By Jim Montague, Executive Editor
Everyone loves soda pop, but it hasn't always been available to many of the most remote communities worldwide. However, ever-expanding markets are leading soft drink manufacturers to invest in more local facilities to ensure there's reliable production to meet increasing demand.
One of these companies is Schweppes Australia (www.schweppesaustralia.com.au) and its facility in Huntingwood, New South Wales. It's one of the company's principle production plants in Australia and has increased its manufacturing capacity substantially in the last eight years.
As part of its own quest to improve reliability and operability along with its expansion, Schweppes Australia recently upgraded the control systems in the syrup room at its Huntingwood facility. The project included migrating process control functions that had been performed by a legacy distributed control system (DCS) to a new control system based on the PlantPAx process control solution from Rockwell Automation (www.rockwellautomation.com).
Syrup, Batch, Clean, Repeat
To rise above mere soda water, carbonated beverage production relies on the preparation of flavored syrups. Syrup manufacture begins with a batch process, using the basic components of raw sugar and treated water. At the Huntingwood plant, a continuous sugar dissolver is used to mix sugar into water to create "simple syrup." This mixture is prepared to a concentration of 62 degrees Brix—62% sucrose and 38% water by mass—before being transferred to one of two 40,000-liter holding tanks.
A batch of flavored syrup is prepared by manually mixing flavor ingredients in a small ingredients tank and routing this mixture to a final destination tank in conjunction with pre-prepared simple syrup and added water. Not surprisingly, the process control system is crucial to managing this mostly automated process. Operators use the control system to call up batch menus and enter details of the required batch volume and the destination tank to be allocated. The system automatically ensures the volumes and proportions are correct and the necessary clean-in-place (CIP) procedures are completed before routing the mixture to the final destination tank.
Schweppes Australia's project engineer, Warren Ung, reports that CIP is a crucial part of the automated process for both the tanks and transfer lines. "All the sugar-based products leave scope for bacteria build-up and contamination," says Ung. "Cleaning involves a simple flushing, a three-step CIP process or a five-step CIP process. The system initiates the appropriate CIP to prevent spoilage from the previous flavor that has passed through the tank. This is critical to ensure no batch contamination occurs."
Combining Controls in Software
Before its latest upgrade, the control system in Huntingwood's syrup room was split between a legacy DCS for process control and batching and an Allen-Bradley ControlLogix system, in conjunction with RSView 32 SCADA software, all from Rockwell Automation. This latter system was installed to provide process control for additional lines transferred from Schweppes Australia's Alexandria plant back in 2001. While these separate systems ran satisfactorily in parallel, the firm's engineers report that they grew increasingly concerned about the reliability of the obsolete DCS, the difficulty in sourcing spare parts and the potential for component failure resulting in significant production downtime.
"We had a choice of either upgrading the control system to a current version of the DCS or integrating these DCS functions into the Rockwell Automation system," explains Ung. "Migrating our process control functions to the ControlLogix platform was a natural choice because it could achieve the same level of functionality as a DCS, but it also allowed for greater flexibility for future expansion."
As a result, Zi-Argus Australia (www.zi-argus.com) acted as system integrator to help manage the upgrade. Ken Maxwell, sales director at Zi-Argus, explains that a key challenge of the project was to extract the source code out of the DCS in order to translate the syrup batching functions into ControlLogix. "To integrate the DCS process control into ControlLogix, we had to painstakingly analyze every aspect of the DCS to be in a position to replicate it in the new system," says Maxwell.
In addition, Zi-Argus was not only assigned to replicate the functions of the legacy DCS using ControlLogix, but also to improve the operator interface and the reporting components of the system. "The operator interface was improved by replacing all of the screens and HMIs, and upgrading from RSView 32 to the newest software version—FactoryTalkView Supervisory Edition," adds Maxwell. "The result is a system that's now more capable, more intuitive for operators, and makes it easier to find faults."
Unified Syrup Process and Support
Thanks to its upgrade project, the primary user interface for Huntingwood's syrup application is a SCADA and SQL server supported by three onsite clients, which each run FactoryTalkView SE software. Operators use the SCADA to specify batch recipes, batch sizes, destination tanks and CIP requirements. The SCADA and clients are linked via EtherNet/IP to the ControlLogix controller, and small HMIs are connected via serial interface. ControlNet communications are used to network various process sensors and drives back to ControlLogix, which had its CPU in the syrup room upgraded to handle the two additional racks of I/O that replace the former DCS.
The project's engineers and integrators report that Schweppes' new syrup batching system is a model example of Rockwell Automation's PlantPAx solution for unified plant process control. In general, PlantPAx provides a scalable portfolio of enhanced process technologies, solutions and services for plant-wide control. With built-in DCS and PLC functionality, PlantPAx can be used for applications involving both process automation and discrete functions.
Maxwell adds that all of Huntingwood's process lines now link back to the SQL server database, facilitating more comprehensive and consistent capture of data and, consequently, better reporting capabilities. "Having all systems feeding data into the SQL database has meant a quantum leap forward in the system's ability to extract data and populate a database," he says. "It allows the system to generate detailed batch and quality assurance reports, which can be archived more easily."
Ung says that the plant's upgrade project had a fallback position just in case. The legacy system remained functional during the changeover, but this capability was never employed. "The new system worked well upon first initialization," says Ung. "The changeover ControlLogix could not have gone more smoothly."
In the wake of its upgrade, Schweppes Australia is also using the TechConnect support program from Rockwell Automation and an ongoing service agreement with Zi-Argus. "Previously, we had no site expertise regarding the DCS system, and there were only a couple of people in Australia with the technical expertise to program or find faults in the system," adds Ung. "The upgraded system is far easier for on-site personnel to troubleshoot, especially with the support from TechConnect. The service agreement with Zi-Argus Australia provides assurance that unplanned downtime can be minimized. This upgrade will help ensure that Schweppes continues to meet rising demand long into the future."