Better Products Through Better Control
Improved control of the production process is a never-ending quest in food manufacturing. It is a factor in virtually every processing initiative, whether it involves MES software, advanced sensors or the latest in controls technology.
Granted, the business drivers for supply chain management and other current initiatives in the food industry have more to do with sales and marketing and key performance indicators than improved process control. But unless there is a residual benefit to production and an acknowledgement of the need to produce consistent products, those initiatives seldom yield the results envisioned.
Traceability is on every food processor’s radar screen, from raw-material receiving through store delivery of finished goods. Key customers are the real drivers, rather than federal regulators, which is why Tillamook County Creamery Association embarked on an ambitious business intelligence project years before homeland security became an issue. Tillamook’s industrial automation initiative has delivered much more than traceability, however. It also is paying dividends in improved process repeatability. “The mandatory part of the system is ensuring that you don’t make any bad product,” says Steve Burge, Tillamook’s information technology director. “But just as importantly, the system helps you discover why you made really good stuff on certain days.”
In 1997, Tillamook’s senior management decided fundamental operational changes were needed at the 100-year-old cooperative. The project’s first stage involved development of a recall system for finished goods coming out of the 54-year-old cheese plant in Tillamook, Ore. Growth had pushed output to one million pounds of gourmet cheddars every four days, and matching production to sales was becoming unmanageable. Better tracking of work in process was viewed as the proper remedy. To accomplish that, the paper charts and tables on which operators transcribed statistical data and qualitative information had to give way to an automated system.
Three years ago, construction began on a second cheese plant in Boardman, Ore. The $50 million project included a $500,000 budget for the process control and business intelligence package that was critical in managing production of 50 million pounds of cheddar annually that would be shipped after 30 days for up to three years of aging in an AS/RS in Tillamook. The tracking, trending and forecasting that needs to be done would be impossible without the technology that was put in place, Burge believes.
“There is no ROI in a traceability system, though it’s mandatory to be able to carry out a recall within four hours of an event,” he adds. “But if you build good traceability, you also build a good WIP (work in process) system to control the process. Therefore the financial benefit is that you’ve streamlined your process.”
More precise meteringIn the quarter century since they were first commercialized, Coriolis mass meters have been firmly established as the most accurate conventional industrial technology for flow measurement. Thanks to continuing refinements, they are gaining a larger presence in food and beverage plants.
Invensys’s Foxboro Measurement and Instrument Division captured industry attention and awards last year with CFT50, a Coriolis meter that uses dual digital processing for flowtube control to overcome signal problems associated with entrained air. Combined liquid/gas flow can freeze the density reading or cause the meter to choke, stopping production. The CFT50 employs controls for the meter drive sequence to provide uninterrupted operation. A second processing system generates measurement data, ensuring precise fluid measurement.
Almost as important from a food processing perspective, the unit gained 3-A certification for the flowtube. The same certification recently was granted to Micro Motion’s H-Series hygienic meters, which meet CIP requirements and come with an optional electro-polish on wetted surfaces for greater purity. “That’s big,” says Jeff Tietz, general manager of the process technology division of KHS Inc., Waukesha, Wis. “We have a lot of food industry customers who have worked around the lack of 3-A certification in the past.” Frequent swab tests and other sanitary validation procedures no longer will be needed with the hygienic meters.
Stated accuracy of Coriolis meters, a conservative guarantee of performance, has improved in recent years, Tietz adds. He credits Micro Motion’s Direct Connect concept for making possible stated accuracy claims of 0.1 percent by weight, from 0.2 percent. Much of the wiring between the sensor, transmitter and control system is eliminated with Direct Connect, he says, and the transmitter itself has been reduced to the size of a hockey puck. On an installed basis, the hardware refinements save $2,500 to $3,000 per meter. One in-line blending system KHS built boasts 23 metered streams, so the savings were about $60,000.
The costlier the ingredient, the stronger the business case for converting from positive displacement and other traditional technologies to Coriolis, which employs electromagnetic pickups to measure sine waves and Delta-T (the time difference between sine waves) as a liquid or slurry passes through a vibrating tube. Consistency of finished goods is the other driver, and Micro Motion’s John Martin believes the new sanitary certification will encourage more food companies to upgrade from volumetric metering.
Closer control“Zero-cabinet AC drive” is the term Rockwell Automation selected for its entry into the decentralized control derby. Instead of networking motors on the production line to a remote control cabinet, variable frequency motor drives are pre-wired and placed in a washdown-ready housing that is mounted adjacent to the motors they control. The idea is to eliminate on-site network wiring and the attendant cost. Also eliminated is the potential for reflective wave phenomenon, according to engineer Stan Ho, Rockwell Automation’s product line manager. When placed at a distance from the motor, fast-switching semiconductors in AC drives have the potential to produce reflective waves that produce high-voltage spikes at motor terminals, damaging and even destroying the motor. By positioning the drive adjacent to the motor, the likelihood for reflected waves is minimized.
While Rockwell’s 160Z AC drive costs more than a conventional unit, the difference is more than made up by savings in set-up time, Ho points out. “You have to take a look at the total installed cost of the system, not just the drive cost.” By having OEM personnel deal with all the wiring issues, the possibility of field errors is eliminated, he adds. In the current vernacular, the zero-cabinet AC drive provides plug-and-play functionality. If maintenance or repair is necessary, the unit can be removed in minutes. With a traditional assembly, the motor must be locked out and the troubleshooting performed at a remote cabinet.
Rockwell rolled out the 160Z a year ago, and Sidel (Canada) Inc. featured it on a conveyor line at last fall’s PACK EXPO show in Chicago. But the concept still is new to North American food processors, Ho concedes, and adoption is proceeding slowly.
The same can’t be said of European processors. Baldor Ltd.’s smart motor has been available for a decade, and SEW Eurodrive is promoting heavily here what it dubbed decentralized control in the European arena. Many plant managers mistakenly think the devices violate electrical codes, so there is an education challenge. And the cost savings accrue to large installations: if a plant uses 10 motors spaced 20 feet apart from each other, the installed-cost savings are negligible, SEW Eurodrive’s Jan Lindholm says. On the other hand, if 50 motors with similar spacing are being installed, a 30 percent savings can be realized.
The repositioning of disconnect switches, variable frequency drives, overload protection, motor brake controls and bus communications right next to motors on the production line is one of many significant advances occurring. As with industrial automation and mass flow metering, it underscores the dynamic nature of process control.
For more information:
John Martin, Micro Motion Inc.,303-530-8450, firstname.lastname@example.org
Jeff Tietz, KHS Inc., 262-787-1630,email@example.com
Jeff Baxter, Progressive Software Solutions Inc., 541-924-1741
Stan Ho, Rockwell Automation, 262-512-2258, firstname.lastname@example.org