Milling with diversity

by Teresa Acklin
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Swiss mill produces a variety of custom flours quickly and efficiently.


   With a milling capacity of 120 tonnes per 24 hours, Bruggmuhle Goldach flour mill in Goldach, Switzerland, is the fourth largest in the country. And with as many as 40 formulations, the mill's flour output is among the country's most diverse.

   To satisfy the demand for customized flours from a variety of end users, Bruggmuhle Goldach relies on a state-of-the-art flour storage and handling system. The system enables the mill to produce many different flours to strict specification with consistently high quality — and to deliver them to customers on time.

   About 65% of the Brugg-muhle Goldach mill's output is delivered to large and small bakeries, with the balance sold to general food manufacturers. In addition to physical dough quality testing, the mill conducts microbiological flour and dough tests to meet the exacting quality needs of these customers.

   Of the many blends produced, six to 10 account for 90% of the mill's output, with the balance accounting for 10%. The mill primarily grinds local wheat, although about 15% is imported. Sources of imported wheat typically are the United States, Canada, Argentina or Saudi Arabia, with the selection based on quality, rather than price.

   Planning for the future and incorporating the latest technology to provide high-quality flours has been a hallmark of Bruggmuhle Goldach's management for decades. The same family has operated the mill since 1922, and over the years, numerous modernization and improvement projects have been completed.

   Today, the mill's crisp architectural design includes a unique rooftop conference room. Even more important to the mill's customers are the sparkling clean interiors and modern technology, which reflect the commitment of owners and personnel to mill hygiene and meticulous quality standards.

   Milling at the site actually dates back to 1670, when the abbots of nearby St. Gallen, located in northeastern Switzerland, founded the original Bruggmuhle beside a covered bridge over the Goldach River. In 1850, J.A. Hatten-schwiller bought the property, razed the existing dyeworks building and built the “modern-day” Bruggmuhle facility.

   The Hattenschwiller family operated the mill for more than 50 years, expanding and modernizing it numerous times. In the mid-1900s, Franz Hatten-schwiller sold most of the mill's stock to the newly formed East Switzerland Mills syndicate, and one of the syndicate's directors eventually took over operations of Brugg-muhle Goldach.

   In the early to mid-1960s, management embarked on a series of major modernization projects. Two new wheat silos were built, along with a 10-story building housing a flour silo.

   This building was designed to allow the future installation of a new mill above the silos. The concept enabled Brugg-muhle Goldach essentially to build a “greenfield” plant while continuing to operate the existing mill without interruption.

   The new mill, planned and built by Buhler Bros. of nearby Uzwil, was completed and began operating in the fall of 1973. Other projects completed through the mid-1970s included the installation of additional flour bins and a new bagging system in the original 1850 mill building.

   The original mill was torn down in 1986 to make way for the new finished products facility. But care was taken in the architectural design to preserve the mill's historic atmosphere and to harmonize the new with the old. The result is a visually appealing, modern complex that still retains some of the original 1850 structures.


   When the new flour storage and handling system was built, the integration of existing and new facilities was not limited to architecture. Indeed, Buhler, who was engaged for this project as well as the earlier plant installation, specifically designed the new section to incorporate the existing flour silo, built in 1965, into the modernized production and handling process.

   The design uses the 1965 flour silo, which has a capacity of 1,300 tonnes, for the collection and mixing of basic flours. These flours already have been homogenized to meet basic quality specifications, with the dischargers powered by remote-control variable drives. Flours from this silo can be directed into the bagging or bulk loadout bins, or they may be transferred to the new bin system for custom blending and mixing.

   The flour destined for blending passes through a fully electronic tubular scale that serves as a transfer and recording device. The scale has a capacity of 12 tonnes per hour and is approved officially for weighing applications requiring calibrated equipment.

   Flour passes over rebolt sifters and through impact machines to Fluidlift pneumatic conveyors, which transfer the flour to the blending and mixing section. This section consists of 18 ingredient bins with a total capacity of about 700 tonnes.

   In this section, flour is blended and mixed batch by batch at a capacity of 15 tph. The product is metered out, according to formula, to a fully electronic 1,000-kilogram scale through vibratory bin dischargers and screw feeders with fast and dribble feed capability.

   The section also features four 100-kg storage cylinders and a 5-kg electronic scale for proportioning and measuring other ingredients, such as vitamin C. A double ribbon flight mixer then blends and homogenizes the ingredients into the required finished product.

   The finished product undergoes final sifting and passes a magnet before being conveyed to the bulk loadout or bagging bins.

   Because of expanding demand for products such as break and whole-wheat flours, Bruggmuhle Goldach also installed a specialty mill in the flour silo section. This mill includes a buhrstone mill, a roller mill and a hammermill; the equipment may be used separately or in combination, depending on the product desired.

   The new finished product section also features a central control room with a state-of-the art computerized system. The system uses two P.L.C.s controlled through personal computers and includes a high-speed printer.

   All data management duties as well as storage and processing of blending formulas are managed through this process control system. The plant also can be operated automatically without process control; each device can be controlled through a terminal keyboard connected directly to the P.L.C.s.

   Because the project incorporated the 1965 flour silo into the process, an updated P.L.C. system was installed in the old silo. Operations in the new finished product section and the old silo also are linked through another computer control system. A screen in the old flour silo provides information about operations in the new facility.

   Bruggmuhle Goldach ships a large percentage of its flour to customers in bulk, and the loadout system was designed to provide flexibility and accuracy in this area.

   The bulk loading system includes separate sections for bright and dark flours to assure accurate loading. Each section consists of four 10-tonne bins, in which flour is prepared and weighed on order from the batch mixing system.

   Flour is transferred by a pneumatic discharger through airslide conveyors to the telescoping loading spouts, which are installed on movable rail-mounted carriages. This feature enables different truck compartments to be loaded with different flours without needing to move the truck. The system accommodates trucks with up to six compartments.

   The bagging section includes 10 bins with a total capacity of almost 300 tonnes. Flour is packed by a high-speed bagging carousel into 25 to 50 kg open-mouth paper bags. The bags are spread, folded, stitched and, if necessary, labeled, automatically. Belt conveyors, with a maximum rate of 600 bags per hour, deliver the product directly to trucks.

   Specialty products and mill by-products such as bran are packed by two separate single-spout baggers with a capacity of 250 bags per hour each. These products also may be shipped in bulk.

   Bags from both packers are closed at a semi-automatic bag closing station. The entire bagging system has its own P.L.C. and also is equipped with an interface to the main control system to log data for record-keeping. A printer also is available for weigh notes and bulk flour and byproducts loadout.

   The Bruggmuhle Goldach mill's most recent updating took place in 1992, when improvements were made to automation systems in the cleaning, mill and wheat silo sections. Various new Buhler equipment was installed, including automatic tempering systems; an online near-infrared system to measure and record protein, moisture, ash and water absorption; a central control room system for wheat intake and cleaning; and a mill yield computer system.