Making a Glass Bottle
Chances are if you’ve sipped a bottled iced tea on a hot summer night, cracked open a bottle of beer with friends, or poured from a bottle of wine, the bottle has come from Anchor Glass.
In addition to serving the beverage industry with a variety of shapes, colors and sizes of glass bottles, Anchor Glass also produces glass containers for jams, sauces and salsa for food and beverage companies around the world.
Its Shakopee, Minnesota, facility is one of six food-grade manufacturing facilities for the company. Here, Anchor Glass takes raw material into the facility – mixing, melting, conditioning and forming it into a finished glass container – producing up to 600 bottles per minute.
The crushed recycled glass and other raw materials arrive by truck or rail, and are offloaded into holding silos. Once the necessary chemicals are added, the glass and other ingredients are sent to a 27-by-46-foot furnace for melting. Here the glass is heated to 2,700 degrees Fahrenheit to melt it into a molten lava state. This lava is then distributed to different forehearths to be formed, conditioned and cooled.
After these vast fluctuations in temperature, the glass’s chemical compound has not stabilized and must be reheated to do so. Once the formed glass has reached 1,000 degrees, it is cooled very slowly to stabilize the chemicals in the glass. This finished product is then inspected for blemishes and inconsistencies before being shipped to one of 55 customers Anchor Glass serves per year.
Losing Control of Temperature
Producing 300 million bottles per year is no small task and the Shakopee facility was relying on two aging furnaces that were running 24/7. The larger of the two furnaces was 17 years old and in dire need of being re-bricked.
The aging bricks meant poor insulation. The furnaces were not retaining proper temperatures, which is vital for the glass manufacturing process. Anchor Glass was wasting energy and money trying to maintain temperatures and keep furnaces efficient. With these unstable temperatures, Anchor Glass was also risking lower-quality glass.
The need for improved thermal control was most evident in the furnace reversal process. This process relies on the regenerative furnace to maximize as much energy (heat) as possible. One side of the furnace captures heat then the entire process is reversed and the captured heat is reused by injecting it back into the furnace. This temperature fluctuation is repeated throughout the day and without tight control during the process, Anchor Glass was losing heat, which in turn was lost revenue
Additionally, the old thermal monitoring system was not user-friendly and required manual adjustments and charting, which was a time-consuming process for operators. The old system only stored two weeks’ worth of data. This lack of visibility into data made monitoring and trending difficult. The limited exposure to historical data and trends prevented valuable analysis to occur
Operators were also relying on an old, analog alarm system with only 12 alarms for the facility.
With so many variables, including furnace pressure, air-to-fuel ratio and controller stability, Anchor Glass knew it needed a new control system to better manage furnace operations and regain control of energy costs.
A Crystal Clear Solution
To help design the new system, Anchor Glass turned to Stone Technologies, a Rockwell Automation Solution Partner and member of the Rockwell Automation PartnerNetwork program. Anchor Glass and Stone Technologies had a 15-year history of working together. After hearing the company’s desire for better data collection, tighter controls and a more intuitive operator interface, Stone recommended a PlantPAx modern distributed control system (DCS) from Rockwell Automation. This scalable, plantwide control system would help increase furnace efficiency and access to real-time temperature information.
“Everything we do relies on temperature control,” said Kyle Fiebelkorn, batch and furnace manager, Anchor Glass. “Implementing the PlantPAx system gives us improved batch management and data collection to monitor our furnace operations.”
The PlantPAx system monitors over 1,000 data tags, and 2,600 detailed and manageable alarms. It tracks which alarms go off most frequently, improving predictive maintenance. Historian software in the PlantPAx solution gathers historical data on furnace temperature, air pressure and other data points. This information is viewable on an intuitive HMI system with detailed sequencing, which allows operators to fine-tune process enhancements to achieve more energy-efficient operations.
The PlantPAx solution allows for an intuitive control system with consistent faceplates that required less training to operate, which is vital with only six staff members at the Shakopee plant.
To address the loss of energy during the furnace reversal process, Stone Technologies implemented a scalable, controller-based sequencing solution. With the added sequencing capabilities, operators have better control over every step of the reversal process.
Stone Technologies also lead Anchor Glass into a new generation of controls for slow processes by utilizing the internal model control (IMC) process function with the new PlantPAx system. The IMC, offered in Rockwell’s Advance Process Controls kit, helped tremendously in slow acting loops such as Glass Level control and Glass Temperature control.
“The IMC for advanced process control applications provides a simplified control algorithm and model to provide better control without reaction to disturbances created by reversal or other factors” said Brad Downen, MES project manager, Stone Technologies.
Serving up Savings
Since implementing the PlantPAx system in 2013, Anchor Glass has been able to better handle the 18 changeovers it does each month.
The increase in visibility allows operators to better manage temperature stability every minute of the day. They can also recognize operational trends and patterns, and pinpoint potential problems faster and more easily – keeping furnaces efficient to produce the optimum number of bottles per day.
“Since re-bricking the furnace and implementing the PlantPAx solution, we have seen huge savings in our gas and electrical expenses,” said Fiebelkorn. “I would estimate an average of 15 percent of the cost savings to having a better control system on the furnace.”
The facility is able to save 350 dekatherms per day, which translates to almost $766,500 in gas savings per year. Additionally, Anchor Glass estimates $337,260 in electrical savings per year.
Operators are also confident they are producing higher-quality glass with fewer blemishes.
The Shakopee plant was the first Anchor Glass facility to implement a PlantPAx solution. Since first installing the system, Anchor Glass has put similar systems into three other facilities, using the Shakopee plant as a blueprint.