Removing water from your thermal system is a task that requires precision: every cold start and every problem with pump cavitation or pressure fluctuations must be approached on the assumption that water is present that needs to be removed if the system is to continue functioning properly in the long term.
Simply running the pump while the liquid temperature is slowly increased is not sufficient: the water does not disappear, but merely seeks a new place to hide.
Many heated systems feature a separate air vent to separate gases from the liquid. This is effective for non-condensable substances such as air or nitrogen, but not for
substances that can condense, such as water.
The water vapor must be able to escape into the atmosphere, and the only place in the system that allows this is the expansion vessel. The key to removing all the water in the shortest possible time is to ensure that the temperature of the expansion vessel remains above 100°C so that the vapor does not condense again. Every drop of steam that falls back into the liquid prolongs the time required to completely boil out the system. Insulation blankets over the top of the expansion vessel keep the walls of the free space warm, and a small nitrogen flush helps to sweep the water vapor out of the tank while simultaneously preventing liquid oxidation.
Does your heating system have a heating pipe connecting the heater's outlet to the expansion vessel? If so, open this valve, along with the manual air vent on the tank. If your heater does not have a heating pipe, consider having one installed. Next, open the control and shut-off valves on each loop so that you do not overlook anything, and check that the overflow vessel is empty.
Slowly increase the heater temperature to 107°C and check for steam and pump noise. If this proceeds well, increase the temperature in increments of 3°C, check again each time, and allow the system to stabilize. Repeat this until the system is stable at a pump suction temperature of 121°C — this temperature is decisive, regardless of the heater outlet temperature.
Always close the heating line before putting the system back into operation. If your installation has an air vent with a thermal buffer tank, check whether it has a drain valve to discharge the collected water; if not, have one installed. Are you unsure whether your thermal system contains water, or do you want to be certain that the dewatering process was carried out correctly? An oil sample analysis by Rodun International provides immediate insight into the water content and condition of your thermal fluid. This prevents unnecessary downtime, pump damage, and pressure problems, and keeps your installation operating safely and efficiently. Our advisors are happy to work with you to determine the right approach for your specific system, from a one-off check to a comprehensive maintenance plan.
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