A fresh approach to compressed air savings
Joe Ghislain sees the issue of compressed air waste in manufacturing from two perspectives. That is impressive on its face, because compressed air waste is often the most invisible, and thus the most insidious, energy waster in a manufacturing plant.
Ghislain is a longtime board member for the Compressed Air Challenge (CAC), a consortium of compressor manufacturers, suppliers, consultants, and utilities. The group’s stated goal is “Helping you enjoy the benefits of improved performance of your compressed air system.”
Ghislain also is a North American regional senior manager for the Ford Motor Company, and one of his areas of emphasis is Lean supplier optimization.
In both roles, the goal is optimization. In speaking to Kaeser Compressor’s “Pressure and Profit” seminar at Guaranteed Rate Field in Chicago in May, Ghislain said the language of optimization is different depending on where you are in the plant. “If you’re an engineer, you talk about psi, you talk about kilowatts,” he said. “When you talk about dollars, you put it in perspective.”
As he noted, “Nobody ever got fired for using too much energy.”
The cost of estimated waste of compressed air is staggering. While compressed air generation accounts for about $5 billion in energy costs annually, Ghislain said CAC research shows that only about 50% of that is put to productive use. He said about one-third of all generated compressed air is dissipated in leaks, and the remaining losses are split between over-pressurizing a system to compensate for leaks and generally wasteful uses of compressed air, such as using a hose to clear debris from the plant floor.
Getting more from your compressed air system requires a fresh approach. “You have to take an actual systems approach. You need to align supply and demand,” Ghislain said. “It’s knowing about what’s driving the cost and driving efficiency. You need to get out of the compressor room and out into the plant facility.”
The Red Coats are coming
At Ford, this has meant establishing an energy management team whose responsibility it is to look for ways to optimize energy usage and reduce waste. At a number of Ford’s stamping plants, the energy teams wear red coats, and Ghislain said they were charged with aggressively pursuing both energy awareness among line workers and finding waste in the process.
The first step is to create a baseline for energy usage that accounts for all factors, including critical machines and seasonal factors. “The guys in the facility will know which ones are the critical systems,” Ghislain said. “You also have to understand winter versus summer usage, because loads can change. These are dynamic machines and they are effected by those kinds of things.”
A dynamic control system is equally important. “The whole purpose of a control system is to run the compressors in the most efficient way possible,” Ghislain said. “The controls system has to operate the right compressors under the right conditions.”
Another big issue is maintenance. “It’s always considered a necessary evil,” Ghislain said. “It seemed I never could do the maintenance. When we had the money, I couldn’t shut down. When we could shut down, we didn’t have the money.”
One way to address maintenance is with a comprehensive predictive maintenance program. “A predictive maintenance system pays for itself,” Ghislain said.
The efforts at Ford produced both tangible and subtle results. At Ford’s stamping plant in Monroe, Michigan, the Red Coats helped drive a cultural change in the way line workers thought about and approached energy usage. As a result, compressed air use fell from 17.4 million cubic foot per day to 9.0 million cubic foot per day and electricity savings topped $2,000 a day. The non-production use—that 8% of inappropriate use of compressed air—fell from 5,400 cfm to just 600 cfm.
There was a similar success story at Ford’s Woodhaven stamping plant, also in Michigan, where the focus was on fixing the leaks in the system. Plant officials and the energy team in place at Woodhaven began by estimating the cost of air leaks and using ultrasonic detection to find and then fix the leaks. There were leaks found in stamping press dies, for example, and this allowed for the reduction of pressure drops at various points in the system.
After the study and repairs, air use fell by 18% and air pressure dropped by 5 psi in the plant. That allowed plant officials to shut down a large 800 hp compressors and six smaller compressors and rework the controls system so the larger compressors used less energy. The plant saved about $400,000 a year and reduced their exergy usage by 7.9 million kWh.
Eight compressed air system design pitfalls
Proper design is as important to a successful compressed air system as proper operations. Ghislain cited eight things to watch for in a proper system design:
Using only full load calculations for savings
Using average cost of kWh for off peak savings
Assuming all unregulated demand when calculating artificial demand
Assuming pressure flow controllers negate the need for a good compressor control system and strategy
Implementing capitol solutions before doing the “low cost” opportunities
Buying only VSDs and/or using them as base load.
Not adjusting centrifugal compressor savings for winter and summer temperature differences
Not using utility rebates.
Bob Vavra, content manager, Plant Engineering, firstname.lastname@example.org.
Typical components of demand
According to the Compressed Air Challenge, the actual use of compressed air in manufacturing is split 50-50 between useful purposes and waste.
- 50% Production
- 33% Compressed air leaks
- 8% Over-pressurizing the system to compensate for leaks
- 8% Inappropriate uses of compressed air.
Source: Pressure and Profit presentation
CFM: Cubic feet per minute (CFM) is a measurement of the velocity at which air flows into or out of a space.