Flange Load - ANSI Check?
Flange Load - ANSI Check?
(OP)
Hi community,
I've been reading about flange load calculations all over the site (ex: http://www.eng-tips.com/viewthread.cfm?qid=191806), but I have a doubt about the equivalent pressure method used in Autopipe and stated on the Kellogg "Design of piping systems".
The Autopipe software clarifies (haven't seen it on the Kellogg) that the force used in the equivalent pressure calculation is only for tension components, it is reasonable since it will tend to open the joint and produce leakage. My problem and doubt is related to that equation.
On my system the external force is of compression, and on Autopipe the ANSI check syas that the flange is not acceptable since the equivalent pressure is greater than the flange rating; the compression force isn't used at all as stated in the help documentation and results.
Doesn't the external compression force aid in closing the joint and thus reducing the possibility of leakage? Is this a correct reasoning?
Best,
José
I've been reading about flange load calculations all over the site (ex: http://www.eng-tips.com/viewthread.cfm?qid=191806), but I have a doubt about the equivalent pressure method used in Autopipe and stated on the Kellogg "Design of piping systems".
The Autopipe software clarifies (haven't seen it on the Kellogg) that the force used in the equivalent pressure calculation is only for tension components, it is reasonable since it will tend to open the joint and produce leakage. My problem and doubt is related to that equation.
On my system the external force is of compression, and on Autopipe the ANSI check syas that the flange is not acceptable since the equivalent pressure is greater than the flange rating; the compression force isn't used at all as stated in the help documentation and results.
Doesn't the external compression force aid in closing the joint and thus reducing the possibility of leakage? Is this a correct reasoning?
Best,
José
In Vino Veritas





RE: Flange Load - ANSI Check?
It is silly to expect a simple one-liner equation to tell you anything about a body under such complex loading and with complex geometry as is a flange.
If you want a half-way decent answer, use ASME VIII Div 2 or preferably EN 1591 to do your flange analysis.
RE: Flange Load - ANSI Check?
RE: Flange Load - ANSI Check?
Furthermore, AFAIK the EN 1591-1, albeit very complex (and still containing a s***load on errors and typo's), is the current best method for flange analysis.
Unfortunately, Im not that in depth educated on flange leakage methods, However I recently picked up this thread on the linked ASME-PVP Pressure Vessels and Piping Division group.
Few guys who have considerable background on BFJ analysis (incl. Warren Brown) stated that both the VIII-1 and VIII-2 methods have nothing to do with leakage. Not saying that that was (in)directly said by others above, but one may draw that conclusion.
RE: Flange Load - ANSI Check?
I have been reading the EN 1591 and as I reasoned, it takes into account if the external axial force is of compression or tension.
I still can't figure out why autopipe only takes a value for tension. I will have to do some research on the bentley forums.
On my design using autopipe, I have a 10% larger equivalent pressure than the flange rating. There are 3 more steam generators on site, one of them has a pipe design (same materials, diameter and schedule, operating pressure and temp) and dimensions similar to the one I'm dealing with. I've analyzed that pipe, and to my surprise the equivalent pressure is twice the flange rating. This pipe and steam generator had being working for over 7 years without any problems.
So I will take the new design as satisfactory without further calculations.
Anyway I will study flanges in greater detail for a future design.
Best,
José
In Vino Veritas
RE: Flange Load - ANSI Check?
The key to leakage is not a design check, or any design number, but the ASSEMBLY!
RE: Flange Load - ANSI Check?
RE: Flange Load - ANSI Check?