Controlling Energy Hogs #1
Foundry Analysis (Induction Furnaces)
Length of study: 18 months
Sensors used: AC Power Monitoring Sensors
Implementation time: 2 hours
Key data points included: measurements of power used by each of 2 furnaces every second, 24/7
Projected Annual Savings: Greater than $730,000/year when combined for all 4 furnaces
Capital investment required: none
Pricing: complete system is under $18,000 (AFS corporate members receive a discount of over 20%). Additional options are available
Projected ROI: Less than 2 weeks
The primary goal of the project was to identify opportunities for saving energy by better understanding the induction furnace usage modes during routine operations.
- Quantify actual energy consumption.
- Correlate energy consumption data with other production and process information.
- Identify significant energy saving opportunities.
- Evaluate process changes, equipment enhancement, management goals, site constraints, and environmental considerations during analysis of energy saving opportunities.
- Perform cost / benefit analysis on savings opportunities and make recommendations for foundries to implement.
What We Looked At
A monitoring system was installed on two induction furnaces (4 MW each) and measurements were taken at 1 second intervals (24/7) for a 3-month period—resulting in over 16 million power measurements. Data was sent to the cloud for analysis and sharing with all interested stakeholders.
Raw power-use data was received from sensors and correlated with foundry activities, equipment faults, and other special issues highlighted by notes on operator's run sheets. Sophisticated software analyzed data and was presented in a variety of formats (charts, tables, detail, etc.). This provided meaningful and understandable information to operators and management in real-time during production activities.
Analytics and advanced reporting offered new insights into operations that were previously unavailable to managers and staff, including:
- Time and energy that furnaces consumed, at four common power levels:
- Energy cost per ton, from charge to tap
- Tap-to-Tap cycle time, for different alloys
- Energy cost per ton, compared to industry standards
Data was explored using “what if” scenarios to evaluate costs and benefits of process related issues.
Power use measurements were correlated with foundry activities by combining run sheet “time of day” information and activities notes with automated power measurements. Also, special issues noted on run sheets with equipment faults or other procedural anomalies were tracked and analyzed with measured power-use data.
The weight of metal added to each heat was correlated with the amount of electricity used by the induction furnace from the end of the prior tapping process to the end of the tapping process for the current heat - we refer to this as the "tap to tap" duration.
- Power usage data of induction furnaces must be collected many times per minute to be able to correctly identify operational issues such as detailed tracking of changing power levels.
- While it is expected that there will be some periods of “off time” while equipment repair and other issues are addressed, data showed longer and more frequent periods of “off time” – dramatically impacting and reducing throughput
- Knowing the costs of issues may help a foundry determine which ones to remedy, and in what priority. For example:
- Equipment in need of frequent repair
- Shift change issues
- Hold power usage, power level during hold, etc.
- Total energy expenditures after ready time.
- Energy measurements identified operational issues that, in some cases, can be remedied with additional operator training
- Real-time power use monitoring can support process improvement studies to reduce energy consumption and improve furnace operations time.
- The addition of automated, real time text message alerts help foundry management respond rapidly to process and operational issues that affect throughput, efficiency and unnecessary utility and maintenance costs.
Examples of Project Savings Recommendations
- Increase efficiency of melting process – Estimated annual savings: $466,000
Inconsistent melting times were found to be a major factor. A 3-day period was selected for a more detailed analysis during which no major equipment failures occurred. During this 3-day segment, data was analyzed in detail with additional analytic and software tools related to the energy usage with 1-second time resolution.
In our analysis we estimated the benefits of more consistent operations. What if some of the ‘worst case’ heats (took too long, used too much energy, etc) could be eliminated from a typical work week and replaced with heats that used an amount of electricity and time similar to the average of the lower 75% of these measurements?
We found that if the worst 25% of melts could be improved to more acceptable performance, the average cost of each heat would drop from $200.18 to $178.11, creating an annual savings of $466,000.
- Reducing “Hold Time at Temperature” –Estimated annual savings: $254,000
Reducing the total number of hours that the induction furnace holds the metal at tap temperature - after the furnace has heated the metal to the appropriate tap temperature - will save over $254,000/year .
- Reducing “Hold Time” – Estimated saving in staff time: 874 hours
By eliminating extra "hold time" in the process and certain unnecessary "off time" delays, the overall length of time that the furnace is operated would be reduced 12.7%, corresponding to 874 fewer hours per year that the furnace must be staffed. Extra savings would come from less overtime hours while producing the same output.