scope:

The scope defines the application (and nonapplication) of NFPA 54/ANSI 2223.1. 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 fuel gas utilization equipment 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 various 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.

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/ft³- 1080 Btu/ft³ (35.0 kJ/m³-40.2 kJ/m³)] and a maximum amount of hydrogen sulfide [typically 0.3 grains per 100 ft³ (6.8 mg/m³)J. Hydrogen sulfide is a natural gas contaminant that is corrosive to copper and brass. Some contractual arrangements also limit the carbon dioxide and water content of natural gas.

Manufactured gas was the first fuel gas that was 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 is a low Btu fuel gas produced by one of several processes, and it was used primarily for lighting and cooking.

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. 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 of curtailment of natural gas supplies.

Propane has a higher heating value per unit of vapor volume than natural gas [approximately 2500 Btu/ft³ (93 kJ/m³) versus approximately 1000 Btu/ft³ (37 kJ/m³) for natural gas], and mixing it 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.

Commentary Table 1.1 gives typical properties of several fuel gases. Their compositions can vary widely, and the table should not be used for design purposes. Instead, the gas supplier should be contacted for data on the fuel gas to be used.