Engineers are constantly seeking cost-effective, easily maintained, efficient and sustainable solutions for industrial water filtration. Considerations regarding the process, the system footprint, ease of maintenance, materials of construction, waste limitation and filtration-system applicability are essential. Saving manpower also is critical.
Choosing an appropriate water filtration system for industrial cooling processes can be a daunting task, but it does not have to be. Although there are several selection criteria for a cooling water filtration system, it all comes down to keeping costs low and efficiency and effectiveness high for the long term. As such, desired features include a system built from long-lasting materials like stainless steel, a design that maintains high efficiency and a system that optimizes filtered waste removal with efficient water use. Other desired features include a design that provides ease of operation and maintenance while minimizing downtime. An automatic self-cleaning feature can save labor and reduce downtime while helping to maintain optimal water quality.
For open-loop cooling configurations, filtering the water helps eliminate the common particulate matter that can contaminate it. This is important because debris reduces the ability to transport heat away. Debris also contributes to piping corrosion and scale and requires manpower for routine cleaning (with the added expense of downtime).
Effective filtration also can eliminate or minimize the chemical additives required to destroy living organisms or deactivate other substances that can lead to corrosion, scaling, slime, debris and other types of buildup.
If chilled end water is to be drained into a body of water, it should be successfully filtered first to keep wastewater acceptably clean for discharge.
The Role of the Filter Media
Filtration mesh is measured in microns from large to small and should be selected carefully based upon the application. An experienced supplier (with many installations) is well-positioned to advise you on mesh selection. Filters are available in mesh so fine that they can be used for prefiltering drinking water that has to pass through sensitive reverse-osmosis membrane filters.
Yet, such fine a filter may not be needed for industrial cooling waters. Selecting an appropriate mesh will extend the life of the filter.
While the list may vary a bit from person to person, commonly desired features of an automatic self-cleaning filtration system include materials, options, multiple filter housing configurations and power source.
The first feature that should be considered is reliability. High quality stainless steel lasts longer than other materials, and it does not have the potential to contaminate the very water it filters. Other construction materials such as non-stainless metals or plastics can slough off, wear out or degrade the water that passes through them.
The range of options should be the next consideration. Ideally, filter screens should be available in a range of meshes. The filter housing unit body should be available in several styles to suit small to large applications. The filter housing unit selected must be able to accommodate the amount of water to be filtered. Also, the unit should be able to be installed within the available footprint area for physical access and connections.
Another consideration is power source. Some filtration systems require heavy-duty power supplies as well as pumping, wiring and controls. Something to be evaluated is the use of water pressure itself as a power source. An efficient system can use the existing water pressure whenever possible (within a certain range). Beyond that range, auxiliary power or a pressure stabilizer can keep the system operating at an optimal flow rate.
Filters are used at an injection well to replace extracted groundwater. | Images provided by Tekleen Automatic Filters Inc.
The Role of Automatic Self-Cleaning in Water Filtration Systems
One of the goals of water filtration is to save labor and downtime. A filtration system with automatic self-cleaning provides an uninterrupted flow of water during the backwash process, which allows the filtration process to continually operate. Furthermore, the self-sustainability via automatic backwashing and self-cleaning processes — combined with the simplicity of design and ease of maintenance — makes a self-cleaning screen filter efficient.
An automatic self-cleaning system should have a sensing system that reliably tells the system to start its self-cleaning feature. A pressure sensor can determine when the filter media needs to be cleaned. At this time, a rotation or pressure wash will initiate and flush out the interior of the unit as well as the filter media. Following self-cleaning, the wastewater is sent out to a separate outlet.
The automatic self-cleaning feature should use the wash water efficiently and complete the cleaning process quickly. It should not require routine disassembly or downtime until a filter is serviced.
Choices in Water Filtration
Bag filters are a low cost, effective option for smaller, low key performance demands. They tend to have a smaller surface area than other types of filtration systems, which can limit how large of an operation they can support. But, ease of maintenance and the time and financial cost for personnel to upkeep the bag filtration systems, as well as the repeating cost of bag replacement, are not optimal for many applications.
Sand filters require a large footprint, produce high volumes of backwash water and require a relatively high level of maintenance. Routine replacement of the sand or media is important to prevent bacterial buildup and ensure that water is being filtered rather than being contaminated. The cost of maintenance is expensive in time and capital.
Cartridge filters can be effective from a performance standpoint. Similar to bag filters, however, for larger operational demands, the cost for time and material for cartridge replacement can provide significant drawbacks on performance efficiency.
Filtered well water is used to manufacture an extensive line of beers at Sierra Nevada Brewing’s North Carolina facility. Filters are used in this beer brewing operation. | Images provided by Tekleen Automatic Filters Inc.
Stainless Steel Self-Cleaning Screen-Filter Systems
An efficient filter for industrial cooling processes is a screen filter. In addition, a self-cleaning screen filter can outperform a non-self-cleaning screen filter.
Self-cleaning filters are used successfully in many applications. A few case studies demonstrate where stainless steel self-cleaning filter systems have been used.
Food/Dairy and Beverage Processing. Filtered well water is used to manufacture an extensive line of beers at a well-known brewery in North Carolina. This brewing water is taken from three wells. One model filters this water down to 5 microns. The filter is used as a prefilter to an existing cartridge filter that previously would have become blinded, or clogged, rapidly, requiring laborious cleaning and downtime. That cartridge has not had to be changed for several years as a result of the system, which is self-cleaning and operates without significant water waste.
The brewery also uses self-cleaning screen filters to clean rainwater for irrigation and other uses.
Power Generation. In Idaho, the Cabinet Gorge Dam engineers opted for filters in a horizontal system that actually uses two screens. The first is a coarse 0.375" screen that removes large particulates that could damage a second, finer 100-micron screen. After the coarse screen, the water passes through the fine screen.
As the dirt and plant particulates accumulate and begin to cause a pressure drop, the change in pressure triggers the filter controller to open 1 or 2" flushing valves. High velocity suction nozzles are activated to vacuum the accumulated particulate matter from the screen. The filtration system flushes it from the system using only a few gallons of water, taking just 10 sec, with no interruption of the main flow. The system returns the wash water to the river.
Plastics. The filter installation at a major plastics manufacturing plant contributes to the company’s goals of overall efficiency through reduced waste of employee time, materials and water, and by supporting high quality output. The filters were chosen because they use less water than other filtration methods and are stainless steel rather than enameled surfaces. They filter the chilled water in the closed-loop systems used in plastic processing and the tower water used to cool hydraulic oil. Prior to the installation of the filters, daily walk-throughs were required to observe and check the older, high maintenance bag filters.
With the self-cleaning filters in place, these daily checkups have been eliminated. The savings in water also has reduced the need for water-treating chemicals. While precise savings have not been fully documented, the reduction in the need for maintenance downtime is noticeable, according to plant management. PC