Gas fittings are specifically designed for use with gases, such as flammable propane or hazardous phosgene. These types of fittings have a reverse thread; meaning, the threads are cut in the reverse direction from all other fittings so that gas lines cannot be connected to air lines, water lines, or vent lines. Common applications for gas fittings include use in gas mains, residential gas lines, propane tanks, medical use, hazardous gas applications, and explosives.
Gas fittings come in a variety for styles, depending on the application. Common styles for gas fittings include adapter, cap or plug, coupling, cross or 4-way, 45 or 90° elbow fittings, 30 or 60° fittings, pitless adapter, quick couplers, return or trap, tee, union, well cap, and wye.
When choosing gas fittings, connection selection is an important consideration that should be made based on the application. Some common examples of gas fitting connections include ball and sleeve, cam-lock (male or female), crimp connections, flange or flare connections, threaded (male or female), straight or tapered connections, luer lock, and compression fitting. There are other, unlisted connection types that may also be considered.
Another factor to consider when choosing gas fittings is the material type used. Fittings can be made from a variety of materials including aluminum, brass or bronze, composite fiberglass or graphite, ceramic, copper, polyvinyl chloride (PVC) or chlorinated polyvinyl chloride (CPVC), fluroresin, glass, cast or ductile iron, rubber or elastomer, polyethylene (PE), polypropylene (PP), carbon or alloy steel, and stainless steel.
Special features are commonly available for gas fittings, including: bulkhead fitting, bullhead fittings, expansion joint, flexibility, insulated and lined fittings, plated gas fittings, size reducing options, side outlets, swivel feature, and underground rated fittings. Gas bulkhead fittings are designed to be mounted in a wall or bulkhead to allow tube connections on either side of barrier. Bullhead fittings are in a T-shape, in which the branch port is larger than the run ports. Expansion joints and couplings connection sections of tube and allow for movement due to service load, shock, or thermal cycling.
Insulated, lined, and plated gas fittings are also available. Insulated fittings contain insulated materials and jacket construction. Lined fittings are commonly for use in applications where cleanliness is important. The lining in these fittings are often made from engineered polymers. Plated fittings are available with nickel or chrome – for appearance or corrosion resistance purposes.
Gas fittings may also be reducing, side outlet, swivel, or underground rated. Size-reducing fittings can collapse in side. Side outlet fittings have more than two connections, which are often placed on the side of the main component. Swivel gas fittings allow one or more fitting ends to rotate of swivel. Underground rated gas fittings are designed and constructed for underground applications. Other, unlisted applications and features for gas fittings may also be available.
ASTM C1541 + REDLINE - Standard specification for shielded transition couplings using flexible polyvinyl chloride (PVC) gaskets to connect dissimilar DWV pipe and fittings
ASTM F2817 - Standard specification for PVC gas pressure pipe and fittings for maintenance or repair
BS EN 10301 - Steel tubes and fittings for on and offshore pipelines - internal coating for the reduction of friction for conveyance of non corrosive gas