Normalized steel for B16.5 Flanges?

[TomBarsh]

Under ASME Section VIII Division 1 what is the benefit, if any, of specifying normalized steel for standard B16.5 flanges?

I have searched Eng-Tips and seen that others have had the same question. There's been discussion of this issue (as in thread292-16359) but there seems to be no satisfying answer, at least in terms of Code references.

Normalizing is often applied for the purpose of improving notch toughness and impact test properties, and consequently the ability to operate at lower design temperatures (or MDMT). But under ASME Section VIII Division 1 the rated MDMT of standard B16.5 flanges is not a function of the material but rather of the flange pressure-temperature rating as per UCS-66(b)(1)(b). Thus specifying normalizing (when not otherwise required) doesn't gain anything in the MDMT rating.

ASTM material specification A-105 paragraph 5.1 requires normalizing for standard flanges over Class 300 so specifying "N" for such flanges should not be required as the manufacturer should do this anyway.

So, is there any need at all to specifically call out normalized B16.5 flanges for an ASME Section VIII Division pressure vessel?

 

[metengr]

For ASME B16.5 Flanges or flanged fittings, the ASTM material specification is referenced with the listed pressure-temperature rating (-20 deg F minimum) for each Class 150, 300, etc.

Using your specific example, I reviewed the SA 105 material specification, and starting with 5.1, heat treatment is not required except for the following components

.....flanges above 300 Class, and special design flanges, pipe components, and special class or design piping components...

Moving on to paragraph 5.2 in SA 105, it lists the acceptable heat treatments for components that are exempted by 5.1. Any of the following heat treatments are acceptable (not just normalizing) - annealing, normalizing, normalizing and tempering and quenched and tempered.

The reason for requiring any of the heat treatments listed above would assure uniform mechanical properties thru thickness to meet the mechanical property requirements in Tables 3 and 4 of SA 105.

 

[deanc]

Think metengr covers it pretty well as to having uniform properties.

T-your 4th paragraph. Not all vessels require PWHT. Some pieces which are supplied as parts and due to the thickness need to be normalized by themselves. So you return to the SA/ASTM spec. See UW-40(f)(5).

How about a vessel that is made with "stub-outs"?