This guide establishes requirements for seamless and welded copper-nickel tubes for use in heat exchangers in water desalting plants. Seamless tubes shall be manufactured by hot extrusion or piercing, and subsequent cold working and annealing as to produce a uniform, seamless wrought structure in the finished product. The welded tubes shall be manufactured from flat rolled strip which is subsequently formed and welded by a forge-weld process or a fusion-weld process. For forged-welded tube, the edges of the strip shall be heated to a required welding temperature, usually by high-frequency electric current, and be pressed firmly together causing a forged-type joint to be formed with internal and external flash or bead. On the other hand, fusion-welded tube shall be mechanically worked to produce a smooth external and internal surface without the application of scarfing or other removal of the weld bead. The product shall be cold worked and annealed as necessary to meet properties of the temper specified. The test specimen shall be free of defects, but blemishes of a nature that do not interfere with the intended application are acceptable for the following tests: expansion test, flattening test, and reverse-bend test. Forged-welded and annealed tubes shall have a completely recrystallized grain structure, and the weld zone shall have a structure typical of hot-forged welds. Fusion-welded and annealed tube shall have a structure typical of a fusion weld on its weld zone. The product shall be clean and free from defects, but blemishes of a nature that do not interfere with the intended application are acceptable.