Implementation of Metal Casting Best Practices - EERE - U.S. ...

2. Areas for Improvement
Even though it is a state-of-the-art facility, the assessment team still identified areas for
improvement at Lost Foam Facility-2 that management could pursue to achieve some energy and
financial savings.
Ingot Size
Lost Foam Facility-2 purchases its alloys from a smelter. During the visit, the assessment team
noted that the facility purchases pallets of large billets of aluminum alloys rather than the smaller
ingots. These large billets are approximately the size of three normal size ingots. The facility
purchases these larger sows because it saves them $0.05 per pound of aluminum as compared to
the smaller ingots, which translates to a $50,000-savings for every 1 million pounds of the alloy
purchased. However, the assessment team noted that these savings are eroded significantly by
the extra energy purchased to melt the larger mass, due to heat transfer restrictions as compared
to the typically much smaller ingot. A detailed study is required on the amount of energy
consumed in the dry-hearth reverberatory furnaces at the facility when melting these two shapes
and sizes. To conduct this study, the facility will need to work with its natural gas utility and
install a gas meter on the furnace to obtain an accurate determination of the gas consumed when
melting the various shapes. Once the natural gas consumed for the various shapes is known, the
facility can compare those costs to the cost saved from purchasing the sows and make an
educated decision as to how to proceed in the future.
Compressed Air System
The 75-hp air compressor at this facility is isolated from the 100-hp compressor and operates
without a refrigerated drier. The entire system lacks an air receiver system. The assessment team
recommended that the facility reevaluate the operation of this system.
The assessment team suggested that the facility conduct a detailed study to determine its actual
compressed air needs. The current system is operating at an unusually high pressure and if that
high pressure can be reduced, the facility can save 1% of the energy cost for each 3 psi reduction
in air pressure. The facility should also consider installing a refrigerated drier for the system. In
general, a compressed air dryer will pay for itself by reducing downtime from water-induced
failures in various valves, thus increasing production and improving the facility’s bottom line.
This is because water buildup in the lines can be damaging to both the machinery and the
castings. Standard air procedures suggest that air should be dried to a dew point of 10ºC (18ºF)
below the lowest ambient temperature that it will encounter. 59 Finally, the facility should
consider installing an air receiver in the system. An air receiver will minimize compressor
cycling by providing a constant air pressure to the facility. However, the receivers must be
properly sized and placed in order to gain these benefits.
The assessment team recommended that the facility utilize the AirMaster+ software to assist in
this analysis. This software tool will help to identify the cost of air leaks, improve end-use
efficiency, reduce system pressure, reduce run time, use unloading controls, adjust cascading
points, use automatic sequencers, and add primary receiver volume. The proper use of this tool
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