coade c2 forum - occ stresses - allowable

7/30/2019 Coade C2 Forum - Occ Stresses - Allowable

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flexMen(Member)15 July, 200511:55 PM

OCCASIONAL STRESS

This is my doubt.

Imagine a piece of piping with 3 cases of load:

T1= 500T2= 25T3 = 560

If I realize the calculation of those 3 cases of load in 3 different files, the verificacion of occasionalstress code, IS CORRECT.

But analysing the 3 cases together in the same calculating file, the occasional stress es higher than the100%.

The reason of that,I believe is due to that the SH of comparison of occasional stress is taken for thehigher temperature of the 3 cases.

The case that gives an error ( code compliance ) is T2. But this way, the Sh material should be Sh at 25,in my opinion.

I wonder : If the Sh considered by the program is the SH maximun for the 3 cases or only Sh for eachone of the 3 cases??????

I think CAESAR uses the value Sh for the higher temperature of calculation, that is, 560, whatever thecalculation is. And what I think it should do is to use the Sh in each one of the cases separately.

I beg of you to give me a due in such a matter.

Thanks a lot.

John Breen(Member)16 July, 200502:51 AM

Re: OCCASIONAL STRESS

Hello flexMen,

Please explain what the temperature of the piping system has to do with Occasional Load stresses.

Temperature is all about expansion (displacement) stresses (please look at B31.1, paragraph 104.8.3) andthose are secondary stresses. Sustained (additive) loads (please look at B31.1, paragraph 104.8.1) resultin primary stresses and Occasional loads (please look at B31.1, paragraph 104.8.2) also result in primarystresses. When you look at Occasional loading cases you do not use load combinations that includeexpansion/contraction (temperature).

Please provide a listing of all the load cases and combinations that you are running. That will benecessary if someone is to help you sort out your problem.

Regards, John.

Richard Ay (Member)16 July, 200503:02 AM


In determining the allowable stress for an "Occasional load case" ( k*Sh

), CAESAR II uses the Sh

corresponding to the highest temperature vector used in the load cases.

So, in your conditions above, if the load cases contain T1, T2, and T3, then Sh3 will likely be the oneused. If the load cases contain only T1 and T2, then Sh1 will likely be the one used.

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This is why in a simple set of load cases:

1) W+T1+P1 (OPE)2) W+P1 (SUS)3) L1 - L2 (EXP)

The Sh

used for case 2 is the Sh

corresponding to T1, and not the Sh

corresonding to ambient.

flexMen(Member)16 July, 200503:26 AM


Hi, Richard and John.

I dont understand the answers.

I will explain what I think about this matter.

If we look at B31.1----------->

Socc=0,75iMa/z + 0,75iMb/z + Pdo/4t < k SH

0,75iMa/z-----> Doesnt depend on temperature0,75iMb/z-----> Doesnt depend on temperaturePdo/4t -------> Doesnt depend on temperature

At this point we agree.

But when we compare the addition of this values with SH,I dont agree with you.

Richard, you say that the value chosen is the lowest one. Where have you read it in B31.1?. I think,thevalue that must be compared to, is the value of basic allowable material stress at the hot temperatureBUT in the case that we are analysing.

I'm so confused,

regards.

Richard Ay (Member)16 July, 200503:31 AM


Say you have these load cases:

1) W+T1+P1 (OPE)2) W+T2+P1 (OPE)

3) W+T3+P1 (OPE)4) W+P1 (SUS)5) L1 - L4 (EXP)6) L2 - L4 (EXP)7) L3 - L4 (EXP)

Now, when evaluating case 4, what Sh

do you suppose you should use? You must use the lowest value

of Sh. The same argument holds when you address SUS+OCC.

flexMen(Member)

16 July, 200503:45 AM


Yes Richard I understand you, but for me, this a hugh simplification.

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But I think that there would be 3 sustained cases and every sustained case compared to correspondingSh.

According to your opinion, if i do 3 separate calculations (one for T1, two for T2 and three for T3 ), theresults of stress obtaineds will be different with yours.

Richard Ay (Member)16 July, 2005

04:29 AM


Quote:But I think that there would be 3 sustained cases ...You're probably right. Check the Technical Reference Manual on how to propely setup the hot sustainedload cases.

Quote:... and every sustained case compared to corresponding Sh.Don't think I'm going to agree with this statement. While you may have different boundary conditions toevaluate primary streses for the various positions/conditions of the system, using anything other than thelowest S

his non-conservative.

John Breen

(Member)16 July, 200505:35 AM


OK, I have to quit posting in the AM before I have had my coffee. From the above I finally understandyour question. Its all about allowable stress limits. Sorry that I misunderstood.

But now that I understand "a little" I am left to wonder what is the "event" that you are evaluating asyour "occasional" load. Can that event happen at only 25 degrees? Can that event happen at any time thesystem is operating?

Regards, John.

flexMen



Hi John. The matter is that, in case the event happens or not, if the event takes place, the material stresswill be the same as the stress of the material according to the temperature that it presents.



I am still thinking that Caesar does not well enough this verification,without the aim of beginning atechnical argument.What is the purpose of it, for the same piping, for the following four models, the results of theoccassional stress are different?

Model 1: with T1Model 2: with T2Model 3: With T3

Model 4 : With T1, T2 and T3.

Best Regards!

John C. Luf(Member)21 July, 2005

01:11 PM


because the allowable S value the code uses is based upon temperature try reading the code

Edward Klein Re: OCCASIONAL STRESS

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Trust me, my well experienced and educated colleagues know their stuff. Regarding you latest post,where you ran four separate models - two of them would not be a valid analysis for the sustained stressesbecause you wouldn't be be checking against the correct Sh.

I think the part that you are not quite getting is that your system has to satisfy the sustained stressrequirement *at temperature*. As such, your operating temperature is what governs the Sh value.

You make this comment:"But I think that there would be 3 sustained cases and every sustained case compared to corresponding

Sh."

Now, for simplifcation, lets assume that none of your supports lift off. In that case, your calculatedsustained stress is going to be the same for each of your temperature cases. Comparing them in two casesto a higher Sh because the temperature is lower provides no useful information, becuase those samecalculated stresses still have to be lower than the minimum Sh, which is set by the highest operatingtemperature. If you system can regularly see a temperature, your sustained stresses have to be good forthat Sh.

Now, as for the business of Occasional stresses, you say as your opening line:

"If I realize the calculation of those 3 cases of load in 3 different files, the verificacion of occasional

stress code, IS CORRECT."

Actually, no, it isn't, for the same reason I gave above with regard to the sustained stresses. Two of yourthree files are not valid for calculating the sustained and occasional stresses because they do not considerthe highest temperature that your system will operate at.

Now, here's the big if that I think had been hinted at - if you can justify that your occasional load casecan only occur when your system is at T=25F, then I think you could make a case for checking youroccasional stresses based on Sh at 25F. Quite frankly, I can't think of what kind of loading that wouldbe, certainly niether wind nor seismic. If this is your situation, I'd like to hear it in detail.

Otherwise, you need to consider Sh based on the highest temperature. Let's take wind - it is meaningless

to say that your pipe won't be overstressed due to wind load when the pipe is 25F when it will beoverstressed at 560F. The fact that is "passes" at 25F doesn't make your design any good. If it fails at560F, then it is an inadequate design and needs to be better supported/restrained.

John C. Luf(Member)22 July, 200502:04 PM


Post a sign at the fence line of the plant... all occasional loads may pass only when the systems are at25F!!!!!!

flexMen(Member)

23 July, 200512:33 AM


First of all, thank all of you for your answers.

I must say I am not agreeing with your opinions and I will say why:

I calculate my seismic cases as it follows:

Seism 1 = OPE 1 + Seism 1 - OPE 1(Case T high)

Seism 2 = OPE2 + Seism 2 - OPE 2 (Case Environment temperature)

In the case of piping and its butts for seism, those two are with enough gap for a good work in

occasional cases.

By this way, the seism 1, will be the obtained load for from the dilatation point of the pipe till the

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According to that, the stress caused by a seism for the case 2 is much bigger than in the case 1. Oncomparing with the Sh smaller, the pipe will fail for such situation.

For all of that, I think that for the stress Sh, it should be the correspondent for each case of operation,since I do not see that the Code indicates what Sh be the higher T of operation of the line, but THEOPERATING TEMPERATURE, that in the case 2 will be the environment temperature.

Best Regards.

Edward Klein(Member)23 July, 200502:55 AM


flexMen,

I'm afraid I'm having trouble understanding some of the terms you are using as they are very differentfrom what I'm used to hearing here in Texas. I'm making some guesses at what you're trying to say. Canyou clarify these terms:

butts (I think your meaning is restraints, line stops, guides)

dilations (thermal expansion?)

escape run (I can't figure this one out from the context)

However, assuming that butts does mean restraints and dilations refers to thermal expansion, then youare saying pretty much exactly what I said with this part:

"Now, here's the big if that I think had been hinted at - if you can justify that your occasional load casecan only occur when your system is at T=25F, then I think you could make a case for checking youroccasional stresses based on Sh at 25F. Quite frankly, I can't think of what kind of loading that wouldbe, certainly niether wind nor seismic. If this is your situation, I'd like to hear it in detail."

It sounds like your seismic2 case won't have thermal expansion (dilations) becuase it won't be at a high

temperature and you therefore want to be able to use the Sh at the lower temperature to check youoccasional stresses for this case.

The only dispute that I have, and I think Mr. Luf agrees, is, how can you justify that your seismic2 casewon't occur when the system is hot? There's not usually any warning for a seismic event like there wouldbe with a hurricane, such that you could have an orderly shutdown of the unit and get the temperaturedown.



Mr. Klein:

I think you have already understand my dispute,and the reason of using the Sh in each case.

According to your last sentence in your post, and the doubt of if the seismic2 case can occur when thesystem is hot, surely, the answer is YES, but if it happens it wouldn't be the seismic case 2 but the 1, inother words,the hurricane can happen in whatever case,when the pipe is cold and also when it is hot.Ifthe seism happens when the pipe is cold, then, there is no reason to use the Sh smaller,since it is takeninto account that the seism can occur when the pipe is hot in a second state of load. It is in this momentwhen it should be correct the use of a Sh smaller.

Regards,

flexMen(Member)26 July, 2005


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Edward Klein(Member)26 July, 200505:19 AM


flexMen,

I think we're getting closer. Let's say that your occasional load case looks something like this:

W+P1+SEISMIC1

Now, unless you've got lifted supports that need to be removed, you are going to get the same calculatedvalues of stress no matter what T you use in an operating case. You agree that the load needs to bechecked against the lower Sh value due to the higher operating temperature.

So you then ask why not use the higher value of Sh when you run, possibly in a different file, with alower operating temperature.

My question is - why run this case at all? Since you have to run this case against the lower Sh value,running it again against a higher Sh value adds nothing to your analysis and gives you no usefulinformation.

Dave Diehl(Member)26 July, 200507:16 AM


Watch it with that "W+P1+SEISMIC1" load case.

I believe most piping codes calculate stress from "W+P1" and add that stress to the values from"SEISMIC1". No signs come through this. In C2 we call this SCALAR summation.

Using stress from your combination would be ALGEBRAIC summation.

For example, if "W+P1" gives a moment of -10 and "SEISMIC1" gives a moment of +5, the algebraicstress would be based on (-10)+(+5) or -5 while scalar summation would yield (10)+(5) or 15.



Dear Edward and Dave:

Thank you so much for your answers.I know all that you have said but I am not agree with it.

Evidently, if we value an only case W+P1+ Seismic1, we have no other chance to calculate in a suitableway, that to compare this value with the lower Sh, but, in my opinion, there are several "mistakes" inwhat you have post:

1) There is not only a sustained W+P1 but 3, one for each case.

2) There is non only a Seismic1 but 3.

3) I could agree to that the 3 sustained cases be equal(forgetting about non-linear), but seismic 1,seismic2, seismic3, never won't be the same for different states of temperature, since the moment thatthe Seismic1,2 and 3 are calculated in the following way:

-Seismic1 = (Ope1+seismic1)-Ope1-Seismic2 = (Ope2+seismic2)-Ope2-Seismic3 = (Ope3+seismic3)-Ope3

In conclusion:

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Best Regards.



the calculated sustained stresses assuming no non-linearity calculated for T1 T2 and T3 with P being thesame for all three temperatures should be identical, however the allowed code stress varies as a functionof the metals strength at the 3 different temperatures. The higher the temperature the lower the codeallowable.

So if the sustained stresses calculated are the same then the % of the code allowable varies. Thus forinstance a system may not be over-stressed @ T2=25Deg.... it is possible with the same calculatedstresses to be over-stresed at T1 and T3.

Now if it is possible for the plant to be operating during a seismic event (most probable) then thecalculated Occasional stress level must be below the code allowable stresses for all the possibletemperatures the event may occur at...

The bottom line is if Dave, Ed or myself checked your worked you would be quickly be re-doing it... thelast time I did a literature review on the codes or flexibilty analysis I did'nt see a "flexmen" authoringany papers nor did I see "flexmen" as a member of any code comittee so read this final reply.

Take a look through the member list of B31.3 and finally I quote Plato...

"Wise men speak because they have something to say; Fools because they have to say something."

http://en.thinkexist.com/quotation/wise_men_speak_because_they_have_something_to_say/218003.htm



Dear Mr.Luf:

It is incredible to read your technical dissertations and also your magisterial lessons for everything.

You should have to take into account the sentence Stupid is the one who makes stupidities and alsoanother, perhaps not of the same cultural level you have but really true: There are not stupid questionsbut stupid who do not ask questions.

It has nothing to do with me if you belong to one or several committees or not, in the same way, I havenot said if I belong or not to a certain seismology committee. What is certain is that you cannot answerin such a pride way to whatever doubt of anybody only for disagreeing with you.

I do not doubt you know a lot about piping, but you should have to take more lessons in life, to treat

people not like stupid without knowing them.

In no order of life does exist an absolute truth.

Plutarch quotes: The real wise is only severe with himself, with the others, he is kind

And also, the great genius Albert Einstein, suggested once: It is a great relief to know the oneslimitations

My best regards.

SUPERPIPER



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It is up to YOU if you want to comply with the code or not. But, if you do want to comply,(mostcompanies insist)then you have to follow the rules wether you like it or not.I am sure somewhere in B31.3 it states that the Calculated code stress has no relationship to the actualstresses whitnessed by individual fibers etc.

The Code had been constructed on the foundations of skill and commitment brandished by the likes ofthe people who post replies here.(Breen,Luf,Deil,)etc, It is silly to dismiss their opinions on the codes,You need to have your analysis agree with these opinions and rules for code compliance, wether you likit or not.

Personaly, i thing the whole (code stress)thing is Nuts, But it works well, Ensures nobody gets hurt, andpays my wages.

Good Luck

John C. Luf(Member)27 July, 200503:29 AM


The code is a little bit nuts... it is the product of many people of a wide variety of talents andbackground. It is a set of guidelines written by comittee. But it has been quite successful overall andB31.3 is an internationally recognized code.

As for others as well as this particular subject I have said all I care to... advice has been given whether itis used or not its not my concern!



My purpose on writing it is to clarify that in no moment I treated to put into doubt the Code but thecontrary. I only wanted to clarify a personal doubt about occasional loads.

I am always paying attention to the other's opinion and the reading they make about the Code, moreovercoming from a person like John C.Luf, who is involved in the developping of it.

Regards,

John Breen(Member)27 July, 200507:10 AM


Hello all,

I have been lurking here around this thread since it was started and I think it is sad that this discussionseems to have drifted away (from the technical issues) to where some of us are showing disrespect forothers. I would like to congratulate everyone who participated in the discussion of this thread. I think it

is good for all of us to try to understand and be comfortable with what we are doing for a living. Iespecially thank those who, although English is not your first language, have made the effort toparticipate in this English speaking discussion board. This was very unselfish of you and by doing thisyou have brought to the forum, your ideas which we would not have had the benefit of considering ifyou would not have posted. This discussion has been truly international and that is a good thing.

But back to the point at issue. After thinking about the statement of the question, perhaps flexMen maysimply be saying that he understands that when calculating stresses the Code stress limit for the materialat the highest design temperature will a limiting factor in the final design of any system. However, Ithink it may be that flexMen would prefer that C2 do a different comparison for each load (combination)for each temperature (T1, T2, and T3). That would show that the seismic event would have to occur atone of the higher temperatures before Code stress limits would be exceeded. From the COADE point of

view I can see where they could be reluctant to do that because that might be confusing if some personwho is not a piping engineer were to just quickly look through the calculated tabular data. But thenagain, maybe I simply do not understand flexMen's point.

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understanding that it can accommodate all credible loading conditions). That piping system will beexpected to provide a reliable service life of some finite number of years. My understanding of theservice scenario is that the piping system at issue will from time to time be operating at its normaloperating temperature and pressure (something less severe than the design conditions) and it will besubject to normal in-service deterioration. For the sake of discussion, allow me to speculate that thehighest calculated bending stress in the system (at a branch connection of course) is at 75 percent of theCode stress limit. Given enough years of service without upsets the system would (since the Codecovers fatigue fairly well) likely eventually fail due to corrosion (I wont be around that many years).But, due diligence dictates that the upset conditions be considered and included in our analysis eventhough it is at least likely that the piping system at issue will never experience a seismic event.

Consider the piping system at a time when the temperature is 25 degrees F (I do not know if this is anoperating condition or a shut-down condition but no matter). The system then experiences an earthquakeof a non-trivial magnitude. The resulting calculated bending stress are well below the Code limit of 1.33x Sh at the 25 degrees F temperature. The highest bending stress at our branch connection is 125 percentof Sh and there is no yielding of the material at the branch connection or at any other location in thepiping (and I hope that no hangers were broken). Should the designer say ah ha, I was right, theearthquake happened and my piping system is not damaged?

A year later the same piping system is operating at normal operating temperature and pressure and letus (again, for the sake of discussion) assume the temperature is 550 degrees F. Stretching probability(and credibility) a bit, the piping system experiences an earthquake of the same magnitude as the even

of the previous year. This time although the calculated bending stress at our branch connection is (justfor discussion) exactly the same at it was due to the previous event, that bending stress is 138 percent ofSh (at temperature) or 104 percent of yield this time and so there is yielding of the material at the branchconnection and maybe at other locations in the piping. Now remember, these are primary stresses andafter the earthquake rings down there is still a pressure loading at the same temperature (noshakedown to elastic response for these loadings). What if it were thin wall pipe and the hoop(circumferential) stresses (twice the longitudinal stresses in our sustained case) were up at about 80percent of allowable? With the material now yielding due to bending stresses....OOOps! Now,considering the above scenario, what Code occasional stress limit should the piping system be designedfor? 1.33 times Sh at 25 degrees or 1.33 times Sh at 550 degrees? So, if I am understanding theresponses of my esteemed colleagues, that is the essence of the answer you are posing for flexMensquestion.

I would be interested in knowing if I have gotten the question right (if you will comment please,flexMen please expand upon my statement of the scenario) and I would be interested in knowing if Iam understanding the answers correctly (please comment my esteemed colleagues).

And, if you are evaluating stress range per the new B31.3 Appendix P, what do you do with the abovescenario? Hey, just wondering.

Regards, (and play nice), John.

John C. Luf(Member)

27 July, 200510:31 AM


God help us as far as Appendix P is concerned....

People have a hard enough time following the code methods that have been around for over 50 years asthis and other threads indicate... and yes I helped with Appendix P and no I add no technical commentshere at this pointin time.



Dear all:

According to John's Breen post,I'll try to explain in other words.

1) The code calculation for this concrete situation is ASME B31.1

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There are 2 different possible situations where the pipe will operate.

a) The first one, where all the pipe, from the boiler to the turbine, will be at the highest temperature, andthe pipe that goes to the condenser will be at environement temperature.

b)The second case, would be when the bypass valve appears in scene, so that the pipe that runs to thecondenser will operate at a certain high temperature and the zone of turbine entry will be cold.

c)The third case won't be described, since it would be a similar case to the first one, where a second

boiler would appear.

Said that, we can understand easily that the pipe of turbine entry may be very hot (Case a, 560 C),or atenvironement temperature (25C, case b)

The verification of this part of pipe is my discussion issue.

Do not forget what I have said previously in my post, the loads due to seismic event(Seismic1,2=Ope1,2+Seismic-Ope1,2(Algebraic), for that, we will have three seismic values instead ofonly one. Evidently, if there is only a value, the question has no sense).

After all, I am not convinced of when we verify the Socc,in the case b., C2 is comparing against a

temperature which is not the one of the pipe when the event happens, but it would be the temperature ifthe event happened when this part of pipe were working in the case a. Due to this fact, I am not totallyagree with what the C2 calculates.

I hope, I had explained better my doubt and, you , Mr Breen could give me your point of view.

Yours sincerely,

P Massabie(Member)28 July, 2005

03:30 AM


Flexmen,

When I was in the university one professor told us that material (any material) stress analysis had twocomponents, and that these components were in both opposite sides of the stress equations. On one sideare the applied loads, your calculated stresses; on the other side are the material properties. Theprevailing condition is that applied side should be always lower than material side (unless we are talkingabout plastic conformation like extrusion, bending or so). You can play with the loads to reduce thecalculated stresses, but you cannot change the material side unless you change the material itself, OR,you conduct a series of experiments and calculations on the material and convince everyone else that thematerial in that particular case is more resistant than expected. In other words, you will play with safetyfactors and material strength.Said that, your situation is LIKE trying to convince everybody that we are using the wrong material side

of the equation. The conservative point of view (wich is always preferred) is saying that we should usethe lowest SH at calculation. You cant go wrong with that, if the strength is higher then better: you havea hidden safety factor.Regarding you specific topic. Im not sure if the material can remember that it was at certain temperature(ergo at certain SH and SA) and then changed to another temperature (to another SH and SA), but everycalculation points into that direction: The material is able to remember that it was at higher temperatureand his strength is related to that particular temperature, even though, is not anymore at that temperatureAnd I think this is why you should consider always the lowest SH (highest temperature in yourcalculations).Now, YOU are the engineer (or the responsible of this design) you can choose to manually change theSH for your calculations. The code gives permission to do so, but be aware that youre playing with fire.If after the earthquake something noticeable happens to your system the insurance companies are going

to look for someone to blame in order to avoid any payment. If someone goes into your stress files thenyou would have to explain WHY you decided to use a higher stress limit. And of course they are goingto call an specialist, if happens to be one of the supporters of the lowest SH theyre so going to nail

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you will be able to say that you followed the codes to the best of you knowledge and nobody would beable to blame you.

Regards



Dear Mr Massabie:

I am TOTALLY AGREE with you, in everything you have mentioned.

Although I am still thinking that the strict calculation must be done with the correspondantSh, any engineer would be quiet if he is on behalf of safety. But referring to Mr Liang-Chuan Peng, atwhat point can go the safety factor against what economically can mean the excedent of such safety?

A teacher at my university said "If an engineer takes too much factors of safety in his calculations,perhaps, this factor of safety is due to his own unsafety".I say that safety is a very important factor but the economical to assure you such safety it is alsoimportant.

Thank you very much for your comments.

Best Regards.



Perhaps I am overly conservative, it seems so are the majority of opinions expressed by various peoplein this thread your opinion seems to be the only voice supporting your position. However in order toclarify this issue as I understand once and for all for the community of people all around the worldengaged in the design and analysis of piping systems I propose the following. Flexmen can send in acode inquiry to the B31.1 and B31.3 code committees. We each will be meeting soon this September soperhaps this can be settled soon.

I suggest you read the chapter of each code book on how to submit an inquiry. Basically you send aquestion, which reflects your point of view and a Yes or No response. (see link below) If I dont see aninquiry by the end of August I will submit an inquiry to both committees as follows

Proposed Inquiries:

Question1:Does B31.X require that all piping systems be evaluated for Occasional loads such as seismicacceleration forces, wind forces or Pressure relief valve unbalanced relieving loads, non-concurrentlywith each other

Answer1:

Yes, occasional loads shall be considered see para. XXXX

Question 2:Does B31.X when evaluating occasional loads such as seismic acceleration forces; wind forces orPressure relief valve unbalanced relieving loads require that the Sh value used for the code allowedvalue be based upon the maximum operating temperature that the system will be operated at?

Answer2:Yes see para. XXXX

This will help all parties concerned and the community as a whole (Interestingly B31.3 and I believeB31.1 recently balloted something concerning seismic design)

An email sent out to the contact information below should suffice.

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Link for preparation of inquiry per B31.3http://cstools.asme.org/csconnect/pdf/CommitteeFiles/3565.PDF

Contact information for B31.1James N. ShihThe American Society of Mechanical EngineersThree Park AvenueNew York, NY 10016Phone: (212) 591-8539Fax: (212) 591-8501

[email protected]

Contact information for B31.3Noel LoboThe American Society of Mechanical EngineersThree Park AvenueNew York, NY 10016Phone: (212) 591-8540Fax: (212) [email protected]

John C. Luf(Member)12 September,2005 06:35AM


Well I looked over the agenda for the upcoming B31.3 meeting and I do not see any inquiries on thissubject so I will submit the following request for interpretations to these comittees....

B31.1Inquiry:In accordance with ASME B31.1-2004, should piping systems exposed to wind be designed to withstandwind load?

Reply:Yes, see paragraph 101.5.2-------------------------------------------------Inquiry:In accordance with ASME B31.1-2004, Should piping systems in an earthquake-affected area considerearthquake lateral load acceleration forces?

Reply:Yes, see paragraph 101.5.3. Also if the piping may experience another type of occasional load such aswind or pressure relieving forces those loads do not have to be considered as acting concurrently.

-------------------------------------------------Inquiry:

In accordance with ASME B31.1-2004, Should piping systems that become loaded by a pressure reliefevent consider the loads and their calculated stresses as an occasional load?

Reply:Yes, see paragraph 102.3.3-------------------------------------------------Inquiry:In accordance with ASME B31.1-2004, when a piping system operates at multiple sets of coincidentoperating temperatures and pressures, and the system may at any random moment be loaded with anoccasional load such as earthquake, wind, pressure relief, or any other type of occasional load that mayoccur during operation, should the occasional load stresses combined with the sustained stresses (ref:paragraph102.3.2 and 102.3.3) be compared against the lowest value of Sh used in paragraph 104.8.2

(12A) (12B) as determined from all of the operating temperatures?

Reply:

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--------------------------------------------------------------------------------------------------B31.3

Inquiry:In accordance with ASME B31.3-2004, should piping systems exposed to wind be designed to withstandwind load?

Reply:Yes, see paragraph 301.5.2-------------------------------------------------

Inquiry:In accordance with ASME B31.3-2004, Should piping systems in an earthquake-affected area considerearthquake lateral load acceleration forces?

Reply:Yes, see paragraph 301.5.3. Also if the piping may experience another type of occasional load such aswind or pressure relieving forces those loads do not have to be considered as acting concurrently.

-------------------------------------------------Inquiry:In accordance with ASME B31.3-2004, Should piping systems that become loaded by a pressure reliefevent consider the loads and their calculated stresses as an occasional load?

Reply:Yes, see paragraph 301.5.5-------------------------------------------------Inquiry:In accordance with ASME B31.3-2004, when a piping system operates at multiple sets of coincidentoperating temperatures and pressures, and the system may at any random moment be loaded with anoccasional load such as earthquake, wind, pressure relief, or any other type of occasional load that mayoccur during operation, should the occasional load stresses combined with the sustained stresses (ref:paragraph 302.3.6) be compared against the lowest value of Sh as determined from all of the operatingtemperatures be used as the basic allowable stress in paragraph 302.3.6.

Reply:Yes

-------------------------------------------------

I hope these will clear up this matter and take opinions out of the equation although I suppose theanswers will only be the opinions of both comitees.

John C. Luf(Member)13 September,

2005 02:58PM


comments window closes tonight....

John C. Luf(Member)13 September,2005 05:56PM


RFI's have been emailed in so my "conservative" opinion or others questionable opinions will be mootwhen these comittess add their opinions to the issue I will update this thread with the results.

B31.3 will render an opinion by the end of of this month... B31.1 I am unsure of but I believe they willbe a bit longer....

John C. Luf(Member)23 September,2005 03:16


Page 13 of 1


14/19

significantly different in philosophy....

B31.3 05-13065

In accordance with ASME B31.3-2004, when a piping system operates at multiple sets of coincidentoperating temperatures and pressures, and the system may at any random moment be loaded with anoccasional load such as earthquake, wind, or pressure relief, should all coincident operating pressuresand temperatures expected during operation be considered and shall the basic allowable stress used inpara. 302.3.6 be based on the applicable temperature for each condition?

Reply Yes.

TG B originally turned down the request as a consulting question... in other words the question was theresponsibilty of the designer (who should be qualified as outlined in B31.3) but after looking over thisthread and asking me why I sent in the RFI TG A provided the question and response!

Ross Sinclair(Member)11 October,2005 11:41PM


Reading through all of these postings there seems to be a common view that you cant check youroccasional stresses at T2=25degC unless you can ABSOLUTELY guarantee that the occasional event

wont occur under the SUS+T2 situation.

However I dont believe flexMen was trying to say this rather he was trying to say that each caseshould be treated individually i.e.

Case 1 calculate OCC stresses from OPE1+SEIS1-OPE1 using Sh for T1Case 2 calculate OCC stresses from OPE2+SEIS2-OPE2 using Sh for T2Case 3 calculate OCC stresses from OPE3+SEIS3-OPE3 using Sh for T3

What seems to have been overlooked in the ensuing discussion is that the stresses arising from the OCCloads in each of these cases can be different.

To illustrate this consider the following (hypothetical) case as per flexMans original example a steamline to a turbine fitted with a bypass to a condenser.Case 1 T1=500 degC (steamline to turbine hot)Case 2 T2 = 25 degC (system on bypass, steamline at ambient)Case 3 T3 = 560 deg C (steamline to turbine hot)

Assume the following situation:- the pipeline runs along the x-axis- there is a linestop installed on the pipeline with:- gap back (-ve x direction) = 5mm- gap forward (+ve x direction) = 100mm- movements under thermal load at linestop are:- Case 1 dx @ T1 = 80mm

- Case 2 dx @ T2 = 0mm- Case 3 dx @ T3 = 90mm- SEIS load acts in +ve x direction- SEIS load has sufficient magnitude that from any operating condition it will close the forward gap tozero

So the displacements arising from the OCC case would be as follows:- Case 1 = SEIS1 = 100mm gap 80mm dx = 20mm- Case 2 = SEIS2 = 100mm gap 0mm dx = 100mm- Case 3 = SEIS3 = 100mm gap 90mm dx = 10mm

Assuming stresses are proportional to displacements in this case, then the OCC stresses for Case 2 will

be much higher than the other two cases. It seems entirely reasonable that for Case 2 the code checkshould use Sh=25degC to take advantage of the higher allowable. This assumes that all OCC cases arecombined with each OPE case.

Page 14 of 1


15/19

John LufI note that your B31.3 RFI wording was slightly different to that posted on 12 Sept. The phrase:

should the occasional load stresses combined with the sustained stresses (ref: paragraph 302.3.6) becompared against the lowest value of Sh as determined from all of the operating temperatures be used asthe basic allowable stress in paragraph 302.3.6.

became:

.should all coincident operating pressures and temperatures expected during operation be consideredand shall the basic allowable stress used in para. 302.3.6 be based on the applicable temperature for eachcondition?

So with the B31.3 committee response of Yes, my interpretation is that the methods proposed byflexMan are correct provided that he checks all OCC cases against each OPE case.

This is where I become confused this seems at odds with your statement If the work you haveperformed as you proposed to do it was under the jurisdiction of B31.3 your questionable method doesnot meet the requirements of the B31.3 code.

Can you explain how you came to this conclusion given the committee's response?

regards

John C. Luf(Member)12 October,2005 08:47AM


It appeared to me perhaps incorrectly that flexmen was trying to avoid looking at all or at the very leastthe most significant OCC case.

As you have stated the gaps may vary on a system based upon temperature and this is why the algebraicdifferences between operating cases (with U and without) and then a scalar addition with the SUS

stresses is the way to handle the mathmatics for a non-linear system.

Flexmen in this post seemed to be refuting what the comittee stated ....

posted July 27, 2005 11:30 AM--------------------------------------------------------------------------------Dear Mr Massabie:

I am TOTALLY AGREE with you, in everything you have mentioned.

Although I am still thinking that the strict calculation must be done with the correspondantSh, any engineer would be quiet if he is on behalf of safety. But referring to Mr Liang-Chuan Peng, at

what point can go the safety factor against what economically can mean the excedent of such safety?

A teacher at my university said "If an engineer takes too much factors of safety in his calculations,perhaps, this factor of safety is due to his own unsafety".I say that safety is a very important factor but the economical to assure you such safety it is alsoimportant."-------------------------------------------------This post about conservatism led me to believe he was agreeing but disagreeing. The B31 codes allow adesigner to be more conservative in their aproach however for a designer to become less conservativerequires some justification...

And the justification should be agreeable to the apropriate parties.

B31.3 has stated unequivocally that all cases must be examined I suspect B31.1 will render a similiarRFI This removes all speculation out of this issue.

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16/19

2005 01:38AM

I agree with everyone who has the opinion that sus stress should be checked with lowest Sh values (i.e.Sh of highest temperature)While adding occasional stress with sustained stress I also compare them with k*Sh where Sh is of thehighest temperature. However i would like to put one point here.Say in my case there are 2 temperaturesT1 - Design Case. (this is eithre a start-up temperature or the temperature the line may see if there issome malfunctioning in the process)

T2 - Operating case. (This is the temperature at which the system will be running for the max time of theplant life.)

with the above two definations we can consider that T1 is a sort of occasional case. So if we compare thestress of SUS + OCC(Say Seismic) with the Sh of T1 then it would mean we are adding 2 occasionalcases and the design will be too conservative which is not called for.

So in some exceptinal case if the system is showing failure in SUS+OCC stress when compared with Shof highest temprature then can we create seperate model for occasional case with only one tempraturei.e. T2 and compare sus+occ stress with Sh of T2?Will this be in line with the code requirement?

Regards

John C. Luf(Member)13 October,2005 02:24AM


The 31.3 RFI seems clear, if your T1 is an operating temperature then it must be considered....

"B31.3 05-13065

In accordance with ASME B31.3-2004, when a piping system operates at multiple sets of coincidentoperating temperatures and pressures, and the system may at any random moment be loaded with anoccasional load such as earthquake, wind, or pressure relief, should all coincident operating pressuresand temperatures expected during operation be considered and shall the basic allowable stress used inpara. 302.3.6 be based on the applicable temperature for each condition?

Reply Yes."

Gimini55(Member)21 October,2005 07:30AM


Mr. Luf,

I apologize but was reading also B31.1 and I was looking for any exact or same meaning of yourstatement to power piping code. I want t know if this is the case too in B31.1. Thank you.

John C. Luf

(Member)21 October,2005 07:37AM


The RFI I sent to the B31.1 comittee has not been answered yet, however I did furnish them this RFI werendered in B31.3 so if I had to guess their response will be similar in nature....

Gimini55(Member)21 October,2005 08:37AM


Thank you very much Mr. Luf.

Gimini55

Page 16 of 1


17/19

UNPUBLISHED

ASME B31.1 INTERPRETATIONS

To be published within the next Edition or Addenda

WARNING: THERE ARE PROBABLY SOME TYPOGRAPHICAL ERRORS IN

THIS DOCUMENT. PLEASE REVIEW THE ACTUAL INTERPRETATIONFOR THE EXACT WORDING.

Subject: B31.1-2001; Use of other code for Nonboiler External Piping Design,Fabrication and Inspection

Date Issued: January 10, 2007

File: 03-670

Question: Does the B31.1 code allow the design, fabrication and inspection of Nonboiler

External Piping to a different code section such as B31.3?

Reply: Yes. The Introduction to the B31.1 Code states It is the owners

responsibility to select the B31 Code Section which most nearly applies to a

proposed piping installation. Factors to be considered by the owner include:limitations of the B31 Code Section; jurisdictional requirements; and the

applicability of other codes and standards. All applicable requirements of the

selected B31 Code Section shall be met. For some installations, more than oneB31 Code Section may apply to different parts of the installation. The owner

is also responsible for imposing requirements supplementary to those of the

selected B31 Code Section, if necessary, to assure safe piping for the proposedinstallation.

Subject: B31.1-1995; Para. 137.4, Hydrostatic Testing

Date Issued: February 14, 2007

File: 06-1144

Question (1): Does B31.1 require a piping system to be completely filled with water or

other acceptable test medium prior to hydrostatic testing?

Reply (1): Yes, to the extent possible using high point vents or other venting methods

per Para. 137.4.2.

Question (2): Does B31.1 have any requirements or limits regarding the addition of test

medium during the hydrostatic test pressurization?

Reply (2): No.

Subject: Applicability of B31.1 for piping in a gas-cooled nuclear power plant


18/19

Date Issued: February 14, 2007File: 06-1173

Question: With consideration of limitations of the Code Section; jurisdictionalrequirements; and the applicability of other codes and standards, does B31.1

prohibit the owner from selecting B31.1 as the applicable code section fordesign and construction of primary heat transfer piping in a gas-coolednuclear power plant?

Reply: No. Refer to the Introduction for additional information.

Subject: ASME B31.1-2004 Para. 104.8.2 Stress due to Occasional LoadsDate Issued: May 3, 2007

File: 05-1275

Question: In accordance with the Code Para. 101.1, when a piping system operates atmultiple sets of coincident operating temperatures and pressures, and the

system may at random be loaded with an occasional load as defined in Para.

102.3.3, may the maximum allowable stress used in Para. 104.8.2 equations(12A) and (12B) be based on the corresponding temperature for each set of

loading conditions that could occur?

Reply: Yes.

Subject: B31.1-2004 Para. 104.8.2, Stress Due to Occasional Loads

Date Issued: June 11, 1007

File: 03-744

Question: Does the ASME B31.1-2004 Edition define the term owner?

Reply: No.

Subject: B31.1-2004 Para. 136, Visual Examination

Date Issued: October 4, 2007

File: 07-752

Question (1): Is it required that flaws which are found using non-required radiography,

but which could have been found during visual observation of an incomplete weld, meet

the acceptance criteria of Para. 136.4.2(A)?

Reply (1): No, the acceptance standards given in Para. 136.4.2(A) only apply to

completed welds.


19/19

Question (2): Is it required that flaws found during radiography, which is not required,meet the acceptance criteria of Para. 136.4.5(A)?

Reply (2): The acceptance criteria for non-required examinations are not given by theCode. See Interpretation 37-2 of B31.1.

Subject: B31.1-2004 Frame Type Pipe Support

Date Issued: February 26, 2008

File: 04-1467

Question (1): Does subparagraph 130.2 apply to frame type pipe supports? In other

words, shall the frame type pipe support be welded in accordance with therequirements of paragraph 127 and the welders and welding procedure by qualified in

accordance with the requirements of ASME Section IX?

Reply (1): Yes.

Question (2): If the answer to Question (1) is yes, are frame type pipe supports

considered as Supplementary Steel as defined in subparagraph 120.2.4?

Reply (2): No.

Question (3): May the welding requirements of ASME Section IX apply to the

supplementary steel?

Reply (3): Yes.

Subject: ASME B31.1-2004 and 2006 addenda; Table 132, Carbon Content of the

Material and Pipe

Date Issued: March 10, 2008

File: 08-26

Question: In Table 132, for P-No. 4 material, is the condition (d), for an exemption from

mandatory PWHT, met if the throat thickness of the weld is less than or equalto in. and the pipe meets the requirements of conditions (d)(2) and (d)(3)

but the fitting or flange does not?

Reply: Yes.

coade c2 forum - occ stresses - allowable

Documents