1) How you determine the code break point and/or decide to apply B31.1 or B31.3 for steam and condensate piping?

2) Boilers use Boiler codes and Boiler external piping clearly uses B31.1.
What does Nonboiler external piping mean and where does it start and end?

3) Opinions to date:
B31.3 starts at the first block valve on the distribution system at the generation plant.
B31.1 is designed and best suited for steam and condensate piping.
Both codes can be used, pick the one best suited to the situation.

Thank you
Arthur34

The best way to determine the code break point is to open up the code book, look at the diagrams and read the text.

You might start with ASME B31.1, Chapter 1, page 1. That's where the scope is defined. Refer to Figs. 100.1.2(A), (B) & (C). The code break point is clearly shown on the diagrams in the first few pages of the code. Use the one that best represents your boiler. Read the text as well.