EN 13445-3 Flange design - Assembly conditions vs Operating conditions 1

[SD12]

Hello!

I have a question: What is the purpose of the moment for assembly conditions? To calculate stresses and thickness of a flange we are using moments for operating conditions.
Moment for assembly conditions just adds confusion during calculation and is urealistic huge compared to operation conditions. Any thoughts on this topic?

 

[Christine74]

I'm not familiar with EN 13445-3 but ASME also requires a check for both the Operating and the Gasket Seating case. The Gasket Seating case actually governs in some cases, especially for relatively small-diameter and/or low-pressure flanges.


-Christine

 

[SD12]

Thank you for information.

I have written some questions but by some reason my reply went to the admins for some kind of controll - strange.
If my reply isn't here by tomorrow, I will write it down one more time.

Sergey

 

[Vikko]

Both ASME BPVC VIII Div 1 Apx 2 and EN 13445-3 11 are almost the exactly same thing, based on Taylor Forge method, so check the literature there.

 

[CuMo]

Any flanged joint must be designed adequately for all possible loadings: operating, shop test, site test, assembly & others if applicable such as mechanical loadings, weight loadings, etc.

The worst case (the one that generates the highest stresses therefore the thickest flanges) governs the design.

The assembly condition quite often is governed by the seating loads of the gasket or the hydrostatic pressure during shop test (typically being the highest pressure the joint will ever experience in normal scenarios).

So if you are designing the flanged joint using hand calculations - you must ensure you repeat the calculations for all possible scenarios and loadings - then see which is the worst case (governs the design).

If you're not sure and this is an actual job - ask someone experienced for help. Otherwise the results might catastrophic and lead to serious injury.

Good luck!

 

[SD12]

@CuMo, I do agree with the safety concerns.
But if there is a metal to metal flange, the assembly condition loads makes no sense. There is no way, in my opinion, for flange to fail.

I am talking specifically about this eqaution: W=0.5*(Amin + A)*f (look at attached picture). Then this load is used to calculate the Assembly moment. This load/moment is way larger than seating and operation conditions. There is no way it should govern the design

 

[CuMo]

https://www.eng-tips.com/viewthread.cfm?qid=312283

https://strathprints.strath.ac.uk/5...ry_for_safe_stress_and_no_leak_conditions.pdf