DN800 Erw Black Steel Pipe

The Classification Principle of Schedule Pipe: How Are Schedule Grades Divided?

The classification of schedule pipe is mainly based on the nominal diameter (NPS) of the pipe and the designed pressure - bearing capacity. The specific classification principle can be summarized as follows:

1. Taking Nominal Diameter (NPS) as the Basic Reference

The nominal diameter is a nominal size used to represent the approximate inner diameter of the pipe, which is not equal to the actual inner diameter or outer diameter of the pipe. In the schedule pipe system, different nominal diameters correspond to different sets of schedule grades. For example, small - diameter pipes (such as NPS 1/2, NPS 1) usually have fewer schedule grades (such as SCH 40, SCH 80), while large - diameter pipes (such as NPS 10, NPS 12) have more schedule grades (such as SCH 20, SCH 40, SCH 60, SCH 80, etc.) to meet the needs of different pressure - bearing scenarios.

2. Determining Schedule Grades Based on Pressure - Bearing Requirements

The core purpose of dividing schedule grades is to ensure that the pipe can withstand the pressure in the working environment. The higher the pressure required by the project, the higher the schedule grade of the pipe to be selected. This is because a higher schedule grade means a thicker pipe wall, and the thicker wall can better resist the internal pressure of the fluid, reducing the risk of pipe burst.

For example, in low - pressure fluid transportation scenarios (such as domestic water supply pipelines), SCH 40 pipes are usually selected; in medium - pressure scenarios (such as industrial water supply and gas transportation pipelines), SCH 80 pipes are more commonly used; and in high - pressure scenarios (such as oil and gas transmission pipelines), SCH 160 or even thicker schedule grade pipes are required.