Dear someone who know,
Our client alway ask about stress checking in operation load case of static calculation, that reported 0 % all node (while sustrain and expansion load case is not 0), and they worry about the stress in operation is over or not if sustrain or expansion load case have stress nearly 100% compare with allowable strss.
How to explain and how to check the stress in operation case.
Thanks you for all reply.

Seng

Since this question has been raised so many times by those who are not familiar with piping code,
I would like to suggest that "N/A" instead of "0 %" be used to avoid "confusion" and repeated explanation.

I suggest a thorough understanding of the piping code which the analysis is predicated upon is required to prevent posts such as this.

If it were up to me people would be required to pass a code specific test before being allowed to use piping flexibilty analysis software. However in todays world of cheaper, faster, better???, this is obviously a sentiment which is out of style and fashion.

"The bad workman blames his tools" American Proverb

Quotes

The "operating load case" (for B31.1, B31.3, and similar codes) is not a stress case. Therefore there is no equation to compute an allowable. This is why CAESAR II puts 0.0 in the allowable stress column for OPE load cases.

The choice of printing "0.0" for the allowable stress is better than having an overflow number to output (Thou shall not divide by zero). However, along the line of thinking by Victor Chen, could the output columns for allowable stress for operating case simply be suppressed?
A closer reading of the query from Seng has the client as the originator of question. I have sympathy for anyone with a client that is not educated enough to understand the Codes that they are responsible to comply for design. But the customer is always right, even when he is ignorant of the facts, logic, laws and Codes. It is not a simple task to explain concepts like the liberal allowable expansion stress, and why the allowable expansion stress could change at each point in the piping system. Any allowable stress for an operating case would be even more complex.
Seng, I would tell your client that the B31 Code considers the sustained stresses separately from the expansion stresses. A different allowable stress value is compared for the susutained stresses and for the expansion stresses. This is a simpler detailed analysis of stresses compared to trying to set an allowable stress for combined loads of an "operating load case". The items of concern for the operating case would be piping deflections plus loads on equipment and support structures.

No not really. Remember, with CAESAR II you can mix codes in an analysis. So perhaps the start of the job is B31.3, where the OPE case allowable stresses are undefined, but later on in the model, you could switch the code to B31.8, where you do have an OPE allowable.

That will not avoid the problem. The question would then be "Why is N/A printed instead of a number?"

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The crux of the issue is that the person asking the question doesn't understand (or hasn't thought about) the logic behind the required load cases. CAESAR II is just a tool that should be used by competent engineers, but by necessity of its complexity, it does require Technical Support from time to time - it just goes with the territory. This particular issue is a favorite.
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Once B31.3-2004 is issued and used for upcoming projects signed say July 2005 or later (Code becomes effective within 6 months after issue/addendum), this issue shall be moot.

B31.3-2004 WILL have an operating stress check requirement apparently limited to Sa the same as the current expansion stress check.

This will be a non-mandatory check for these operating stresses. As such I would expect some mechanism in place in all piping analysis programs to trigger this non-mandatory operating case analysis on a requested basis versus the mandatory code stress compliance.

Note: This will not alleviate the need t review support lift-off the "hot sustained" analysis.

Unfortuanately I see in your statement what may be the tip of a large iceberg bearing down on TG B of B31.3

I hope this helps stay tuned for the published work.

Even though i am relativly new to this buisness, i am constantly fustrated and amazed that any engineering 'muppet' can (and do) perform stress analysis without any proper regulation (ex code)
If i need a licence to drive a car, then surely i must require a licence or authorisation to pass
judgement on engineering/piping issues which can have catastophic consequences.

because of the way the current codes and regulations are set up, people who have absolutly no engineering abillity whatsoever, can bluff and blagg engineering establishments who are only intrested in the number of isometrics which are
produced.

A good example of this is the issue of PRV relief
conditions in a closed system.
Most of these systems can have multiple bends and configurations yet even the COADE caesar course only deals with single bend open systems.
If we search this forum for a discussion on these types of systems, then answers ranging from no analysis to full blown dynamics are offered.

Until the industry tackes this issue, then
these uneducated questions will continue to be asked, and people who just happen to have an engineering charter in knitting will continue to offer opinion on stress analysis.

For someone who is genuinly and honestly trying to become proficient in pipe stress analysis, the lack of information and clarity is most disapointing.

Superpiper,

Waiting for industry to self regulate is like waiting for the next ice age, its coming but not very soon. In our worldwide economy price is the single most important variable.

Clarity and the lack thereof in the piping codes is sometimes deliberate and sometimes unintentional. The committee members do feel strongly that the code is not a hand book nor a cook book.

The next time you have a complaint on the grayness of the code I suggest the following exercise.... Get 50 friends and arrange to meet them at a time and place of your choosing I doubt that you get more than 75% there. The Codes are written and maintained on a consensus basis. And they committees are deliberately structured to have a wide variety of interests. While this structure has proven successful it is slow and tends often times toward gray rather than black and white.

As for qualifications the B31.3 code speak on the qualifications needed, the bottom line is the designer must have demonstrated competence in the field. Its doubtful any of the people on this forum asking about operating stress and why there is no code value, have demonstrated competence (Indeed their questions indicate the opposite) and yet companies merrily hire them because they are the lowest price service available.

That’s it I now relinquish the soap box to somebody else!