Process Automation, Controls Boost Production at Yogurt Plant

PC-based Controls Provide DCS Capabilities, But They Can Also be Implemented and Reconfigured More Easily than Dedicated, Hardwired, Less Software-Based Systems

By James Montague

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"Our new facility allows us to produce more yogurt, but also produce it more consistently,” adds Groetsch. "Our manual process had many inconsistencies and many times resulted in lost batches of yogurt. With the PlantPAx system, we've decreased lost batches by 95%.”

Finally, because demand for its yogurt is continuing to accelerate, Noosa is presently working on another plant expansion, which it expects to finish by the end of 2014. Aided by the scalability of PlantPAx, this new plant will have a redundant, fault-tolerant server architecture. "As new equipment and process units are needed to support demand, Noosa can add more I/O, PAC controllers and servers without adversely affecting the base characterized architecture of the PlantPAx system,” says Malyszko.

Careful Carbonation
Along with aiding the migration from manual to automated processes, PC-based solutions let users maintain much tighter control and tolerances in their applications.

For example, Allied Petro Chemical (www.alliedpetrochem.com) produces petroleum-based distillates at its facility in Alvin, Texas, just south of Houston. The facility has two main sections, including the refining side with two vacuum-distillation towers that separate petroleum distillates to produce naphtha, kerosene, diesel and residual fuel oil, and the additive side that has three reactor units where high-molecular-weight alkylates are sulfonated to produce Allied's SA-320, SA-470 and SA-490 additives. Following initial production, these additives are neutralized and carbonated to create neutral- and over-base calcium sulfonate products. However, sulfonation is a rapid, highly exothermic reaction, so its reaction mass must be continually cooled, and the amount of sulfur trioxide added must be precisely controlled to avoid side reactions and unwanted carbon from forming.

Previously, Allied controlled its refining process manually, but this was labor-intensive, increased potential for errors, and made it difficult to expand the firm's operations and business. Consequently, Joey Kessel, Allied's manager, researched several process control solutions, and selected Opto 22's (www.opto22.com) Snap PAC hardware and software mainly because control points could be easily mapped and changed in its PAC Control programming software. Specifically, Allied installed Snap PAC S- and R-Series controllers, I/O processors, I/O modules, PAC display software and a plant-wide Ethernet network.

Kessel reports that changing distillation from manual to automatic control delivered several benefits. "It's now easier to achieve and maintain the quality of the final distillate products,” he says. "Instrumentation added to the control system makes extensive process data available for production and regulatory purposes, while new equipment monitoring and logging capabilities allow preventive maintenance that keeps downtime to a minimum. Having the new control system in place reduced the number of personnel needed to operate the plant by half. Operators are needed at the plant 24 hours a day, so this resulted in significant savings. This also gives staff time to fine-tune production processes, maintain equipment and scale up production.”

Contacting, Coordinating Controllers
Beyond enabling quicker reconfiguration and tighter performance, PC-based controls often can use more closely integrated network connections to achieve more efficient operations — and even help users break into new industries and markets.

For instance, Repete Corp. (http://repete.com) in Sussex, Wis., has been building and integrating automation and controls for agricultural milling applications for almost 50 years. These include process-specific controls and plant-wide automation systems for manufacturing fertilizer, mixing animal feed, batching and pelletizing pet food, and processing seed and other products (Figure 2). The company traditionally uses Rockwell Automation's PLCs and data servers, but when it recently began working with users outside the U.S., it encountered some less familiar PLCs and communication protocols, such as those from Siemens and Mitsubishi. It needed a way to interoperate with any control protocol, as well as prevent downtime that can cost $50,000 to $200,000 per hour, so two years ago it launched its FLX software, which interoperates with different controllers with help from Kepware Technologies' (www.kepware.com) KEPServerEX that uses an OPC server and supports more than 150 communication protocols.

"Our goal has been to become hardware agnostic, so our conveyors, motors, valves, pellet lines, grinders, mixers and other equipment can plug-and-play with different controllers, and allow us to deliver 100% tested solutions,” says Wade Leverett, Repete's president. "Over the years, PC-based controls have outstripped PLCs, and these PC tools enable us to do regression testing at the push of a button and simulate solutions before we go to a customer's site.”

Mike Peters, Repete's operations director, explains that FLX and its OPC server let Repete's devices communicate with different controls more easily, convert ladder logic instructions with fewer adjustments and handle customers' change requests much more quickly. FLX also helps operators schedule production runs by taking raw material and other input data, and then creating a unique plan for executing product formulas with users' available equipment and controls—much like enterprise resource planning software takes in orders. Finally, FLX also allows remote monitoring, diagnostics and control, so Repete can troubleshoot and service clients' systems without having to be on-site. Consequently, the company is presently building an average of six major integration systems per month, and its ability to communicate with almost any PLC is even enabling it to expand beyond its core focus on food production to serve new industries, such as recycling in Asia and cargo-handling in Europe.


"Every job is a custom job, and we still create many unique solutions, but FLX's software plug-ins enable us to pull components from our equipment library far more often and implement them faster with less programming and the right controls. Our software and OPC server also link seamlessly with other ERP and management executions systems,” says Peters. "As a result, automation system installations that used to take five or six weeks to put together can now be done in just two or three weeks. In fact, we can simulate a full mill in one business day, and this means a lot less errors and time on-site than with traditional controls.”

Jim Montague is Control's executive editor.

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  • I worked with Noosa Yoghurt to implement the process control solution discussed in the article above. While most of the details on the application are accurately described within the article, this particular application does not use PC-based control. Noosa uses a Rockwell Automation PlantPAx process control system built on a server and thin client architecture – the actual control resides within a programmable automation controller (not a PC), despite how it’s referenced in the article.

    In my experience, PC-based control takes the control functions found on a programmable controller, encapsulates them in software, and executes program tasks and I/O communications on the PC’s processor along with other overhead related to the host operating system. PLCs and PACs, on the other hand, are more robust and include more control capabilities than those offered through PC-based control. These could include motion control, integrated safety and advanced PID process control. At Noosa, the PAC-based PlantPAx platform provides the ability to add additional I/O, controllers, and servers without adversely affecting the base characterized architecture of the system – this flexibility would not be possible within a PC-based system. Dan Malyszko Director of Operations Malisko Engineering, Inc. Denver, Colorado

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