Metalcasters are always concerned with conserving their own limited resources, and there is a continuing need to manage increasing operating costs. They know they must maintain ‘lean’ operations but also want to save costs wherever possible.
That’s why furnace system builders develop ways to optimize performance, even for advanced systems like induction melting technologies. Inductotherm Corp. undertook a review of furnace cooling systems recently, and identified two new water system options that can reduce initial installation and operating costs by reducing water consumption and power usage.
Water systems are a crucial component in every foundry melt shop. Water consumption and treatment can cause significant costs. Older evaporative cooling systems with high water consumption and water treatment are expensive to run.
Heat recovery systems can provide significant energy and cost savings, as well as environmental benefits, by offering metalcasters a solution to reduce costs associated with heating the facility in the cooler months. Even greater savings may be realized by reducing water consumption, power usage and chemical additives. Heat recovery systems can be coupled with “smarter” water-saving systems to reduce costs significantly.
Modern water-cooling systems incorporate the low-cost advantages of dry air coolers (DAC) with the heat-removing capabilities of evaporative systems. Recent developments have led to two versions of a more cost-effective water-saving system: the DACXtreme™ and DACXtreme Plus™.
Both versions employ dry air coolers that pull air over heat exchanger tubes to cool water flowing through the tubes, providing cooling for the system. Dry air coolers alone are a cost-effective cooling technology, but their effectiveness is limited by ambient temperatures.
In the past, for metalcasters in hotter climates, the preferred approach to provide sufficient cooling was to use a closed industrial tower. The closed industrial tower cascades external water over a tube-bundle heat exchanger to cool the process water. A fan provides fresh air to promote additional evaporation cooling.
Although effective at cooling the internal water on very hot days, closed industrial towers tend to have high water maintenance costs, high water consumption, and high initial cost. Also, they require external water freeze protection in cold climates.
Reducing water consumption in moderately hot climates
Inductotherm Corp.’s DACXtreme system is recommended for metalcasters in moderately hot climates. It consists of a standard dry air cooler with a fog trim system (FTS) and a demineralized water storage tank. When the temperature begins to rise above the standard dry air cooler’s limitation, a temperature sensor activates the FTS to release a demineralized misting spray. As the demineralized water evaporates in the air around and on the surface of the tubes, heat is removed, effectively lowering the local ambient temperature around the cooler.
It is important that the water used is demineralized so the dry air cooler does not get plated with minerals, which would insulate the cooler tubes and create a self-degrading system where more external water is required to maintain proper cooling.
During hot weather, the expected water consumption is 2.5 gallons per minute per 1,000 kW, compared to 6.0 gallons (average evaporation and bleed) per minute per 1,000 kW year-round for a standard industrial tower. The DACXtreme system offers many of the cost advantages of a dry air cooler with some additional cooling associated with an evaporative system.
Reducing water consumption in very hot climates
The DACXtreme Plus is especially well suited to metalcasting operations in very hot climates. It is comprised of a standard dry air cooler with a compact evaporative tower (CET) and plate-type heat exchanger. As with the DACXtreme, when the temperature begins to rise above the standard dry air cooler’s limitation, a temperature sensor activates the CET.
The furnace cooling water passes through both the dry air cooler and a plate-type heat exchanger. The CET will begin to provide additional cooling to the cold side of the plate-type heat exchanger during hot weather. Water consumption is 3.0 gallons per minute per 1,000 kW.
The DACXtreme Plus offers many of the cost advantages of a dry air cooler with all the cooling capabilities of an evaporative system. The DACXtreme Plus will only consume water during peak hot weather. It is designed so the CET basin is drained during periods of low temperature, eliminating the need for freeze protection.
Unlike the internal tube-type heat exchanger in a closed industrial tower, the external plate-type heat exchanger used with the CET can be accessed easily and disassembled for cleaning. In most cases this will eliminate the need for tower water treatment, reducing costs further.
Reducing water usage, power consumption
Both the DACXtreme and DACXtreme Plus are ideal for hot regions where there is little-to-no water supply available, and when water must be trucked in at a premium.
By converting to a water-saving system, external water requirements can be reduced significantly, which will reduce operating costs and address environmental concerns associated with water usage.
Evaporation is a thermally efficient way to remove heat from water-cooling systems, but it uses a lot of power. To continue increased cooling efforts and to reduce water requirements significantly, the dry air cooler would operate normally, without the aid of evaporation, during the cooler months.
Only during periods of hot weather conditions would it be assisted by either the FTS (DACXtreme) or the CET (DACXtreme Plus) for additional cooling capacity. Power consumption can be reduced further by using a control system that cycles fans and pumps as required instead of allowing them to run continuously.
There are many variations when it comes to water systems, and every foundry melt shop should work with experienced professionals to ensure that they have the ideal cooling solutions for their melt system.
Delta Centrifugal Corporation — a producer of specialty centrifugal castings in stainless steel, nickel, cobalt, and copper based alloys — recently installed a new induction melt system with the DACXtreme Plus water-cooling system. The company has been an Inductotherm customer for over 30 years, and since 1968 has been expanding its foundry, machining and testing capabilities, as required to ensure continued growth.
In 2003, Delta continued its progress toward world-class manufacturing by adopting lean manufacturing integrated with Six Sigma. Lean manufacturing reduces the time from customer order to manufacturing and delivering products by eliminating non-value added waste in the production stream. A lean manufacturer is continuously improving.
In keeping with its lean manufacturing commitment, Delta Centrifugal also studied other ways to reduce waste. According to Robert Rose, CEO and President, Delta Centrifugal selected the DACXtreme Plus in order to cool the melt system during the very hot Texas summers, while reducing the water usage significantly and eliminating the requirement for emergency city water. Because the DACXtreme Plus evaporator operates only on days when the temperature begins to rise above the standard dry air cooler’s limitation, the system reduces water and energy waste. It is just one way that Inductotherm and Delta are helping to reduce waste.
The DACXtreme Plus water-cooling system was shipped with a new 3,000 kW VIP® Power-Trak® unit with a 5 metric ton Heavy Steel Shell furnace. This system will be the tenth melting system that Delta has ordered from Inductotherm over the past three decades.
Too much cooling capability will cost more than what is required and will result in losses. Without proper cooling, equipment can be damaged due to overheating and other damages may occur.
Bill Newbold is a District Manager for Inductotherm Corp. Visit www.inductotherm.com