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Hose fittings are a category of components used to connect hoses and tubes for in-line, offset, multi-port, and mounting configurations. Typically, hoses and tubes are configured with straight sections connected by fittings or specially-formed connections and joints. Fitting construction and material selection is application-dependent. Some hose fittings rotate or swivel on one or both ends. Others can be disconnected and reused as necessary. Hose fittings are available in both English and metric measurements. English sizes include fractional, inch-based measurements such as 1/16, 3/32, 1/8, 3/16, 1/4, and 1 1/4. Whole-inch measurements between one and ten inches are also available. Metric hose fittings are usually measured in millimeters; however, some centimeter-based devices are also available. Important measurements for hose fittings include inside diameter (ID) and outside diameter (OD). Both must match the connecting line.
There are many types of hose fittings. Examples include adapters, bulkhead fittings, caps compression fittings, couplings, crosses, crimp sockets, elbows, expansion joints, ferrules, glands, nipples, offsets, plugs, reducers, returns, side outlets, tees, and wyes. Typically, elbows are configured for 30°, 45°, 60°, or 90° changes in direction. Concentric reducers join tube sections on the same axis. Eccentric reducers join tube sections that are parallel but not aligned. Tees and wyes are three-port fittings. Tees are shaped like the letter "T" and wyes are shaped like the letter "Y". For both types of hose fittings, standard configurations feature a straight-through path or run with the same size ports as the perpendicular section or branch. With reducing tees and wyes, the branch port is smaller than the run ports. With bullhead tees and wyes, the branch port is larger than the run ports. Union devices are three-part fittings that connect two pieces of tube and allow for disconnection without cutting.
Hose fittings include one or more ports with the same or different styles. Some port styles are defined by a combination of thread type and gender. Common thread types include national pipe thread (NPT) and British standard pipe (BSP). Automotive applications use threads defined by the Society of Automotive Engineers (SAE). Metric thread male, metric thread female, straight thread male and straight thread female hose fittings are also available. Male ends are inserted into female ends to establish connections. Port styles that are not defined by a combination of gender and thread type are often denoted by sealing mechanism, locking mechanism, or shape. Examples include face seals, cam-locks, compression fittings, crimps, flanged, pipes, and tube ports.
Hose fittings are made from a variety of metals and plastics. Aluminum is a lightweight metallic element that offers good electrical and thermal conductivity, high reflectivity, and resistance to oxidation. Brass is an alloy of copper and zinc that provides excellent corrosion resistance, good bearing properties, and low magnetic permeability. Bronze, another copper alloy, is commonly available. Steel is a commercial iron that differs from cast iron both in terms of its malleability and lower carbon content. Stainless steel is chemical and corrosion resistant and can have relatively high pressure ratings. Plastic materials for hose fittings include thermoplastics such as nylon and fluoropolymers.
There are a variety of applications for hose fittings. For example, chromatography fittings are designed and rated for use with high performance liquid chromatography (HPLC) or gas chromatography (GC). Similarly, biomedical and pharmaceutical fittings are designed and rated for use with drugs and/or medical fluids. Specialty fittings are used with lines and systems that transport gases, refrigerants, compressed air, and hydraulic fluids. Insulated, plated, and sanitary fittings are also available.
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