The paper provides information from one-day assessments of HSRGs with concentrations on the cycle chemistry and thermal transients. The primary goal of the work was to assist operators in being proactive in identifying the key drivers for cycle chemistry and thermal transient induced failure and damage mechanisms. In the former, the assessments have addressed the key factors for flow-accelerated corrosion (FAC), under-deposit corrosion (UDC) and pitting. In the latter, the assessments have addressed thermal fatigue and creep fatigue. In each area, the assessments have provided a clear picture of exactly where the weaknesses in the approaches are occurring, and it is not surprising that the current ranking order for HRSG Tube Failure has remained rather static for the last 10 years. The paper outlines the approaches to optimize the cycle chemistry to avoid FAC and UDC, the operation of attemperating systems and the configuration of drain systems to avoid the thermal transient driven damage mechanisms. These key messages can easily be applied by operators to change the current situation of waiting for failure to occur.

The improvement of condensate and feedwater quality in power generating plant is an on-going process in the power industry in light of the ever increasing use of high pressure and temperature boiler and turbine systems. One area of research that has become very topical is the removal of natural organic matter from power station make-up water. Where potable water is produced, which is also of concern to Eskom, the presence of organics can also lead to taste and colour problems, they can act as precursors for the formation of disinfection by-products and they can stabilise dispersed and colloidal particles during the clarification process. Although water demineralisation processes can cope with the removal of inorganic salts from raw water, the removal of organic matter poses a far greater problem. Some organic compounds can be removed via the ion exchange process, however fouling of the anion exchange resin, and to a lesser extent of the cation exchange resin, occurs during this process which can have an impact on the overall performance of the water treatment plant. Those organics that are not removed will find their way into the steam/water circuit, where they are decomposed through thermohydraulic processes, and these decomposition by-products can influence the quality of the steam and condensate. The mechanistic impact of organic matter on the materials of construction of the steam/condensate cycle is a very controvertial issue and the aim of this paper is therefore not to contribute to this debate, but rather to demonstrate the impact of organics on treatment processes and the quality of the water in the steam cycle.

British Energy has been investigating the potential use of dimethylamine as an alternative to ammonia for boiler water treatment in order to mitigate rising boiler pressure drops in the once-through boilers at some of its advanced gas-cooled reactor (AGR) nuclear power stations. A programme of corrosion testing has taken place at British Energy's Wythenshawe Boiler Rig test facility to investigate whether dimethylamine or its thermal decomposition products could lead to enhanced boiler corrosion, in particular of austenitic superheater sections that have the potential to operate wetted. Tests carried out to-date appear to show corrosion defects resulting from dimethylamine chemistry, although the precise mechanism of formation of these defects remains unclear. This paper will present the latest findings in the test programme and the conclusions being drawn about the possible implication of dimethylamine, or its decomposition products, in the defects being observed.

For almost 50 years, the power industry has used condensate polishing to ensure high purity feedwater to once-through boilers and nuclear steam generators and, more recently, to drum-type units operated on oxygenated treatment (OT) or all volatile treatment (AVT). High purity polisher effluent is required for these types of units during both normal operation and during a condenser leak. The major challenge is to maintain polisher performance during a condenser leak when the most important determinant of polisher performance is ion exchange kinetics. If the surface of a resin bead is fouled, diffusion of an ion across the thin liquid film surrounding each resin bead may be adversely affected resulting in slower exchange kinetics and "leakage" of contaminant ions. Consequently, the introduction of chemical additives to units with condensate polishers causes concern because of the possibility of resin fouling.

This paper discusses potential sources of polisher resin fouling and provides suggestions and data on resin cleaning techniques that have been tested in the laboratory and successfully used at power plants. Results indicate that appropriate resin cleaning may make the use of some chemical additives compatible with condensate polisher operation.

This paper provides a brief history and timeline of condensate polishing from the 1950s to the present. It then discusses the equipment, designs, process strategies, and operating techniques that are being employed and developed to address the increasingly stringent requirements of plants in the 21st century.