GB/T 28708-2012Specification for size selection of seamless and welded steel pipe used in piping engineering (English PDF)

3.1 Outer Diameter Series of Pipes

The outer diameter of pipes is divided into Series I and Series II. Series I is a general-purpose series and a recommended series for selection; Series II is a non-universal series. The nominal dimensions and outer diameters of steel pipes are shown in Table 1.

A.1 Definition of Pipe Schedule Number (Sch)

Pipe schedule number, code name: Sch, is defined as follows:

The ratio of the design pressure to the allowable stress of the pipe material at the design temperature is multiplied by 1,000, and rounded off, which is the code representing the pipe wall thickness series.

A.2 Source of Pipe Schedule Number (Sch)

Pipe schedule number (Sch) was firstly specified in the American standard ANSI/ASME B36.10"WELDED AND SEAMLESS WROUGHT STEEL PIPE"and has been used to this day.

A.3 Correspondence between Pipe Schedule Number (Sch) and Steel Pipe Wall Thickness

The calculation formula for the steel pipe wall thickness is as follows: Where, t---the wall thickness, expressed in (mm); P---the design pressure, expressed in (MPa); D---the outer diameter, expressed in (mm);

S---the allowable stress of the material at design temperature, expressed in (MPa); 2.54---the corrosion allowance and thread depth, expressed in (mm);

1.75---2 (1 12.5%), 12.5% is the negative deviation of steel pipe wall thickness.

Take Sch = P/S 1,000. The wall thickness value corresponding to the Sch number can be approximately obtained from the above Formula. For example, the wall thickness corresponding to Sch 40 is approximately equal to the calculated value of t = 0.040 D/1.75 + 2.54.

A.4 Significance of Pipe Schedule Number (Sch)

---Pipe schedule number (Sch) does not indicate the specific wall thickness, but the wall […]