Water poses enormous safety risks to operating and maintenance personnel. As your thermal fluid temperature is increased above 100°C / 212°F, water is converted to steam. The volumetric expansion can be quite dramatic – up to a ratio of 1100 to 1. Let us put that in perspective. That is 1 quart of water in your heat transfer fluid system expanding into 275 gallons of steam. As water turns into steam, the expansion displaces a significant amount of heat transfer fluid from the thermal fluid circuit. With nowhere else to go, hot thermal fluid is returned to the expansion tank or the holding tank. In some cases, hot thermal fluid has been known to gush out through the tank vent causing burns to production personnel.
In another instance, steam expansion resulted in excessive pressure that ruptured a pipeline and caused severe burns to a maintenance technician. It is simply unlikely that your expansion tank and heat transfer were not designed for this kind of dramatic volumetric increase. Water also causes corrosion problems within heat transfer systems and allied equipment. Heat transfer inefficiencies and process control issues will also likely occur since water is not an ideal heat transfer fluid above its boiling point. There is no gainsaying in concluding that water has a potential to cause catastrophic production problems and equipment damage, which can lead to bodily harm and property damage.