Improving the Efficiency of Die Casting Machine Hydraulic Systems With the Retrofit of Adjustable Frequency Drives

Die Casting is a common method of light metal processing which is used to produce accurately dimensioned, sharply defined metal parts. Most die casting machines in use today utilize a complex hydraulic system to perform the necessary work required for the process. The pressure and flow rate demands on the hydraulic system vary significantly throughout the cycle. Many older systems are greatly oversized so that they are able to meet the peak hydraulic demand at any point. These systems operate inefficiently because there is typically no way to limit the hydraulic capacity during periods of low demand. As a result, fluid is throttled to lower pressures and excess fluid flow is routed directly back to the system reservoir, wasting motor energy and increasing the thermal load on the cooling system. One option for improving the efficiency of older die casting machines currently in use is the retrofit of an adjustable frequency drive, or AFD. An AFD allows the speed of the pump motor to be varied, changing the pump output to suit the cycle demands. This minimizes the amount of wasted energy without affecting other process parameters. This paper will discuss the die casting process and examine the energy savings potential of retrofitting die casting machines with adjustable frequency drives. (download PDF )

The Use of Variable Speed Drives to Retrofit Hydraulic Injection Molding Machines

Injection Molding is a common method of plastic processing in which thermoplastic materials can be molded into arbitrary comples shapes. Most injection molding machines use complicated hydraulic systems to perform the necessary work of the process. Hydraulic system flow and pressure requirements vary throughout the cycle and in many cases, excess fluid that is not required by the process is throttled back to the reservoir, wasting motor energy and producing additional thermal load on the cooling system. Variable speed drives can be used to allow injection molding machine hydraulic systems to vary the amount of fluid being pumped and thus reduce the amount of fluid that is throttled, reducing the amount of wasted energy. This paper discusses injection molding machine processes and develops a protocol for assessing the efficacy of variable speed drive retrofits for hydraulic injection molding machines. (download PDF )

Benchmarking an Energy Evaluation Tool for Chilled Water Systems

Following the development of an energy evaluation tool for chilled water systems there was a need to determine the accuracy. The tool quantifies the energy usage of various chilled water systems and of typical energy conservation measures that are applied to these systems. It can be used as a screening tool to identify potential areas that can be further examined, while only requiring a minimum number of inputs. The tool is evaluated against the data obtained from an actual chilled water system consisting of three 630-ton centrifugal chillers and a three-cell cooling tower complete with two-speed fans. The collection and analysis of this data along with the problems encountered are discussed. Chiller performance curves and cooling tower power requirements are compared. Data was also obtained to investigate the effects of raising the condenser water temperature on chiller efficiency. Based on this data, a discussion of some of the tool's inaccuracies is presented. It was found that the tool closely reflected actual cooling tower performance. The prediction of chiller performance and the chiller condenser water reset relations may require further improvement. (download PDF)

The Development of an Energy Evaluation Tool for Chilled Water Systems

An energy evaluation tool for chilled water systems was developed. This tool quantifies the energy usage of various chilled water systems and typical energy conservation measures that are applied to these systems. It can be used as a screening tool to identify potential areas that can be further examined while only requiring a minimum number of inputs. The tool is useful for analyzing chiller plants with up to three electric chillers consisting of reciprocating, helical rotary, and/or centrifugal chillers. Both air-cooled and water-cooled systems can be analyzed with the tool, however, this article focuses on water-cooled systems.The tool is capable of analyzing the economics of the following energy conservation measures: 1) raising the chilled water temperature, 2) lowering the condenser temperature, 3) replacing the chiller(s), 4) using variable speed drives on centrifugal compressors, 5) utilizing free cooling, and 6) replacing electric chiller(s) with gas engine centrifugal chillers. For each of these measures, the tool calculates the annual energy and cost savings. (download PDF)

Process Parameters and Energy Use of Gas and Electric Ovens in Industrial Applications

The study was conducted to evaluate the energy use of natural gas and electric ovens in the production of polymer bearings and components. Tests were conducted to evaluate and compare the performance of natural gas and electric ovens in the process of sintering billets which are made from a broad range of materials such as PTFE and other fluoropolymers, elastomers, thermosets, thermoplastics and composites. The purpose of this study was to compare the process parameters under similar conditions for industrial applications where electric ovens have predominant use. Tests were performed to obtain the process efficiency and examine cost savings potential in converting electric ovens to natural gas. Preliminary results show that, for the plat studied, cost savings of about $10,000 per oven can be achieved, with a simple payback period of less than two years. The results also show that additional energy savings will be realized if the oven size and exhause flow are carefully selected. The data obtained from these experiments were used to calculate process efficiency. Design features and environmental issues are discussed. (download PDF)

System Wide Economic Benefits of Distributed Generation in the New England Energy Market

Distributed generation (DG) is generation of electricity close to the point of use. Combined heat and power (CHP), the most energy-efficient form of DG, is the simultaneous production of electrical and thermal energy by one system. A CHP system can be nearly twice as efficient as conventional power systems. Although CHP is recognized for its energy-saving, environmental, and economic benefits, no one has developed a method of calculating externality benefits - which are non-energy-related benefits, such as transmission, distribution, and emissions - or determined who would benefit and to what extent. (download PDF )

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