tubes

A tube is a hollow cylindrical object typically used to convey fluids, to serve as a structural member, or as a protective or functional cover. Tubes have an outer diameter (OD) and an inner diameter (ID); the difference is the wall thickness. Cross-sections are usually round, but square and rectangular tubes are common in construction and framing.

Materials and production vary by application. Metal tubes include steel, stainless steel, and aluminum; plastic tubes include PVC, polyethylene, PEX, and PTFE; glass and ceramic tubes are used in specialized settings. Tubes are manufactured as seamless products, formed by drawing or piercing a billet, or as welded products made from rolled sheets joined by seams. Extrusion is common for plastic tubes. Tolerances and surface finishes are specified by standards such as ASTM or ISO, and sizes are described by outer diameter, inner diameter, and wall thickness.

Applications span plumbing and water supply, HVAC and refrigerating systems, automotive and aerospace components, fencing and structural framing, electrical conduits, and medical or laboratory tubing. Medical and biotech fields use sterilizable or biocompatible tubes for catheters, IV sets, and lab fluid handling, while industrial uses emphasize strength, chemical resistance, and dimensional stability.

Key properties to consider include material strength, corrosion or chemical resistance, temperature and pressure ratings, and flexibility or stiffness. Selection depends on fluid compatibility, sanitary requirements, mechanical loads, and manufacturing constraints.