Pipe: tubing, instruments, and concepts

Materials and construction

Pipes are made from a wide range of materials chosen for strength, chemical compatibility, temperature tolerance and cost. Common groups include metals (steel, stainless steel, copper, cast iron), plastics (PVC, CPVC, PE, PP), glass and ceramic, and composite materials. Manufacturing methods vary: seamless extrusion or drawing, welded or cast construction, and plastic extrusion. Surface treatments, linings and coatings are frequently applied to reduce corrosion, erosion or deposit formation.

Dimensions, standards and joints

Pipes are described by internal and external dimensions and by wall thickness; many industries use nominal sizing systems and standardized pressure or temperature ratings to ensure interchangeability. Joining techniques depend on material and service: welding and flanging are common for metal pipes; threaded connections or mechanical couplings are used for smaller lines; solvent welding and heat fusion are used for many plastics. Fittings such as elbows, tees and reducers adapt direction and size within a system.

Applications

• Water and wastewater: delivery mains, distribution and sewer systems.
• Energy and process: oil and gas transmission, chemical plant piping and steam systems.
• Building services: plumbing, heating, air conditioning and fire protection networks.
• Laboratory and instrumentation: small bore tubing for sampling and control.

Other meanings and cultural uses

Outside engineering, "pipe" names several distinct objects. A tobacco pipe is a hand-held bowl-and-stem instrument for smoking, traditionally made of briar, meerschaum, clay or metal. Musical pipes include organ pipes, panpipes and flutes: any hollow resonator that produces sound when air flows through or across it. In computing the word "pipe" denotes a mechanism that transfers data between programs or processes, often in a unidirectional stream.

Safety, inspection and lifecycle

Safety concerns for piping systems include pressure containment, material compatibility, corrosion, blockage, and life-cycle impacts. Inspection and maintenance commonly use pressure tests, nondestructive examination and corrosion monitoring. Design choices favor materials and protective measures appropriate to temperature, pressure and the transported substance. End-of-life considerations and recycling vary by material, and environmental factors influence selection and regulation.

Terminology and distinctions

Practitioners often distinguish "pipe" and "tube": pipe is typically specified by nominal internal diameter and wall schedules for flow-based applications, while tube is commonly specified by precise outside diameter and wall thickness for mechanical or heat-exchange applications. Both terms overlap in everyday use, but the technical distinction helps select the right product for a particular function.