Keeping within ASME guidelines for total iron in boiler feedwater below 0.1 ppm and total copper below 0.05 ppm copper requires attention to the maintenance of steam traps, knowledge of the metallurgy of the steam/condensing equipment in the steam distribution system and in particular the pH of return condensate.
When measuring pH in condensate, it is important to cool the sample with an in-line water sample cooler to minimize the CO2 flashing off from the sample. When the CO2 flashes off it is not present in the condensate sample so it will not form carbonic acid. Without carbonic acid present, the pH will be measured with a false high pH. The difference between in-line cooled condensate samples and ambient cooled condensate temperatures can be 2.0 or more pH units. This difference in pH will dramatically increase the corrosion rate.
In addition to ensuring proper measurement of pH, an in-line water sample cooler enables safe handling of the high temperature condensate. Water sample coolers are available in carbon steel or stainless steel. Certain sample cooler models have easily accessible coils that can be cleaned or replaced as needed.