What is the maximum diameter of threaded fittings permitted above according to NFPA 54?

The National Fire Protection Association (NFPA) 54 outlines regulations for the installation of gas piping systems, including specifications for the materials and fittings used. Under these regulations, threaded fittings are permitted for gas piping, but there are limitations on the maximum diameter to ensure safety and integrity in gas systems.

The maximum diameter for threaded fittings specified by NFPA 54 is indeed 4 inches. This restriction is in place to prevent issues that can arise with larger diameters, such as difficulty in achieving a proper seal and increased potential for leaks at the joints. Using fittings larger than this size typically requires different methods of joining, such as welding or flanged connections, which are designed to handle the increased risks associated with larger diameters.

This regulation helps maintain the safety and reliability of natural gas systems by ensuring that fittings can withstand the pressures and stresses involved in gas transportation. Understanding these specifications is crucial for anyone involved in the installation or maintenance of gas piping systems.