NON STANDARD FLANGE DESIGN AS PER ASME SEC. VIII DIVISON 1 V/s DIVISON 2 9

4.16 is essentially identical to Appendix 2.

As the Division 1 is design-by-rule approach and based on normal stress theory, Division 2 is a design-by-analysis approach and based on maximum distortion energy, Von Mises criteria.
It's possible that the specific non-standard flange design is passed per Div.1 calculation but failed per Div-2 criteria, or vise verse.

thanks TGS4,
mk3223, thanks and ASME SEC. VIII DIV.2 PART 4 also have design by rule approach,
as u said it is possible that flange pass through DIV-1 criteria can fail DIV-2 criteria, does it mean DIV-2 have more stricter rules than DIV-1?
as so far i have designed flanges as per DIV.1, if i try to look into DIV.2 part 4, would i be able to grasp it by self or it is bit difficult and will take some time?

mk3223 - you couldn’t be more wrong. Division 2 is a design-by-rules Code. It also contains the design-by-analysis rules. You are also very wrong about the stress basis, as well - especially for the 4.16/App. 2 flange rules.

So stated above, the 4.16 rules are essentially identical to Appendix 2. Ignore the recommendation from mk3223. Check it out for yourself.

It is an interesting topic. In the US, most flanges used on power plants and some refineries use ASME B16.5 specifications. Those very heavy flanges were designed and qualified around 1933, apparently thru the process of guessing the proportions and proving their capability by pressure testing to failure and dividing that failure pressure by 2 or so. Perhaps no calculations were used.

Fast forward to the 1950's , and Div 1 calculations were developed and non-standard, lighter flanges were then possible for unique situations. Fast forward again to the 1970's and the finite element method of analysis using available computing power was incorporated in the practice of flange design, so Div 2 then adopted this option. The end result appears to be much lighter flanges , generally due to using many more smaller bolts than specified in B16.5, to the result of less pipeline loading and lower thermal stresses during fast startups and shutdowns. In my opinion,the issue with non standard flanges is documenting their applicability ( as each one is designed for a unique situation ) and the possible lack of conservativeness in the assumed max pipeline loads imposed on the flange- I am aware of many situations where excessive pipeline loads can occur due to hitting bumpers or other interferences, negating the designers assumptions.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

Petrotrim Services, LLC

Thanks Davefitz for mentioning the history of calculation evolution, actually you are right that considering external loads is pretty complex task and have to consider lots of things.
Thanks jbeckhou for giving me important information in crisp short manner.

@ jbeckhou
Be careful with this blog. Some things are out of concept or wrong.

Regards

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Petrotrim Services, LLC

OP,
One thing I always think is that Appendix 2 (or 4.16 of Div 2) provide rules for only hydrostatic end loads and gasket seating flange design.
Does anyone considers high external loads (Forces and Moments) from the attached piping caused by thermal expansion and weight that may cause excessive leakage?
Flanges should also pass the rigidity rule.

GDD
Canada