“We converted to a Delta Cooling Tower to overcome the inefficient open-loop system that had collapsed the fill under the weight of dirt and scale in the water,” he notes. “The closed-loop clean water system made it possible to go with the different cooling tower design. Instead of having a splash bar fill, which is about the best you can do for dirty water, we were able to go with a PVC film fill — what’s in the Delta tower. That also allowed us to change from a crossflow tower to a counterflow tower, which gives us greater cooling capacity for its size. We had a limited footprint for the tower, so that has worked out great.”
“The new plastic tower is corrosion proof, and so we don’t have to worry about rust,” Niemeyer adds. “It was also the most economical price, and we were very pleased about that.”
Environmental testing of equipment for oil drilling and production operations poses special demands, notes test engineer Burroughs. “I needed a cooling tower with water-distribution power that is far from normal operating conditions… Secondly, I hate doing maintenance.” The cooling tower supports electrodynamic shakers that check whether the equipment is tough enough. “These shakers emit a great deal of heat and they’re cooled by a closed distilled water system because distilled water doesn’t conduct electricity,” he explains. “Once heated, the distilled water flows through heat exchangers that are cooled by a chill water loop. A three–year-old, 100-ton Delta plastic tower is on the other end of the chill water loop. Another similar unit was also used to reject the heat created by two 1,000-hp drilling mud pumps. It has been working fine for over 13 years.”
Increasing size and efficiency
In the past, plastic cooling towers were considered “too small” for many plants and galvanized-steel cooling towers were generally chosen for packaged applications above 250 tons. However, factory-assembled plastic towers such as Delta’s TM Series can now be combined to provide up to 2,000 cooling tons in a single modularized unit. The modular design makes it easy to provide an extra margin of capacity to handle heat-load or outflow changes, or to upgrade to meet future requirements.
The modular design also introduces new flexibility for conserving valuable real estate. By molding towers in a rectangular shape, some manufacturers enable users to cluster cooling towers in a group that occupies a much smaller footprint. “With the new Delta system we actually got more cooling with less tower,” says Richer. “Our old 45 × 20 ×18 metal cooling tower was replaced by a lightweight plastic model that is only half that size, yet has slightly greater cooling capacity.”
While the cost of electricity to drive cooling tower fans may seem minor compared to process costs, it adds up. Direct-drive motors are more efficient and hence deliver substantial energy savings as well as more horsepower. “The two motors installed on the old tower were each 40-hp, 3-phase, 480-volts. On the new tower there are four 10-hp motors,” Richer says. “So we now have only half the power requirement. Plus the new motors are more efficient than the old ones. We have not measured the energy saving, but it’s there.”
In some cases an engineered-plastic cooling tower allows users to completely re-vamp the technologies supporting their cooling systems, achieving greater productivity and savings in the process.
“The molded-plastic cooling tower is the only way for us to go, as I was able to eliminate double cooling — which was the case when we had metal cooling towers cooling down chillers for the process water,” says Doug Henderson, project engineer for Cerro Wire & Cable, Hartselle, Ala. “We switched over to plastic cooling towers and they give us enough cold water that we can do the job without any problems and we don’t waste the energy.” Today Cerro Wire & Cable uses four 200–ton Delta cooling towers for four different process areas. Three go through heat exchangers to cool process water, while the fourth cools an open loop that runs through water troughs to cool wire as it is encased with plastic.
As engineers learn to recognize that plastic cooling towers aren’t just for small applications, these towers will continue to expand into areas once dominated by towers made of metal, concrete and wood.
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Dave Jurgensen is national sales manager for Delta Cooling Towers, Inc., Rockaway, N.J.; e-mail him at firstname.lastname@example.org.