High purity water and the steam produced from it constitute the lifeblood of most process plants. Equipment failures and curtailed production due to water/steam issues can cost a site hundreds of thousands of dollars or more annually. Much worse, some failures can cause injury or death. So, here, we’ll examine several of the most important issues related to proper water treatment and chemistry control in steam generators.
Let’s begin with a case history. A number of years ago, a colleague and I visited an organic chemicals plant in the Midwest that every two years or so had to replace the steam superheater bundles in four 550-psig package boilers due to internal scaling. We first were shown a recently removed bundle; roughly ¼-in.-thick deposits covered the internal tube surfaces. We then inspected the boilers and immediately noticed foam issuing from the saturated steam sample lines. Subsequent investigation revealed that total organic carbon (TOC) levels in the condensate return to the boilers sometimes reached 200 ppm — ASME guidelines  call for a maximum TOC concentration of 0.5 ppm in boilers of this pressure. So, it was easy to see why much foam existed in the boiler water and why impurities carried over to the superheaters on a continual basis.