If your heart or lungs are not working properly, other parts of your body will be affected and your health will suffer. Similarly, if your cooling tower or heat exchanger is not clean, the efficiency of your production and process cooling systems will be compromised.
Process cooling systems that rely on cooling towers to dissipate heat from cooling water accomplish this task by drawing massive volumes of air into the cooling tower as the water travels through the fill material on its way back to the basin. Through the natural evaporative process, heat dissipates from the water before it reaches the basin. From the basin, the water is recirculated first through the chiller, then through the heat exchanger and back again.
It is important to realize that cooling towers are gigantic air scrubbers that capture all airborne debris. If your system lacks effective filtration, this debris can clog the fill and become trapped in the heat exchanger, where it can build up, restrict water flow and cause process equipment to malfunction due to overheating. Using the proper filtration technology can help ensure that your process cooling system will stay clean and run efficiently all season long.
Filtration System Selection for Cooling Towers, Exchangers
The operational efficiency of your evaporative cooling system can be optimized by combining a chemical treatment regimen with some type of filtration. While chemical treatment specifically targets suspended solids and particulates of 40 µm and below, filtration systems are designed to prevent larger debris from entering the cooling system, especially materials that cause system clogging and fouling.
Two general filtration technologies exist for cooling towers: water-based systems and air-intake filtration systems. With water-based systems, the choices include basic water strainers that remove debris by passing water through a mesh strainer; sand and media filtration systems that remove debris by passing the water through sand or filtration media; and centrifugal separators that spin the water and remove the debris through centrifugal action. In contrast, air-intake filter systems, which cover the intake opening, remove the debris by filtering the air as it is drawn into the cooling tower, thereby keeping the debris out of the system in the first place.
When evaluating the various filtration options, consider the following questions.
- What is the cost associated with downtime due to heat exchanger or cooling tower fouling or clogging? (This information can help you justify the filtration system cost.)
- What type of debris is the most problematic? Is it clearly visible or microscopic?
- What is the origin of the debris (airborne or waterborne)?
- What part of the system will the filter protect?
- Which system provides the greatest filtration surface area? (The surface area can impact the required frequency of cleaning; smaller filters generally need to be cleaned or flushed more often than larger filters.)
- Can the filter system be installed without shutting down the cooling tower? (If the cooling tower must be shut down for installation, you should factor lost productivity into the cost of the filtration system unless it will be installed during a scheduled shutdown period.)
- What is the cost associated with both the filter and installation?
- How easy is the system to install and maintain?
As a general rule, do not select a small-debris solution to solve a large-debris problem. Conversely, do not select a large-debris solution to solve a small-debris problem.
Both water-based and air-intake filtration systems play an important role in process cooling systems, but it is important to choose the right technology for your application. If the problem-causing debris originates in the water, or if you are trying to protect only the downstream part of the cooling loop (chiller and heat exchanger), then a water filtration system combined with a good water treatment program likely will be sufficient. However, if the debris is from an airborne source, or if you are trying to achieve full cooling loop protection, consider using air-intake filtration. An air-intake filtration system will prevent the debris from getting into your system in the first place and will protect the fill, sump, blowdown valve, chiller and heat exchanger. It also can reduce water treatment chemical consumption by reducing the bio-loading on the cooling system.