A sudden increase in source water colloidal silica can ultimately lead to significant impacts on boiler chemistry compliance and costly unit load reductions if not adjusted for in primary water treatment systems. In this paper an actual event is described in which significant quantities of colloidal silica in the source water passed through into the condensate system of a coal-fired plant undetected. The steps taken to correct the situation are discussed, as well as the lessons learned and measures taken to prevent such an occurrence in the future.

In their work the authors have noted great diversity in the Flow-Accelerated Corrosion (FAC) Programs used at conventional fossil power plants. The results and findings of FAC Program assessments conducted at 22 conventional plants are summarized and discussed. By comparing the FAC Program characteristics and relevant unit features with damage and failure experiences, a number of common factors requiring attention from fossil utility organizations have been identified. The assessment experiences have also provided a picture of trends in specific FAC activities and general awareness within the conventional fossil fleet. One of the most important aspects of these studies is that while a few new locations of FAC have been found, there is some consolidation of the most frequently found locations.

The PowerPlant Chemistry® editor has received an e-mail with comments and questions on the article

Václav Koula, Martin Dráb, and Michal Havavka: Possibilities for the Acoustic Emission Method for the Detection of Flow-Accelerated Corrosion, PowerPlant Chemistry 2010, 12(6), 358–367

This e-mail and the reply from the first author are presented.

A decade of experience with flow-accelerated corrosion in heat recovery steam generator pressure parts is summarized in the paper. Flow-accelerated corrosion problems in the earlier combined cycle plants are compared to those in later plants. Further development of predictive models for flow-accelerated corrosion in heat recovery steam generators as well as improving technology for nondestructive evaluation of poor accessible finned tube areas and bare tube segments at headers of horizontal gas path heat recovery steam generators is required.

Flow-accelerated corrosion is shifting from a rapid wear phenomenon over large areas of affected heat recovery steam generator components to a slower wear process with the risk of locally higher rates. In many cases the higher wear rates are not detectable by wear measurements in other more accessible locations in relation to gross flow models. More detailed fluid modeling tools are required to identify local high-risk locations as well as the impact of operational changes on flow-accelerated corrosion wear.

Quick and reliable monitoring for hydrocarbons in wastewater, cooling and heating water is valuable to industrial facilities. Water monitors using fluorescence are capable of detecting hydrocarbon concentrations in water as low as 5 µg · L^–1, and can thus give operators an early warning of oil leaks and spills, allowing costly repairs, cleanup and fines to be avoided. This paper introduces the fluorescence monitors and presents data from recent studies to illustrate the detection levels of the technology.

Power plants continue to experience failures in various components as a result of numerous corrosion mechanisms. Changes in chemistry regimes alone are often not sufficient because there is no real measure taken of their effectiveness. Corrosion monitoring provides a simple and economical method for evaluating the effectiveness of water chemistry and operational controls on the corrosion of plant materials. It provides important insight into the condition of plant materials, including the timing of degradation, the influence of plant operating history, and the effectiveness of treatments. This paper reviews the principles of corrosion monitoring tools, and how and where to best apply them.

In order to apply a computer simulation code of flow-accelerated corrosion to evaluate the effects of water chemistry improvement on the wall thinning of pressurized water reactor (PWR) secondary piping, the accuracy and applicability of the code were confirmed based on verification and validation processes. The verification process of the code and the validation process based on data from laboratory experiments have been reported previously. In the present paper, the validation process of the code based on wall thinning rates measured at a PWR plant is discussed. Corrosive conditions were calculated with a O₂-N₂H₄ reaction analysis code. Precise flow turbulence at major parts of the system was analyzed with 3D CFD codes to obtain mass transfer coefficients at structure surfaces. Then, wall thinning rates were calculated with the coupled model of electrochemical analysis and oxide layer growth analysis by applying the corrosive conditions and the mass transfer coefficients. From comparison of the calculated wall thinning rates with hundreds of measured results at the secondary piping of the actual PWR plant, it was confirmed that the calculated wall thinning rates agreed with the measured ones within a factor of 2 and the accuracy of the evaluation model for residual pipe wall thickness was less than 20 %. Finally, the FAC simulation code was applied to the evaluation of the effects of oxygen injection into the feedwater line.