ANSI B16.5 flanges; reduced length through hub
ANSI B16.5 flanges; reduced length through hub
(OP)
Hi there,
I have a supplier of a component with 4" WN ANSI B16.5 600# RJ flanges. In order to reduce the overall lenght of the component, they reduce the lenght through the hub from stated 4 inch to 3.15 inch, thus saving a total of 1.7 inch on the lenght. The machine new welding ends, seems to be in line with the standard. But what about the lenght? Is it okay to reduce it without any notes or 'special considerations'?
Regards
I have a supplier of a component with 4" WN ANSI B16.5 600# RJ flanges. In order to reduce the overall lenght of the component, they reduce the lenght through the hub from stated 4 inch to 3.15 inch, thus saving a total of 1.7 inch on the lenght. The machine new welding ends, seems to be in line with the standard. But what about the lenght? Is it okay to reduce it without any notes or 'special considerations'?
Regards





RE: ANSI B16.5 flanges; reduced length through hub
Regards,
Mike
RE: ANSI B16.5 flanges; reduced length through hub
RE: ANSI B16.5 flanges; reduced length through hub
Just curious.
Regards,
Mike
RE: ANSI B16.5 flanges; reduced length through hub
RE: ANSI B16.5 flanges; reduced length through hub
RE: ANSI B16.5 flanges; reduced length through hub
Guys, you're being a bit harsh. Note that 11echo stated that as long as you/client are happy. So either I, as the client, don't care about liability due to use of nonstandard components or I've satisfied myself that the design can meet some other generally recognized and accepted engineering standard. We don't know whether this flange has been qualified by burst testing or anything else... Either way, as long as I'm happy... And why should I let a maintenance issue 10 years from now worry me?
jt
RE: ANSI B16.5 flanges; reduced length through hub
So it's not that you're incapable of designing something that's maintainable - you just don't care?
RE: ANSI B16.5 flanges; reduced length through hub
Ummm... ok, you don't know me well... Let me make it loud and clear: That was a huge dose of sarcasm. Believe me, I'm the one harassing project engineers to put in 24" manways instead of saving $100 by putting in an 18".
jt
RE: ANSI B16.5 flanges; reduced length through hub
However, the diameter "X" is the fixed dimension of the hub. The taper of the hub varies between 1:3 and 1:4, continued by the straight portion of the hub. If you can control the machining precision of your machining centre, then make all the hubs of 1:3 taper and make the weld prep at the end of taper, without the straight portion, as allowed by the ASME code. This will shorten the standard flange without modifying or altering the strength of the flange. How much saving, you work it out.
Also, you might need to advise the vessel fabricator to provide extra welding up on the hub taper to generate the required transition of 1:4 taper. You old liar, have you deviced this all by yourself, testing the limits of the conservative people, or intend to propose a fine change to the old cookbook?
Cheers,
gr2vessels
RE: ANSI B16.5 flanges; reduced length through hub
RE: ANSI B16.5 flanges; reduced length through hub
RE: ANSI B16.5 flanges; reduced length through hub
Perhaps we should take it a bit further.
1. The shortened flange geometry resembles the B16.5 shape, but does not conform to the standard requirements.
2. The lengh of the hub, beyond the joint of the taper with the cylindrical end, has nothing to do with the rating. I have requested a FEA analysis for both shapes;- I'll keep you informed as soon as I have the results.
3. The question, in my opinion, is beyond the compliance with the B16.5 requirements. The oldliar seems to be confused by a flange most likely passing the P&T requirements for the equivalent B16.5 flange, despite of some geometric non-conformance. The B16.5 / B16.47 is still under constant review and open for improvement. Perhaps the "short" flange supplier took a little too early step selling them, but is stepping likely in the right direction. Obviously, he will have trouble convincing people to accept his short flanges, without proper backing from the code or other sources.
Any other opinion?
gr2vessels
RE: ANSI B16.5 flanges; reduced length through hub
Hopefully, these are not those damned Chinese flanges ...... or are they ?
That is a topic for another forum..
MJC
RE: ANSI B16.5 flanges; reduced length through hub
If you make these flanges a little shorter still, don't they essentially become slip-on flanges?
RE: ANSI B16.5 flanges; reduced length through hub
My question is only if it's allowed by code to do modifications. In my opinion it's not. And for gods sake, I don't machine these flanges in my garage (or in China for that sake). It's a sub-supplier having some clever idea that he's struggling to give me some good support on.
RE: ANSI B16.5 flanges; reduced length through hub
I think the bottom line is that a modified B16.5 flange is no longer B16.5. It may be safe, it may even be legal (with the proper backup in the form of testing and/or calc's). But it isn't a B16.5 flange. When my wife's boss put a Chevy V-8 into his Volvo wagon (as I found out, not as uncommon as you might think...), you wouldn't expect him to drive in to a Volvo dealer and expect them to cover the engine under warranty... But it is legal, and probably even safe...
jt
RE: ANSI B16.5 flanges; reduced length through hub
jte (Mechanical) Good point.
Now Modified to ASME CODE: Section VIII, Division 1 Replace Flange by Appendix 2 Flanges; Or ASME CODE: Section VIII, Division 2 Add Appendix 3 Flange. This would be legal, and safe.
RE: ANSI B16.5 flanges; reduced length through hub