ASME B16.5 Pressure-Temperature Ratings

[Mailo]

Hello!

I didn't deal with ASME Codes in the past, so I hope you can help me. Thank you in advance.

Problem: I do not understand the Pressure-Temperature Ratings described in B16.5

Example: If I choose a forged ANSI 600 flange (material: A350 LF2), I can stress the flange with a pressure of 87,6 barg at a temperature of 200°C (according to Table 2-1-1). But what's with the wall thickness? Are these ratings related to the ANSI Schedule "STD"?

with best regards
Daniel

 

[jte]

If you expect the flange to fail because it is overstressed, then it is way too thick.

Most folks believe a flange fails not because the steel fails but because the steel deforms and allows the gasket to become unloaded which then opens up a leak path. You might be surprised at how rigid flanges have to be to not rotate off the gasket...

ASME B16.5 flanges have no relationship to ASME pipe schedules.

jt

 

[Mailo]

Thanks for your answer. But where can I read what wall thickness I have to choose ? By today we simply ordered flanges with the wall thickness of the pipes welded on the hub of that flanges. So no flange calculations were done so far.

I don't understand why there are then that pressure-temperature ratings without paying attention to the wall thickness of the flanges

DIN Flanges for example have always the same wall thickness or bore (same diameter and design pressure of course assumed). Therefore, pressure-temperature ratings make there more sense to me.

 

[jte]

Ok, so you're concerned about the thickness at the weld end where the flange is welded to the pipe... I think the simple answer is pretty much what you did: The flange should be ordered with a nominal bore to match the pipe to which it will be welded. If you read B16.5 you'll find that a simple hoop stress calc is made in checking the flange rating.

jt