Process, Power and Plant Controls Join Forces To Achieve Performance Gains

In a recent article published by Control Global, they took a look into three control types which have evolved to use more software and digital components, thus removing many of the functional obstacles, and allowing them to communicate more freely.

In past years, power distribution/conditioning and building management/automation systems (BMS/BAS) historically provided the energy and environment for production, while process control monitored and optimized operations as they happened. However, as all three control types evolved to use more software and digital components in recent years, they’ve also grown more similar in appearance and in how they’re applied.

Anchor Glass Container Corp. reports one of two old melting furnaces at its food-grade container plant in Shakopee, Minn., was causing energy inefficiencies, threatening productivity, and not allowing more than two weeks of production data to be viewed. The facility is one of six that takes crushed, recycled glass; chemicals and other raw materials, melts it at 2,700 °F, and produces about 600 bottles per minute, or about 300 million per year with about 18 changeovers per month.

The larger, 27 x 46-foot furnace is 17 years old, and needed to be re-bricked because its aging bricks provided poor insulation. This meant the furnace couldn’t maintain consistent temperatures, wasted energy, and risked producing lower-quality product. The glassmaker adds its furnace’s need for better thermal control was most evident in its reversal process, which relies on the regenerative furnace to maximize heat utilization. One side of the furnace captures heat; the process is reversed; and captured heat is reused by injecting it back into the furnace. Without tight control during this process, the furnace lost even more heat, and Anchor lost even more revenue.

In addition, the furnace’s old thermal monitoring system wasn’t user-friendly, required time-consuming manual adjustments and charting, and only stored two weeks of data. This lack of data visibility made monitoring and trending difficult, and prevented valuable analysis. Furnace operators also relied on an old, analog alarm system with only 12 alarms for the plant. To develop a new furnace control system, Anchor Glass worked with longtime collaborator Stone Technologies Inc., a CSIA-certified system integrator from Chesterfield, Mo., and they implemented a PlantPAx DCS from Rockwell Automation to monitor more than 1,000 tags and 2,600 alarms, which are tracked for frequency to improve predictive maintenance.

Historian software in the PlantPAx system also gathers data on furnace temperature, air pressure and other data points, which are viewable on an intuitive HMI with detailed sequencing that allows Anchor’s operators to fine-tune processes for more energy efficiency. PlantPAx also let Anchor Glass adopt more intuitive controls with consistent faceplates that require less training to operate, which was essential because only six staffers run the Shakopee plant.

To address energy losses during furnace reversal, Stone Technologies implemented scalable, controller-based sequencing that gives Anchor Glass’ operators better control over each step of the reversal process. The system integrator also convinced Anchor Glass to employ new controls for slow processes by using the PlantPAx internal model control (IMC) process function, which assisted slow-acting loops such as Anchor’s glass level and temperature control.

“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,” explains Brad Downen, MES Project Manager at Stone Technologies. This enhanced data visibility lets the glassmaker’s operators manage temperature stability better during every minute of their day, recognize operational trends and patterns, pinpoint potential problems faster, and efficiently produce the optimum number of bottles per day. Since implementing PlantPAx at the Shakopee plant in 2013, Anchor Glass has also installed similar systems in three of its other facilities.

“Since re-bricking the furnace and implementing the PlantPAx solution, we’ve seen huge savings in our gas and electrical expenses,” adds Fiebelkorn. “I’d estimate an average of 15% of the cost savings is from having a better control system on the furnace.” In all, re-bricking the melting furnace and implementing PlantPAx have improved glass quality and saved the Shakopee plant about 350 dekatherms per day, or about $766,500 in gas per year gas and $337,260 in electricity per year.

Visit the link for more insight into the Control Global article, additional information about the projects and technologies featured.

For information about Gray Solutions, and our open positions, visit our Careers Page.