of an evaporative cooling tower where it is cooled by water from a sump. Or, it can be housed in a dry air cooler where it is cooled directly by air flow. It also can be part of a hybrid cooling system. Closed water systems keep water
desired outflow temperature is reached. Inline water heaters also may be used to bring the water up to temperature.
Open vs. Closed Systems Two basic types of cooling systems
are common in metalcasting: open and closed. In open systems, heated water travels through pipes from the furnace to the cooling tower. Tere it is sprayed through the air and flows down through a porous material. Evaporation, enhanced by the air flow generated by powerful fans, serves to cool the water, normally collected in a sump at the bot- tom of the tower and pumped back to the furnace. City water must be added to replace the water lost through evapora- tion and to dilute the buildup of minerals in the water. All open systems use evapo- rative cooling towers. Open cooling systems are the simplest to build and operate and can achieve the lowest water temperatures. But they expose the water to dirt, debris and scale that can build up over time and clog the pumps, pipes and furnace coils, restricting water flow and substantially reducing cooling effectiveness. Open water systems, therefore, must include filters and strainers to capture solids and chemical treatments to reduce scale formation. Other treatments are needed to prevent disease-causing organisms, such as Legionella, from developing in the water. Overall, open water systems
require more regular maintenance than closed systems and use more water. Te sumps also require protection from freez- ing in cold climates. In closed cooling systems, heated water also travels through pipes from the furnace to the cooling tower. But unlike open systems, when the water reaches the cooling tower, it continues to travel under pressure through pipes in a heat transfer coil, where the cooling takes place. Te cooled water is then pumped directly from the heat transfer coil to the furnace. Te heat transfer coil can be part
clean and free of debris and require minimal maintenance. However, closed water systems cost more to build. Tis is because as closed-loop systems they require heat exchange coils, expansion tanks, air vents and air scoops—all items not needed in open systems. Whether a metalcasting facility uses an open or closed system to cool its furnaces, the water that recirculates through an induction power supply must be a closed system. Its electronic compo- nents require the water to be clean and deionized to ensure it is not electrically conductive. Typically, a heat exchanger provides cooling for the water in the power supply without intermingling with the water used to cool the furnace. Te new cooling system at Chas- six is open, like its former equipment. Te decision to continue to use an open system reflects the metalcaster’s desire to incorporate existing plant piping, controls and electrical network into the new cooling installation. “Being able to reduce our costs
by using our existing cooling system infrastructure within the foundry was a key requirement,” Burton said. “It probably saved about $100,000 and
Chassix operates a variety of large induction furnaces, some batch melting and some heel melting. February 2014 MODERN CASTING | 35
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