4.8　Foreign Materials

4.8.1　When selecting foreign materials，the proven materials allowed by the latest foreign codes for the tanks shall be used.Their service limitations shall satisfy the requirements of the applicable codes and standards of the country in which the materials are produced，and certificates of quality for the materials shall be provided.

4.8.2　Chemical composition and mechanical properties of foreign materials，if used，shall not be lower than the requirements of similar materials in this Standard.

4.8.3　The allowable stress of steel plates shall be the lesser of Rm/2.7 and ReL/1.5（Rp 0.2/1.5 for high alloy steel）.