Final answer:
The maximum allowed spacing for supports on NPS 3 horizontal piping is approximately every 10 feet according to ASME B31.1 for carbon steel piping, but the actual requirements depend on the specific piping code, standard, or manufacturer's guidelines applicable to the installation.
Step-by-step explanation:
The maximum allowed spacing for supports on NPS 3 (Nominal Pipe Size 3 inches) horizontal piping is determined by the type of piping, the contents it is carrying, and the standards established by different codes and regulations like the ASME B31.1 for Power Piping, ASME B31.3 for Process Piping, or specific plumbing codes that may vary by jurisdiction. Generally, support spacing is contingent on factors like pipe diameter, material, temperature, and pressure. For example, according to ASME B31.1, the approximate spacing for carbon steel piping is every 10 feet.
However, for definitive guidance on spacing requirements for NPS 3 horizontal piping, one should refer to the specific piping code or standard that is applicable to the installation and the service conditions of the pipe. Furthermore, installation manuals or guidelines from the pipe manufacturer may also have recommendations on support spacing.