A new era of control
by Laurie Gorton
Now is not the time for nostalgia, so don’t envy the old-time baker who could fire up his oven and determine its baking power by the feel of the heat on his skin. What passed as oven controls in a simpler era won’t do the job now. Even today’s sophisticated computer-run systems will need upgrading to answer questions posed by Food Safety Modernization Act (FSMA) regulations now being written and finalized by the Food and Drug Administration (FDA).
In less than two years, bakers will be required to document a great deal more about the performance of their ovens than currently demanded by regulatory authorities. Specifically, they must not only detail the oven as a critical control in hazard analysis and critical control point (HACCP) programs, but they will also need to verify — or “validate,” as regulatory speak goes — that it acts as a preventable control under FDA’s new hazard analysis and risk-based preventable controls (HARPC) protocols and does indeed effectively serve as the kill step for food pathogens.
Toward a new paradigm
The move from critical to preventable controls ups the ante for ovens, the baking companies that operate them and the OEMs that make them. It’s not that current systems don’t generate control data, but rather such data are about to take on much more importance.
More detail than ever is available about the many variables of oven operation. The programmable recipe system, which enables baking parameters and set points that fit the exact needs of each product style to be pre-entered into the control system, makes this possible.
In the collaborative process of configuring an oven, baker and OEM usually decide first which thermal processes will be used — direct, indirect, forced air, infrared, impingement and so forth. The matter of controls then brings them to discussion of bakery variables.
Control systems display the temperature at the heat source and at the product transfer points, as well as exhaust temperature and air turbulence. According to Amanda Hicks, director and co-CEO, Auto-Bake, Hornsby, Australia (represented by Dunbar Systems, Lemont, IL), this allows bakers to optimize the baking environment, creating conditions unique to every product within their range. “All these parameters are stored to the individual product recipes to ensure consistent and repeatable product performance,” she said.
Such recipes ensure the oven is set up the same way each time, explained Frank Achterberg, president, BABBCO, Raynham, MA. If not, an alarm notifies the operator. “With our high-end control package, an email also can be created to notify operators, supervisors, maintenance and management when the oven is out of set-point range,” he added.
Control recipes can be programmed as default settings according to each SKU, explained Ken Johnson, president, Gemini Bakery Equipment, Philadelphia. The company’s systems are also capable of capturing “last run” settings and repeating them reliably.
Because of the high volume and speed of today’s ovens, problems take on extra urgency, making real-time control essential. Mr. Johnson described such an approach: The company’s oven controls record and display temperature in each zone on a real-time, on-screen chart recorder. “This data can be sent to other in-plant systems for further evaluation,” he noted. All real-time data can be stored to document oven profiles and conditions.
Along with more complex baking requirements comes a longer list of oven control variables. Jerry Barnes, vice-president, engineering, Baker Thermal Solutions, Clayton, NC, observed, “By focusing on a broader range of key process inputs beyond simple air temperature, such as thermal mass loading, desired bake profiles are more readily obtainable. Individual product recipes now allow pre-set heat input on a per-zone basis to create more consistent results.”
Reporting aspects have gained attention. “All of our ovens have temperature trending and the ability to integrate with offline systems for recording valuable product data such as throughput, temperature, recipe and time,” said Phil Domenicucci, EPM Thermal Solutions, AMF Bakery Systems, Richmond, VA. “This adds a valuable time stamp to specific products being baked.”
Such information more directly describes actual baking conditions, especially when augmented by separate data-gathering methods. Scott McCally, product manager, thermal group, Stewart Systems, Inc., Plano, TX, described current work to develop a system that uses programmed analytics to automatically monitor a product’s “S” profile, also known as its baking curve. “This system will identify and correct profile drifting during operation and is heavily dependent on the data retrieved from data loggers operating continually within the production environment,” he explained.
Air quality issues also get involved. Franz Haas Machinery of America, Richmond, VA, recently integrated regulation of internal air pressure within the oven chamber. “The bakery has to maintain a slight negative pressure within the baking chamber, and with a thermal oxidizer, you have to control the exhaust rate to satisfy Environmental Protection Agency regulations,” said Kevin Knott, the company’s technical sales manager.
Upgraded state of the art
Programmable logic controllers (PLCs) and computers have become more capable in recent years with greater computing power and more abundant storage memory. But the list of variables that oven controls monitor and adjust control systems has also grown.
“Of course, at the heart of baking is accurate, real-time measurement of heating,” Ms. Hicks said. This includes individual zone temperatures, burner temperatures, burner efficiencies and temperature trending. This information is readily available through touch-screen human-machine interface (HMI) and remotely via local-area network (LAN). Yet security provisions properly limit access to more sensitive settings, admitting only authorized personnel, thus ensuring that vital parameters are not lost or inadvertently changed.
The predominant type of PLCs, HIM units and other controls used by Gemini Bakery Equipment is Allen-Bradley, “but we can accommodate other control platforms,” Mr. Johnson noted.
Control capabilities include speed adjustment of the main blowers to improve power consumption efficiency of the ovens. Burner ratios can be adjusted automatically to reduce fuel consumption and improve temperature regulation. Gemini also offers gap control, if requested.
Regulation of gas flow, noted Mr. Knott, is important when bakers prefer to monitor energy input variables in place of temperature. Franz Haas recently added this to its oven control package.
Another new aspect is regulation of the moisture within the oven, that given up by the product itself and that added by use of live steam. “Only recently have bakers been able to measure and thus control the humidity within their ovens,” Mr. Knott said.
Deeper data means better management of operating costs. “Data collected by the Simatic system controlling the oven helps the baker track operating costs and energy consumption,” said Damian Morabito, president, Topos Mondial Corp., Pottstown, PA. The company represents J4 cyclothermic, indirect- and direct-fired and hybrid ovens.
Full management of process variables takes place via a touch-screen HMI and can be monitored and adjusted remotely through connection to a computer network, Mr. Morabito explained. Controls operate the servo drives that operate the dampers throughout the oven, including those for exhausting excess steam. The system allows automatic oven startup and safe, efficient shutdown. It tracks maintenance requirements of safety elements and records nonstandard events that occur during operation.
Additional benefits accrue to bakers with networked oven controls, according to Tremaine Hartranft, director of engineering, Reading Bakery Systems, Robesonia, PA. He cited remote burner control, which allows recipes to be saved for quicker changeovers. “This also creates a repeatable process to help the operators set up the oven on a more consistent basis.”
Controls that automatically throttle back burners during idle periods save energy when there are significant gaps in product feeding into the oven, Mr. Hartranft explained. Oven control packages can also be designed to manage the heat exchangers on the oven stacks that supply heated makeup air to the oven and to control fuel flow meters that regulate gas usage.
An OEM can tailor oven controls to suit baker needs. Mr. Achterberg described the company’s standard vs. high-end packages. “The standard control package … assists management, bakers and maintenance personnel in the daily tasks of operating and maintaining the ovens.” It incorporates a main-screen overview of the oven, showing recipe type, set points and oven status. A trending feature logs and displays temperatures. There’s a vision system to detect color variations and a fingerprint reader for personnel login that does away with passwords.
“The high-end control expands the standard package with extensive reporting, data logging and notification features,” he continued. For example, all collected data is stored in a database using structured query language (SQL) and can be accessed through other computers on the same network. This version enables email notification and more detailed logging of recipe changes with date stamps on when loaded, created, changed and deleted. Equipment manuals can also be made available on the HMI operator interface.
It’s not enough to collect data; it must also be shared to maximize its value. In companies with supervisory control and data acquisition (SCADA) systems and enterprise resource planning (ERP) programs, the data generated by oven control systems must be accessible.
SCADA systems centralize management of industrial processes by integrating multiple equipment stations into a smoothly running operation. They can be applied to single lines or whole manufacturing facilities and facilitate the bakery’s statistical process control (SPC) capabilities. “AMF Bakery Systems’ recipe management system can integrate with SCADA systems where certain SPC functions can be realized such as temperature logging relative to recipe,” Mr. Domenicucci observed.
For many oven OEMs, such capability is well-established. “Auto-Bake adopted use of SCADA software over a decade ago to ensure the seamless integration of oven system information with clients’ emerging ERP systems,” Ms. Hicks said. The oven-control software provides real-time information and historical data in all standard formats for easy assimilation into the bakers’ own systems.
Here’s where LAN systems come in, too. “Improved industrial control networks are more reliable and easier to interface and obtain real-time information to better monitor and control the processes as well as create statistical and data reporting,” said Darren Jackson, COO and vice-president, sales and marketing, The Henry Group, Greenville, TX.
“We have continued to reduce the number of control communications networks as technology allowed,” he added. “By consolidating all communications to Ethernet IP away from obsolete DeviceNet and ControlNet platforms, systems are now compatible across traditional networks.”
Use of variable-frequency drives (VFDs), now becoming more common in bakery equipment, provides another means for facility-wide control. Mr. Hartranft noted that connecting such drives via Ethernet allows motor data feedback. “Certain bakeries monitor this motor data to know that the motor is getting close to failure,” he said.
Mr. Hartranft also cited Ethernet as the emerging platform of choice. “Having the standard Ethernet platform allows our oven control systems to integrate with multiple ERP systems,” he said.
Ethernet-capable PLC technology is used on the ovens installed by Gemini Bakery Equipment, according to Mr. Johnson. “We can organize data into the customer ERP/SAP file formats for upload on a real-time basis.” SAP is the ERP software most widely by bakers.
Communication can work both ways to link baker and OEM. Mr. Johnson explained, “We have the ability to remotely connect to, monitor operation of and make adjustments to ovens on customer sites.”
Mr. Knott described control systems that enable third-party usage to monitor variables such as gas flow and other key performance indicators (KPIs). “Such systems can also include maintenance manuals, giving the operator a copyright at the product line,” he added. “There are also built-in diagnostic software and alarm monitors. We have done some initial work allowing the customer to bring up a spare parts diagram of the oven and order parts directly from that screen.”
Improved baking, too
It’s not only oven controls that have improved through ongoing efforts, but the ovens themselves also have gained efficiencies and capabilities. Often, the enhanced controls set the stage.
For example, Baker Thermal Solutions used control technologies to balance radiant and convective heat transfer in response to changing load, according to Mr. Barnes. “This control method has been proven superior to more basic zonal temperature control. The end effect is a highly responsive system able to quickly adjust between varying states such as loading, unloading, steady-state or intermittent,” he said.
The company also revised its Coloraider convective systems to provide more consistency and fine-tuning of the color control.
Programming enabled AMF Bakery Systems to address flash heat problems, Mr. Domenicucci noted. “Newly designed anti-flash-heat and cut-back programs reduce the amount of flash heat between changeovers and prevent overheating with long gaps,” he said.
Bake quality across the width and down the zones of ovens also improves, Mr. Jackson observed. “The Henry Group designed adjustable settings that allow maximum control on 10-ft intervals for indirect-fired and burner-to-burner on direct-gas-fired ovens.” This is accomplished by control over upper and lower lateral heat settings and air speed and turbulence.
“Settings give a baker maximum control for a premium bake including internal core temperature, wall and cell structure, and color density,” he said, “and offer a latent benefit to provide the needed controls to support FSMA food safety concerns.”
Better baking with less waste is the aim of newly emerging gap control options. During product changeovers, the empty belt continues to travel through the oven. Without product present to absorb the heat, it collects and causes flash-heat problems and rapid fluctuations in oven temperature. “The first few rows of the next product loaded into the oven can come out burnt with the next few rows under-browned,” Mr. Knott said. Franz Haas has installed various systems with control programs set up baking profiles that regulate the temperature in the baking chamber as the system returns to production. “This benefits the baker in controlling waste,” he added.
Stewart Systems used what it learned from oven control systems to work on heat management methods. “In the past few years, we have moved to a multiple thermocouple temperature averaging strategy whereby heat input is controlled by zonal loading,” Mr. McCally explained. This helps improve energy usage and avoid inconsistent product baking during production gaps. It gives the operator control over early bottom- and late top-heating, based on product specifications.
Better information means better control and promises better product profiles. “It also allows quantitative baselines when looking to improve operational efficiencies in the bakery,” Ms. Hicks said.