The design codes and standards discussed in Section 4.3 list materials that may be used in heat exchangers. Other materials may be used subject to agreement between purchaser, inspecting authority, and the manufacturer; in general, design codes and standards specify minimum qualities of materials.

Materials and the corresponding design stresses to be used in conjunction with the TEMA heat exchanger standards are given in the ASME Boiler and Pressure Vessel Code, Section 8, Division 1. (Codes are mandatory; standards are recommended practice.)

In the case of the United Kingdom, the design stress values of recommended materials for heat exchangers are given in BS 5500.

In the F.R. Germany, the TUV (Technische überwachungs Verein) is the general approving body for heat exchangers (and many other products). Design methods for pressure vessels (including heat exchangers) are given in the A. D. Merkblätter, while the yield stress values for insertion in the A. D. Merkblatt formulas are obtained from the relevant DIN (Deutsche Normenanschuss) standard.

Before discussing the different metallic and non-metallic materials for heat exchangers, it will be useful to consider the product forms used for various shell-and-tube exchanger parts.