It is the owner's responsibility to determine which code section is applicable. Sometimes the owner is pushed in the "correct" direction by legal requirements or by their insurence company.

The first article or section of the construction code describes the scope of the document and what type of system it applies to. There is some overlap in some cases and it is the owners responsibility (usually through a design profesional) to select the construction code, i.e., Section I, Section VIII, B31.1, etc., that best suits their needs.

In the case of B31.1 and B31.3, the end use of the system, as described in the first chapter that helps the owner determine which code is applicable. If the piping system is part of a (steam) power system or central heating, or auxillary piping for a power system, B31.1 would typical apply. If the piping is part of a processing system or refinery piping, B31.3 would typically apply.

Pressure or temperature isn't usually the determining factor as to which pressure piping code is applicable.

Good luck - Al

Hi Shane,

In the scope section of each Code there is a detailed description of what is covered by that code.  In general, steam piping and feed water piping is covered by B31.1 and all other process (system) piping is B31.3. 

If you get into oil or gas transmission, or compressor/valve stations fo the same; it is B31.8.

Charles (posting from away from my codes, but pretty cetain of my response) Hall

PS - One thing to consider, many customers want piping installed; and either specify an inappropriate construction code, or none at all.  The first place to look for the appropriate code of construction is the contract specifications.  If it is not specified, good practice is to specify the appropriate code "in house"; and to make the owner aware of any addition cost due to NDE, etc.