Standard system of commonly used flange pipes for pressure pipelines

At present, most pressure pipelines and their components have been standardized and are supported by corresponding application standards. Therefore, when designing pressure pipeline materials, the first issue to be considered is the selection of the standard series for pressure pipelines and their components. 

Application standard system: A collection of series standards used for each component in a pipeline system (route). These standards should include pipe series standards, pipe fitting series standards, flange and its connection component series standards, valve standards, etc. They are applied in a pipeline system through certain rules, and they are interconnected and coordinated with each other, thereby determining the basic parameters of the pipeline and its components. 

The standards applied by countries around the world can generally be divided into two major categories. 

◆Pipe - that is, the series of outer diameters of steel pipes 

It is divided into the international standard series (large outer diameter series) and imperial pipe. 

Domestic standard series (small outer diameter series) Metric pipe (or metric tube) 

◆Flange: European flange and American flange 

Pressure level: 

PN0.1  0.25  0.6  1.0  1.6  2.5  4.0  6.3  10.0  16.0  25.0  40.0  MPa  European flange (DIN) 

PN2.0 5.0 6.8 10.0 15.0 25.0 42.0 MPa American flange (ANSI) 

CL150 300  400  600  900  1500  2500 Psi

From this, it can be seen that regardless of whether it is a flange or a pipe, the two series or two systems mentioned above cannot be used together. 

ANSI - American National Standards Institute 

ASTM - American Society of Testing Materials, the American Materials Testing Association 

◆ Method for indicating the wall thickness of steel pipes 

The methods for indicating the wall thickness of steel pipes include pipe number, pipe wall thickness dimension, and pipe weight. 

1) The wall thickness is indicated by the pipe designation "Sch". 

The pipe number is the ratio of the material's allowable stress at the design pressure and design temperature of the pipe, multiplied by 1000, and then rounded off to the nearest whole number. 

That is: Sch = P / [σ]t × 100 

ANSI B36.10 Wall Thickness Grades: There are ten grades including Sch10, Sch20, Sch30, Sch40, Sch60, Sch80, Sch100, Sch120, Sch140, and Sch160. 

ANSIB36.19 Wall Thickness Grade: There are four grades: Sch5s, Sch10s, Sch40s, and Sch80s. 

2) Represented by the wall thickness of the steel pipe 

Some steel pipe standards of China, ISO and Japan are adopted. 

3) It is expressed in terms of the weight of the pipe. 

It divides the pipe wall thickness into three types: 

a. Standard weight tube, represented by "STD" 

b. Thickened tube, represented by "XS" 

c. Extra-thick tube, represented by XXS. 

For pipes with a diameter (DN) of 250mm or less, Sch40 is equivalent to STD, and for pipes with a diameter less than 200mm, Sch80 is equivalent to XS.