How much energy does it take to produce a pound of finished casting?

The honest answer to this seemingly simple question is: “It depends.”

Why is that?

Energy benchmarking is the tracking of energy use using standard metrics to compare past and future performance. Such metrics sometimes can be used to set usage standards to compare your energy use to similar machines in the same facility or to similar machines at other facilities. But our industry brings significant challenges that complicate the issue.

Efforts have been made to establish energy usage standards for the metalcasting industry by the U.S. Department of Energy (DOE) and others, without much success. An ideal benchmarking methodology continues to be sought, but has not yet been identified.

You can’t manage what you don’t measure. Energy benchmarking requires a regular regimen of data collection of energy consumed correlated in time with the amount of finished product produced. The time interval of the data collection is critical; it will provide your smallest time window into the operations of your organization. Putting time-resolved power meters on major energy consumption devices helps provide a better understanding of your power consumption and provides new insights into your production operations.

Perhaps an analogy is in order. We can easily calculate the actual mileage that our car gets for each tank of fuel. Establish your mileage and you can compare the cars’ fuel cost and performance over time. This is a simple form of benchmarking. Collecting mileage metrics has led to estimated mileage standards by the EPA to help us when we shop for a new car. But such standards are established for only four categories of vehicles, based on two factors: vehicle type (passenger cars or light trucks) and size of the vehicle. As the sticker on the window warns, “Your Mileage May Vary.” Many factors, such as driving style, traffic congestions, tire pressure, etc., will influence the mileage that you get in your car.

Energy usage in the metalcasting industry is affected by many more variables than calculating car mileage. Hold times on furnaces, power settings, energy types and costs, metallurgy type (including which alloy), insulation levels, maintenance issues, outside temperatures, and other operational issues can be the metrics you include in the values to be benchmarked.

Two operations are rarely identical in energy performance—even in the same facility with similar equipment. In fact, performance between different shifts with the same equipment can be significantly different. For example, certain mechanical properties of the final product may require different heat treatments using different amounts of energy.

When benchmarking against the amount of finished product produced, plant recovery operations will greatly affect results. Benchmarking metrics will all be affected by melt loss, planned recovery from machined material losses and unplanned recovery losses, like spills and scrap.

Establishing the Baseline
Tracking essential metrics does not have to be difficult. A spreadsheet can be used to establish basic benchmarking capabilities. This simple analysis is only useful for the case in which the electricity monitored by the meter in this example is primarily used for production equipment and not building HVAC.

If you’re looking for a more comprehensive spreadsheet-based tool, Energy Performance Indicator (EnPI) has been developed by the DOE Advanced Manufacturing Office (AMO). EnPI V4.0 is a regression analysis-based tool developed to help plant and corporate managers establish a normalized baseline of energy consumption. This tool can track annual progress of energy-use improvements, energy savings, Superior Energy Performance (SEP) metrics, and other energy-related metrics that account for variations due to weather, production, and other factors. This DOE tool is designed to accommodate multiple users including Better Buildings, Better Plants Program and Challenge Partners, SEP participants, other manufacturing firms, and non-manufacturing facilities such as data centers. The EnPI add-in can be downloaded at https://ecenter.ee.doe.gov/EM/tools/Pages/EnPI.aspx.

There is a great benefit from energy benchmarking in order to monitor vital metrics within your own organization. It will give you the ability to find serious cost savings, improve process efficiency, and increase production throughput… often with little or no capital expense. Is it time to better understand how a major expense for your company is spent? The choice is yours; the electric bill will continue to arrive in the mail. 

Click here to see this story as it appears in the April 2017 issue of Modern Casting.