In steam-generating systems of all types, producing and testing pure water is of utmost importance for the life of the system. A 1000-MWe (megawatt electric) power plant generates 6 million pounds of steam per hour if fossil fueled and 11 million pounds per hour if nuclear. Should an impurity have a concentration of only 10 ppb, in a year's time, 550 to 1000 pounds of solids can accumulate in the power-generating cycle. These solids may initiate numerous problems, including preboiler-cycle corrosion, boiler-tube failure, and turbine damage.

At the Babcock & Wilcox (B&W) Alliance (Ohio) Research Center and throughout the industry, three principal methods are used to monitor water chemistry. On-line continuous analyzers measure parameters such as pH, conductivity, chloride, and sodium. Grab sampling (followed by laboratory analysis) is used for parameters that are measured less frequently; for example, sulfate. For some parameters, such as corrosion products, special sampling techniques are required. This is because no on-line instruments are available, and grab-samples are not chemically stable. Corrosion products are collected near the sample tap using a 0.45-micron filter-disc followed by a stack of resin-impregnated membranes.