The scope defines the application (and nonapplication) of NFPA 54/ANSI Z223.1. The scope is important because users of this or any code must know whether or not the right document is being used.

Applicability.

The National Fuel Gas Code is the American National Standard that applies to the installation of fuel gas piping systems and equipment and appliances that are supplied with natural gas; manufactured gas; liquefied petroleum gas (LP-Gas) in the vapor phase only; LP-Gas-air mixtures; mixtures of these gases; and gas-air mixtures in the flammable range.

Natural gas, as its name implies, is a naturally occurring product found in many parts of the world. It is recovered by drilling wells into underground pockets of natural gas. The recovered gas is piped to homes and businesses via collection, cleanup, transmission, and utility distribution piping. Another source of natural gas is synthetic natural gas, which is produced by cracking naphtha or other chemical feedstocks to supplement natural gas supplies. Under suitable conditions of elevated pressure and low temperature, natural gas can be liquefied to reduce its volume for purposes of storage or transportation. Liquefied natural gas (LNG) is the source of a larger amount of the natural gas used in North America over the last 5 years, and it appears it will have a larger share in the foreseeable future. The increased use of LNG will have minimal impact on this code, as the gas being delivered to homes and businesses remains the same.

There are no standards or conventions that specify a composition of natural gas. Natural gas consists principally of methane, but it also contains ethane and small amounts of propane, butane, and higher hydrocarbons. Also, natural gas can contain small amounts of nitrogen, carbon dioxide, hydrogen sulfide, and helium. Normally, natural gas contracts specify a heating value [usually 940 Btu/fP to 1080 Btu/ttl {35.0 kJ/ml to 40.2 kJ/ml)J and a maximum amount of hydrogen sulfide [typically 0.3 grl100 tt3 (6.8 mg/m3)]. Hydrogen sulfide is a natural gas contaminant that is corrosive to copper and brass. Some contractual arrangements also limit the carbon dioxide content and water content of natural gas.

Manufactured gas was the first fuel gas distributed in piping systems in cities. It was used in most communities in North America until the early 1950s, when the natural gas transmission system was significantly expanded in the United States. Manufactured gas, a low Btu fuel gas produced by one of several processes, was used primarily for lighting and cooking. Although no longer used in North America (except where produced as a by-product of the manufacture of metallurgical coke), manufactured gas is still used in some other parts of the world.

Manufactured gas was the first fuel gas distributed in piping systems in cities. It was used in most communities in North America until the early 1950s, when the natural gas transmission system was significantly expanded in the United States. Manufactured gas, a low Btu fuel gas produced by one of several processes, was used primarily for lighting and cooking. Although no longer used in North America (except where produced as a by-product of the manufacture of metallurgical coke), manufactured gas is still used in some other parts of the world.

LP-Gases include propane and butane, which are used as fuel gases. Pure propane, due to its low boiling point of approximately -44°F (-42°C), vaporizes rapidly and is used extensively as a fuel gas in colder climates. Pure normal butane, due to its higher boiling point of approximately 31°F (-0.6°C), requires a vaporizer for most applications. It is not widely used in the United States as a fuel gas. It is used in warmer countries as a fuel gas and for other applications not covered by this code.

Propane-air mixtures are used by some gas utility companies to supplement natural gas supplies during peak demand periods, such as in extremely cold weather, and by some large users of natural gas as a standby fuel during periods when natural gas supplies are curtailed or are economically unattractive.

Propane has a significantly higher heating value per unit of vapor volume than natural gas [approximately 2500 Btu/ft³ (93 kJ/ml) versus approximately 1000 Btu/ft³ (37 kJ/m³) for natural gas], and mixing propane with air provides a fuel with burning characteristics similar to those of natural gas. Propane-air mixtures are always well above the upper flammable limit of approXimately 10 percent for propane in air.

The storage, handling, and use of liqUid LP-Gas are not included under the scope of NFPA 54/ANSI Z223.1. NFPA 58, Liquefied Petroleum Gas Code, covers liquid LP-Gas. LP-Gas has two sources: it is a by-product of natural gas production that is removed during the cleanup of natural gas prior to its entering the gas transmission system and it is a product of petroleum refineries.