The conventional sand filtration systems and chemistry used in most cooling towers may not be enough to capture small, corrosive andhealth-endangering contaminants.

The destructive effects of cooling tower water contamination are both varied and far-reaching. Polluting particles can contribute to corrosion of equipment. They also spur the growth of bacteria that erode the state of human health, can contribute to system fouling and a reduction in system efficiency. Fortunately, there are now filtering technologies available that trap particles of virtually microscopic size. These advanced systems do more than just clean. They self-clean, slimming substantially the amount of time, money and effort required to maintain them.

A cooling tower does more than just cool. It also acts as an air-scrubber for removing dust, pollen and pollution circulating through the system. Three types of chemicals are used to control such contaminants, says Alain Blais, President, Sonitec, Inc., a Holyoke, Massachusetts and Montrealbased manufacturer of quality-enhancing technologies for water used in heating and cooling. One prevents scale build-up, another reduces the potential for corrosion, and a third eliminates bacterial algae, microorganisms and mold.

“Chemical treatment will dispense with a lot of this stuff,” he explains. “Ultimately, however, you get too many particles so it’s best to use a system employing both chemicals and filtration. There are a number of filtering strategies available in the marketplace, and price will depend on the sophistication of the technologies involved.”

Sand-Based Filtration Solutions

Sand filters are often deployed in cooling towers, mainly because they tend to be more economical than alternative filtering systems such as membranous solutions or systems employing reverse osmosis.

Conventional sand filters have drawbacks, however. As static systems, they absorb solids and gradually become impregnated by them, necessitating a filter sand media change on a roughly biannual basis. The filtering medium in an ordinary sand filter is also of a fairly dense grain owing to the possibility that the sand will clog the system. For this reason, conventional filters are sometimes less effective than they should be at trapping particles of extremely small size.

Sonitec’s Vortisand filter is a step beyond convention. Combining centrifugal force with sand filtration, the system forces suspended solids to accumulate near the inside walls of the tank and removes them via an automatic backwash cycle. This unique design makes it possible to use a much finer grain of sand to remove very small particles (down to 0.45 micron) without the risk of clogging the system.

Taken as a whole, these attributes make for a better mousetrap. Via the turbulence strategy, the work of chemical dispersing agents is enhanced, inhibiting the elements that contribute to corrosion and bacteria growth. Economic payback is also considerable. Because the system more effectively traps particles, the amount of chemistry required (especially bacteria-killing biocides) can be trimmed by as much as 50%.

Energy-use efficiency goes up as well, along with production quality. Temperature is a critical factor in robotic auto-welding, for example. Cooling water loops are used to provide cooling to the welding tips. A variation of just a few degrees can be enough to increase the need for welding tip replacement and experience possible downtime. A sand filter driven by the concept of centrifugalseparation and automatic backwash willconsistently provide a reduction in TSS (totalsuspended solids) that can contribute to a reduction in fouling of suspended iron,typically found in welder water systems.

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