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

machines, spraying die lubricant, and blowing loose flash from trim equipment. Compressed air
use is higher in typical sand foundries than in die casting operations. The compressed air
pressure at a foundry ranges from 95-110 pounds per square inch (psi). In most cases,
temperature control is only necessary to ensure that the dew point of the compressed air is kept
low enough so that condensation does not collect in the line. However, some core-making
processes require air at a - 40° F dew point to prevent chemical reaction between the resin and
the moisture in the sand and air. 27
Improving compressed air systems offers an opportunity for metal casters to reduce their energy
consumption and lower their costs. According to the Energy Use in Selected Metalcasting
Facilities – 2003 study, most compressed air system installations were the result of progressive
growth needs and, thus, were often engineered poorly, were saturated with water, and exhibited
numerous leaks. Furthermore, facilities often misapplied air in a variety of situations and
selected air driers and other compressed air components based on initial capital cost rather than
functionality, leading to poor operating efficiency.
AirMaster+, another free software tool offered by the ITP BestPractices portfolio, can help
casters identify energy-saving opportunities in compressed air systems throughout the casting
operation. Using plant-specific data, the tool assesses the compressed air systems and evaluates
operational costs for various equipment configurations and system profiles. The tool estimates
savings based on potential energy efficiency improvements and calculates the estimated payback
periods.
AirMaster+ evaluates the energy-savings potential based on reduced air leaks, improved end-use
efficiency, reduced system pressure, the use of unloading controls, adjusted cascading set points,
the use of automatic sequencers, reduced run time, and the addition of a primary receiver. The
tool includes a database of generic or industry-standard compressor specifications and creates an
inventory specific to the individual metal caster’s air system. Based on user-provided data, the
tool simulates existing and modified compressed air system operations. It can model part-load
system operations for an unlimited number of rotary screw, reciprocating, and centrifugal air
compressors operating simultaneously with independent control strategies and schedules. The
application also develops 24-hour metered airflow or power load profiles for each compressor,
calculates lifecycle costs based on inputs of seasonal electric energy and demand charges, and
tracks maintenance history for system components.
In 2002, a foundry located in California that specializes in centrifugal casting implemented the
AIRMaster+ tool in assessing its compressed air systems. Two rotary screw compressors served
the facility: a 100-horsepower (hp) unit and a 50-hp unit. Results from the analysis enabled the
facility to replace the 100-hp and 50-hp compressor with a new 50-hp compressor and upgrade
the compressor controls to increase the system’s efficiency. The foundry then used the old 50-hp
unit as a back up. Implementing the recommendations allowed the foundry to reduce its
compressor capacity by 50%, resulting in annual compressed air energy savings of 242,000 kWh
and an annual maintenance cost savings of $24,200. The implementation required the foundry to
invest $38,000; however, the plant received a $10,000 incentive payment from the California
Public Utilities Commission, reducing the total cost for the investment to $28,000 and its
payback period for the foundry to 14 months.
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