Material substitution issue
Thread Content
For steel used in the pressure-bearing components of pressure vessels, is it sufficient for the mechanical properties and chemical composition of the materials to be identical in order to approve substitution?
If the chemical composition and mechanical properties of a material are the same, then it is the same type of material; what else could be used to represent it?
There are many issues related to the design of material substitutions, so processing such requests usually involves several departments including design, manufacturing processes, welding, and materials. The design requires verification to ensure that the alternative materials meet safety requirements (calculations are needed; in some cases, using thinner plates instead of thicker ones can be unsafe when stress levels change). It is also necessary to consider the compatibility between the new alternative materials and the surrounding medium, as well as whether this will lead to any changes in the technical requirements (for example, special attention must be paid when the thickness of Q345 reaches 30). The impact on installation procedures must also be taken into account (for instance, using pipes to construct the heat exchanger shell, with thicker pipes instead of thinner ones, may make it difficult to install the tube bundles). Weldability must also be considered during welding. . . . One cannot blindly assume that thicker can replace thinner, or better quality can replace inferior quality
Different mechanical properties and chemical compositions can also be approved for use!