Raised face height on flanges 1

[tigny]

Hello,

In the following flanges Standards/Norms, the raised face height is presented or tabulated.


[ol 1]
[li]In ASME standards, the higher the pressure/temperature class, the higher the raised face height:[/li]

ASME B16.5-2020 states "1,5 mm raised face regularly furnished on Classe 150 and 300 unless otherwise ordered"; "6,4 mm raised face furnished on Classe 400 and higher unless otherwise ordered"
ASME B16.47 is essentially saying the same.​

[li]European norm EN 1092-1:2018 gives raised face height depending on DN rather that on Pressure/Temperature relation[/li]
[/ol]

2 mm from DN 10 to DN 32; 3 mm from DN 40 to DN 250; 4 mm from DN 300 to DN 500; 5 mm from DN 600 to DN 4000.​

However, there seems to no writing in Design by Rules ASME BPVC.VIII.1 APPENDIX 2 about raised face height.


I am wondering if there is a rationale for the value of raised face height on those flanges ?

Has is something to do with bearing stress on the outer diameter location of the raised face (especially if using a self energizing gasket in a groove, which implies contact of raised faces, but also with ring joint gasket of the ASME B16.21 or EN 1514-1); the higher the raised face, the better the strain and stress repartition?
Do you know of papers dealing with this subject?

Or is it just in relation to the general dimensions of the flange (which is more obvious with EN 1092-1 flanges)?


best regards

 

[SnTMan]

tigny, per Apx 2 (disremember where exactly) raised faces of up to 1/16 in may be included in the calculated thickness. Greater RF thicknesses are additive.

No idea on basis for RF thickness in those flange stds.

Regards

Mike


The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[r6155]

A thick RF is very useful, sometimes it is necessary to remachine in situ.
It may be that this detail has been considered in the standards, but I don't know.

Regards

 

[jt1234]

Go ask flange manufacturer why. One I have used in the past: Forged Components Inc. They have shops in Texas, Alberta Canada.

 

[LittleInch]

My guess is that it just makes for one mould or machining for both RF and RTJ flanges. You don't normally see RTJ below class 600 and 400 is obsolete.

Sometimes things just ARE, the reason is lost in history.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[tigny]

Hello SnTMan, r6155, jt1234, LittleInch,

thank you for your diverse anwsers to my questions.

best regards