IHS Markit is your source for standards and codes related to power and Process Piping.

Power piping means piping systems and their component parts, that are not building services piping systems, and that may be installed within electric power generating stations, industrial and institutional plants, utility geothermal heating systems, and central and district heating and cooling systems. Power piping includes, but is not limited to, piping used in the distribution of plant and process steam at boiler pressures greater than fifteen pounds per square inch gauge, high temperature water piping from high pressure and high temperature boilers, power boiler steam condensate piping, high pressure and high temperature water condensate piping, and compressed air and hydraulic piping upstream of the first stop valve off a system distribution header.

Process piping means piping systems and their component parts, that are not building services or power piping systems, and that may be installed in petroleum refineries, chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants, and related processing plants and terminals.

ASME B31.1 - Power Piping
This code contains requirements for piping systems typically found in electric power generating stations, industrial institutional plants, geothermal heating systems, and heating and cooling systems.

ASME B31.3 - Process Piping
This Code contains requirements for piping typically found in petroleum refineries; chemical, pharmaceutical, textile, paper, semiconductor, & cryogenic plants, & related processing plants terminals.