In ASME B31.8, Page 102 & Clause A842.27 it is given that Support or any attachment should be welded to encircling member & not to pipe directly.

Also on Page 28, Clause 834.5, if pipe is designed to operate at a hoop stress of more than 50 % of the specified minimum yield strength, and then support will be attached to encircling member & not to pipe directly.

Can anyone guide me about these criteria? Why this criterion is been set for? I mean why criteria of 50 % hoop stress is been set?

Please review your undergraduate course material on linear analysis of elastic solids under superposed loads. Then answer your own question.

Honestly, you shouldn't be working on a B31.8 application if you have to ask this question. You're a walking time bomb until you understand what this Code is all about.

it was the silliest answer which i have seen.

I am convince with you perth..Answer like this must be discouraged..

Thanks for your reference. i will go through it.

but here onwards give suggestion only with respect to whatever question asked. & if you dont know the answer or dont wanna share anything on that topic ; then please dont advice whether i have to work on this application or not ? that i will see what to do.

I’ll infringe your rule because I have a great proposal.
What about opening your own Caesar II forum? As a moderator, you can have all the harmony and low-cost knowledge you are looking for. You can get banned CraigB and many others (not me, please, I’ll be your personal adviser).
A lot of advantages, cannot you see the opportunity?

hey guys ,

i just want explanation to my query. why you are sending this irrelevant reply.
i have high respect to Craig B & many other members of the forum. So please if anyone knows something about this please share the information.

I have no idea what is relevant or irrelevant for you.
For example, for me to find-out information by Google is relevant, but I’ve discovered it’s relevant to know some basic words for searching, I mean using hands for asking the display was not relevant…
May you find relevant to buy a book on the subject? I recommend you "Pipeline design and construction: A practical approach". This book has a lot of good information on the subject. It includes relevant words as "localized stress in the pipe", "excessive local stress" "pipes operating with high hoop stress" and so on. You must spend your money to buy it- this would be relevant. But I can see for you is relevant to improve your education so this shouldn’t be a problem.

instead of irrelavant giving advice about education , its better for you to educate yourself about how to behave & how to talk with others. i think it is more important for you. instead of wasting time on sending this irrelavant replies. its better for you to do some work.

now stop giving sending any irrelavant replies.

Dear friend,
The main meaning of education is "the act or process of imparting or acquiring general knowledge"… I really think is better for you to buy a book instead to wait for information from people like me (giving you a head hoop stress over 50%SMYS)
But in a way you are right, I’m just loosing time!

PS I quit the "personal adviser" job :-)

Here's a tip...
You might generate more useful response to your question if you pose it along with your own conclusions.

For example, instead of asking why B31.8 does not allow welding attachments directly to pipe wall where hoop stress exceeds 50% yield, you might want to want to add something like: Is it because B31.8 pipe, with simplified design rules to minimumize pipe wall for pressure, has little residual strength remaining for any additional localized stresses at attachments?

And my answer would be:



Oh, yes AAD, your understanding is correct!
In fact you can analyze how the Code considers the hoop stress by looking in 841.11 Steel Pipe Design Formula. You might note which thickness the Code considers and the fact all the Code (and the Code background and history) is focused to maximize MAOP/ minimize pipe wall. As you say, Code includes just simplified rules for hoop stress and having practically no margin here, the Code has to improve something where is necessary.

PS AAD, buy the book!

thanks mate ,

thanks for all your advice. i will go through the book.

thanks again.

my freid,
you r right but it is important to now 31.8 is not a simplified method for all cases. sometimes the calculated wall thickness in 31.8(class location 4) is thicker than 31.3.

I think you say that, for safety reasons, the B31.8 pipeline hoop stress is not always at high value- that’s why the class location/type of construction exists. Makes sense to consider this fact as invalidating a general rule for supports welded on pipelines operating at high hoop stress?

I think the concept is not to add any local stresses that may be created and transmitted to pipe due to "stress concentrations".

As Dave said:



Any external steel members or supports should not be directly welded to the pipe, instead, you can put a steel pad fully encircled to the pipe and then be welded to the pipe by a full encirclement weld, and the support or steel member can now be attached to the steel pad (not directly to the pipe).