one of my calculation are
Flexibility/Gasket Compression Model (Leakage).. 16.87
ANSI B16.5/Equivalent Pressure (Stress)......... 0.35
ASME Model Operating (Stress)................... 1.45
ASME Model Seating (Stress)..................... 1.64
it is OK or faliure?

The program output tells you:

Flexibility/Gasket Compression Model (Leakage).. 16.87 <font color="#0000ff">If less than 1.0 leakage is predicted. You're over 1, so leakage is not predicted.</font>

ANSI B16.5/Equivalent Pressure (Stress)......... 0.35 <font color="#0000ff">If less than 1.0 leakage is predicted. You're less than 1, so leakage is predicted.</font>


ASME Model Operating (Stress)................... 1.45
ASME Model Seating (Stress)..................... 1.64 <font color="#0000ff"> According to ASME Appendix S, these values should be less than 1.0, or leakage is predicted. You're over 1, so leakage is predicted.</font>

To

Richard Ay,

In your above response, please check:

"ASME Model Operating (Stress)................... 1.45
ASME Model Seating (Stress)..................... 1.64
According to ASME Appendix S, these values should be less than 1.0, or leakage is predicted. You're over 1, so leakage is predicted."

ASME SEC VIII Div 1 App-S asks for rigidity factor 'J' to be kept lesser than 1, not the ASME Operating/Seating Stress safety factors. These ASME Operating/Seating Stress safety factors should not be less than 1.


regards,

sam

SO the calculation result can be say not OK, normally it should be all not predict leagage.right?

Sam - You're right, my post above is incorrect. The corrected response is below.

The program output tells you:

Flexibility/Gasket Compression Model (Leakage).. 16.87 If less than 1.0 leakage is predicted. You're over 1, so leakage is not predicted.

ANSI B16.5/Equivalent Pressure (Stress)......... 0.35 If less than 1.0 leakage is predicted. You're less than 1, so leakage is predicted.


ASME Model Operating (Stress)................... 1.45
ASME Model Seating (Stress)..................... 1.64 If these values are less than 1.0 leakage is predicted. You're over 1, so leakage is not predicted.

The ASME Rigidity Factors (which) you didn't quote, should be less than 1.0. If the rigidity factors exceed 1,leakage is predicted.

ASME SEC VIII DIV 1 APPENDIX 2 provides a Flange design guide and a set of stresses to be computed and checked against certain allowables.This is more of a joint integrity approach and there are number of research papers ( past and present) to show that Flange leakage is not a simplistic problem which can be addressed by joint integrity alone, although the approach of this appendix is to address it that way ( this can be read between the lines in the forward for APPENDIX S where reference has been made of APPENDIX 2 ).

APPENDIX S tries to give more insight by adding the flange rigidity factor J.

So to summarize : If your project requirement requires the use of Equivalent pressure approach and your equivalent pressure computation shows that the value is less than that permitted by B16.5/16.47 , It is ok but not a guarantee for a leakage no leakage situation.

If the requirement is the stress check and your allowable is less than computed value you have a problem ( but this is in no way a guarantee for a leakage/no leakage situation)

Thirs if your project requirement calls for a flange rigidity factor check and your value is greater than 1, you have a problem, again this is no guarantee for a leakage/ no leakage situation.

If your project requirements call for a simultaneous qualification by all the methods and there is exceedance in any case , you have a problem.

So first meet the requirements of your project and remember that these approaches are very old ( if I remember correctly the Waters , Rossheim paper was dated 1937 ). Although these approaches are based on solid mathematical foundation and were pioneering works and I am too small a person to comment on them, but based on the published works from that time till date ( many WRC Bulletins have addressed this problem), I think we should opt for more advanced tools and standards like EN1591 which in my opinion addresses this issue in a more involved and state of the art way.

Regards

.........and you might benefit from having a look at this:

http://www.sealeng.com/ase/documents/EN1591_Basis/index_f.html

Regards, John.

See also this book...

http://www.amazon.com/exec/obidos/tg/det...nce&s=books

A fellow Austrian (landsemann) was the originator of some of our problems... (It figures)

Anyhow we have a lot of discussion going on here, on our side of the issue... the design method and science... but ultimately the mechanic in the field also to a great extent determines how leakproof the assembled joint will be...

IMHO he needs to be given clear direction as to what you need... A read of any Dr. Bickfords books will leave you absolutely amazed that ANY flanges can be made leak tight...

So have a nice theoretical discussion but the mechanic with the wrench is the last person in control!

Will Coade include EN 1591 calculation capability in next Caesar-II version ? Will it be possible to use EN 1591 with ASME B 16.5 flange with ASME Sec VIII Div 1 allowable stresses instead of EN 13445 & EN 13480 ?

Till that happens within Caesar-II environment, how are we expected to best perform flange design (stress analysis & leak-tightness) calculation with tensile/compressive forces &/or bending moments ?

Let all the requirements in flange leakage calculation in caesar-ii except equivalent pressure computation be met at least, if project requirement does not specifically asks for equivalent pressure conformance ?

Perfect functioning of bolted joint depends on materials of gasket, flange, bolts, proper assembly procedure of preload specification, flange surface and bolting tools & techniques.
As designers of piping, let us perform our part in the team, at least.

regards,
sam

EN-1591 will not be in CAESAR II Versioon 5.00.

Sam,

CAESAR II uses the equivalent pressure method in the stress check also as the pressure term used is the "equivalent pressure".So there is no escape from "equivalent pressure".

In WRC Bulletin 473 it has been shown that external bending moments do not have a significant effect on the Flange leakage. So many times when we try to "qualify" our system in terms of reducing the external moments by changing layout/supporting is actually not contributing much in solving the real problem.Even if we go in theoretically to address a problem there cannot be any significant insight without considering the creep relaxation effect of gaskets ( particularly at high temperatures) an issue not addressed in the ASME Codes.

I 100 % agree with John C Luf that it is finally the mechanic and the wrench that have a very significant role to play.

To the extent I know PVRC is drafting a new document to specifically address the theoretical analysis of leakage and most of the analysis methods of SEC VIII DIV 1 Appendix 2 will go away ( forum members pl. correct me if I am wrong).

So till that time I feel that we should not try to break our heads much on the 1937 methods.Of course we have to follow project requirements ( I mentioned this in my first response also) religiously even if they are based on the 1937 requirements.

Regards

Wow you have read between the lines peefectly!!!! My cryptic message was meant to convey that all of our work may be quiclkly negated by a bad mechanic. Indeed to do any calculation and then not to provide written directions to the mechanics assembling the joint is like pouring a tablespoon of water on a massive fire.

I have reviewed actual failures of bolted joints in service and usualy they fail for a variety of reasons with no single factor sticking out.

Indeed in one instance a joint failed after being sucessful in service for over 35 years... I finally tracked down the problem... The mechanic who had assembled, maintained and broke down the joint on and off for the 35 years retired. He was replaced by an unskilled mechanic who had no idea how to make up a tight well assembled joint. Therefore this joint experienced a leak....

Everybody felt that it had to be re-designed.... all it needed was a better trained mechanic.

As our mundane questions elicit good discussions from learned minds, we never feel ashemed to 'break our head' by raising query. We do not have enough knowledge or experience and opportunity to paricipate in ASME, WRC, PVRC meetings.

But, we have problems to solve and mentors like you all who help us in need. Let our value system protect us from hiding anything erroneous & compel us to learn continuously keeping customers' safety and interest in mind.

regards,

sam

PS:

http://www.mech.uwa.edu.au/DANotes/threads/home.html

has some study material on this topic.

Sam

Thanks for proving a very informative link on threaded fasteners.

Regards