How Clean Is Your Cooling Water
During the cooling process, the cooling water absorbs large volumes of airborne particulate - acting as an air scrubber filtering the surrounding air. With time, these fine particles can build up and settle within the system, adversely affecting cooling performance while lowering the life of wetted sub-components. Typically, 85% of suspended solids in cooling water and hot water loops are smaller than 5 microns in size1. Scientific studies have shown that these fine particles (5 microns and less) tend to be the adherent contaminants causing fouling of the cooling tower water, chilled water and heat exchangers, thereby reducing cooling system efficiency2. High volumes of fine suspended particles will not always be eliminated with the sole use of a chemical program – therefor fine filtration is becoming a vital addition.
Side Stream Filtration Explained
Side stream filtration is used to filter a portion of the systems circulating water, removing debris and particles that are adversely affecting the cooling loop and its components (heat exchangers, chillers and more). Over time, filtering 1% - 10% of the cooling loop flow results in the filtration of the total volume of water every 12 – 72 hours. Keep in mind, the filtration rate will highly depend on the application and filtration technology at hand. Side stream filtration technology generally falls into the following categories: screen filters, centrifugal filters, bag & cartridge filters, sand/media filters and high efficiency media filters. Such filter technology, in HVAC applications, are evaluated based on their performance in filtering fine particulate (ranging from 1 – 50 microns). Choosing the right filtration side stream filtration system can yield significant savings.
6 Signs Your Cooling Tower Requires a Side Stream Filtration
Consider the following signs your facility requires a side stream filtration system.
- Make-up water source is high in suspended solids, iron, biological and organic activity.
- There is a concern for biological growth, even though a strong biocide treatment is in effect.
- Frequent cleaning of heat exchangers and chillers (regular cleaning should occur approximately every 12 - 16 months).
- Signs of excessive rates of corrosion within the water loop and its components.
- Loss of heat transfer and efficiency in the overall cooling system.
- High buildup of solids within the sump and/or fill of the cooling tower.
Benefits of Using a Side Stream Filtration System
Below you will find common benefits that yield a high ROI for facility and maintenance managers implementing a side stream filtration system. The benefits listed below will not be applicable in all applications and environments. It is important to understand your water and the suspended solids that are adversely influencing the overall system, before committing to improved efficiencies and reduced operating/maintenance costs.
- Now that the fine particles are being filtered through the system, your chemical treatment program will yield improved results.
- The removal of abrasive suspended solids will aid in reducing the potential for erosion and corrosion. It is important to note that the chemicals circulating in your system will now protect the raw surface of the cooling loop. Over time, you will experience reduced maintenance costs and chemical consumption. A cleaner system will yield cleaner components, resulting in improved heat-transfer efficiencies and reduced energy costs.
- A cleaner system requires fewer resources to maintain its integrity, keeping the overall system performing as intended. Potentially offering decreased downtime and increased uptime, ultimately improving profitability.
Review of Side Stream Filtration for Cooling Tower Applications
One thing is clear! Choosing the right side stream filtration system can help keep your cooling system operating efficiently year round. Assessing your need for a side stream filtration system may require significant resources upfront, although these resources can potentially provide a large ROI for years to come. Protect your facility, your investments and your bottom line!
References
1 Based on multiple laser particle distribution tests completed in-house
2 U.S. Department of Energy (2011). Cooling Towers: Understanding Key Components of Cooling Towers and How to Improve Water Efficiency. DOES/PNNL-SA75820
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