Tubing is used to transport fluids and gases in a variety of pneumatic, hydraulic, and process applications. Tubes are usually cylindrical in shape, but may have round, rectangular, or square cross-sections. Tubing is specified in terms of outside diameter (OD) and, depending upon the material of construction, either rigid or flexible.              There are several basic types of products. Metal tubes are made of aluminum, brass, bronze, copper, steel, stainless steel, or precious metals. Plastic tubes are made of ethyl vinyl acetate (EVA), polyamides, polyethylene (PE), polyolefin, polypropylene (PP), polyurethane (PU), polytetrafluoroethylene (PTFE), polyvinyl chloride, or polyvinylidene fluoride (PVDF). Rubber tubes are made of natural compounds such as polyisoprene or synthetic materials such as silicone. Glass and quartz tubes are commonly available. Electrical tubing is designed to contain wires and minimize the risks posed by electrical hazards. Fiberglass tubing is impervious to many caustics and suitable for extreme temperatures. Mechanical tubing includes stronger cross-sections and is designed for structural applications. Medical tubing is usually sterilized and relatively small in diameter.

Selecting tubing requires an analysis of dimensions, performance specifications, opacity, finish and temper. Tubes are specified in English design units such as inches (in) or fractions of an inch, or metric design units such as millimeters (mm) or centimeters (cm). Inside diameter (ID) is a tube’s longest inside measurement. Outside diameter (OD) is a tube’s longest outside measurement. Wall thickness is another important factor to consider. Performance specifications for industrial tubes include pressure rating, maximum vacuum (if applicable), maximum bend radius, and temperature range. In terms of opacity, some tubes are clear or translucent. Others are solid or multi-colored. Polishing or pickling imparts a bright finish. Galvanized tubes are coated with zinc for improved corrosion resistance. Painting, coating, and plating are other common finishing techniques. Annealing improves machinability by removing mechanical stress and altering ductility. Half-hard tubes are manufactured to a Rockwell hardness range of 70 to 85 on the B scale for steel. Full-hard tubes are fabricated to a Rockwell hardness of 84 and higher on this same scale.

Tubing differs in terms of features, applications, and materials transported. Some tubes are coiled, conductive, corrugated, explosion-proof, finned, multi-element or multi-layered. Others are reinforced, spark resistant, sterilized, seamless, welded, or welded and drawn. General-purpose tubing is suitable for a variety of applications. Specialized products are used in aerospace, automotive, chemical, cryogenic, food processing, high purity, high temperature, high viscosity, medical, pharmaceutical and petrochemical applications. Depending on the application, industrial tube is used to transport coolants, hydraulic fluid, salt water, slurries, or water. Slurry tubing is rated to resist the abrasion associated with its transport.