16.34 Compliant Valve Min Temp vs B31.3 Material Min Temp

[DesmoFan]

A manufacturer claims their valve is ASME B16.34 compliant. The material, A351 Gr CF8M, pressure and temp rating listed in B16.34 2004, Mand Appd. VII only goes as low as -20F. B31.3 Table A-1 min temp for the material is -425 F. In paragraph 2.3.2, B16.34 it states the pressure rating at any temperature lower than -20 cannot be greater than that at the lower temp, which it is not. Is this enough to say the valve is compliant or is there further testing that would have been performed such as impact testing? I need to prove to my customer that the valve is compliant with both codes but it is unclear how to connect the dots. Thanks for any help.

 

[XL83NL]

Did you ever find a resolution to this problem?

 

[metengr]

B16.34 it states the pressure rating at any temperature lower than -20 cannot be greater than that at the lower temp, which it is not.

Please read on in this same section of B31.1......

2.3.2 Low Temperature. The pressure rating for service
at any temperature below −29°C (−20°F) shall be
no greater than the rating shown in Table 2 for −29°C
(−20°F). Some of the materials listed in Table 1, notably
some carbon steels, may undergo a decrease in ductility
when used at low temperatures to such an extent as to
be unable to safely resist shock loading, sudden change
of stress, or high stress concentration. Some codes or
regulations may require impact testing for applications
even where temperatures are higher than −29°C (−20°F).
When such requirements apply, it is the responsibility
of the user to ensure these requirements are communicated
to the manufacturer prior to the time of purchase.

So what does this mean?? It means that the pressure rating cannot be greater than the pressure rating for -29 deg C. It does not limit the service temperature to -29 deg C. Therefore, for A 351 Gr CF8M we know this material is austenitic and does not have a ductile to brittle transition temperature (exempt from impact testing), therefore this material is acceptable for use at low temperature (-425 deg F).

 

[metengr]

The above reference to 2.3.2 is from B16.34, and not B31.1.