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Low-Cost Energy Saving Improvements in Metalcasting

Cindy Belt

Every plant would benefit from an energy program to continuously improve efficiency. Such a program should include working toward major upgrades to improve energy efficiency of the processes and establishing a three-year plan for new and efficient equipment. But sometimes, smaller but easy projects can help metalcasters save energy too. Below are a few.

Compressed air leaks—A sad fact is that most plants lose 20-30% of the compressed air produced to leaks. It is not unheard of to have even 50% of the air lost to leaks. Given the cost to find and repair leaks, zero leaks is impractical but a good goal is 10-20% leaks. These leaks can be found on down days when the plant is quiet. Or, use ultrasonic equipment to find the leaks anytime. A rule-of-thumb is that if you can hear a compressed air leak, it is costing you at least $700 per year.

Gas leak survey—Just as compressed air systems always have leaks, natural gas lines also leak. One-percent losses are normal, and even a 12% loss has been recorded in one plant. These leaks can be found using ultrasonic equipment or gas sniffers. However, the quickest method is hiring a firm to use a special infrared camera that detects gas leaks. This camera is not a typical infrared and costs much more, so hiring a firm with expertise using the equipment can make sense.

Conveyor heat loss—Every time a product is heated in heat treat furnaces, the cart is also being heated. The official term for this is conveyor heat loss. Businesses can reduce the weight of the carts to save on energy cost. At one plant, a 3,000-lb. grating was used to provide a flat surface when the cart began to warp. A redesigned grating trimmed 2,000 lbs. and saved $5,000 in energy costs for the year.

Reduce door open time—Every time a furnace door is open, heat is lost. Facilities can reduce this time by adjusting the door opening and closing time, staging charges, and staging equipment such as skimming tools, etc. This can be a subject of a Kaizen event.
Redirect fans—Many plants use fans to cool personnel. Unfortunately, they are sometimes aimed at the furnace too. This air flow increases heat loss in the walls. Aim fans correctly.

Document down-time procedures—Every plant has downtime for maintenance or plan it during weekends. By documenting what equipment (for example, heat treat furnaces, fans, baghouses, lights, and air compressors) should be shut down during this time will save energy. This can be a simple checklist.

One plant put stickers on the switches that should be shut off. These procedures will help new personnel know what equipment should be shut off (and remind current personnel).

Use infrared cameras—Infrared cameras are used in many plants to detect hot spots in electrical systems. The same cameras can be used to observe the walls and doors of furnaces, looking for poor seals and defective insulation.

Learn from the best—Look at data by shift. Which shift is more energy efficient and/or produces more product? Learn best practices from them and transfer the knowledge to other shifts. In one study, a shift was regularly producing 15% more product.

Fully utilize the most energy efficient furnace—First, know which furnaces are best, then do everything possible to fully utilize them. This may include better scheduling or optimizing the process before and after that furnace.

Air-fuel ratios—Check the air-fuel ratio on a scheduled basis. One reverb furnace operator was wasting $10,000 a month due to operating with dirty filters.

Motors—Surveys have shown numerous motors are left running during periods of downtime or even weekends. Thousands of dollars are wasted. Document shut-down procedures or automate shut-downs, such as shutting off conveyors when there is no product.  

Click here to see this story as it appears in the March 2018 issue of Modern Casting