A tube, a pipe, and a hose are all long hollow tubular shapes, usually but not always of circular cross-sections, used to convey fluids. The terms "pipe" and "tube" are almost interchangeable, although a tube may sometimes have tighter engineering requirements than a pipe. Both pipe and tube imply a level of rigidity and permanence, whereas a hose is usually portable and flexible.
Tube/pipe fitting is the process of installing or repairing piping or tubing systems. The fitting process includes selecting suitable sizes and materials of tubes, arranging, joining, and installing them to desired functions and routes at specific location. It may also involve detecting and repairing leaks. More specifically, fitting may emphasize on connecting straight pipe sections to adapt to different sizes, directions, and/or shapes, and regulating fluid flow.
Tubes/pipes have very wide range of applications: HVAC, manufacturing, hydraulics, refineries, computer chip fab plants, power plant construction and other steam systems. The common pipes/tubes materials include copper, brass, steel, aluminum, and plastics such as polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC). The bodies of fittings for pipe and tubing are most often of the same base material.
Common fitting shapes for splitting or changes in direction include Elbow, Tee , Cross, Cap, Plug, Nipple, Barb, Reducer. Common methods/fittings to join two tubes/pipes include Threading, Solvent welding, Solidering, and Flanges.