Schedule for steel pipes is a method for classifying them, which is established in ASME B 36.10 as in many other standards or standards, and is represented by "Sch". This representation (SCH) is the abbreviation of "Schedule", and can generally be found in the US standards for steel tubes, which is a prefix for the numbering of series of tubes. For example, Sch 80 (ID 80), 80 is the tube number found in a table / table within the B 36.10 standard.

Since the main use of the steel tube is to transport liquids under pressure, its internal diameter must be considerably critical. This critical size is calculated based on the nominal diameter (Nominal Bore or NB, which is equal to "NPS" and "DN"). Therefore, if the steel tube carries pressurized liquids, it is very important that the tube has sufficient strength, strength and wall thickness. This wall thickness is expressed in Schedule, with which the identification of the tube is identified, abbreviated as "SCH”. This is the definition found within the ASME standard for the definition of Tube ID.

Formula to know the ID of Tubes:

Sch. = P / t × 1000

Where "P" is the designated pressure, units expressed in MPa;

t is the fatigue of the material under the designated temperature (thermal fatigue), units expressed in MPa.