Section I and II-D - SA312 Pipe Permitted but not SA403 fittings?

[Sealboot]

For an ASME Section I superheater coil, SA312 austenitic grades 304,347, etc are permitted to 1500F in ASME II-D, but the corresponding SA403 fittings are listed as not permitted in ASME IID. Does anyone know the reasoning behind this?

 

[XL83NL]

No. Code committee choices or something like that usually, of which the reasoning isn’t filed anywhere. If you need it, write the committee for a chance using a code case.

 

[r6155]

SA-182 304 and 347 (forgins) are OK for 1500F, see note G5

Regards
r6155