First of all, it is necessary to understand the type, specification, performance and scope of use of the pipe. It is better to investigate the application of the pipe in other similar pressure pipes, and then determine the material of the pipe according to the following principles.
(1) The preferred pipe
In the selection of pipe material, generally consider the use of metal material first. Ifmetal material is not suitable, and then consider non-metallic material. Steel pipe is preferred for metal materials, and non-ferrous metal materials are considered after that. In steel pipe, carbon steel should be used first, and stainless steel should be used when it is not suitable. When considering carbon steel material, the welded steel pipe should be considered first, and the seamless steel pipe should be selectedthen.
(2) The influence of medium pressure
The higher pressure of the conveying medium, the thicker the wall of the pipe is, and the higher the requirements of the pipe material are generally.
When the medium pressure is above 1.6MPa, seamless steel pipe or non-ferrous metal pipe can be selected. When the medium pressure is below 1.6MPa, the welded steel pipe can be considered. For water pipes, when the water pressure is below 1.0MPa, welded steel pipes made of A53 GR.B are usually used. API 5L GR.B seamless steel pipe is generally used when the water pressure is greater than 2.5MPa.
(3) The influence of medium temperature
Tubes of different materials are suitable for different temperature ranges. When the temperature of hydrogen gas is less than 350℃, API 5L GR.B seamless steel pipe is generally used.
(4)The influence of chemical properties of the medium
Conveying different media, using different pipes. Some medium is neutral, general material requirements are not high, can choose ordinary carbon steel pipe; Some medium is acidic or alkaline, be about to choose acid or alkali resistant pipe.
(5) The influence of the function of the tube itself
Some tubes in addition to the need to have the function of the transmission medium, and has the function of shock absorption, coefficient of heat bilges cold shrink function, under the working condition, can often move function, such as civil liquefied petroleum gas, oxygen, acetylene in bottling parts, pipe often adopt high pressure wire braided hose, and cannot use mobile hard steel pipe is not convenient.
(6) The influence of pressure drop
After the material of the pipe is initially selected, the pressure drop of the pipe should be calculated to determine the inner diameter of the pipe. Through the calculation of pressure drop, to see whether the selected materials meet the requirements.
Pressure pipeline calculation, in the engineering design, generally according to the production scale of material balance, energy balance and equipment calculation, preliminary determination of material flow. And refer to the relevant information, assuming a material flow rate, calculate the inner diameter of the pipe, check the manual or standard, choose the standard pipe, usually choose the standard pipe diameter should be equal to or slightly greater than the calculated inner diameter of the pipe. Then calculate the pressure drop in the pipe.