4　Principles for Material Selection

4.1　Material selection for equipment and piping is based on proper process corrosion prevention measures taken in process units，specified process parameters to be met and strengthened field corrosion supervision and operation management.

4.2　Materials for equipment and piping shall be selected according to operating temperature，operating pressure and fluid properties as well as other factors such as material processability，weldability，etc.

4.3　In the implementation of this Guideline，materials shall be selected according to process characteristics and corrosivity of different crude oils so as to ensure economy and reasonabitlity of material selection.