Tunnel Ovens: Rekindling Efficiency
April 01, 2009
by Shane Whitaker
With the slumping economy, most bakeries probably are not thinking about purchasing new ovens, especially a tunnel or tray oven, which could cost as much as seven figures. However, now may be an opportune time to make this investment, whether you operate a growing bakery looking to replace deck or rack ovens to go to a more automated process or an older bakery and want to replace a less efficient oven.
Over the past several years, costs for materials such as stainless steel and components to build ovens rose sharply, but the economic downturn has decreased prices for raw materials and components, according to Joe Zaleski, executive vice-president, Reading Bakery Systems, Robesonia, PA. “We can lower our prices on the equipment we manufacture,” he explained.
Additionally, Mr. Zaleski said that the company has more time to devote to projects because the overall industry is down.“We maintained much of our experienced staff because it is not easy to replace that experience in six to 12 months when we get busy again,” he added. “Order now, and the most experienced people will work on these projects. The result will be a new line tailored to the customer’s needs with the greatest attention to detail.”
Dieter Knost, managing director of Werner & Pfleiderer Industrial, Tamm, Germany, noted also that lower material prices would translate to less expensive ovens.“If someone has the money, it is a good time to invest,” he said.
Larry Gore, director of product marketing, AMF Bakery Systems, Richmond, VA, said new ovens are highly efficient compared with ovens of even 10 years ago, thus it would be an ideal time to replace 30- to 40-year-old ovens from both an energy perspective and maintenance costs.“Capital investment with a measurable efficiency increase that can be tied to a top project ranking in regards to return on investment would still make this a good time to invest in new oven technology,” he explained.
“An oven is always an investment in the future,” noted Malene Pedersen, marketing manager, DFE Meincke, Copenhagen, Denmark. “An old oven may be able to last through financially rough times before replacement, but a new oven can easily be more economical to run, which improves the attractiveness of the investment.”
Bill Foran, vice-president, C.H. Babb Co., Raynham, MA, noted that if most every company is being conservative and not investing in the future, then a company that has a good business plan and invests in an oven to move forward with that production line would have a leg up when the economy turns around.
Bakeries generally switch from rack, deck or revolving tray ovens to automated or continuous tunnel ovens for capacity and efficiency reasons. A general rule of thumb used in Europe is that when a bakery produces more than 5,000 pieces of bread (typically 1 kg, or 2.2 lb, each) per day, then an investment in a multilayer tunnel oven is the right choice, according to Mr. Knost.
When outputs are high, the batch baking process can be expensive, according to Mr. Zaleski. “Loading, unloading, heating and reheating the oven are a waste of time and energy,” he said. Reduced labor costs associated with eliminating the handling of pans and racks is another savings bakeries should consider when thinking about making this switch.
In addition, Mr. Gore said bakeries should expect to significantly reduce fuel costs by switching to tunnel ovens. “Also, an automated oven will even help in increasing the efficiency in the packaging department,” he said.
However, product quality and consistency are probably the factors that have the greatest influence on this decision.
“Product bake quality and consistency is easier to achieve and repeatable from one product run to the next when baking in tunnel ovens,” said Ken Johnson, president of Gemini Bakery Equipment Co., Philadelphia, PA.
“The cost of oil and natural gas has fluctuated wildly and unpredictably in recent years,” Mr. Johnson said. “Energy efficient oven operation has become a very important criterion in our customer’s decisionmaking process.”
To this end, he said Gemini’s latest generation of indirect-fired tunnel ovens have been tested against direct-fired ovens running similar products and throughputs. “Our indirect-fired ovens bake with significantly reduced energy consumption, up to 30% for some products ,” Mr. Johnson observed.
C.H. Babb works with its customers to help them cut fuel costs, and it recently helped a customer using an older style oven reduce its fuel costs by 30 to 40%, according to Mr. Foran. “C.H. Babb has always been focused on improving the efficiency of our multiple types of ovens,” he said. “For example, we use the ovens in our technical center to complete efficiency studies.”
The company recently added a second oven to its test center. The new indirectheated oven features both a stone hearth and steel belt so customers can see how their products would bake on both surfaces. But more importantly, the oven also features air-impingement technology, which will greatly improve the flexibility of this style of oven.“Radiant heat ovens do a great job with hearth breads and rolls, but we want the oven to be able to bake a variety of things like croissants , bagels, batter products, etc.”
C.H. Babb manufactures eight different style of ovens including indirect-fired, direct-fired, air-impingement, thermaloil, electric, infrared, radiant-tube and hybrid varieties. “We have the ability to discuss the efficiencies and benefits of each type of oven,” Mr. Foran noted. Bakeries are using advanced electronic controls for greater real-time feedback to significantly improve oven performance, according to Mr. Gore. “An example of this control is analysis of real-time temperature relative to production capacity,” he said. “This trend has come about as a result of providing more consistent product quality and to address energy consumption reductions.”
Also, Mr. Gore noted that production efficiency is the key to profitability. “Advanced thermal controls for maximized energy efficiency and advanced insulation designs have a significant impact on energy efficiency,” he said. “In addition, today’s new high-efficiency burner designs result in significant fuel savings while simultaneously providing improved baking consistency.”
DFE Meincke has shown that bakers can increase their energy efficiency with a few innovations, according to Ms. Pedersen. For example, the company has updated and reintroduced a previous concept of using covers for the return band. “The covers help to preserve the heat in the return band and reduce the energy used on heating the band when it enters the oven,” she said.
The OEM also recently introduced heat recovery units to its ovens. This unit is placed on the exhaust stack of each zone, and the warm and humid exhaust is used to heat cold intake air before it enters the heat exchanger, saving approximately 15% energy consumption.“The heat recovery unit is produced for the Turbu Three convection oven and can be placed on all zones where the exhaust vent is more than 60% open,” Ms. Pedersen said.
Today’s tunnel ovens feature many electronic devices to control the baking environment, which means controlled climate and temperature profiles, according to Mr. Knost. “Bakers can even control when changeovers causes a gap on the belt between products,” he said. “You can shut the dampers and then run without heat. This also helps save on energy costs.”
The electronic controls Mr. Knost referred to also play a major role in making tunnel and tray ovens flexible for baking a wide variety of products.
In fact one of the ovens offered by Werner & Pfleiderer that is still fairly new to the US market, according to Pat Kennedy, president, Kemper USA, Shelton, CT, a subsidiary of the WP Bakery Group, is the Megador, a multilevel tunnel oven. This oven is available with either thermal-oil heating or cyclothermic radiation. The Megador has up to eight different levels and can be feed by two production lines, allowing companies to bake multiple products in a single oven at the same time.
Processors want flexible ovens that have a wide baking range and capacity, according to Mr. Zaleski. “New snack products may or may not have staying power in the market, and new product development is risky especially if an oven is purchased specifically for that item,” he added. “Manufacturers want a fallback position where they could bake other products on the line.”
The baked foods market is demanding product variety more than ever. “Bakers are looking for production flexibility that will allow them to broaden their production capability to meet the needs of a more diversified market,” Mr. Gore said.
Many bakers today are baking several products on the same line to minimize the risk of their investment, according to Ms. Pedersen. “This demands a high level of flexibility from the oven, which has to make quick changes in baking profiles from one product to the next,” she said. “With a precise control of airflows, heat distribution and moisture level inside the DFE Meincke ovens, this is actually done very easily.”
AMF has unveiled new ovens in the past five years, allowing it to integrate new technology into its current oven designs instead of rehashing 40-year- old ovens, according to Mr. Gore.
AMF introduced two new directfired ovens — the Vesta 70 Traveling Tray Oven and Vesta 60 Tunnel Oven. The advanced designs of these ovens feature newly configured burners with greater lateral heat control and exhaust gas management. Advance controls monitor burners and product tracking. “Our ovens are designed with stainless steel construction on sides, flat-top roofs and hoods,” he noted. “We also provide significant insulation designs to optimize operational efficiency.”
The company also launched the Vesta Indirect Fired Tunnel Oven, a heavy-duty indirect-fired mesh-belt tunnel oven with up to three burner towers, high-ratio burners, integral steam system, electronic belt tracking and dual-roller-drive system. “This oven offers extremely even baking for all types of products from hearth bread and rolls to pan breads and buns to sweet goods,” Mr. Gore said.
Gemini recently introduced to North American bakers the Thermador oven, which is manufactured by Werner & Pfleiderer, according to Mr. Johnson. “The Thermador is the latest generation of efficient, modular and versatile indirect-fired tunnel ovens offered by Gemini,” he said. “Significant design enhancements further improve energy efficiencies and reduce maintenance requirements.”
The ability of the Thermador to add turbulence zones in every section of the oven helps decrease bake times and reduce energy usage, Mr. Johnson noted. “The vertical hot air movement complements the radiant heat generated by the oven and results in more efficient transfer of heat to the product, lower baking temperatures and less energy usage,” he added. “The air turbulence produces a very uniform bake, color and improved side walls and bottoms.”
Reading Bakery recently launched its multi-pass dryer. While the company has manufactured dryers for many years, it developed a multipass dryer to complement its ovens for snack products, according to Mr. Zaleski. “The benefit of multi-pass drying is to allow snack products to dry from 10 to 11% moisture to 1 to 2% moisture,” he explained. “This is done at low temperatures for relatively long periods of time to minimize product coloring and ‘checking’ — cracking after the product is dried.” The dryer uses forced convection through the product bed to ensure even drying across the belt, and the multi-pass dryer turns the product over to evenly dry both sides.
DFE Meincke extended its oven range for bread production by adding a new direct-fired oven this past year. The high-temperature oven has a maximum temperature of 842°F (450°C), according to Ms. Pedersen.
New oven options abound. And for processors looking to improve their energy efficiency or who would like an oven capable of baking a wider variety of products, now may be the best time to consider adding a new tunnel or tray oven to their plant.
“Bakeries that offer consistent quality for a more competitive price will be those that are in a much better position to take advantage of the market opportunities as they arise,” Mr. Johnson said. “Being the more efficient manufacturer offering the higher quality product is always a distinct advantage, especially during a turbulent economy.”