Fitting thickness ASME Section I

[coolniks37]

In boiler piping, as per ASME Section I, is there any requirement that fittings (elbow/tee etc) should have thickness above the nominal thickness of pipe?

I have a pipe layout where the pipe size is 406.4x60mm and required min thickness as per ASME is 40mm.
Can I use a elbow of 406.4x50mm thickness?

Is there any flow/pressure drop considerations to be taken other than strength calc?

 

[GenB]

is it Boiler Propper? BEP. blowdown or other?

 

[coolniks37]

It is boiler proper. ASME Section I design

 

[GenB]

In my opinion The ASME Code sets the minimum sizes, pipe sizes and Schedules according to pressure and temperature. The piping shall be free of restrictions merely for maintenance purposes. Read on Part PG: a cleaning tool needs to have free passage.
other than that a couple millimeters will not affect performance. You have to comply with Part PW regarding welding transitions and that's another thing.