What method does Caesar II use for calculating "nominal wall thickness of the matching pipe" per ASME B31.3 note (4) table d300?

The code does not define what is "matching pipe".
I have found this article "Method calculates SIF for branch piping connections"
:
http://www.ogj.com/display_article/18694...ng-connections/

does Caesar II use this method? If not - what method does it uses?

"Matching Pipe" parameters are not computed, they are (defined) input. The diameter and wall thickness of the matching pipe come directly from the spreadsheet (Diameter / Thickness) values.

What thickness of the matching pipe should I use? The actual adjoining pipe to which the branch is connected cannot be interpreted as the matching pipe in many cases because it is not required that adjoining pipe and branch connection have the same design pressure-temperature rating.
ASME B31 Codes provide equations for calculating in-plane and out-plane SIFs for some types of branch connections. These equations are based on the nominal wall thickness of the matching pipe. Therefore, a definition of matching pipe is required, along with a method for determining the nominal wall thickness of matching pipe. The definition of matching pipe, follows from the principle used in pressure design of branch connections: The matching pipe of the branch connection is the calculated straight seamless pipe that has the same pressure-temperature rating as the branch connection.
When using this method It takes a lot of time to calculate wall thickness of the matching pipe...

The thickness you use for "matching pipe" is going to come from the spreadsheet's value of "wall thickness". If the pipe thickness differs from the tee thickness, then model the tee as three short pipes (instead of a point) and specify the wall thickness you want to use.

CAESAR II is not going to "compute" the "matching thickness", it has no idea.

In order to understand the wording of this note, you need to understand how SIF's for tees were developed. This was done using a fatigue testing machine, and real hardware. So, it was convenient for the fatigue tests of tees to be based on the nominal dimensions of the pipe attached to them.

You also have to understand that there is no dimensional standard for tees other than the requirements on overall dimensions and the requirement that the end connections be sized to allow welding to standard pipe sizes. Each vendor is free to use wall thicknesses, crotch radii, and other nonessential dimensions of their own choosing. And they all do. There are burst pressure requirements, and other such things, but they can be, and are, met with many different combinations of internal dimensions.

If you choose to, for example, use a Schedule 80 tee in a Schedule 40 piping system, you probably should use SIF's assuming that the "matching pipe" is Schedule 80 rather than Schedule 40. Richard's note is probably correct from the viewpoint of the internal workings of CAESAR II. The good news is that, if you just accept the values for the Schedule 40 "matching pipe" that CAESAR II will assume, you will calculate a lower number of acceptable fatigue cycles for the schedule 80 tee than you would for doing the calculation rigorously.

And, as Richard's replay states, there is an easy workaround for this if you want to be mathematically rogorous.

You want to say that I have to simply use the nominal wall thickness of tee as "wall thickness of matching pipe"?

yes

Thank you for information