Even at extremely low concentrations, they interfere with measurement of dissolved solids by increasing conductivity. One of the disadvantages of using specific conductance is that some gases common to steam (such as carbon dioxide and ammonia) ionize in water solution. Measurement of this increase provides a rapid and reasonably accurate method for determining steam purity. When boiler water is carried over in steam, the dissolved solids content of the boiler water contaminates the steam, and steam sample conductivity increases. The specific conductance of a sample, measured in microsiemens (µS) or micromhos (µmho), is proportional to the concentration of ions in the sample. Specific conductance is one of the most commonly used methods. Several methods of measuring steam purity have been available and used for many years. Of these, only silica contributes to the difficulties commonly associated with impure steam the other constituents are of concern only where they interfere with the measurement of steam purity. Gaseous constituents commonly found in low-pressure steam (less than 2000 psig) are ammonia, carbon dioxide, nitrogen, amines, and silica. Because water treatment practices are such that most soluble chemical constituents of boiler feedwater are converted to sodium salts, most solids present in steam are sodium salts, with minor amounts of calcium, magnesium, iron, and copper also present. Solids are usually dissolved in water droplets or are present as dust. Impurities present in steam can be solid, liquid, or gaseous.
The test results make it possible to determine the effect of changing boiler operation on steam purity. Fortunately, techniques are available to determine steam contamination in the parts per billion range to satisfy the demands of most systems. One reason for this is that superheated steam turbines have an extremely low tolerance for solids contamination in the steam. SUEZ's boiler water internal treatment programs provide highly effective protection against corrosion and scale formation to ensure optimum performance and availability of our your steam system while reducing the total cost of ownership and environmental footprint through energy and water savings.Īccurate measurement of steam purity is essential to identifying the cause of potential or existing steam purity problems in modern boiler plants.