Pipe and Tube

Thread Content

Pipe and Tube are two different series of pipes, with varying diameters, connection methods, representation styles, and areas of application. The differences between Pipe and Tube lie mainly in the following five aspects: 1. Pipe refers to tubes with large diameters, with diameters generally ranging from 15mm to 1500mm (1/2in to 60in). There are also Pipe pipes that are smaller or larger than this range, but they are used very rarely. Tube pipes are pipes with a small diameter, generally ranging from 3mm to 12mm (1/8in to 1/2in). 2. The connection methods for pipes include flange connection, threaded connection, and welding connection. Flange connection is used in most cases, while threaded connection is permitted in low-pressure applications. The wall of the Tube is very thin, so threading cannot be applied to it; after annealing, it is connected using a ferrule. 3. The nominal diameter DN of a Pipe is used to indicate the size of the pipe. The nominal diameter is neither equal to the outer diameter nor the inner diameter of the pipe. It is a standard dimension value common to all components in a piping system, including pipes, flanges, valves, fittings, etc. Pipes, flanges, valves, and fittings with the same nominal diameter can be connected to each other, regardless of whether their other dimensions (outer diameter, inner diameter, wall thickness, etc.) are identical. In short, the use of nominal diameter simplifies and standardizes the connections between pipes and fittings; this is why the pipe diameter in Pipe systems is denoted by DN. The outer diameter OD (outside diameter) of a Tube is used to indicate its size; for example, 1/4 in OD Tube refers to a Tube with an outer diameter of 1/4 inch. Since Tube pipes are connected using a ferrule connection method, this type of connection focuses on the outer diameter; pipes and fittings with the same outer diameter can be connected together via ferrules. This is why the diameter of Tube pipes is indicated by OD. 4. The wall thickness of pipes is standard, and it is generally indicated by a wall thickness series number (abbreviated in English as Sch.No. – Schedule Number). Sch.No. is also known as the pressure rating number; pipes with different diameters or materials range from Sch.No. 5 to Sch.60, each having its own standard wall thickness series. In other words, pipes with the same Sch.No. but different diameters or materials do not have the same actual wall thickness. The wall thickness of a Tube is expressed in its actual thickness dimension (inches or mm). 5. Pipe is widely used; it is employed in both process pipelines and utility pipelines. The Tube is used only in the measurement pipelines of instrument systems, pneumatic signal pipelines, and sample pipelines of on-line analyzers.