A.O.M. conference presentations focus on efficiencies gained from “compactness.”
July 01, 1998
by Teresa Acklin
Technology that shaves wheat processing costs while meeting the increasingly exacting flour specifications of customers could be described as the Holy Grail of the flour milling industry. For some millers at least, the search for that technology has led them to the concept of compactness in their milling operations.
“Compactness” became somewhat of a buzzword at the Association of Operative Millers 102nd annual technical conference and trade show May 2-6 in Phoenix, Arizona, U.S., where several technical sessions focused on the subject. Specific approaches have taken different forms, ranging from double-high rollermills in a conventional flow to the short-flow milling system. Regardless of the approach, several millers in their presentations said “compactness” had enabled them to move a bit closer to the difficult goal of reducing costs and satisfying customers.
For Siemer Milling Co., compactness was designed into the company's greenfield mill in Hopkinsville, Kentucky, U.S., which began operations in mid-1995. The Hopkinsville facility has a daily capacity of 315 tonnes in terms of flour and was the first mill in the Western Hemisphere to use double-high roll stand technology for all of its flour output.
The double-high technology in which first and second breaks go through one of the double-high mills and third and fourth breaks go through a second was selected specifically to minimize the plant's equipment requirements and area to keep capital investment costs down. After a nearly three-year track record, the system, which was supplied by Buhler, Inc., has more than proven itself, according to Vernon Tegeler, Siemer Milling's vice president, production.
“It has exceeded our expectations in terms of maintenance, quality of finished product and reduced costs,” Mr. Tegeler said.
In addition to saving on space and equipment investments, auxiliary installation costs, such as for spouting and pneumatics, also were reduced, he said. Other operational cost savings have resulted from lower fumigation and energy expenses, he said.
The double-high technology also stands out in terms of milling performance, Mr. Tegeler said. Because the rollermills operate at 500 to 600 r.p.m. versus 300 to 400 in a single configuration, the double-high rollermills can grind harder, he said. The higher speed also contributes to better feeding of the roll.
The Hopkinsville plant uses fewer sifters, leading to a reduction of sifter surfaces, Mr. Tegeler said, and the double-highs offer greater flexibility to control starch damage.
Flour yield at the Hopkinsville plant is consistently higher than at Siemer Milling's other U.S. mill, a 415-tonne-per-day facility in Teutopolis, Illinois, that uses conventional single rollermills, Mr. Tegeler said. But he cautioned that direct comparisons were difficult because other factors related to environmental conditions, size, screenings and tempering influenced performance and costs.
Mr. Tegeler noted that double-high rollstands required greater attention to several operational areas. Preventive maintenance is more important, he said, because “a bad product will be produced faster” with the double-high technology. Precise roll adjustments and aspiration settings also are more critical, he said.
“It's easier to get out of balance,” Mr. Tegeler noted. “When you do the same job with less equipment, it means each step becomes more important.”
Dover Mills Ltd., Halifax, Nova Scotia, Canada, adopted compactness for its capacity expansion by incorporating a conventional mill flow within a confined area, according to Paul Brennan, the company's director of operations. Rather than adopting a traditional five-story layout, the company in 1996 added about 109 tonnes per 24 hours of capacity in a two-story structure. The wheat preparation flow also was remodeled to supply wheat for both mills.
The new two-story structure is about 11.5 meters long, 8.5 meters wide and 12.75 meters high, bringing the plant's total daily capacity in two buildings to 290 tonnes. The new unit's design and installation include provision for an additional capacity increase of 25%.
Mr. Brennan told A.O.M. participants that the company considered several options when deciding how to expand capacity.
“Budgetary and space constraints both contributed to our serious consideration of the concept of compactness,” Mr. Brennan said. “Insofar as there is more than one way to skin a cat, there is more than one way to mill flour and semolina.” In making its decision, Dover Mills first considered market requirements and adopted a “backwards from the customer approach” to assure that whatever system was installed would result in acceptable products. In the end, the company decided on a mill with a conventional flow in a compact layout after engineers from Sangati S.p.A. presented an economical design incorporating the two-story concept.
The new flow consists of four breaks with a fifth break fine, two sizing passages, two coarse and six fine reduction passages and four purification passages. The upper level contains purifiers and cyclones immediately above the sifters. The entire layout requires no additional staff and has resulted in a more user-friendly system, Mr. Brennan said. Overall mill maintenance also is more efficient, he said.
A need to keep building, equipment and labor costs down contributed to the decision to open a new mill with a 45-tonne-per-day Kice Shortflow flour mill, according to Steve Curran, president and co-founder of the Rocky Mountain Flour Milling Co., Platteville, Colorado, U.S. R.M.F.M., which began operations in June 1997, mills flour exclusively from organically grown wheat and is owned by farmer groups.
The fact that R.M.F.M. handles only organic wheat also played a major role in the selection of the short-flow unit, Mr. Curran said.
“The ease of clean-out, in a very short time and with limited staff, eliminates the possibility of cross-contamination,” he said.
In his A.O.M. presentation, Mr. Curran, who developed the patented short-flow milling system in the course of his studies and previous teaching work at Kansas State University, Manhattan, Kansas, U.S., outlined other advantages of the short-flow system for R.M.F.M. The company produces 10 different flours as well as custom flour, and the short-flow system enables quick changes in raw material and product, he said.
“We have the capability to make short runs and a wider range of flour types, soft to hard, and to achieve various extraction levels,” Mr. Curran said. “And we can make whole wheat flour with minimum hassle.”
As far as disadvantages, the short-flow system is more sensitive to wheat quality and mill adjustments than a conventional mill, a characteristic requiring a high degree of vigilance in process control, he said. The short-flow mill also does not allow for production of farina or semolina.