Closed Water Systems
Closed Water Systems

Closed circuit water systems

The term ‘closed circuit’ refers to a water system that is sealed from the elements i.e. it has no contact with open air. The water in closed systems has a fixed volume that circulates continually with only a low loss of volume over time. A closed circuit water system actually refers to two interrelated systems; a completely sealed system for recirculation of water and a heating or cooling exchanger which is commonly used to either exchange heat into or remove heat from the closed circuit water system. 

An air conditioning is an example of a cooling exchange closed circuit water system. As a general rule, air conditioning systems have a closed circuit water system that circulates throughout buildings to provide the required reduction in air temperature. The second part of an air conditioning system is usually an open cooling water system. The closed circuit water system pipes run the water through the cooling water system where the cold air cools the surface area of the closed circuit water system pipes and, therefore, the water inside them.

A good example of a heating closed circuit water system would be a domestic central heating system. This closed circuit water system works using the same principle as a cooling system but the closed pipe runs through a boiler instead of a cooling water system. Heat is transferred to the pipe and then to the water. The hot water then continues to flow through the system, heating as it goes through.

In order to prevent scale and corrosion of the pipework of a closed circuit water system B & V Water Treatment can implement a chemical water treatment regime.

The Difference between Closed & Open Water Systems

To understand the best way to approach the treatment of a closed system it is important to recognise the key differences between closed and open water systems. As mentioned previously, a closed circuit water system is a system that is sealed from the elements. It therefore follows that an open water system refers to any system where water is exposed to an external environment outside of the water process; examples include cooling towers and hot and cold water systems (e.g. taps and showers).

The following table illustrates the main differences between closed and open water systems:

Closed Open
Low make-up High make-up
Low oxygen levels High oxygen levels
Wide range of water temperatures Narrow range of water temperatures
No contact with site processes Possible contact with site processes
Composed of multiple metals Mainly steel and yellow metals
Chemical treatment remains within system Chemical treatment lost through water loss

As you can see there are many clear differences between open and closed systems which result in different approaches to the water treatment in these systems.

Semi closed water systems are systems that are mainly closed with one exception, such as the water leaving the system to cool an element of the industrial process.

scale on a colsed circuit pipeScale

Closed circuit heating systems, particularly those using hard water, are more vulnerable to problems with scale than cooling systems as increased temperatures make suspended solids more insoluble. In order to limit the issues caused by scale within your closed system it is important to understand the factors that lead to high scale levels within systems and the treatments which are available to combat scale within this type of system.

corrosion on pipeworkCorrosion

Although closed systems generally have low oxygen levels, the wide range of temperatures that are often present can still lead to high rates of corrosion within the systems. This is especially true in heating systems where heat enables what oxygen is present within the closed circuit water system to react with the surface of the metals used in the system at a faster rate. As a result, corrosion is still a concern within closed circuit systems, and understanding its cause and possible solutions is vital in combatting it.

microbiological fouling pictureMicrobiological

Even though there is no actual risk of legionella within closed systems, microbiological fouling can still cause many difficulties and should be treated accordingly. Unwelcome microbes within your system can decrease and even prevent the efficiency of your other corrosion and scale treatment regimes, costing money in wasted chemicals and leading to scale and corrosion and the problems related to them. Understanding what can be done to reduce the amount of microbes present within your closed water system is important when trying to maintain an efficient closed system water treatment regime.


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