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Tube and pipe,what is the difference? (1)
Jul 19, 2017

Tube and pipe,what is the difference? (1)

Since the introduction of ASME specification, which Article I , II and VIII has become an essential reference standard for boiler industry.After a period of application and digestion, the understanding of this standard has gradually deepened, and the difficulties of certain translation terms have gradually dissolved. For example, the understanding of tube and pipe has gradually deepened.

Tube and pipe has the same meaning in Chinese, it is hard to distinguish. However, the requirement is different in ASME specification. There are two basic formulas in ASME Article I .

For tubing, calculate the thickness according to formula PG-27.2.1,


For piping, calculate the thickness according to formula PG-27.2.2,


Computational requirements and results are not the same, which will inevitably involve the Chinese understanding and difference between tube and pipe. What is tube? What is pipe? For a long time,different technicians have different distinguishing ways according to their own  experience, understanding and the speculation about the up and down temperature of ASME.

The first method is to be measured by the tube diameter. Below 5 inches or 6 inches belongs tube, which is acceptable by most people.

The second method id to be measured by section shape. The round section shape belongs to pipe and the other shapes are tubes.This statement was inferred from a paragraph in ANSI B31.1, but not very strict.

There are other ways of distinguishing, such as from the view of the process, the average wall thickness, tolerances, etc.. Most of these methods are speculative and have no proper source.

In the United States, Mr. E.A.Steen has been questioned about this problem. From the view of Mr. E.A.Steen, a person teaching in national inspection and Regulatory Commission, says it is also hard to distinguish in the language of German and Spanish, the boundaries are obscure in applying the PG-27.2.1 and PG-27.2.2 formulas. In fact, ASME did not focus on the size of the pipe or the cross section of the pipe during the formulation of this rule. Instead, they focus on the nature use of tubes and pipes. In the range of boiler and pressure vessel, tube is mainly used in internal and external heat conduction, heat exchange purposes. While the pipe is mainly based on function by transferring the pressure medium from one place to another, so that the pipe is generally connected with various accessories (Tee, elbows) and valves.

From this point of view, the provincial gas pipe, water wall pipe and so on must belong to the Tube class, and the main steam pipe, down pipe, etc., or even have three links, valve lines must be Pipe class.

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