Options for fixing Bolt Material requirement from UG-44b, ASME Section VIII, Div.1 Ed.2021

[M. Qaisar]

Generally, bolt material of flanges in vessels & Heat Exchangers under 4-inch size are not meeting the minimum allowable stress limit as specified in UG-44b, ASME Sec. VIII, Div.1. So far what options are available for fixing it. While bolt materials generally have an issue SA-193 Gr. B7 and SA-193 Gr.B8M.

Option already considered but not effective is "Custom flange design with standard flange sizes as per ASME B16.5 /16.47"

 

[cbPVme]

The code is pretty clear here. Look is ASME II-D Table 3 for material with an allowable stress that is equal to or greater than that of SA-193 B8 Cl. 2. If you can't find one than use SA-193 B8 Cl. 2.

 

[M. Qaisar]

As I told earlier that we generally use SA-193 B7 in carbon steel vessels due to several reason one of which is cost as well. So far if we use any other material then we need to ensure compatibility of that bolt material with vessel. And as a mechanical perspective we can't fix this. That's why I ask what we can do for this issue. And if we change the bolt material then on which basis?