RTJ Flange Bottom Groove Radius

[roca]

Anyone seen this before? Typically the radius is 0.8mm in acc with ASME B16.5

Requirement:
Ring type joint in high pressure and elevated temperature environments. The bottom groove radius shall be 3mm minimum

Reasoning:
Leakage from ring joint flanges in these services has occurred due to cracking emanating from the bottom groove radius - this is typically only 0.8mm and stresses imposed on such a sharp radius causes increased stress intensity which can crack under imposed mechanical and thermal loads.

 

[gr2vessels]

Interesting roca,
Does it require a custom ring gasket also? Would this B16.5 RTJ flange turning into a custom designed flanged joint or will be considered fully B16.5 compliant flange?
Cheers,
gr2vessels

 

[roca]

Thanks - trying to get more info on why it is asked for.
Will be expensive too as these will need special machining to comply.