NFPA 56

Abstract

Scope: Applicability. This standard shall apply to fire and explosion prevention during cleaning and purging activities for new and existing flammable gas piping found in electricgenerating plants and in industrial, institutional, and commercial applications.  Coverage of fuel gas piping systems shall extend from the point of delivery or source valve to the gas-consuming equipment isolation valve.  For other than undiluted liquefied petroleum gas (LP-Gas) systems, the point of delivery or source valve shall be the outlet of the service meter assembly or the outlet of the service regulator or service shutoff valve where no meter is provided. [54:1.1.1.1(A)] For undiluted LP-Gas, the point of delivery shall be considered to be the outlet of the final pressure regulator, exclusive of line gas regulators where no meter is installed. Where a meter is installed, the point of delivery shall be the outlet of the meter. [54:1.1.1.1(A)]  For facilities that produce flammable gas for consumption on site, the point of delivery or source valve shall be the discharge isolation valve for the gas-producing equipment. Coverage of flammable gas piping systems other than fuel gas piping systems shall extend from the source valve serving the gas supply system to the gas-consuming equipment isolation valve.  Purpose. This standard provides minimum safety requirements for the cleaning and purging of flammable gas piping systems, including cleaning new or existing piping systems, and purging piping systems into or out of service, from the point of delivery or source valve to the equipment isolation valve. For the purposes of this document, a piping system shall be understood to mean a complete piping system, including valves, regulators, and other appurtenances, and any segment thereof that can be isolated from the system.