Piping Stress Analysis 12

[ChrisProcess]

Hello, first time poster with a query regarding piping stress analysis.

At the moment I work in plant design Process Engineer. Before issuing drawings we send selected lines out for Stress Analysis (our somewhat simplified criteria for Stress Analysis is D>2", dT>100 Deg C). It is now desired to do this analysis in-house.

I've taken it upon myself to research this.
I've assembled numerous guides (including the CASTI guidebook to ASME B31.3 & Process Piping the Complete Guide by Charles Becht).

I know that Caesar, Autopipe and others are used, but for various reasons they don't want to go this route. Instead they want to establish either a guideline or program that will cover the stress analysis.

We can characterise out piping networks quite easily, in terms of fittings, equipments dimensions, operating conditions etc. via our database system and 3d model.

So what I'm really looking for is somebody that works at this day to day, to give some pointers. I've spoken to my former mechanical engineering lecturer who thinks developing it from the ground up is a bad idea (i.e. go the Caesar route). I would like to get some other opinions on this. If it really is a bad idea, its best to find out at this early stage.

From reading the guides, a lot of it seems pretty vague, or at least up to the designers dicretion.
I would like to know how those working at it proceed and if to develop our own properitary procedures/software is feasible.

I'm assuming for all this that ASME B31.3 is the main guideline to consider regarding Stress Analysis for Process Piping.

Thanks for getting this far!

 

[BarryClearwater]

Why is CAEPIPE never mentioned in these forums (or very rarely anyway)?

 

[JohnBreen]

Barry,

Could you please supply the Internet address for the CAEPIPE users discussion forum?

Thanks, JB

 

[BarryClearwater]

John
CAEPIPE internet address is:

http://www.sstusa.com/

The product seems well presented and the website reads well, but there seems little mention of it outside of it's own website. I do not know about the product myself, though I have downloaded the evaluation version and played around with it. From that limited perspective it seemed good. I wonder if there are any CAEPIPE advocates out there that could tell us something about it, useability, validity, strengths, shortcomings.
REGARDS
Barry

 

[tigny]

Hi,

I've been using CAEPIPE from 1998 (dos version) to 2003 (windows version) and then switched to C2, because I entered another company.

For my usage (oil and gas, power piping, mostly B31.3 and french CODETI codes) it took almost no time to change from one to the other.

And I still go to SST USA - CAEPIPE site to look for their tips!

If I had not changed company I may still use CAEPIPE.

yours truly.

 

[StressGuy]

Work has kept me out of the forums for a while, so I've missed this thread until today.

Trying to set up to handle stress work in house essentially starting from nothing is certainly a daunting task.

In truth, if your company is serious about this (though, their balking at the cost of a Caesar license suggest otherwise), I would recommend that your company find a senior, experienced stress engineer to come and and effectively give you a brain dump and create a stress design basis for your company.

As for the long term, my boss, one of the finest stress guys I've ever known, has said that it takes five good years of development to build a stress engineer. Most of us that do this for a living stand on the shoulders of the giants who came before us.

Edward L. Klein
Pipe Stress Engineer
Houston, Texas

"All the world is a Spring"

All opinions expressed here are my own and not my company's.

 

[NolanM]

I am the Mechanical Integrity Engineer for our US Operations. I have spent much of my career in projects and design. We run across this quite a bit. Your criterion for pipe stress is much too tight. You normally wont see a problem with pipe stress in small lines like that because they are usually somewhat flexible. Normally you use analysis for temperature changes (installation to operating) of about 400 F. If you do an expansion calculation, you will also see that the growth below that is usually not too bad. You also need to look at the configuration--long, stiff and straight will need some type of restraint, whereas, long with bends to allow some type of spring action, will not need anything.
If your company doesn't normally do business with a good Engineering Design firm, spend a little money and get Caesar II with a limited run license (probably $1000 or less), model the sytem and run it. After you do it for quite a while, you'll be able to look at a system and determine what level of analysis is needed--detailed with spring supports, or just a visual review.

 

[stanier]

If you are budget restrained look at Algor's Pipepak. It doesnt have all the bells and whistles of C2 but it does a workmanlike job for far less cost.

http://www.pipepak.com.

I have used it sonce 1985 (DOS version). Most of these programs came out of the Mare Island Naval program so have similar engines.

But remember the cost of the software is but a minor cost compared to learning how to use it effectively and far less than if an inexperienced engineer makes a mistake that translates into a catastrophe.

If an engineer were to join the Institution of Mechanical Engineers he/she would have access to over 1000 books including those on pipe stress analysis. Refer

http://www.imeche.org.

 

[DSB123]

stanier,
Well pointed out - it's not just a case of getting some software and using it as you so well indicate. The previous post seems to suggest that by buying C2 with a $1000 limited run license is all you need to become a proficient Pipe Stress Analyst. We have too many of these at the moment without any more. I do have to venture out on Plants and do not like the thought of working around pipework which has been "designed" by a "two week experienced" Stress Engineer.

 

[JohnBreen]

Hi Stanier

Please bear with me as I do a little "nit-picking".

A little history. Strictly speaking, NONE of these new software products have anything in Common with the Navy Mare Island Mec-21 (and its derivatives like Mel-40) pipe stress analysis program (except that they use Castigliano's second theorem for the basic structural solution). I began using Mec-21 in 1963 and I had the responsibility to maintain and update it for 12 years (we made the conversion from IBM 7094 dependent Fortran II to Fortran IV). MEC-21 was written by Bob Creamer based upon the chapter of “The Piping Handbook”, Fifth Edition, (S. Crocker and R. King) by John Brock (If anyone has a fifth edition, this chapter is historic and you should read it again). Mec-21 used the flexibility method in its solution engine (I still have the original manual – yes, I know, “get a life”). This (flexibility method) greatly limited what we could do with Mec-21 as far as adapting it to perform dynamic analyses was concerned. All these new products use the stiffness method.

The first "break-through" came when the SAP IV software became available in the public domain. The Sap series of structural analyses programs came out of U-Cal Berkley and they used the stiffness method and beautifully written "top-down" Fortran IV in writing the program. Due to the "clean-ness" of the SAP analytical engine, it was adapted by several proprietary software products in 1970's and 1980's. The SAP software included a TRUE curved beam element and this was something else that Mec-21 lacked (Mec-21 created many lengths of slightly angled straight pipe to approximate the bend). If you did side by side comparisons of an analysis of the same structure there would be differences. If you analyzed a close coupled piping system with a dominant large radius bend in it the SAP software would give you an accurate solution but MEC-21 would "go wrong". One of the dominant software products at that time, TRILFEX (by Reid McNally), was originally based upon the MEC-21 analytical engine and then they (Dan Yongue at TRIFLEX – a great guy) created another version based upon the SAP analytical engine. TRIFLEX offered both versions ("Flexibility and "Stiffness") for a while. Tony Paulin’s approach, when he originally wrote Caesar II, was completely different and all his code was original – an entirely new analytical engine.

ASME published at least two books for the purpose of piping software verification. These books has many "benchmark" sample piping systems with solutions from several software products (including ANSYS) and the solutions were all within about 7 percent of each other. What we learned from these "benchmarks" was that if you used commercial software to model a piping system for analysis and your "answers" were more than about 7 percent "off" you better go look at YOUR model to find the errors. I think that is also the case today – there are so many ways you can model a piping system in various programs that it is really easy to “create” differences. Conversely, it is too easy to in advertently describe the same system differently. This is usually the reason for “different” answers.

Folding his collapsible “soap box”, the old guy now toddles off to take his afternoon nap ;-)

Regards, John.

 

[stanier]

Dear John,

What a valuable lesson you have given me. I used Triflex back in the 1970's , punched cards and all. I made the mistake of repeating what my mentor had told me in those days without keeping up to date. You have certainly put me straight.

I have a copy of Crocker & King 5th Edition. I will certainly re read it now. It has been a while since I did read it.

Perhaps I am hoarder but I have Piping Design Manual Kellogg's , Piping Engineering by Tube Turns, Piping Design and Engineering by ITT Grinnell and Process Equipment Design Brownell & Young. They do me no good sitting on the shelf I have to re read them. I used to study them on the train but now have a home office so do not get the chance.

Be assured we readers appreciate your insights into the history of the tools we use. I hope I can pass on such useful information when it is time for me to get the collapsible soapbox, still using an upturned milk crate at the moment.

 

[LSThill]

TEAM MEMBER'S:


Add to the above Reference

DAVID BURGEEN
1 DESING OF POWER PLANTS STRUCTURES
2 PRESSURE VESSEL ANALYSIS
3 PIPING ANALYSIS
4 ELEMENTS OF THERMAL STREESS ANALYSIS

Leonard Thill, Jakarta

 

[JohnBreen]

Hi again Stanier,

Sincere thanks for your kind words.

Leonard Thill mentions the Burgreen books. David originally published them himself when he was a professor at Brooklyn Polytech. The "publisher" was C-P Press, Jamaica, NY. David became a good friend and he allowed me (in writing) to use excerpts from his books in my ASME piping analysis seminars. David's "Piping Analysis" book provides a rigorous treatment of the math involved in this science - don't look for much "nut and bolts" stuff there. However, it is still one of the books (as are the other three) that I pull down off my (many) shelves and read periodically.

The title of David's book "Design Methods for Power Plant Structures" (again, C-P Press, 1975, 446 pages) is a little deceiving as it is a wonderful treatment of the development of the equations and methodologies found in the ASME B&PV Code. David carefully explains the importance of each of the shell stresses (primary and secondary) in the context in which the Code uses them. This is far and away the most lucid treatment of this subject matter that I have ever seen. The complete description of the various theories of failure that David presents is worth the price of the book. The bad news is that it is out of print (albeit it can be found on the used book market at a price). In my view, the novelty of these books is that they were written by a teacher and they were intended for university students so they assume the reader brings very little background knowledge to his/her first reading.

After David's passing, These books were again printed by Arcturus Publishing and offered for sale for a while (Arcturus Publishing, 1971-06-01, list price: $48.00, ISBN: 0916877027). Regrettably, even these have been out of print for a while. The Arcturus published books can also be found on the used book market.

Ooops, sorry, I seem to have gotten out the collapsible “soap box” again.

Regards, John.

 

[LSThill]

Paulin Research Group presents a series of complimentary Piping and Pressure Vessel webinars by Mr. Tony Paulin, President of Paulin Research Group, and the original author of CAESAR II. Each presentation will be 15 minutes with the opportunity for participants to send email questions after the presentation for direct answer by Mr. Paulin.

To register for any or all of these webinars, please go to Webinar Registration.

Thursday March 13, 2008 9:00 AM CST:
"Part 2 Fatigue Design – Fatigue Evaluation with ASME Section VIII Div 2, 2007"

Tuesday March 18, 2008 9:00 AM CST:
"Beams (CAESAR, AutoPIPE, Triflex, etc), vs. Shells (WRC?) vs. Bricks (FEA) - Who's Right"

Thursday March 20, 2008 9:00 AM CST:
"Part 3 Fatigue Design - Comparison of Fatigue Design Lives Using ASME, BS, and EN Design Codes"

Tuesday March 25, 2008 9:00 AM CST:
"Rules of Thumb for Expert Analysis of Piping Systems"

Thursday March 27, 2008 9:00 AM CST:
"External Loads on Nozzles (Comparisons of WRC107, B31, EN13445, VIII Div2 and.Mean-Life-to-Failure)" (web042)

Tuesday, April 1, 2008 9:00 AM CST:
"What is 100% of the Allowable Stress for Pipes and Pressure Vessels".



Houston 9:00 AM Start Time

New York - Tue 10:00 AM
London - Tue 3:00 PM
Berlin - Tue 4:00 PM
Moscow - Tue 6:00 PM
Dubai - Tue 7:00 PM
New Delhi - Tue 8:30 PM
Beijing - Tue 11:00 PM
Sydney - Wed 2:00 AM *
Auckland - Wed 4:00 AM *


TRAINING:

Second Qtr 08 Training: Two Days – Beginning and Intermediate Content. Two Days – Advanced Content.
Course Description: PRG FEPipe and NozzlePRO Course Outline
Course Registration: PRG FEPipe and NozzlePRO Course Registration.

NEW WEBSITE:

Topics include WRC107 experimental validation, Stress Intensification Factor explanations, Accurate SIFs, Pipe stress errors, Freeware downloads and more. Paulin Research Group Website


Software Bundling – PRG FEA Technology is included in each copy of Compress sold by Codeware Inc. Compress - PRG Bundling


TEMA Thick Walled Expansion Joints – PRG FEA Technology is used in the new TEMA Flanged and Flued Stiffness and Stress Analyzer.

http://www.tema.org/software.html

ASME ST-LLC – PRG Research Projects include alignment of stress intensification factors and external load design rules. See for more information.
Paulin Research Group Website


FOR MORE INFORMATION:

For more information call 1-281-920-9775 ext. 808, or email information@paulin.com


L S THILL

 

[ChrisProcess]

Hi All,

I've been away for a while and just got to catch up with this thread again.

Well, as I said this was originally intended as a research exercise. The overwhelming response is that it's not a straightforward operation.

To do things properly it seems more economically viable to continue contracting out the work (at least for the number & size of jobs we deal with).

Thanks for the suggestions & pointers - the experienced views were both appreciated & helpful. I'll keep everyone updated if things go any further.

 

[LSThill]

Chris Process (Chemical), John and Team Members:

Question??

continue contracting out the work neet the verification and validation (DOE STANDARD REQUIREMENT)??

Reference ASME B31.3 PIPING CHECKLIST by PRG

http://www.paulin.com

SYSTEM SPECIFIC B31.3 CODE REFERENCES - Short

300.2 Normal Fluid Service: a fluid service pertaining t omost piping covered by [B31.3].
i.e., not subject to the rules for Category D, Category M, or High Pressure Fluid Service.
Normal Fluid Service applies to piping that can be designed in accordance with the first
chapters of the Code and the fluid service is not Category D Fluid Service, nor is the piping
in severe cyclic conditions.

304.3.5(b) Branch pipe connections made by welding the branch pipe directly to the run pipe should be avoided
under the following circumstances:

1) when the branch size approachs the run size, particularly if the run pipe is formed by more than 15%
cold expansion, or expanded, or of a material subject to work hardening.
2) where repetitive stresses may be imposed on the connection by vibration, pulsating pressure, temperature
cycling, etc. In such cases, it is recommended that the design be conservative and that consideration
be given to the use of tee fittings or complete encirclement types of reinforcement.

304.3.5(e) Where branch connections do not meet the following requirements, integral reinforcement,
complete encirclement reinforcement, or other means should be considered:

1) D/T < 100 and d/D<1
2) If D/T>=100, d/D < 0.5
3) The angle between the run and the branch is greater than or equal to 45 deg.
4) The axis of the branch intersects the axis of the run.

306.5.1 Fabricated branch connections can be used in Normal Fluid Service if designed according to the
[B31.3 pressure design rules for intersections - 304.3] and [welded with the standard B31.3 acceptance
and examination criteria (311.1)]

Note 1 to the B31.3 Flexibility, and Stress Intensification Factor Table D300 states, (1) Stress intensification
and flexibility factor data are for use in the absence of more directly applicable data. Their validity has
been demonstrated for D/T ratios less than or equal to 100.

Note 6 to the B31.3 Flexibility, and Stress Intensification Factor Table D300 states, (6) The designer is cautioned
that cast buttwelded fittings may have considerably heavier walls than that of the pipe with which they are
used. Large errors may be introduced unless the effect of these greater thicknesses is considered.

Note 12 to the B31.3 Flexibility, and Stress Intensification Factor Table D300 states, (12) The out-of-plane
stress intensification factor (SIF) when > 0.5 d/D < 1.0 may be nonconservative. A smooth concave weld
contour has been shown to reduce the SIF. Selection of the appropriate SIF is the designer's responsibility.

Note 13 to the B31.3 Flexibility, and Stress Intensification Factor Table D300 states, (13) Stress
intensification factors for branch connections are based on tests with at least two diameters of straight
pipe on each side of the branch centerline. More closely loaded branches may require special consideration.


GENERAL B31.3 CODE REFERENCES - Short

300(c)(3) Engineering requirements of this Code, while considered necessary and adequate
for safe design, generally employ a simplified approach to the subject. A designer capable
of applying a more rigorous analysis shall have the latitude to do so; however, the
approach must be documented in the engineering design and its validity accepted by the
owner. The approach used shall provide details of design, construction , ... with calculations
consistent with the design criteria of this Code.

300(c)(5) The engineering design shall specify any unusual requirements for a
particular service. This may include, but not be limted to, two-phase flow,
hydraulic shock, mechanical/flow induced vibration, and unusual operating, relief,
or clean-out procedures,

300.1 The Designer is the person(s) in responsible charge of the engineering design of a piping
system and shall be experienced in the use of [B31.3]. The qualifications and experience
required of the Designer will depend on the complexity and criticality of the system
and the nature of the individual's experience. The owner's approval is required if the
[individual performing the engineering design] does not meet at least one of the following
criteria: (a) ... Engineering degree requiring 4+ years of full-time study, plus a minimum
of 5 years experience in the design of related pressure piping. (b) a [professional engineer]
experienced in the design of related pressure piping. (c) Associates Degree: 2+ years of
full time training + 10 years of experience, or (d) 15 years of experience in the design
of related pressure piping including design calculations and pipe flexibility...

301.3 ... The maximum design temperature ... may be established by test or calculation, and
may be the fluid temperature, but for uninsulated components shall not be less than: 95% of
the fluid temperature for valves, pipe, lapped ends, welding fittings ..., and 90% of the
fluid temperature for flanges (except lap joints), including those on fittings and valves,
and 85% of the fluid temperature for lap joint flanges, and ... 80% of the fluid temperature
for bolting. Per 301.3.3, for externally insulated piping, the design temperature shall be
the fluid temperature unless calculations, test or experience , ... show otherwise.

301.5.1 Hydraulic shock, liquid or solid slugging, flashing and geysering shall be taken
account in the design of the piping system.

301.5.4 Piping shall be designed, arranged and supported so as to eliminate excessive
and harmful effects of vibration which may arise from such sources as impact, pressure
pulsation, turbulent flow vortices, resonance in compressors, and wind.

301.7.2 [Piping shall be designed to accomodate or eliminate an unequal temperature
distribution at any cross section that may result in thermal bowing. This often occurs due
to thermal stratification, partial filling, or during startup or shutdown. See F301.7.

301.10 Fatigue due to pressure cycling, thermal cycling and other cyclic loadings shall be
considered, including the surface effects due to mixing flows at intersections, [and the
surface evaporation effects downstream of desuperheater valves.]

302.2.4 [A VARIATIONAL temperature and pressure does NOT need to be included as a design condition for
wall thickness calculations providing all the following are true (LIST IS SUMMARIZED):

a) All metals are ductile for variational temperature range
b) The hoop stress: (PD/2t) < Material Yield Stress at variational temperature.
c) SL + Occasional (Variant) Stresses < 1.33 Sh
d) Number of variations above design conditions occurs less than 1000 times in the piping system life.
e) Increased variation in pressure does not exceed test pressure.
f)(a) Variation does not exceed 33% for more 10 hr. at any one time, or more than 100 hr/yr, or
(b) Variation does not exceed 20% for more than 10 hr. at any one time, or more than 500 hr/yr, and
(c) Designer determines effects are safe and owner accepts, (See Appendix V).
g) Combined effects of sustained and cyclic variations on serviceability of all components is evaluated.
h) Temperatures below the minimum allowed temperature are not permitted unless per 323.2.2.
i) Sealability or operation of any valve or other component are not jeopardized by the variation.

302.3.5(c) The thickness of pipe used in calculated (SL) (the sustained stress) shall be the
nominal thickness minus mechanical, corrosion, and erosion allowance for the location under
consideration. (Mill tolerance must be removed from the nominal wall.) The loads due to weight
should be based on the nominal thickness of all system components unless otherwise justified in
a more rigorous analysis. [Many piping product specifications, for example SA-106 allow the
minimum provided thickness to be 12.5% under the nominal wall thickness. More stringent
requirements may optionally be provided by contractual agreement permitted by the piping product
specification.]

302.3.5(d) Footnote 3) B31.3 fatigue rules apply to essentially noncorroded piping. Corrosion can sharply
decrease cycle life; therefore, corrosion resistant materials should be considered where a large number
of major stress cycles is anticipated.

302.3.5(d) Footnote 4) The minimum value for f is 0.15, which results in an allowable displacement stress
range, SA, for an indefinitely large number of cycles. [For SL=0, and Sc=Sh=20,000 psi, the endurance
limit for an infinite number of cycles is (0.15)[(1.25)(20,000+20,000)] = 7,500 psi.

302.3.5(d) Footnote 5) The designer is cautioned that the fatigue life of materials operating at elevated
temperature may be reduced. [See NH reports in NozzlePRO or FE/Pipe to evaluate this reduction.]

302.3.6 (a) The sum of longitudinal stresses (SL), due to sustained loads (pressure and weight), and
of the stresses produced by occasional loads, such as wind or earthquake, may be as much as 1.33 times the
basic allowable stress given in Tables A-1 and A-2.

302.3.6 (b) It is not necessary to consider occasional loads such as wind and earthquake as acting
concurrently with test loads.

304.3.1(b) The [B31.3 pressure design equations] are minimum requirements valid only for the following
branch connections.

1) D/T < 100 and d/D<1
2) If D/T>=100, d/D < 0.5
3) The angle between the run and the branch is greater than or equal to 45 deg.
4) The axis of the branch intersects the axis of the run.

When these requirements are not satisfied, the pressure design shall be quaified by successful prior
experience, tests, finite element analysis or other calculations per 304.7.2.

304.3.5(a) [B31.3 pressure design requirements] do not include considerations for external forces and moments,
or movement at terminal points.] Special consideration shall be given to the design of of a branch connection
to withstand these forces and movements.

304.3.5(b) Branch pipe connections made by welding the branch pipe directly to the run pipe should be avoided
under the following circumstances:

1) when the branch size approachs the run size, particularly if the run pipe is formed by more than 15%
cold expansion, or expanded, or of a material subject to work hardening.
2) where repetitive stresses may be imposed on the connection by vibration, pulsating pressure, temperature
cycling, etc. In such cases, it is recommended that the design be conservative and that consideration
be given to the use of tee fittings or complete encirclement types of reinforcement.

304.3.5(c) Adequate flexibility shall be provided for small pipe at small d/D intersections to accomodate
thermal expansion and other movements of the larger line.]

319.1.1 Piping systems shall have sufficient flexibility to prevent thermal expansion or contraction or
movements of piping supports and terminal points from causing failure of piping or supports from overstress
or fatigue, leakage at joints, or detrimental stresses or distortion in piping and valves or in connected
equipment such as pumps and turbines....

319.2.1(c) Movement due to earth settlement, since it is a single cycle effect, will not significantly
influence fatigue life. [A displacement stress range greater than that permitted by f[1.25(Sc+Sh)] in
302.3.5(d) may be allowable if it can be shown that excessive localized strain and end reactions do not
occur. Some type of plastic analysis including full material plasticity or plastic hinges can be used
to demonstrate that localized strains do not occur. Similar systems subject to the same settlement
magnitudes may be qualified per 304.7.2]

319.2.1(d) Thermal displacments, reaction displacements, and externally imposed displacements all have
equivalent effects on the piping system, and shall be considered together in determining the total
displacement strains in various parts of the piping system.

319.2.3(a) In contrast with sustained stresses, displacement (thermal) stresses may be permitted to attain
sufficient magnitude to cause local yielding in various portions of a piping system. [These displacement
(thermal) stresses diminish with time due to yielding or creep, but the algebraic difference between
strains remains substantially constant during any one cycle, which is used as the criterion in the
design of piping for flexibility...]

319.2.3(c) Average axial stresses over the pipe cross section due to longitudinal forces caused by
displacement (thermal) strains are not normally considered as part of the displacement or thermal solution
since large axial loads are not present in typical piping layouts. In special cases consideration of
average axial displacement (thermal) stress is necessary. Examples include buried lines containing hot
fluids, double wall pipes, and parallel lines with different operating temperatures connected at more
than one point.

319.2.4 When cold spring is properly applied there is less likelihood of overstrain during initial
operation, hence cold spring is recommened especially for piping materials of limited ductility. There
is also less deviation from as installed dimensions during initial operation, so that hangers will not
be displaced as far from their original settings. [Cold spring can also reduce the hot operating stress
and as such may significantly improve creep life of a piping system.]

319.3.1 The temperature range for thermal displacement analysis is from the minimum to maximum
operating temperature for piping operating above the installed temperature, and from the maximum
to minimum operating temperature for piping operating below the installed temperature.

319.3.4 The allowable displacement stress range: [ f[(1.25)(Sc+Sh)-SL] ] shall be for systems primarily
stressed in bending and/or torsion.

319.3.6 In the absence of more directly applicable data, the flexibility factor k and the stress intensification
factor i shown in Appendix D shall be used for flexibility calculations ... [FESIF provides calculated
stiffnesses and stress intensification factors using the exact branch geometry for the user to compare with
values from Appendix D. This comparison with Appendix D values is done automatically by FESIF.]

319.4.3 ... the restraint introduced by support friction shall be recognized [in the evaluation of the piping
system as a whole.]

319.7 Where the piping lacks built-in changes of direction, or where it is unbalanced, large reactions or
detrimental overstrain may be encountered. The designer should consider adding flexibility by one or more
of the following means: bends, loops, offsets, swivel joints, corrugated pipe, expansion joints or other
devices permitting angular, rotational or axial movement. Suitable anchors, ties or other devices shall be
provided as necessary to resist end forces produced by fluid pressure, frictional resistance to movement,
and other causes. When expansion joints or other similar devices are provided, the stiffness of the joint
or device should be considered in any flexibility analysis of the piping.

321.1.1 The layout and design of piping and its supporting elements shall be directed toward preventing
the following: (a) excessive pipe stresses, (b) leakage at joints, (c) excessive thrusts and moments on
connected equipment, (d) excessive stresses in supporting elements, (e) resonance with imposed or fluid
induced vibrations, (f) excessive interference, (g) unintentional disengagement of piping from its
supports, (h) excessive pipe sag in piping requiring drainage slope, (i) excessive distortion or sag of
piping subject to creep under conditions of repeated thermal cycling, or (j) excessive heat flow,
exposing supporting elements to temperature extremes outside their design limits.

321.2.2(c) Sliding supports or shoes and brackets shall be designed to resist the forces due to
friction in addition to th eloads imposed by bearing. The dimensions of the support shall provide for
the expected movement of the supported piping.

321.3.1 If the weight of a vertical pipe is supported by a clamp, [or other nonintegral attachment],
it is recommended to prevent slippage that the clamp be located below a flange, fitting, or that support
lugs be welded to the pipe.

345.9.2 A flexibility analysis of the piping system to be leak tested using an alternative
(sensitive) shall be made in accordance with the requirements of 319.4.2(b) if applicable,
or 319.4.2(c) and 319.4.2(d).

M300(d) Consideration [shall be given to the possible need for additional containment, personnel
protection, shutdown, startup, or failure scenarios that might be damaging to personnel. See
Safeguards Appendix G.]

Note 1 to the B31.3 Flexibility, and Stress Intensification Factor Table D300 states, (1) Stress intensification
and flexibility factor data are for use in the absence of more directly applicable data. Their validity has
been demonstrated for D/T ratios less than or equal to 100.

Note 6 to the B31.3 Flexibility, and Stress Intensification Factor Table D300 states, (6) The designer is cautioned
that cast buttwelded fittings may have considerably heavier walls than that of the pipe with which they are
used. Large errors may be introduced unless the effect of these greater thicknesses is considered.

Note 12 to the B31.3 Flexibility, and Stress Intensification Factor Table D300 states, (12) The out-of-plane
stress intensification factor (SIF) when > 0.5 d/D < 1.0 may be nonconservative. A smooth concave weld
contour has been shown to reduce the SIF. Selection of the appropriate SIF is the designer's responsibility.

Note 13 to the B31.3 Flexibility, and Stress Intensification Factor Table D300 states, (13) Stress
intensification factors for branch connections are based on tests with at least two diameters of straight
pipe on each side of the branch centerline. More closely loaded branches may require special consideration.

Precautionary Appendix F301.7 warns about bowing during cooldown, an effect that can occur usually in
horizontal piping on introduction of a fluid at or near its boiling temperature and at a flow rate that
allows stratified two-phase flow causing large circumferential temperature gradients and possibly
unacceptable stresses at anchors, supports and within pipe walls. Two-phase flow can also generate
excessive pressure oscillations and surges that may damage the piping.

Precautionary Appendix F301.10 warns about the potential for thermal fatigue on surfaces exposed to the
fluid when mixing fluids of different temperatures occur, e.g. cold droplets impinging on the pipe
wall of a hot gas stream as often occurs downstream of desuperheater valves.

Precautionary Appendix F301.11 warns about the possibility of condensation occurring inside
gaseous fluid piping. Means shoudl be considered to provide or trap drainage from low areas to avoid
damage from water hammer, corrosion or erosion.

Precautionary Appendix F309.1 recommends the use of controlled bolting procedures for high, low, and
cycling temperature services, and under conditions involving vibration or fatigue to reduce the potential
for joint leakage due to differential thermal expansion, or the possibility of stress relaxation and loss
of bolt tension.

Precautionary Appendix F323.1 provides the following design points for considerations:

(a) exposure of the piping to fire and the melting point, or point of significant loss of strength.
(b) susceptibility to brittle or other failure from thermal shock when exposed to fire protection measures.
(c) ability of thermal insulation to protect piping against failure during fire exposure
(d) possibility of crevice corrosion under backing rings, in threaded joints or in socket weld joints.
(e) eletrolytic effects in dissimilar metal welds
(f) compatibility of lubricants or seals used on threads with a particular fluid service.
(g) compatibility of seals, packing and o-rings with the fluid service.
(i) chilling effect of sudden loss of pressure on highly volatile fluids in determining lowest temperature.
(j) possibility of pipe support failure due to low or high temperature embrittlement
(k) compatibility of materials in strong oxidizer fluid service, i.e. oxygen or fluorine.

Precautionary Appendix F335.4.1 recommends that consideration be given to the susceptibility of
microbiologically influenced corrosion (MIC). This condition is especially prevalent in no flow,
high moisture environments. Internal MIC may also depend on the characteristics of the treated or
untreated test fluid. Intenral MIC may be lesssened or possibly eliminated by properly draining and
drying systems and/or by proper selection or treatment of the test fluid.

G300(a) Safeguarding is the provision of protective measures to minimize the risk of accidental damage
to the piping or to minimize the harmful consequences of possible piping failure. (b) In most instances
the safeguarding inherent in the facility is sufficient... (c) ... where safeguarding is required by
B31.3 it is necessary to consider only the safeguarding that will be suitable and effective for the
purposes and functions stated in B31.3 or evident from the designer's analysis of the applications.

G300.1 The following items should be reviewed when determining any added degree of safey or precaution
needed with the piping system being designed:

(a) the hazardous properties of the fluid
(b) the quantity of fluid that could be released by piping failure
(c) expected environmental conditions and how it effects a piping failure
(d) the probable extent of operating, maintenance, personnel exposure, and possible damage
(e) the probable need for grounding of static charges to prevent ignition of flammable vapors.
(f) the safety inherent in the piping by virtue of material of construction, method of joining and
history of service reliability.

G300.2 Adding extra safety to an installation (safeguarding) might include:

(a) plant layout, spacing, slopes, buffer areas, etc.
(b) protective installations such as fire protection systems, barricades or shields, instruments for monitoring
(c) containment and/or recovery or facilities for emergency disposal of hazardous materials.
(d) operating practices, such as restricted access, work permit systems or special training.
(e) means for safe discharge of fluids released during a pressure relief, operating, blowdown, cleanout, etc.
(f) procedures for startup, shutdown, and operations management, such as gradual changings of temperature, etc.

G300.3(a) Engineered added safety may be added to systems that includes: (a) thermal insulation, shields or
process controls, (2) armor, guards, barricades, or other protection from mechanical abuse, (3) damping
or stabilization of process or fluid flow dynamics to minimize destructive loads, e.g. severe vibration
pulsations or cyclic operating conditions.

G300.3(b) Engineered added safety may be added to systems to protect people and property against possible
piping failures such as confining and safely disposing of escaped fluid by shields for flange joints, valve
bonnets, gages, or sight glasses, by automatic shutoff or excess flow valves, flow limiting orifices, or
automatic shutdown of the pressure source limiting the quantity of fluid in the process at any one time.

P300(a) Appendix P provides alternate, more comprehensive rules for computing the stress range
and includes an operating stress allowable and recommendations for axial stress intensification
factors. Axial stress intensification factors can be found in FESIF and NozzlePRO for use in
P319.4.4 calculations.

V300(a) B31.3 Appendix V covers applications of the Linear Life Fraction Rule, which provides a method
for evaluating variations at elevated temperatures above design conditions where material creep
properties control the allowable stress at the temperature of variation. Appendix V is a Code requirement
only when specified by the owner in accordance with the last sentence of para 302.2.4(f)(1) for variations
in operating pressure and temperature.

X300 ... The detailed design of all elements of the expansion joint is the responsibility of the manufacturer.
X301.1 The piping designer shall specify all necessary design conditions including:

(.1) The design conditions including any possible variations of pressure or temperature.
(.2) The cyclic conditions including operating, startup, shutdown and abnormal operation.
(.3) All other loads that should be considered including dynamic effects, snow, ice, etc.
(.4) The properties of the flowing medium, its velocity and direction
(.5) Any other conditions that might effect design such as the use of shrouds, external or internal
insulation, limit stops, constraints, and additional attachments such as drains or bleeds.

X302.2.1(c) A full fillet weld may be used as a primary weld to attach a bellows element to an adjoining
piping component.


ANALYSIS NOTES and COMMENTS

1.0 General

Have cyclic system, but good layout should minimize thermal stresses.

The minimum required pipe thickness = 0.0285 in
The nominal pipe thickness = 0.25 in

The pipe minimum thickness is below 20% of the required minimum thickness. Pressure stresses
will likely be low providing good external sustained load carrying capacity.

Per 319.4.1 this system may NOT need a formal analysis.
When Dy/[(K1)(L-U)^2] is less than 1.0 a formal analysis is not required. Max and min
estimated values for Dy/[(K1)(L-U)^2] are given below:

Dy / [(K1)(L-U)^2] = 0.004365 to 0.2420748

2.0 SIFs and Flexibilities

Including intersection flexibilities at full sized branch connections may reduce loads
on the intersections by up to 22.074 %

Thermal Fatigue Safety Factor (Normal)= 3.387
Thermal Fatigue Safety Factor (+Corrosion) = 3.387
Thermal Fatigue Safety Factor (+Corrosion + Sif Anomalies) = 3.387
Thermal Fatigue Safety Factor (+Corrosion + Load Redistribution) = 3.222

Estimated Actual Thermal Fatigue Safety Factor (with Flexibilities) = 3.837 This value reflects
the fact that the general trend is for loads and stresses to be reduced in a more flexible system although this
is a function of geometry and interacting changes in line size.

4.0 Rain Effects

Restrained Stress on Uninsulated Pipe due to Rain = 9519. psi
Top of Pipe Temperature on Uninsulated Pipe in Rain = 95.29 degree F
Free End Liftoff in 100 ft. (30 m.) Due to Bowing = 35.66 in

5.0 Probability of Failure

The calculated probability of failure of this piping system in any one year will
be a function of the line routing, types of intersections, etc. An estimate of
the possible ranges of these probabilities (%) is 0.0001809 % to 0.000216866 %

The calculated probability of injury due to a failure of this piping system in any one
year will be a function of the line routing, types of intersections, etc. This probability
can be compared to the probability of being in an auto accident in any one year. An
estimate of the range of this probability ratio is 0.0302 % to 0.0361 %
In a worst case scenario, it is safer to work near this pipe system than it is to ride
in an automobile.

The calculated risk of operating this piping system in dollars per year is a function of the
line routing, types of intersections, etc. An estimate of the possible ranges of this risk
per year is between $2.71 to $3.25 By comparison, the approximate risk for
operating a car per year is $2.00.


SAFETY EVALUATION

1.0 General

System is relatively safe. Analysis should be reviewed by a senior analyst.
Some design sensitivities exist that should be carefully evaluated.

The pipe is small bore which is easier to analyze. Fewer stress related problems
occur with small bore pipe.

There are elements of the design that require review by a senior analyst.

The fluid service appears to be Normal Fluid Service per B31.3. This type of fluid
applies to most piping covered by B31.3, and is all piping not expressly included
in Category M, D or High Pressure service.

The pipe minimum thickness is below 20% of the required minimum thickness. Pressure stresses
will likely be low, providing good external load carrying capacity.

Per B31.3 319.4.1 the maximum estimated value for Dy/[(K1)(L-U)^2] is 0.242 This value may
or may not be conservative, but when less than 1, indicates that a formal analysis
is not required.

2.0 SIFs & Flexibilities

For a normal system with no SIF, load or flexibility anomalies and D/T < 100, the thermal
(or operating case) safety factor, taken as the mean stress to failure divided by 100% of
the allowable stress is 3.387 This is an acceptable normal safety factor.

For a piping system subject to SIF anomalies, load redistributions due to flexibilities, corrosion or
environmental effects the lowest thermal (operating) safety factor is estimated to be 3.222
Even considering SIF anomalies, environmental effects, corrosion, and load redistribution
due to flexibilities, the system shows to be very safe.

The estimated actual thermal safety factor in this system analyzed with flexibilities = This value
reflects the fact that the general trend is for loads and stresses to be reduced in a more flexible
system although this is a function of geometry and interacting changes in line size.

3.0 Non-Insulated Pipe Rain Caution

If sections of the system are not insulated, stresses due to restraint of the system
caused by bowing developed due to a rain surface temperature differential may be 47.6 %
of the hot allowable stress. In this case the cooled top of the pipe would drop to approximately
95.29 degree F. Movement at free ends can be on the order of several inches in these cases.

4.0 Probability of Failure

Probability of Failure during system life (as calculated) (%) = 0.0180911 %
Probability of Failure during system life (Anomalies in SIFs) (%) = 0.0180911 %
Probability of Failure during system life (Flexibility Reduces Load) (%) = 0.0115075 %
Probability of Failure during system life (Flexibility Increases Load) (%) = 0.0216866 %

Likelihood of plant injury vs automobile accident in any year (as calculated) = 0.030152
Likelihood of plant injury vs automobile accident in any year (Anomalies in SIFs) = 0.030152
Likelihood of plant injury vs automobile accident in any year (Flexibility Reduces Load) = 0.019179
Likelihood of plant injury vs automobile accident in any year (Flexibilityh Increases Load) = 0.036144

Estimated possible injuries per year operating this system (as calculated) = 0.
Estimated possible injuries per year operating this system (Anomalies in SIFs) = 0.
Estimated possible injuries per year operating this system (Flexibility Reduces Load) = 0.
Estimated possible injuries per year operating this system (Flexibility Increases Load) = 0.

Estimated possible dollars per year at risk due to failure (as calculated) = $2.71
Estimated possible dollars per year at risk due to failure (Anomalies in SIFs) = $2.71
Estimated possible dollars per year at risk due to failure (Flexibility Reduces Load) = $1.73
Estimated possible dollars per year at risk due to faiulre (Flexibility Increases Load) = $3.25

Regard

Leonard Stephen THill

 

[Gator]

THill, where did you get that? Are you with PRG?

 

[LSThill]

Gator (Industrial) and TEAM

Gator (Industrial): Mr. LEONARD STEPHEN THILL, Independent Contractoris not with PRG.

Tony gave me the ASME B31.3 Piping Check List on March 31, 2008. in Houston.

Additional work is beeing done on the ASME B31.3 Piping Checkand will be update for Design Verification / Design Validation

Team Member are working on the ASFME SECTION VIII Div 1 and Div 2 Check List.

Best Regards

Leonard Stepehn Thill

L S THILL

 

[Gator]

Leonard, thanks for the reply.

Did you get the 'plug-in-the-variables' software version or just the text you posted?

The software version I saw a month earlier is pretty neat, I hope it gets released soon. Maybe we're not talking about the same thing.

Paul

 

[LSThill]

Gator (Industrial)

Paul contact Tony Paulin for additional Technical Information in regards to ASME B31.3 Piping Checklist build Date March 15th 2008.

Regards
Leonard Stephen Thill, Bombay India

 

[Sid7]

Leonard,

no offense but its no more Bombay, it is Mumbai.

regards

Siddharth
These are my personal views/opinions and not of my employer's.