Under the SIF's and TEE's side window in the input spreadsheet, there is a drop down list to select the type of connection.

What is the effective difference between the type 8 and type 9 for socket weld fittings? I see socket fittings coded both ways (I generally use type 9) and I find that either one will give you the 2.1 SIF's as indicated in B31.3.

I've looked through the documentation and the help on the input screen and it's not very clear, other than the "as welded" and "no undercut".

Some codes differentiate between the different types of socket weld fittings, and some do not. For the codes that make a distinction:

Type 8 is a socket weld with a smooth transition of the weld leg parallel with the pipe axis (achieved by grinding and finishing the weld). In other words, a very gradual concave weld surface to minimize the stress intensification at the socket connection. The default SIF here is 1.3, unless the applicable code specifically addresses this configuration.

Type 9 is an unfinished socket weld. The default SIF here is 2.1, unless the applicable code specifically addresses this configuration.