Posted by Mike Hinz on April 27, 2000 at 01:16:55:
In Reply to: Why not 0 TDS for boiler water ? posted by Mike on April 25, 2000 at 08:00:22:
First, chemicals such as sodium sulfite are added to the water to scavenger O2. Other chemicals fight scale. These chemicals cause some solids in the water.
Another reason is that TDS relates to cycles of concentration of the water. Unless you are using distilled water in the boiler--an impossibly expensive situation--there are at least SOME dissolved minerals in the water. (While softeners change this material so that it won't stick to surfaces, but it still remains in the water.) As the water is evaporated away as steam the concentration of solids increases. At least in our plant, ten cycles of concentration is about all our boilers will handle before foaming begins. This relates to around 3000 PPM of TDS.