The influence of corrosion and fouling on steam condenser performance

Abstract

The performance of steam power plant condenser tubing alloys, as influenced by design, operational procedures and materials of construction is discussed. Emphasis is placed on the changing and increasing performance requirements that the industry is imposing on steam condensers. Several types of films that form inside tubes are identified and their influence on heat transfer and corrosion are discussed. Biofouling activity is reviewed with regard to past and present water quality. Future trends of increasing biofouling activity are anticipated in view of a reduction in water pollution. Special attention is drawn to the biofouling resistance of copper-nickel alloys in seawater. This is identified as an important materials characteristic not only in condenser tubes, but also in inlet cooling water systems. It is pointed out that a biofouling-resistant intake water system would be of benefit to all condensers, especially those tubed with other than copper-base alloys. Corrosive attack on the cooling water side is reviewed including pitting and crevice corrosion, inlet end and blockage erosion, and the effect of hydrogen sulfide. On the steam side, several other aspects of materials performance, including vibration and corrosion by the condensate, are discussed. Several seawater condenser tubing performance surveys are reviewed. Comparisons are made between alloys in those cases where a sufficient body of field experience exists, after all the surveys are normalized on an equivalent basis. In addition, the performance of condenser tubing alloys in fresh water, brackish water and in cooling systems utilizing a cooling tower is reviewed. The common theme throughout the paper is the “systems approach” to improving condenser reliability and performance. It is emphasized that the full benefit of any condenser tube material will only be realized when all associated components of the system are carefully reevaluated and optimized. Finally, two new nickel-containing condenser tube alloys which show promise of improving performance relative to the more fully established alloys are discussed. One is CA-722, an inlet end erosion resistant copper-nickel alloy which increases the water velocity capabilities beyond that of the established copper-nickel alloys, CA-706 and CA-715. The other new material, AL-6X, is a highly pitting resistant stainless alloy specifically designed for seawater condenser service.