(1) Pipes Metal material selection principles
　　① operating conditions to meet the requirements of the first conditions of use should determine whether the pipeline under pressure, is what kind of pressure pipe. Because different types of stress the importance of different channels, the degree of harm caused by the accident is different from the material requirements are also different. Pipes should be considered while the use of the environment and the transmission medium and the medium on the corrosion of the pipe body. For example, steel pipe piles into the seabed, tube corrosion rate in the splash zone for the seabed soil six times; tidal range area of seabed soil corrosion rate four times. In the selection and anti-corrosion measures should be of particular concern.
　　② machinability required material should have good workability and weldability.
　　③ durable and economical requirements of pressure pipe, first safe, durable and economical. A piece of equipment, number of pipeline projects in the investment selection before, if necessary, conduct a feasibility study that economic and technical analysis, the material can be used to develop several programs, economic and technical analysis, some material is slightly higher initial investment, but the use of reliable, maintenance costs usually Province; some initial investment material seems to province, but poor reliability in the operation, usually high maintenance costs, high life-cycle cost.

        (2) Pipes limit the application of commonly used materials
　　(3) Pipes used the name of metal materials and specifications