Ovens: Hot, But Under Control
June 1, 2011
by Shane Whitaker
Making finished baked foods is impossible without an oven; however, industrial bakers use many different oven styles from rack and deck ovens to tunnel and conveyorized systems that bake products with radiant, convection, conduction or impingement heat and often combinations of all. So how does a bakery determine which oven is best suited for its operation? Bakers must investigate and closely compare the various oven features and qualities to make that decision.
Whether a bakery seeks to purchase a new oven or improve the efficiencies of its existing oven, knowing about the latest oven technologies is beneficial. Today’s ovens feature new control systems and designs for improved energy efficiencies. Also, oven manufacturers are reducing installation times and making ovens easier to maintain and clean.
The use of complete PLC management systems is one of the latest developments in oven technology, according to Charles Foran, president, C.H. Babb Co., Raynham, MA. “A high-end management system can include items such as custom reporting, increased data storage for trending, downtime analysis, images for individual recipes to help the operator achieve the target product as well as access to the equipment manual through the [human-machine interface],” he said.
Turkington USA, Clayton, NC, offers a new oven control philosophy, known as eBake that allows bakers to select basic oven controls when running long continuous runs, or if a bakery is producing many varieties, management controls assist with quick changeovers, according to Jerry Barnes, vice-president of engineering, Turkington USA.
“A lot of customers are asking us to help them understand more of the actual science behind baking. For us, that means monitoring more of the key parameters that measure what’s going on within the oven and, to whatever extent that we can, provide some ability to control that,” he said. “The new control system puts these parameters upfront so the customer can highlight process and quality issues in a real-time fashion rather than discover an issue at a slicer.”
By adding greater control over the baking process, bakers can use a zoned approach in Turkington’s ovens, which promotes product flexibility, Mr. Barnes noted. Bakers can track products in the oven and anticipate when the next item will be coming through, allowing the oven to change settings across the entire zone to prepare for the next product, he said. This feature will benefit bakeries that produce many SKUs at large economies of scale.
EFFICIENCY AND FLEXIBILITY.
In a mature market such as North America, bakeries often consolidate production from two older ovens or even update a single oven with new larger systems, according to David Kuipers, vice-president, sales and marketing, Reading Bakery Systems, Robesonia, PA.When doing this, care should be taken to maximize the line’s ability to run a variety of products. “Even on systems that will be dedicated to a particular product such as sandwich cookies, the manufacturer wants to know the full range of products it could produce in the future,” he said. “To help meet those requirements, we enter into a dialogue with [our customers’] R&D and engineering teams about options available to make the oven more flexible. The discussion usually centers on the ability to change the radiant/convective mix to produce the widest range of products.”
When suitable, Mr. Kuipers noted, many bakeries increase use of convection in the baking process to improve efficiency and reduce bake times.
Many bakers, he observed, are trying to understand and benchmark energy usage in their ovens to target improvements. To assist such efforts, Reading will install fuel flow meters to record fuel usage during a production shift to determine actual product cost per kilogram and identify opportunities for improvement in fuel usage, according to Mr. Kuipers.
Many oven manufacturers assist bakeries in improving energy efficiencies by installing heat exchangers on oven exhaust stacks. The hot air pre-heats oven makeup air in convection baking zones, usually in later oven zones when the exhaust dampers are fully open. And the company installs oven downtime software to reduce the oven to low-fire during prolonged breaks in production.
Mr. Kuipers pointed out that the company recommends use of lighter-weight baking meshes, when appropriate, to reduce the energy required to reheat the mesh belt on its return path beneath the oven.
To provide a more energy-efficient oven, Gemini Bakery Equipment Co., Philadelphia, PA, redesigned the fire box, heat exchanger and hot gas circulation system of its WP Thermodor indirect-fired tunnel ovens. Mark Rosenberg, Gemini’s president, said customers should expect to reduce gas consumption by 10 to 15% with these latest improvements. “We have a client who recently did a fuel consumption evaluation and confirmed that he has seen a dramatic reduction in his fuel consumption,” he said. “The company previously baked the majority of its specialty breads and rolls in indirect- and direct-fired traveling tray ovens. Their total gas consumption has been reduced by 30 to 35%, when including the oven and boiler consumption.
“The oven’s ability to reduce steam demand from the boiler also allows our clients to expect additional future savings of 10 to 20%,” Mr. Rosenberg continued.
Gemini’s indirect-fired tunnel ovens are predominantly used for baking specialty bread and rolls, and many bakers want to employ a single oven for baking a wide variety of products from small dinner rolls to 2-lb specialty breads. “We also provide a unique steam and moisture environment to give ideal crust and shine,” he noted.
To design its newest ovens from the ground up, AMF Bakery Systems, Richmond, VA, employed the latest in computer-aided engineering (CAE), according to Phil Domenicucci, AMF’s thermal product manager. The company used CAE tools such as finite element analysis, computational fluid dynamics and mechanical oven simulation to look at earlier designs and help determine how they could be improved. “Scientifically exploring the subsystems of our ovens has given AMF greater understanding of the possible functionality and performance with little added risk,” he said.
AMF added energy management options to allow bakeries to better track energy consumption trends and energy per pound of product baked. Also, it uses newly designed ribbons in its burners to improve the efficiency of the gas/air mix, according to Mr. Domenicucci.
Stewart Systems, Plano, TX, improved its conveyorized ovens by supplying hardened curve tracks for longer life, according to Keith Dietz, the company’s conveyorized products manager. He explained that an ion-nitriding process hardens the metal of the curved conveying tracks, and the company reinforced the curves on the vertical inside faces to prevent the distortion that can occur when the horizontal wheels roll on the inside of this surface.
The company’s ovens also monitor the main drive motor’s power consumption to detect any problems such as high starting, running and rising power. “This is a much more accurate way to detect a problem and shut down the oven than monitoring the motor current,” Mr. Dietz said.
Also, Stewart Systems places chevron-style burners in its ovens to offer full coverage of the pan. “The entire width of the pan is exposed to each of these burners twice for better and more uniform heating,” Mr. Dietz observed.
He pointed out the company zones its ovens for heat input to improve customization of the baking profile. Depending on the number of burners, Stewart Systems breaks its ovens into three to five zones. “Four zones are typical,” Mr. Dietz said. “The heat input from each zone can be proportionally varied relative to each of the other zones for every product code. This allows fine-tuning of the baking profile for each product.”
Stewart Systems’ ovens also use recirculation systems that take hot air off the top of the ovens above the burner areas and blow it onto the pans in the corners. “In this way, the hot burner-heated air is used twice to heat the pans, once directly at each of the burner locations and again in each of the 180° corners,” Mr. Dietz said. “This makes a much more efficient oven.”
The oven manufacturer offers heat recovery options and uses 8-lb-per-cu-ft density mineral wool insulation to minimize heat transfer through the walls, roof and floor panels. Also, aluminized steel on the interior of the walls, roof and floor radiates heat back into the product, he said.
To lessen metal-to-metal contact on oven belts, The Henry Group improved design of the chevron beds, or conveying surfaces, inside its tunnel ovens. “Reducing drag on the belt reduces friction and thus prolongs the life of the belt but also reduces the energy required to convey the belt,” said Darren Jackson, COO for the Greenville, TX-based company. “This is a mechanical improvement that has green results.”
In addition, The Henry Group’s E4 Hybrid tunnel oven has been a front-runner in green oven technology, he said. The E4 is equipped with a catalytic oxidizer and an indirect-fired first zone followed by direct-gas fired zones for the remainder of the oven. This enables the oven to exhaust the direct zone to the catalytic oxidizer to burn off the ethanol and heat the oven’s first zone before exhausting into the air. “Results are cleaner-burning exhaust, the use of latent energy and lower energy consumption,” Mr. Jackson said. “Add heat exchangers in the oven stacks to supply hot water to the proofer, and your energy consumption is dramatically affected. The initial investment in such systems, however, is higher, but the ROI should justify [this decision]. We estimate up to 17% energy usage savings.”
Gashor ovens, available from Cinch Bakery Equipment, LLC, Little Falls, NJ, can assist bakeries in improving energy efficiency by reclaiming the hot air from combustible chimney gases to heat water for use in the bakery. “Now, the bakery can have hot water with free energy,” said Cindy Chananie, president of Cinch.
SANITATION AND INSTALLATION.
Bakers and snack manufacturers often desire improved access to the baking chamber for sanitation. “Many have expressed concerns about sanitation and allergens,” Mr. Kuipers said. “They want good access to the oven for cleaning between production shifts. We provide several hinged access doors as standard and can provide many more as options.”
C.H. Babb offers clean-in-place (CIP) systems for its ovens, which can assist bakers making pizza, stuffed pockets or similar products that must be made in UDSA-inspected plants. CIP systems wash out ovens using cycles of heated water, detergents and caustic solutions. They come in a range of complexity from manual pressure-wash methods to a fully integrated and automated cleaning system that collects and recirculates cleaning fluids.
Stewart Systems reduced the number of labor-hours required to maintain multistrand insulated wires used for ignition and flame sensing by switching to solid stainless steel rods with double insulation. Additionally, the oven manufacturer offers as standard on its ovens an air blow-off station ahead of the oiler to keep the chain clean by removing loose particles of debris before they have a chance to build up and stick to the chain.
Bakers are always looking for equipment that is easier to maintain and want features that increase the value of their equipment, according to Mr. Domenicucci. For example, AMF offers product energy tracking, predictive lubrication, dynamic chain management and redundant subsystems.
In addition, bakers want to reduce costs for maintenance. “Features such as predictive lubrication, dynamic chain management and lubeless chain are the answers to some of these challenges,” he added.
To reduce installation time, control manufacturing quality and ensure performance, Reading supplies modules of ovens preassembled at its factory.
Stewart Systems fully pretests its control panels and combustion platform prior to shipment to the bakery to lessen startup times at installation,
Because welding an oven can be time consuming and disruptive to a bakery and not every bakery can accept a fully assembled oven, Cinch can deliver a rack oven that can be assembled in one day without welding, according to Ms. Chananie.
As a matter of fact, many new developments are occurring with regard to the current state of oven technology, and bakeries may want to investigate further how these new designs and improvements can benefit their operations.