Nothing in this world is perfect, and therefore nothing comes without its own set of issues that always need to be addressed. In the industrial and commercial worlds, many people are well-acquainted with the problems facing heat exchange systems. From leaks, reduced air flow, and vibration issues, there’s always something to deal with – although how frequently you deal with such issues depends on whether or not you rely on professional maintenance providers. Of all of the issues that pop up with heat exchangers, though, fouling has to be the most common.
What Exactly Is Fouling?
It sounds scarier than it actually is, but fouling can still be very problematic. It might conjure up images of foul, oozing liquids and horror-movie-quality corrosives (anyone thinking of the acid blood from the creature in Alien?) but fouling is a bit less dramatic than all of that. It simply refers to the buildup that occurs in heat exchange systems that causes a reduction in water flow, pressure, and efficient heat exchange. This buildup is a result of various minerals, particulates, or organic matter present in the liquid within the system. As there are several varieties of factors that cause fouling, there are also several different types of fouling.
Also known as scaling, this type of fouling involves the crystallization of different salts and minerals within the system, often during the process of cooling. These buildups become extremely widespread over time and are very hard, making it virtually impossible to remove them from the heat exchanger with tools without damaging any of the parts.
Sedimentation or Deposition Fouling:
With this type of fouling, various particulates present within the liquid settle and build up over time. This type of fouling is easier to manage, as the sediments usually won’t fuse to the surface the way in which salts will in the crystallization process. This means that if enough velocity can be maintained within the system, particulates can be kept moving. Also, such particulates tend to break down into smaller pieces over time. These factors mean that this type of fouling isn’t typically as widespread and is generally just concentrated in a few key areas where the flow of water has finally brought all of it to a resting point.
Small organisms are often present in the liquids – typically water – used in the heat exchange process, and these organisms create a layer of fouling across services over time. Usually, these organisms include various algal species, as well microbial organisms. However, even marine organisms such as barnacles and mollusks can find their way into heat exchange systems, especially if water is being pumped from nearby natural waterways.
This occurs when chemicals introduced to the system react with the metal present and cause the formation of a layer of buildup. This is somewhat similar to the crystallization process, but whereas with that process the fouling is due to a scale deposit related to the buildup of crystalized salts, this process produces a scaling entirely based on chemical reactions.
All of the aforementioned fouling processes can lead to corrosion, but in those instances the corrosion is a secondary element to the original fouling process. With corrosion fouling, the immediate process is corrosion, often caused by high acidity levels or chemical imbalances. This commonly leads to major rusting throughout the system; something that can easily lead to an entire system break down.
Common Control and Cleanup Methods:
It’s extremely important to respond to fouling as soon as possible, so the best means of protecting your heat exchange system is to schedule regular maintenance and cleaning with a professional service, such as Mahan’s Thermal Products. Another means of combating the fouling process starts before the heat exchange system is even built and installed. Carefully designed systems can be engineered to create environments that are far less conducive to fouling processes, either by creating a system that maintains a certain velocity, or by including materials or substances that actively inhibit certain types of fouling.
For example, copper will create an environment that is poisonous to organisms that contribute to the biological fouling process. Chlorine can also be added to the liquid within the system in order to prevent/inhibit biological growth.
In terms of cleanup, fouling processes that create hard scale buildups can only be thoroughly cleaned with the use of chemicals. Scale caused by chemical fouling can sometimes be cleaned manually with special brushes, but crystallization can really only be dealt with through the use of a chemical cleaner. Particulates can be removed manually and filters can be installed in order to prevent or drastically limit the amount of particulates capable of entering the system.