISBN-10: 0872017591, ISBN-13: 978-0872017597

Also look at this list: http://www.pipingdesign.com

Of interest, a couple of “out of print and unavailable Classics” have just popped up again and are available. One of these is the “olde” Tube Turns book “Design of Piping Systems”. The ASME B31 Pressure Piping Codes include fatigue rules that came from basic testing in the late ‘40’s and early ‘50’s. The transition from testing results to Code rules was explained in classic papers written by Arthur R.C. Markl. This book includes (in addition to much basic data on piping components) many of the papers written by A.R.C. Markl that provide the background and theory of the B31 Pressure Piping rules. The company that was “Tube Turns” is now Sypris (www. sypris.com) and “Design of Piping Systems” is available again for the price of $35.00 (including shipping – by today’s standards, a REAL bargain). There are ten papers/articles included in the back of the book:

Fatigue Tests of Welding Elbows vs. Mitre Bends - A.R.C. Markl, 1947

Fatigue Tests of Flanged Assemblies - A.R.C. Markl and H.H. George, 1949

Fatigue Tests of Piping Components - A.R.C. Markl, 1951

Piping Flexibility Analysis - A.R.C. Markl, 1953

Effects of Internal Pressure on Flexibility - E.C. Rodabaugh and H.H. George, 1956

Balanced Quality as a means of Attaining Maximum Economic Safety For Critical Piping - A.R.C. Markl, 1957

Fabricated Pressure Piping as Related to Nuclear Applications - J.J.Murphy, C.R. Soderberg, H.S. Blumberg, and D.B. Rossheim, 1957

On the Design of Bellows Elements - A.R.C. Markl, 1964

Why Branch Connections Fail - A.R.C. Markl, E.C. Rodabaugh and H.H. George, 1955

Tests of Pups Support “Bridging Effect” - E.C. Rodabaugh and H.H. George, 1959

The first half of the book includes typical properties of pipes, Pressure - Stress Ratios, Flow of Fluids, Line Expansion and Flexibility, and Layout Dimensions of Fittings and Flanges. This is an old book and some of the data is dated but any piping engineer will benefit from reading it cover to cover.

The other book that has suddenly become available again (veteran piping engineers will appreciate this) is the olde NAVCO Datalog. This little spiral bound gem includes all sorts of valuable piping data. Probably the most data in a small package. Look here:

http://www.basicpsa.com

This will help but at times there is no good substitute for asking the piping engineering community for some help. It is important to know where you can go to ask good questions. The sources of information cited above will serve you well for about 70 percent of the piping systems that you are called upon to design. There are many “except for’s” in piping design. You will learn techniques for the analysis of buried systems, double containment piping systems, non-metallic piping systems (plastic, glass, etc.), very large diameter (relatively thin wall) piping systems, systems with “strap-on” heating jackets and …….well you get the picture. But the good news is that the community of piping engineers is rich in advice and in most cases quite approachable.

Learn where to go (forums) to ask “good questions” of the community. Then, observe the protocol of discussion forum etiquette. First, learn how to use the search function provided by the forum – it is likely that your question may have been asked before, several times . And, do your homework and try to find answers to your “good questions” using your own intelligence. Learn how to frame a “good question” unambiguously – take the time to provide all the information in support of your “good question” (the better thought-out the question, the more response you will get). Control you sensitivities when reading the responses (be prepared for the occasional “put down” by some egocentric self styled “expert” who is so unsure of himself that he must degrade others to elevate his own sense of self importance – it comes with the territory). Visit the forums even when you do not have a question as there will be questions asked there that you may not have thought of.

If you follow this path you will only need to add years of actual experience to become a piping engineer who is competent in the static structural analysis of linear elastic piping systems. Then you will be motivated to learn about dynamic analyses and inelastic non-linear systems.

tarunstress
Thanks a lot, John. I apreciate your painstaking, patient and enlighting reply. It has been very helpful to me and scores of starters like me in piping engineerng.

Once again thanks for the valuable information. I wish I could reach your level some day and help others in the manner you did.

pennpiper
tarunstress, John Breen has given you some very fine guidance.

I would also suggest that you and others might want to get the book
“Piping Engineering Leadership For Process Plant Projects”
James O. Pennock
Gulf Professional Publishing
ISBN 0-88415-347-9

LSThill
“API 579-ASME FFS”

Also, Piping Stress Analysis and additional Engineering Tool’s:

Nozzle/PRO Fitness for Service Local thin areas and crack like flaws may be evaluated for most Nozzle/PRO geometries using the Nozzle/PRO fitness for service input form. Fitness for service evaluations are conducted using API 579-ASME methodologies for Level 2 & Level 3 checks. Up to ten flaws may be defined for each model. To access
the fitness for service options, click the “API 579-ASME FFS” http://paulin.com/

What is new in Piping Stress Analysis: Good Engineering Tool’s help your clients

18 Degree of Freedom Beam Element
• Permit element interaction of ovalization and warping effects
• Supports and loads may be attached to the outside pipe surface
• A pseudo-WRC 107 type stress calculation is made for all supports attached to
the outside of the pipe.
• Improved thermal and dynamic solutions
• Modeling of stiffening rings
• Activated from 6dof model by single click of radio button
• Shell Stresses due to thickness changes

Section 1: 18 Degree of Freedom Beam Elements
General Discussion
The 18 degree of freedom piping beam element is an industry first implementation for piping and pressure vessel analysis. The element formulation includes the effects of ovalization, dilation and warping that are not considered in the 6 degree of freedom classical elements found in traditional pipe stress programs. Functionality not included in a typical 6dof beam
element includes:

  1. Modeling of stiffeners (stiffening rings)
  2. Simulation of flanges at any cross section in the model (not just at bends)
  3. Loads and stiffnesses acting on the surface of the pipe
  4. Interaction of ovalization between adjacent elbows
  5. Differential thickness or thermal expansion between adjacent elements
  6. Shell Stress Formulation to obtain more accurate stress calculations.
  7. Inclusion in Dynamic analysis for more accurate shapes and frequencies
  8. Correction of bending/torsional shear errors in most 18dof formulations
    An example of ovalization and warping modes not explicitly included in typical 6dof beam elements are shown below:

The strong interaction of ovalization modes between bends can cause one bend to either augment or retard another’s ovalization modes, resulting in greater or less system stiffness depending on bend orientation. The distored plot below shows how bend cross sectional deformations can interact.

KernOily
A couple things I would add is to make sure you have a solid, working, fundamental knowledge of solid mechanics. You must know these things down cold:

  • Mohr’s Circle, or else the equations that are used to generate Mohr’s;
  • The generalized 3D state of stress (triaxial) on an element (three normal stresses and six shear stresses);
  • The concepts of combined loadings, in- and out-of-plane normal and shear stress, and how the principal stresses and max shears are caluclated;
  • The failure criteria, e.g. von Mises, Tresca, etc. and the knowledge of how they are applied in which piping code.

These items form the basis of the toolset you need to properly evaluate the output from the computer stress analysis programs. They also are invaluable at understanding why certain pipe segments are loaded the way they are and they will provide clues as to where to adjust the system to reduce loadings.

It’s all about the fundamentals and the Code!

LSThill
Pipe stress analysis in refinery, oil and gas, LNG , GTL etc industries ?

TITLE: Stress for Welded attachments to Cylindrical Shells

Abstract
This program performs an analysis of the stresses in a cylindrical shell caused by external loading through a welded attachment. The source equations are from WRC-198 by Dodge, Rodabaugh and Moore. The program will analyze a rectangular or a circular attachment for baring loads. Bending moments, shear forces and torsion moments. The output consists of two set of stresses, Dodge’s original analysis, and the modified analysis, applied to the PRIMARY STRESS indices equation form ASME Section III. Paragraph NB3652.

Technical Note:
The analysis found in WRC-198 is not the same as that found in WRC-107, and therefore should not be expected to yield the same results, WRC-107 is based on Bijlaard’s equations and id a very involved analytical approach to attachment or nozzle stresses. WRC-198, on the other hand, is an empirical approach which develops stress indices for the welded attachments based on the shape and dimensins of the attachments, and the diameter-to-thickness ratio of the cylinder.

On page 28 of WRC-198, the authors summarizes their comparisons with WRC-107

“In summary, for both thrust and moment loadings, comparison among the WRC-107 method, Dodge’s direction calculation of Bijlarrd’s analysis, and the stress-index method, developed in Ref. 2 (egs 4a, 4b and 4c herein) show that the stress-index method tends always to be conservative. For square loaded areas, the WRC-107 method gives about the same results as the stress-index method. For loaded areas that are not square (i.e…, ?1 ? ?2), WRC bulletin 107 uses an approximate method (based on Ref. 7) which appears to be for thrust loadings over the parameter range considered and fair for moment loading within the parameter range ¼ <= ?1 ? ?2<=4);within this range, the magnitude is conservative, but the location and direction may be in error. On the other hand, the WRC-107 method may be misleading for moment loadings on integral lugs which are long and narrow (i.e for causes where ?1 ? ?2 <4 or ?1 ? ?2 >4.”

KernOily
Great write-up John.

A couple things I would add is to make sure you have a solid, working, fundamental knowledge of solid mechanics. You must know these things down cold:

  • Mohr’s Circle, or else the equations that are used to generate Mohr’s;
  • The generalized 3D state of stress (triaxial) on an element (three normal stresses and six shear stresses);
  • The concepts of combined loadings, in- and out-of-plane normal and shear stress, and how the principal stresses and max shears are caluclated;
  • The failure criteria, e.g. von Mises, Tresca, etc. and the knowledge of how they are applied in which piping code.

These items form the basis of the toolset you need to properly evaluate the output from the computer stress analysis programs. They also are invaluable at understanding why certain pipe segments are loaded the way they are and they will provide clues as to where to adjust the system to reduce loadings.

LSThill
A1): ASME
http://catalog.asme.org

A2) WRC BULLETINS you need to do your home work in the WRC & PVRC
http://www.forengineers.org

JohnBreen
When you go to the ASME “bookstore” per Mr Thill’s recommendation you might want to look for another rather recent offering:

Applying the ASME Codes, Plant Piping and Pressure Vessels, By James A. Wingate:

http://catalog.asme.org

Mr. Wingate has included a nice review of Mohr’s circle of stress there and the book in general is a gem. Also, Phil Ellenberger’s recently released book, Piping Systems and Pipeline: ASME Code Simplified, should also be reviewed.

LSThill
Tarunstress Please reference to DR. LC Peng Technical Papers

Reference to Piping Engineering and Piping Stress Analysis

LC Peng, president of PENG ENGINEERING, is a leading author in the field of pipe stress analysis and piping engineering.
LC Peng has authored, co-authored and presented many technical papers on these subjects. Electronic versions of his most popular papers are available below.

Please note, documents are in Adobe PDF format and require Adobe Acrobat Reader to view.

The Art of Checking Pipe Stress Computer Programs

Treatment of Support Friction in Pipe Stress Analysis

Local Stresses in Vessels - Notes on the Application of WRC-107 and WRC-297

Quick Check on Piping Flexibility

Toward More Consistent Pipe Stress Analysis

Evaluation of Flanged Connection Due to Piping Load

An Interpretation on Pressure Elongation in Piping Systems

The Art of Designing Pipe Support Systems

Rethinking the Allowable Pipe Load on Rotating Equipment Nozzles

Stress Analysis Methods for Underground Pipe Lines: Part 1 - Basic Calculations

Stress Analysis Methods for Underground Pipe Lines: Part 2 - Soil-Pipe Interaction

Equipment Reliability Improvement through Reduced Pipe Stress

Cold Spring of Restrained Piping System

Computer Application to the Piping Analysis Requirements of ASME Section III, Subscribe NB-3600

Thermal Insulation and Pipe Stress

Hazardous Situations Created by Improper Piping Analyses

AVincent
tarunstress:

This useful book from 1985 is back in print.

Introduction To Pipe Stress Analysis (Reprinted 2008), Author: Sam Kannappan,

ISBN: 978-1-60530-514-1

tarunstress
Thanks a lot.

#2

@LittleInch, @zdas04 and others, do you have other books (or codes) to recommend, or any comments about the above discussion?