SA-563 DH Nut Impact test?

[jdmech]

When you use SA-354 BD studs, the ASME Section II says they shall be used with SA-563 DH nuts.
ASME VIII DIV.1 UCS-66 gives an impact exemption temperature of 20°F (-7°C) for the SA-354 BD studs but I cannot find the exemption temperature for the nuts.
Does anyone know where to find this?
The vessel design has an MDMT of 6°F so I know the studs will have to be impact tested, but I am trying to figure out what is required for the nuts.

Cheers,
JDMech

 

[jdmech]

I just discovered that in ASME II, SA-563 table 3 note (D) says SA-194 2H nuts are an acceptable equivalent (and they are good to down to -55°F). So, I'm going to use those.