Kondensatorrohre aus Kupferwerkstoffen Richtlinien für Werkstoffauswahl und Betriebsbedingungen

Condenser tubes made of copper materials

• 1 Today, the copper alloys most generally used for condenser tubes are CuZn28Sn (Special brass 71 — Admiralty brass) CuZn20Al (Special brass 76 — Aluminium brass), as well as the copper-nickel alloys CuNi10Fe and CuNi30Fe. The high corrosion resistance of these materials is due to the electropositive normal potential of their base metal — copper — and to their ability to form a highly adhesive, protective sealing film. To counteract the dezinzification of copper-zinc condenser tube materials, alloying with arsenic or phosphorus is indispensable, and generally resorted to.
• 2 The properties of normal-type cooling waters and the phenomena of tube corrosion are discussed. In practice, the only difficulties are likely to arise if polluted waters are used. Especially at the time of commissioning, the tubes must be kept free of polluted water so as to ensure the formation of a dense and firm protective film.
• 3 The reaction of the tube material to the cooling water depends mainly on the p_H-value, on the carbonate, chloride and oxygen contents, and on the temperature and flow rate of the water.
• 4 The following practice rules are advised: For fresh water (containing less than 0.1 pC matter in dissolution) and flow rates exceeding 1.4 metres pr. second, tubes consisting of CuZn20Al or of a copper-nickel alloy should be used so as to avoid erosion-corrosion. If the sea water is greatly polluted, it is advisable — especially at flow rates around or above 3 metres pr. second — to use tubes consisting of CuNi10Fe or CuNi30Fe.