The type of piping joint used shall be approved for the pressure-temperature conditions and shall be selected giving consideration to joint tightness and mechanical strength under the service conditions. The joint shall be able to sustain the maximum end force due to the internal pressure and additional forces due to temperature expansion or contraction, vibration, fatigue, or the weight of the pipe and its contents. [NFPA 54:5.6.8]
Pipe joints shall be threaded, flanged, brazed, welded, or press-connect fittings made in accordance with CSA LC-4. Where nonferrous pipe is brazed, the brazing materials shall have a melting point in excess of 1000°F (538°C). Brazing alloys shall not contain more than 0.05 percent phosphorus.
Tubing joints shall either be made with approved gas tubing fittings, be brazed with a material having a melting point in excess of 1000°F (538°C), or made by press-connect fittings in accordance with CSA LC-4. Brazing alloys shall not contain more than 0.05 percent phosphorus. [NFPA 54:18.104.22.168]
Flared joints shall be used in systems constructed from nonferrous pipe and tubing where experience or tests have demonstrated that the joint is approved for the conditions and where provisions are made in the design to prevent separation of the joints. [NFPA 54:22.214.171.124]
Metallic pipe fittings shall comply with the following:
- Threaded fittings in sizes exceeding 4 inches (100 mm) shall not be used unless acceptable to the Authority Having Jurisdiction.
- Fittings used with steel or wrought-iron pipe shall be steel, copper alloy, bronze, malleable iron, or cast-iron.
- Fittings used with copper or copper alloy pipe shall be copper, or copper alloy.
- Fittings used with aluminum alloy pipe shall be of aluminum alloy.
- Cast-iron fittings shall comply with the following:
- Flanges shall be permitted.
- Bushings shall not be used.
- Fittings shall not be used in systems containing flammable gas-air mixtures.
- Fittings in sizes 4 inches (100 mm) and larger shall not be used indoors unless approved by the Authority Having Jurisdiction.
- Fittings in sizes 6 inches (150 mm) and larger shall not be used unless approved by the Authority Having Jurisdiction.
- Aluminum alloy fitting threads shall not form the joint seal.
- Zinc-aluminum alloy fittings shall not be used in systems containing flammable gas-air mixtures.
- Special fittings such as couplings; proprietary-type
joints; saddle tees; gland-type compression
fittings; and flared, flareless, or compression-type
tubing fittings shall be as follows:
- Used within the fitting manufacturer's pressure-temperature recommendations.
- Used within the service conditions anticipated with respect to vibration, fatigue, thermal expansion, or contraction.
- Installed or braced to prevent separation of the joint by gas pressure or external physical damage.
- Acceptable to the Authority Having Jurisdiction.