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NFPA 56: Standard for Fire and Explosion Prevention During Cleaning and Purging of Flammable Gas Piping Systems
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What is NFPA 56?
NFPA 56: Document Scope

1.1 Scope. 1.1.1* Applicability. This standard shall apply to fire and explosion prevention during cleaning and purging activities for new and existing flammable gas piping found in electric-generating plants and in industrial, institutional, and commercial applications. A.1.1.1 Industrial applications encompass a wide variety of manufacturing and other operations such as, but not limited to, petroleum refining and petrochemical and chemical applications. 1.1.1.1* Coverage of fuel gas piping systems shall extend from the point of delivery or source valve to the gas-consuming equipment isolation valve. A.1.1.1.1 The piping system includes segments located between pieces of equipment, such as gas conditioning or compressing equipment. This document does not cover the commissioning or maintaining of such equipment. However, the standard can be applied to the commissioning or maintaining of those piping segments and equipment as a system where the complete system is purged into or out of service as a unit. The equipment manufacturer’s written instructions should be included as part of the written purge procedure. The equipment isolation valve is intended to be the final isolation valve prior to the manufacturer’s or supplier’s equipment gas train. For some common pieces of equipment in NFPA standards, the isolation valve is identified and referenced as follows: (1) NFPA 37, Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines, uses the term equipment isolation valve in 5.2.1. (2) NFPA 85, Boiler and Combustion Systems Hazards Code, uses the term manual shutoff valve in FigureA.5.3.2.3 for single burner boilers; in Figure A.6.6.5.1.5.4(a) and FigureA.6.6.5.1.5.4(b) for multiple burner boilers; and in Figure A.8.8.5.8(a) through Figure A.8.8.5.8(c) for heat recovery steam generators. (3) NFPA 86, Standard for Ovens and Furnaces, uses the term equipment isolation valve in 6.2.4.1. (4) NFPA 87, Recommended Practice for Fluid Heaters, uses the term equipment isolation valve in 6.2.4.3. 1.1.1.1.1 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)] 1.1.1.1.2 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)] 1.1.1.1.3 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. 1.1.1.2* 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. A.1.1.1.2 Flammable gas container, cylinder, or tank filling operations are not included in the scope of NFPA 56 because there is no gas-consuming equipment. 1.1.2 Nonapplication of Standard. This standard shall not apply to the following items: (1)*Piping systems covered by NFPA 2, Hydrogen Technologies Code A.1.1.2(1) The application of NFPA 2, Hydrogen Technologies Code, is included here for the convenience of the user: 1.3 Application. [2:1.3] 1.3.1 This code shall apply to the production, storage, transfer, and use of hydrogen in all occupancies and on all premises. [2:1.3.1] 1.3.2 The use of hydrogen shall include stationary, portable, and vehicular infrastructure applications. [2:1.3.2] 1.3.3 The fundamental requirements of Chapters 1 through 8 [of NFPA 2] shall apply in addition to the use-specific requirements provided in Chapters 9 through 20, as applicable. [2:1.3.3] 1.3.4 Exemptions. [2:1.3.4 ]This code shall not apply to the following: (1) Onboard vehicle or mobile equipment components or systems, including the onboard GH2 or LH2 fuel supply (2) Mixtures of GH2 and other gases with a hydrogen concentration of less than 95 percent by volume when in accordance with NFPA 55, Compressed Gases and Cryogenic Fluids Code (3) The storage, handling, use, or processing of metal hydride materials outside of metal hydride storage systems defined in Chapter 3 [of NFPA 2] [2:1.3.4] (2)*Piping systems covered by NFPA 51, Standard for the Design and Installation of Oxygen–Fuel Gas Systems for Welding, Cutting, and Allied Processes A.1.1.2(2) The scope and application of NFPA51, Standard for the Design and Installation of Oxygen–Fuel Gas Systems for Welding, Cutting, and Allied Processes, is included here for the convenience of the user: 1.1 Scope. [51:1.1] 1.1.1 This standard applies to the following: (1) Design and installation of oxygen–fuel gas welding and cutting systems and allied processes (see 3.3.2), except for systems meeting the criteria in 1.1.5 (2) Utilization of gaseous fuels generated from flammable liquids under pressure where such fuels are used with oxygen (3) Storage on the site of a welding and cutting system installation of the following: (a) Gases to be used with such systems where more than one cylinder each of oxygen and fuel gas are stored in any single storage area [includes storage of more than one cylinder each in any single storage area even though all such stored cylinders may be intended for use in systems of the kind described in 1.1.5(1)]. (b) Calcium carbide [51:1.1.1] 1.1.2 Unless specifically indicated otherwise, the term welding and cutting systems shall be considered to include allied processes in this standard. [51:1.1.2] 1.1.3 Where only a portion of a fuel gas system is to be used for welding, cutting, or allied processes, only that portion of the system need comply with this standard. [51:1.1.3] 1.1.4 Where only a portion of an oxygen system is to be used with fuel gas for welding, cutting, or allied processes, only that portion of the system need comply with this standard. [51:1.1.4] 1.1.5 This standard shall not apply to the following: (1) Systems consisting of a single cylinder not exceeding 3.4 m3 (120 ft3) of oxygen and a single cylinder not exceeding 3.4 m3 (120 ft3) of fuel gas used for welding and cutting (2) Systems in which fuel gases are not to be used with oxygen, as described in NFPA 54, National Fuel Gas Code, and NFPA 58, Liquefied Petroleum Gas Code (3) The manufacture of gases and the filling of cylinders (4) Storage of empty cylinders (5) Compressed air–fuel gas systems [51:1.1.5] (3)*Piping systems covered by NFPA 51A, Standard for Acetylene Cylinder Charging Plants A.1.1.2(3) The scope and application of NFPA 51A, Standard for Acetylene Cylinder Charging Plants, are included here for the convenience of the user: 1.1 Scope. This standard shall apply to plants that are engaged in the generation and compression of acetylene and in the charging of acetylene cylinders, either as their sole operation or in conjunction with facilities for charging other compressed gas cylinders. [51A:1.1] 1.3 Application. This standard shall not apply to plants that only produce and compress acetylene for chemical operations or to plants that only produce and compress acetylene below a gauge pressure of 15 psi (103 kPa). [51A:1.3] (4) Fuel-dispensing facilities covered by NFPA 52, Vehicular Gaseous Fuel Systems Code. (5)*Piping systems covered by NFPA 54, National Fuel Gas Code A.1.1.2(5) The scope of NFPA 54, National Fuel Gas Code, is included here for the convenience of the user: 1.1 Scope. [54:1.1] 1.1.1 Applicability. [54:1.1.1] 1.1.1.1 This code is a safety code that shall apply to the installation of fuel gas piping systems, appliances, equipment, and related accessories as shown in 1.1.1.1(A) through 1.1.1.1(D) [of NFPA 54]. [54:1.1.1.1] (A) Coverage of piping systems shall extend from the point of delivery to the appliance connections. For other than undiluted liquefied petroleum gas (LP-Gas) systems, the point of delivery 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. For undiluted LP-Gas systems, the point of delivery shall be considered to be the outlet of the final pressure regulator, exclusive of line gas regulators. [54:1.1.1.1(A)] (B) The maximum operating pressure shall be 125 psi (862 kPa). [54:1.1.1.1(B)] Exception No. 1: Piping systems for gas–air mixtures within the flammable range are limited to a maximum pressure of 10 psi (69 kPa). [54:1.1.1.1(B)] Exception No. 2: LP-Gas piping systems are limited to 20 psi (140 kPa), except as provided in 5.5.1(6) [of NFPA 54]. [54:1.1.1.1(B)] (C) Requirements for piping systems shall include design, materials, components, fabrication, assembly, installation, testing, inspection, operation, and maintenance. [54:1.1.1.1(C)] (D) Requirements for appliances, equipment, and related accessories shall include installation, combustion, and ventilation air and venting. [54:1.1.1.1(D)] (6)*Piping systems covered by NFPA 55, Compressed Gases and Cryogenic Fluids Code A.1.1.2(6) The scope of NFPA 55, Compressed Gases and Cryogenic Fluids Code, is included here for the convenience of the user: 1.1 Scope. [55:1.1] 1.1.1 Applicability. This code shall apply to the installation, storage, use, and handling of compressed gases and cryogenic fluids in portable and stationary containers, cylinders, equipment, and tanks in all occupancies. [55:1.1.1] 1.1.2 Specific Applications. This code shall not apply to the following: (1)* Off-site transportation of materials covered by this code (2) Storage, use, and handling of radioactive gases in accordance with NFPA 801, Standard for Fire Protection for Facilities Handling Radioactive Materials (3)* Use and handling of medical compressed gases at health care facilities in accordance with NFPA 99, Health Care Facilities Code (4) Systems consisting of cylinders of oxygen and cylinders of fuel gas used for welding and cutting in accordance with NFPA 51, Standard for the Design and Installation of Oxygen–Fuel Gas Systems for Welding, Cutting, and Allied Processes (5)* Flammable gases used as a vehicle fuel when stored on a vehicle (6)* Storage, use, and handling of liquefied and nonliquefied compressed gases in laboratory work areas in accordance with NFPA 45, Standard on Fire Protection for Laboratories Using Chemicals (7) Storage, use, and handling of liquefied petroleum gases in accordance with NFPA 58, Liquefied Petroleum Gas Code (8) Storage, use, and handling of compressed gases within closed-cycle refrigeration systems complying with the mechanical code (9) Liquefied natural gas (LNG) storage at utility plants under NFPA 59A, Standard for the Production, Storage, and Handling of Liquefied Natural Gas (LNG) (10) Compressed natural gas (CNG) and liquefied natural gas (LNG), utilized as a vehicle fuel in accordance with NFPA 52, Vehicular Gaseous Fuel Systems Code (11)* Compressed hydrogen gas (GH2), or liquefied hydrogen gas (LH2) generated, installed, stored, piped, used, or handled in accordance with NFPA2, Hydrogen Technologies Code, when there are no specific or applicable requirements in NFPA 55 (12) Nonflammable mixtures of ethylene oxide with other chemicals (13) Ethylene oxide in chambers 10 scf (0.283 Nm3) or less in volume or for containers holding 7.05 oz (200 g) of ethylene oxide or less [55:1.1.2] A.1.1.2(1) For regulations on the transportation of gases, see 49 CFR 100–185, “Transportation,” and Transportation of Dangerous Goods Regulations. [55: A.1.1.2(1)] A.1.1.2(3) Bulk compressed gas and cryogenic fluid system installations are intended to be covered by the requirements of this code. Instrumentation and alarms that are attendant to the system and designed to interface with the application in a health care facility are to be retained within the purview of NFPA 99, Health Care Facilities Code. [55: A.1.1.2(3)] A.1.1.2(5) For information, see NFPA 52, Vehicular Gaseous Fuel Systems Code, or NFPA 58, Liquefied Petroleum Gas Code. [55: A.1.1.2(5)] A.1.1.2(6) The storage and use of compressed gases and cryogenic fluids outside the boundaries of laboratory work areas are covered by this code. [55: A.1.1.2(6)] A.1.1.2(11) NFPA 55 is used as the source document for the fundamental requirements for compressed hydrogen gas (GH2), or liquefied hydrogen gas (LH2) system installations. Correlation between NFPA 55 and NFPA 2, Hydrogen Technologies Code, is the responsibility of the two technical committees involved. The installation requirements for bulk GH2 or LH2 are viewed as fundamental provisions. On the other hand, use-specific requirements for designated applications such as vehicular fueling are not resident in NFPA 55 and are under the purview of the NFPA 2 Technical Committee. Where there are specific provisions or controls included in NFPA 55, the specific controls of NFPA 55 will govern except that modifications made to provisions that have been extracted can be followed when the modifications have been made within NFPA’s extract procedure as indicated in the Manual of Style for NFPA Technical Committee Documents. [55: A.1.1.2(11)] (7)*Piping systems covered by NFPA 58, Liquefied Petroleum Gas Code A.1.1.2(7) The scope of NFPA58, Liquefied Petroleum Gas Code, is included here for the convenience of the user: 1.1 Scope. This code shall apply to the storage, handling, transportation, and use of liquefied petroleum gas (LP-Gas). [58:1.1] 1.2 Purpose. (Reserved) [58:1.2] 1.3 Application. [58:1.3] 1.3.1 Application of Code. This code shall apply to the operation of all LP-Gas systems, including the following: (1) Containers, piping, and associated equipment, when delivering LP-Gas to a building for use as a fuel gas. (2) Highway transportation of LP-Gas. (3) The design, construction, installation, and operation of marine terminals whose primary purpose is the receipt of LP-Gas for delivery to transporters, distributors, or users, except for marine terminals associated with refineries, petrochemicals, gas plants, and marine terminals whose purpose is the delivery of LP-Gas to marine vessels. (4) The design, construction, installation, and operation of pipeline terminals that receive LP-Gas from pipelines under the jurisdiction of the U.S. Department of Transportation (DOT) whose primary purpose is the receipt of LP-Gas for delivery to transporters, distributors, or users. Coverage shall begin downstream of the last pipeline valve or tank manifold inlet. [58:1.3.1] (8)*LP-Gas (including refrigerated storage) at utility gas plants (see NFPA 59, Utility LP-Gas Plant Code) A.1.1.2(8) The scope of NFPA 59, Utility LP-Gas Plant Code, is included here for the convenience of the user: 1.1 Scope. [59:1.1] 1.1.1 This code shall apply to the design, construction, location, installation, operation, and maintenance of refrigerated and nonrefrigerated utility gas plants. Coverage of liquefied petroleum gas systems at utility gas plants shall extend to the point where LP-Gas or a mixture of LP-Gas and air is introduced into the utility distribution system. [59:1.1.1] 1.1.2 When operations that involve the liquid transfer of LP-Gas from the utility gas plant storage into cylinders or portable tanks (as defined by NFPA 58, Liquefied Petroleum Gas Code) are carried out in the utility gas plant, these operations shall conform to NFPA 58, Liquefied Petroleum Gas Code. [59:1.1.2] 1.1.3 Installations that have an aggregate water capacity of 4000 gal (15.14 m3) or less shall conform to NFPA 58, Liquefied Petroleum Gas Code. [59:1.1.3] (9)*LNG facilities covered by NFPA 59A, Standard for the Production, Storage, and Handling of Liquefied Natural Gas (LNG) A.1.1.2(9) The scope of NFPA 59A, Standard for the Production, Storage, and Handling of Liquefied Natural Gas (LNG), is included here for the convenience of the user: 1.1 Scope. [59A:1.1] 1.1.1 This standard shall apply to the following: (1) Facilities that liquefy natural gas (2) Facilities that store, vaporize, transfer, and handle liquefied natural gas (LNG) (3) The training of all personnel involved with LNG (4) The design, location, construction, maintenance, and operation of all LNG facilities [59A:1.1.1] 1.1.2 This standard shall not apply to the following: (1) Frozen ground containers (2) Portable storage containers stored or used in buildings (3) All LNG vehicular applications, including fueling of LNG vehicles [59A:1.1.2] (10)*Vehicle fuel dispensers A.1.1.2(10) Vehicle fuel dispensers are covered by NFPA 2, Hydrogen Technologies Code, NFPA 30A, Code for Motor Fuel Dispensing Facilities and Repair Garages, NFPA 52, Vehicular Gaseous Fuel Systems Code, and NFPA 58, Liquefied Petroleum Gas Code. (11) Commissioning and maintenance of equipment (12) Vent lines from pressure relief valves or devices unless such vent lines are also used for purging of flammable gas piping systems (13)*Systems regulated by U.S. Department of Transportation (DOT) 49 CFR 100–199 A.1.1.2(13) DOT regulations in 49 CFR 100–199 govern the transport of gases in commerce by pipelines, motor vehicles, and rail systems. The transportation of compressed gases or cryogenic fluids, including offsite pipeline transmission systems and loading and unloading functions as regulated by 49 CFR, is not within the scope of NFPA 56.

This standard provides minimum safety requirements for the cleaning and purging procedures of flammable gas piping systems, including cleaning new or existing piping systems, purging piping systems into service, and purging piping systems out of service. Official document scope
What does NFPA 56 address?
Provisions apply to all flammable gas piping systems, including those in electric-generating plants, refineries, petrochemical plants, and other commercial and industrial applications. Coverage of piping systems extends from the point of delivery to the equipment shutoff valve, including all valves, regulators, and other appurtenances.
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