The plant’s air compression system is crucial to the production process. Comprised primarily of five large centrifugal air compressors, the system provides air across the 1.2 million-sq.-ft. plant for various machine processes, automation and drying engine components.
Compressed air systems are energy intensive by nature. The system at the Huntsville plant is no exception; it accounts for 25% of the plant’s annual energy costs.
The legacy controls made the system an even bigger energy user than it needed to be. The aging controls were slow to start up the compressors and didn’t allow them to work together as an integrated system. They also didn’t have enough compressed air storage to draw from during high peak air demands.
Because of these limitations, team members had to keep compressors online more than necessary for most of the day to guarantee enough air capacity to ride through short, occasional demand surges in the plant.
“We need a minimum of 81 psi for machines to run without stoppage,” says Eddy Kiggen, a facility specialist at Toyota. “But because the compressors took so much time to start up, we had to maintain 91 psi just to make sure we didn’t fault out at 81 psi low compressed air pressure.”
The plant’s electrical contract created more challenges. The contract charges more for energy consumed during peak usage hours. When team members needed to start one of the large compressors during these times to keep the plant at capacity, a single machine start-up could increase the plant’s electricity bill by 100% of one day’s energy charges.
Local and Plantwide Upgrades
To help rein in energy costs and support its 2050 energy initiative, Toyota Motor Manufacturing, Alabama (TMMAL) decided to upgrade the plant’s air compressor control systems.
For the job, Toyota asked for help from Rockwell Automation OEM Partner Case Engineering and IZ Systems, a supplier of compressed air vacuum systems and equipment. Together, they delivered a two-part solution that included local and plant-wide controls.
Locally, Case migrated the controllers on the five large compressors to its AirLogix control solution. It’s based on the CompactLogix™ control platform from Rockwell Automation and includes an Allen-Bradley® PanelView™ Plus 7 operator interface to give workers performance and diagnostics data at each compressor.
At the plant level, Case used its AirMaster load-sharing solution to create a master air control system, which is based on the Rockwell Automation ControlLogix® platform and uses the FactoryTalk® View SE software for data collection and visualization. Case worked with IZ Systems, which also installed a 5,000-gallon storage tank for boosted compressed air of 500 psi to allow the system recovery time without faulting.
A modulating valve delivers air during high air demand periods. This stored air provides a smooth transition when an additional centrifugal machine is required to meet the plant’s air demand.
Revving Up Savings
The new, more efficient air compressor controls have helped the Huntsville plant reduce annual energy usage by nearly 1 million kilowatt hours per year. This doesn’t include the savings realized by avoiding start-ups during peak-usage hours.
As a result, the plant recovered its investment in the new controls faster than its goal of two years.
“We’ve been able to reduce our setpoint for the system from 91 to 85 psi,” Kiggen explains. “That’s where the majority of the savings are on this project.”
The updated local controls help the compressors run more efficiently than the legacy controls by increasing the throttle capacity from each machine. The new master controller monitors pressure, and air flow will start or stop compressors to match demand. It will draw compressed air from a high-pressure storage tank while a compressor comes online, ride through demand surges and protect against potential issues.
“The way it’s set up now, we always have enough pressure in the storage tank for any dips or compressor failures,” Kiggen says. “Even if the next compressor we try to start fails, we can start yet another compressor, and people on the plant floor won’t know anything happened.”
The new system gives workers trending information to monitor air pressure and flow, energy usage and critical data at each machine, including vibration. And because this information is available in near real time — something team members previously didn’t have — it helps to analyze the compressed air system and assist when troubleshooting.
Team members can view the information locally at each machine as part of their routine operations monitoring. Toyota and Case Engineering can view it from anywhere using remote access.
“After electricity, air is the most important utility we have, so we keep a close eye on it,” Kiggen says. “I look at the data daily to see how the system is performing and to review its efficiency. I get a text message if we have an issue, like a pressure drop or the storage tank falling below a certain level. We also like having Case connected and let them know of an issue so they can get online to fix the problem right away.”
Toyota is looking at replicating this project elsewhere for similar energy savings while continuing to drive toward zero CO2 emissions.
“Producing zero CO2 in the process of building a vehicle is a very big task,” Kiggen says. “Right now, we’re trying to save as much energy as possible before we jump into renewables. And for this plant, these control upgrades are the most successful energy projects we’ve done in a long time.”
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