auzie5
Mechanical
- May 8, 2009
- 94
Is it a code requirement (ASME B31.3 or CSA Z662) that flanges have matching inner diameters?
For example:
Can an NPS 8 x STD (ANSI Class 300) RFWN flange be joined to an NPS 8 x XS (ANSI Class 300) RFWN flange without any consideration given to the step introduced from the different flange IDs?
In my mind, the 6.3mm step between flange bores would encourage turbulent flow into the gasket and increase the potential for gasket failure. However, I’ve searched through ASME B31.3 and CSA Z662 and cannot find any restrictions on mating flanges of unequal wall thickness.
In cases where pipe of unequal wall thickness (i.e. XS vs. STD) mate at a flange connection, I’ve always understood it to be prudent to use identical flanges (i.e. matching IDs) and make the following butt joint tapered (as per code allowed detail) to suit the mating pipe wall thickness.
Thanks in advance for any replies.
For example:
Can an NPS 8 x STD (ANSI Class 300) RFWN flange be joined to an NPS 8 x XS (ANSI Class 300) RFWN flange without any consideration given to the step introduced from the different flange IDs?
In my mind, the 6.3mm step between flange bores would encourage turbulent flow into the gasket and increase the potential for gasket failure. However, I’ve searched through ASME B31.3 and CSA Z662 and cannot find any restrictions on mating flanges of unequal wall thickness.
In cases where pipe of unequal wall thickness (i.e. XS vs. STD) mate at a flange connection, I’ve always understood it to be prudent to use identical flanges (i.e. matching IDs) and make the following butt joint tapered (as per code allowed detail) to suit the mating pipe wall thickness.
Thanks in advance for any replies.