It's time to get wise to cooling-water treatment.
Yet with today's engineered water-treatment systems, intensive doesn't have to mean continuous human involvement or hand feeding of chemicals into the old cooling-water tank. The newest water-treatment systems can automatically control a battery of chemical or physical remedies. "Water treatment can be as easy as taking care of a swimming pool once the homework has been done upstream," says Jack Altschuler, president of Maram Corp., water consultant to equipment supplier Thermal Care/Mayer.
Ideally, that "homework" should fall on the shoulders of a specialist who can pair the correct chemical package with the prevailing water conditions. Otherwise, inadequate treatment or misdiagnosis can result. "Some people buy a generic water softener or biocide and think they have themselves covered," says David Young, president of cooling-equipment supplier Budzar Industries of Euclid, Ohio. "Unfortunately, it's really not that simple."
Just how bad can untreated water get? At its worst, mineral scaling can stop production altogether by clogging water lines, and suppliers had no shortage of horror stories in this department. Young, for instance, recalls an extrusion plant where the condenser on a 120-ton chiller became so clogged that it had to be taken out of service and undergo expensive repairs--all the while halting production. "The company found religion after that," Young says.
Long before production grinds to a stop, scaling can exert a more insidious influence, says Mike Davis, parts manager for AEC/Application Engineering. Mineral deposits do some real harm to heat-transfer efficiency even while they are building up. Davis points out that a mere 0.006 in. of scale can reduce the heat-transfer efficiency of a chiller condenser by 30%, driving up power usage significantly (see facing page).
And, as Calgon market manager Ben Brock notes, the inconsistency of heat transfer resulting from progressive scale build-up results in non-uniform cooling within molds, which can throw off part tolerances and increase cycle times. "When you run under fouled conditions, product quality will be affected," Brock warns. Nonetheless, he frequently encounters a "denial factor" on the part of many processors who stubbornly resist the connection between some processing problems and a lack of water treatment. "Some people will try to change their process when it's really the water," he says.
The most common type of mineral deposit, or lime scale, forms from the calcium carbonate found in most water supplies. According to Maram's Altschuler, the most susceptible areas for the scale to form are those with high temperatures and low water velocity-important places like oil coolers, injection molds, or the condensers of chilling units.
Other threats to productivity are biological rather than mineral. "Biomass," such as algae or bacteria colonies, can clog water lines and reduce efficiency just as scaling does. An even scarier scenario involves the possibility of people becoming ill: The deadly bacteria that causes legionnaire's disease has been traced to cooling towers.
Finally, add corrosion problems to the list of ills that water treatment can prevent. AEC's Davis points out that water is "a universal solvent that tries to dissolve nearly everything it comes into contact with," including your cooling equipment.
To ward off all these water-borne threats, cooling equipment manufacturers recommend the kind of diligent chemical delivery that an automatic system can best provide. "How the chemicals are delivered is every bit as important as what is delivered," says Altschuler.
Human nature enters the picture too. Suppliers say that hand-fed treatments are likely to be forgotten frequently. All the more so, says Al Fosco, sales and marketing v.p. at Conair Tempro in Elgin, Ill., because the very places that scale strikes are the least visible to processors. "You can't see inside of molds," he points out. Of course, automatic systems don't release operators of all their responsibility. Chemicals must be replenished, and daily checks are a good idea. "Training people on-site to recognize the danger signals is a critical link," says Calgon's Brock.
The latest engineered systems for evaporative cooling towers (see Fig.1) all begin by continuously monitoring dissolved solids levels as a basis for controlling the valves that bleed off the old water and let in the new. At the same time, these systems employ feeder pumps to conkol the release of scale and corrosion inhibitors. Biocides, meanwhile, are released on a timed cycle
Finally, a backflushing filter is often employed to remove undissolved solids. "We're seeing a trend toward finer filtration," notes Young. In place of a coarse screening for leaves and dirt, filtration now goes after particles as small as five microns (0.0002 in.) because any amount of sediment in your cooling equipment is too much, suppliers say.
Altschuler emphasizes that these state-of-the-art systems increasingly rely on programmable controllers and real-time monitoring as opposed to strictly volumetric methods that lack the on-line monitoring capability. Thermal Care, for example, takes this approach with its Tower Water Care System. AEC's version of this approach is called the Tower Water Management System. Alpha Equipment, another maker of cooling equipment, has a similar system called the Alpha Water Treatment System. The systems, "footprints" are small enough to accommodate tight spaces; AEC's version, for example, takes up less than 9 sq ft.
Calgon's Brock also credits improvements in controller technology as the real innovation in water-treatment systems. For example, with today's controller technology, Calgon offers modem diagnostics for its automatic treatment systems, allowing technicians to make adjustments of chemicals or valves from a remote location.
Brock notes that this trend, arose when programmable controller prices fell to the point I where the devices became attractive for water-treatment applications. Depending on the size of the cooling equipment, automatic water-treatment systems cost between $1000 and $4000, including controllers, valves and chemical pumps. Annual outlays for chemicals run about $2000 for a 100-ton cooling tower operating three shifts every day of the year, Altschuler estimates.
MAGNETS AND OZONE
The systems approach also fits in well with alternative water-treatments--those that do not rely solely on chemicals. Calgon, for instance, augments its chemical scale inhibitors with its Tri-Ox system. It kills bacteria and algae with ozone, which works by rupturing the microorganisms, cell walls.
Aqua-Flo also sells a system that uses ozone to kill the bacteria. And to stay completely "chemical-free," the company employs magnets to treat the mineral content of water. Aqua-Flow's side-stream system positions magnets in a permanent housing through which water is drawn with a suction pump.
Use of magnets is somewhat controversial, partly because it's not widely understood how it works. John Deming of the Magnetizer Group Inc., a magnetic water-treatment supplier, explains that magnetized water undergoes an alteration in its molecular structure and ultimately takes on a higher "electron potential" than the surrounding pipe. According to Deming, this potential, which is revealed by voltage readings in the water, is what allows the water to attract calcium-based scale that would otherwise build up on the pipes. Over time, the magnetically conditioned water would even re-dissolve existing scale, Deming adds.
Electromagnetic treatment still draws fire from the skeptics. Altschuler, for one, says he would recommend magnets in a flash--if he believed they would work. "I've seen no evidence that they do the kick against minerals," he says. And Fosco adds that Conair didn't find them appropriate for its lab or any other situation where the cooling equipment can experience extended shutdowns.
DON'T DO IT YOURSELF
Whatever the method of water treatment, it does not appear to be a do-it-yourself project. Most processors will need technical help primarily because treatment goes beyond the experience of shop personnel. "The person responsible for maintenance typically has multiple responsibilities, not just water treatment, so he really needs on-site coaching," explains Brock.
More important, water problems have a geographical component--so what works in one locale doesn't necessarily work everywhere else because of variations in mineral content, climate, and many other factors influencing biological growth. Altschuler explains that a typical customized chemical treatment package contains up to six different raw materials, including up to three antiprecipitants to stop calcium deposits; corrosion inhibitors; a rotating cycle of biocides; and polymeric materials to conkol silt and other solids. "One size definitely doesn't fit all," Altschuler says of the chemical packages.
Not that individual chemicals don't play an important role. Calgon, for example, just introduced a new scale inhibitor under the Phreedom trade name. According to Brock, this "next-generation" material can reduce scale by; as much as half, cutting the expensive practice of bleeding off water by a similar factor. But Brock notes that chemical suppliers usually sell treatments to processors who have already received some expert help from Calgon itself or another specialist.
Given all the complexity surrounding water treatment, it's not surprising that cooling-equipment suppliers strongly counsel that you consult a specialist who will put together the chemical package best suited to your local water conditions. As for finding help, some suppliers recommend local contractors--the kind you find in the phone book. Fosco explains that Conair once provided treatment services itself but found that local contractors could do a more economical job for its customers. Other cooling-system manufacturers supply customers with sample vials and provide an analysis service by mail, as do AEC and Alpha Engineering. Whether by mail or through a local consultant, professional analysis of individual water requirements is the key.
FOR DETAILS ON WATER-TREATMENT EQUIPMENT, USE READERS' SERVICE CARD AEC/Application Engineering, Inc., Wood Dale, Ill. (CIRCLE 16) Alpha Equipment, Fayetteville, Ga. (CIRCLE 17) Aqua-Flo Inc., Baltimore (CIRCLE 18) Calgon Corp., Pittsburgh (CIRCLE 19) Magnetizer Group Inc., Gardenville, Pa. (CIRCLE 20) Maram Corp., Northbrook, Ill. (CIRCLE 21) Thermal Care/Mayer, Niles, Ill. (CIRCLE 22)
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|Date:||Oct 1, 1993|
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