Energy Savings: It’s Time to Act, It’s Time to Report
How many case studies are needed to light a fire under a managerial team so they take on energy saving as a serious and profitable activity? One? Two? Ten?
Would more case studies convince you it’s worth the time to take on one more task? Here’s a few for your consideration:
The heat loss of a 75kW-500lb capacity holding furnace is about three times greater when uncovered vs. covered (at 1,400F it’s 26.6 kWh vs. 9.4 kWh), according to a NADCA paper, “Heat Losses in Aluminum Holding Furnaces and Transfer Ladles.” Do the numbers for your own situation. The paper also has specific information on transfer ladles. (Heat loss with an insulated ladle is about one-half of what is experienced with a simple castable refractory.) Imagine the cost of induction melting of iron at 2,700F without a lid or cover!
Do you have hydraulic motors left running for hours and hours when no production is occurring? Do a quick calculation and determine what would it be costing you.
One facility was wasting energy to the tune of over $35,000 per year. It was a simple fix (5-minute effort) to program a change in the controller to turn off the hydraulics after 15 minutes of no activity. You pick the time that fits your situation.
A major automaker paid an hourly associate a very large bonus for simply bringing this to the attention of management.
An old gas-fired aluminum melting furnace was operating with a burner that resulted in a measured efficiency of 6%. It was reequipped with an updated burner, and a measured efficiency approaching 40% was achieved. Sounds good, but the burner was removed because the melt-deck operators couldn’t handle the improved melt rate. (There was nothing in it for them to use the increased efficiency burner.) To the best of the authors’ knowledge, it’s still running with the old burner.
Maintenance liked to use compressed air vortex cabinet coolers because they wanted to avoid potential problems associated with other choices such as a small AC system. A vortex cooler costs 10 times as much to run as an AC unit. Eventually, the plant did change to an AC system and—wow—it experienced no maintenance problems while being used for several years.
Table A summarizes several of cabinet-cooling choices. Try one yourself and generate the metrics so a sound economic decision can be made. You don’t know until you know. How many pounds of die castings must be made off that one machine to generate the dollars needed to pay for what would appear to be questionable choices? What is the impact on profit? Stop making castings just to pay for making what seems to be an “easy-way out.”
A 40-ton/hour cupola operating with an uncovered runner system from the cupola to a holding furnace resulted in a 25F temperature drop. What are the savings by covering the trough against cost of accomplishing this? You can find out by running a well-documented trial over a one-week period.
Document. Document. Document. Be sure to let all participants know the results. Don’t lose money by ignoring easy changes. A case study means that someone has done the hard work for you. Now modify it to your situation and improve your plant.
Click here to see this story as it appears in the March 2019 issue of Modern Casting