Tubes are hollow and have circular cross-sections, which are used for conveying media such as fluids, particles, powders and others. The term Pipe is different from tube, because it is mainly used for pipelines and piping systems. The main implementation standard of the pipe is ASME B36.10.
The difference between pipes and tubes
In piping systems, the term pipe is mainly used. NPS is usually adopted for the size of the pipe. SCH is used for wall thickness of pipes. Outside diameters OD and wall thickness WT are usually used for describing tubes (using a Birmingham wire gauge or 1/1000 of an inch). For example, pipe NPS 1/2 Sch40 means that the outer diameter of the pipe is 21.3mm and the wall thickness is 2.77mm. Tube 1/2 × 1.5 means that the outer diameter of the tube is 12.7mm and the the wall thickness is 1.56mm. Tubes are mainly used for heat exchangers, instrumentation tubes and micro-interconnected systems such as compressors, boilers, etc
Materials of the tube
Plumbing companies have materials engineers in-house. Materials engineers determine the materials used in the piping system. Carbon steel is the most used material, depending on service conditions, which is usually manufactured according to various ASTM standards.
Carbon steel has appropriate strength, plasticity, weldability, machinability, durability, and lower costs than other materials. If carbon steel meets the requirements of pressure, temperature, corrosion resistance and hygiene, it is the first choice. There are other materials such as alloys that are added with copper, lead, nickel, aluminum and other composition and various stainless steels. These materials are more expensive, and they were chosen for their advantages of special corrosion resistance, excellent heat transfer or good tensile strength at high temperatures. Copper and copper alloy pipes are traditional instrumentation pipes, food processing pipes and heat transfer pipes. Nowadays, stainless steel pipes are more and more used in these fields.
Lined pipes
Some pipes are used in combination with lining materials. For example, carbon steel pipes may need to be lined with materials such as polyethylene to resist chemical corrosion. Other lining materials include glass, various plastics, cement, and external coating materials such as epoxy materials, asphalt, zinc and other materials, which can protect the lined pipes.
Many factors will influence the choice of materials. The most important factors include pressure, temperature, type of finished products, sizes of piping systems and budgeted costs.