The pipeline classification and grading

The pipeline project is a very widely used construction technology, occupies an important position in the construction project, the type of pipeline, mainly in the transport fluid medium for the primary purpose.

Tubing and Casing, Line Pipes

For example, our daily lives can not be separated from the water supply and drainage, heating with hot water or steam, gas, etc..

Piping ships classified in several different ways, commonly Sorted by press working pressure, operating temperature, the transmission medium of the classification commonly used classification method is as follows:

Pipeline classfication

Class Name  Design Pressure P (mpa)
 vacuum piping  P<0
 low pressure piping  0<P≤1.6
 medium pressure piping  1.6<P≤10.0
 high pressure piping 10.0<P≤42.0

Under pressure in the medium, the pipeline must meet has sufficient mechanical strength and sealing performance. Pipes and piping accessories used in the pipe network as well as the connection way have to be safe and reliable under the action of pressure medium and does not leak tight.

 Class Name  Medium temperature T (℃)
 Low temperature pipes  T<-40 ℃
 Atmospheric pressure pipeline  -40 ℃<T<120 ℃
 Temperature pipeline  121 ℃<T<450 ℃
 High temperature piping  450 ℃<T

Pipe under the effect of temperature in the medium should have a stable and reliable heat resistance to withstand the medium temperature and pressure pipes must be in terms of both heat and pressure to meet the requirements of the pipe network. The interaction of medium temperature and ambient temperature, the pipeline will have a thermal deformation of the pipe to withstand thermal stress.

Pipeline grading

 Grade  operating pressure (Mpa)  operating Temperature (Mpa)
 Ⅰ  P>6.4  T>450        T>-140--45
 Ⅱ  P>4-6.4  T>350-450   T>-45--30
 Ⅲ  P>1.6-4  T>200-350   T>-30--20
 Ⅳ  P≤1.6  T>-20-200

The pipeline classification is based on two parameters of the maximum operating pressure and maximum operating temperature of the pipe network transmission medium to determine the level of the pipeline.

The pipe is coupled into the device for conveying gas, liquid or solid particles in the fluid pipe, pipe couplings and valves.

The oil casing is used to support the oil and gas well walls to ensure the normal operation of the entire well after the drilling process is completed. Each well is based on different depths of drilling and geology, using several layers of casing. After the casing is down, the cement is to be cemented. It is different from the oil pipe and the drill pipe and cannot be reused. It is a disposable material. Therefore, the consumption of casing accounts for more than 70% of all oil well pipes. Casing can be divided into: conduit, surface casing, technical casing and oil casing.

The American Petroleum Institute API standard specifically targets oil and gas: casing, tubing and line pipe standards used in industry. In the standard, the casing and tubing steel grades are divided into several grades, namely H-40, J-55, K-55, N-80, L-80, C-90, T-95, P-110, Q- 125, each level has a different heat process. In API 5CT, the raw materials were divided into four groups. The first group is H, J, K, N, the second group is C, L, T, the third group is P, and the fourth group is Q. The numbers represent the intensity level, and the codes K, N, L, C, and T represent nothing to explain. The following numbers represent the minimum yield strength of the material. The unit is KSI (thousands per square inch), H, N, K, J is the first group, the yield strength of the material is 200 MPa, L, C, T are two groups, the yield strength of the material is 100 MPa, P110 is the third group, and Q125 is the fourth group.

The API is divided into 4 groups.
The first group represents an ordinary pipe, that is, a low-strength pipe;
The second group represents a tube resistant to sulfur and corrosion;
The third and fourth groups represent high intensity levels.

J is the code name, and the API specification states that the value after the steel grade code is the minimum yield strength in units of 1000 psi (6894.7632 kPa).
For example, J-55, J is a steel grade symbol, and "55" means 55 x 1000 psi, which refers to the minimum yield strength of steel.



Seamless pipe Specification, standard and identification

Seamless pipes are extensively applied for the nuclear device, gas, petrochemical, ship building and boiler industries. Seamless pipes dominates 65% of market share in Chinese boiler industry.