Water Treatment for Hydronic Systems
Water Treatment falls into one of three main categories: Closed loop recirculation heating and cooling systems, Glycol systems and Open loop cooling systems.
Closed Loop Heating and Cooling Systems
These systems function as carriers of a fluid to either heat or cool the environment that they service.
The most common problems associated with closed loop recirculation systems are corrosion, deposition and to a limited extent microbiological fouling.
Corrosion: The first defense against corrosion in any system is a properly engineered installation with consideration given to mixed metallurgies, adequate heat exchange, and flow patterns. In any case, water and most anti-freeze compounds are corrosive to metals by nature and are enhanced by make-up water, with the infusion of fresh oxygen and untreated fluid. Chemical treatment is a necessity in all hydronic installations to prevent corrosion to the various metallurgies. The type of treatment selected will depend on the metals in the system, the temperature of the heat exchange surfaces, environmental concerns and process considerations, where applicable.
Please Note: All new installations should always be pre-cleaned chemically prior to operation. This procedure is required to remove oil, grease, mill scale and debris. This provides a precleaned system to ensure that when the chemical treatment is installed it can provide a uniform protective film over all the metal surfaces.
Scaling (or deposition): Since closed loop recirculation systems require very little make-up hard water deposits are normally not a problem. Most chemical programs incorporate sequestrants and dispersants to look after minor hardness incursions. However, in situations where excessive hard filling and make-up water must be used or make-up requirements are high, additional chemicals may be required. Here are also systems where the temperature at the ehat exchange surfaces is high enough to cause hardness salts precipitation and scale. With these systems partial to total zeolite softening of the filling and make-up could be justified.
Monitoring: Treatment levels in the system should be tested regularly and treatment added as required to maintain proper level; it is good practice to install corrosion coupons in an area that can be easily isolated. to check corrosion rates and monitor water line monitor and record water consumption. This ensures an inexpensive way to ensure that losses are detected before a major problem develops.
Glycol Systems: In many Industrial, Institutional and Commercial buildings, closed loop heat exchange systems normally containing water are exposed to potentially freezing conditions. This could result in system failure resulting in process or building shut down. There are a number of alternatives to fight this problem but the most common one is the addition of glycol. Propylene glycol is usually the product of source because of its lower level of toxicity and environmental contaminations. Glycol systems do still require treatment with inhibitors, pH buffers and other specific inhibitors to protect the metallurgy.
Open Systems (Cooling Towers): Since the water is in almost constant contact with the atmosphere, the problems that can arise with this type of system are: corrosion; scale; micro-organic activities and general fouling. Problems that can result are: reduced system efficiency; increase in maintenance; premature equipment failure and shorter life span of capital equipment. Treatment includes a number of chemicals and the best way to control the water in this environment is through either a sophisticated censoring/control system that will direct the automatic injection of the appropriate chemical(s) as the conditions change.
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