New equipment designs yield enhanced milling performance

by Teresa Acklin
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Developments in flour milling equipment enhance quality, provide easier maintenance and quick installation.

   In the highly competitive, increasingly global flour milling industry, lower capital and operating costs, reliable equipment and high product quality have become critical to success. To help millers achieve their goals in these areas, milling equipment manufacturers are constantly developing and testing new technologies. This article offers a look at some of the latest in new equipment and processes available to millers.

    The grain supplied to mills is often very dirty and full of impurities. Food legislation often demands a high flour quality from an environmentally acceptable production process.

   On the basis of this requirement, Buhler Ltd., Uzwil, Switzerland, has developed a grain cleaning system offering increased cleaning efficiency. The 1995 cleaning concept includes — in addition to the Combi cleaners — the indented-surface separator and the scourer with an air-recyling aspirator. This new concept offers significant advantages over earlier systems. Power consumption, operator attendance and space requirements have all been reduced.

   The first machine in any cleaning system is the separator, which is also used for classification and grading. By launching a new development in the successful separator series, Buhler is meeting the demand for higher plant efficiency.

   The MTRB “classifier,” built to satisfy the highest requirements, is preferably applied in grain storage and cleaning facilities. The machine's sturdy design with two screen decks and a curtain-type feed of material across the entire screen width offers efficiency, high performance, and ruggedness. Its separating efficiency is excellent, maintenance is low, the power requirement has been minimized, and operation is easy even when the task to be accomplished is difficult.

   The stroke and the angle of throw of the free-swinging screen box are adjustable. The screen slope is selected to suit the particular application. This allows the machine to be used for a multitude of different tasks. The coarse impurities, tailing over the top screen, are separated a second time at the lateral outlet into coarse waste and finer components, the latter being reusable under certain circumstances.

   If the classification work to be performed is demanding, two in-line machines can be stacked one on top of the other.

   The grain, freed from coarse impurities (pieces of wood, strings, straw, earth clods) and fines (sand, kernel fragments, foreign seeds), is still mixed with fines such as dust and straw particles. These must be removed at the outlet of the separator by means of air classification. The MVSQ air-recycling aspirator is of invaluable service for this purpose.

   The aspiration channel MVSH has been developed to allow combination with the new MTRB separator. The experience gained with the air-recycling aspirator, of which the second generation is already in service, was incorporated in this new design.

   The stream of material entering the machine across its entire width is whirled up with air. The low-density particles are thereby directed to the actual separation zone of the aspiration channel. Thanks to selective control of the air flow and appropriate setting of the double-adjustable wall, excellent separating efficiency is achieved. Positioning scales serve as adjustment aids. Wear parts are resistant and can be quickly replaced.

   If a higher degree of sanitation and a lower bacteria count are to be achieved, thorough cleaning of the grain surface is indispensable. The key to clean, low-bacteria grain is the newly launched MHXS scourer.

   In the first cleaning process, the bacteria count is reduced by intense scouring, and the so-called filth count — the number of insect fragments present in the material — is considerably improved. In the second cleaning process, the hull particles detached by dampening can be gently removed.

   The scouring action can be adjusted as required by means of a retarding device, ensuring consistent quality. The machine dimensions of the large type MHXS 45/80, which is designed for a maximum capacity of 30 tonnes per hour, are up to 40% smaller than those of the previous models.

   The reduced space requirement has a positive impact on the building cost, both in new plants and in remodels. Despite the shorter processing length of the machine, the scouring degree has been improved without increasing the maintenance costs, thanks to the use of wear-resistant components. The ease of operation offered by the machine reduces operator workload.

   Whether the material processed is soft wheat, rye or durum, the MHXS scourer is always followed by an MVSG aspiration channel or an MVSQ air-recycling aspirator. This allows the surface dirt detached from the kernels to be neatly separated from the grain.

   The requirements of today's milling market call for larger and larger capacities while maintaining high flour quality. To fully satisfy its customers, Ocrim S.p.A., Cremona, Italy, has developed a new series of super-giant square plansifters (SFL models).

   The new plansifters provide 33% more sifting surface than Ocrim's BQG models and incorporate a new sieve design that improves sanitation and avoids sediments. The new plansifters are available in three models, one with four, one with six and the third with eight sifting sections.

   The new models' main characteristics are a net sifting surface of 0.40 square meters, with up to 27 sieves in each plansifter section; sturdy sieve boxes and a central drive frame structurally tested by high technology methods; a simplified flowsheet using standard sieves; improved sanitary design to avoid increased microbial counts in flours; an external sieve locking device allowing easy maintenance; and lightweight, insulated fiberglass doors to prevent internal condensation and to facilitate access.

   The design concepts developed for the plansifters type SFL also have been incorporated into the manufacture of Ocrim's BQG plansifters, thus providing a wide range of sifting units to meet any milling capacity needs with a reduced number of machines and to satisfy customers with high standards of quality products.

   Prokop Milling Machines, Pardubice, the Czech Republic, has developed a new generation of rollermill, which was expected to be introduced to the market in the fourth quarter of 1995. Prokop also has drawn on the history and technological evolution of purifiers in the development of its semolina purifier, model PCK 2345.

   The invention of a purification and separation machine for semolina and small middlings originated in France at the end of the 18th century. This originally simple machine, which achieved separation with blown air, was soon improved by the American G.T. Smith, who built a sieve purifier.

   The construction elements of Mr. Smith's machine are still the basis for development of new machines, but equipment suppliers worldwide race to seek ways to increase effectiveness and quality. The original material, wood, has been replaced by stainless steel, and state-of-the-art computers have replaced simple control elements.

   The up-to-date purifier is characterized by high output. This is accomplished through the use of a large sifting area, typically three stacked sieve decks of equal dimension. The product yield and quality also can be multiplied using a double-deck screen arrangement.

   Modern machines are usually driven by two vibro-motors to provide a quiet run. They are equipped with modern electronics and are connected to the mill's central computer control system.

   Simple design allows for reliable operation and easy maintenance. Aspiration ducts are illuminated with fluorescent lamps for easy checking. Sieve frames are made of aluminum alloys to enable sieve replacement while the purifier is operating. Spouting tubes are passed through the central part of the machine to leave space around the purifier for servicing.

   As part of the ongoing development program at Satake U.K. Ltd., Stockport, U.K., two new core machines and an important new compact milling system have been introduced this year.

   The Rollermill SRMA uses an innovative design, which has resulted in a machine that offers great strength and low noise and vibration. The Rollermill SRMA also offers a dramatically short roll change time, which means less downtime. An intelligent automated feeder, oil free differential and direct pickup all add up to a machine with low operating costs.

   The Purifier SPUA is a high-capacity triple deck machine that is easy to maintain with the highest possible sanitation.

   The PeriCom Compact Mill uses the PeriTec debranning process developed by Satake, along with full-scale equipment such as the Rollermill SRMA and the Purifier SPUA. The PeriCom range of mills offers flexibility while matching a conventional mill in quality of product.

   With capacities ranging from 35 to 120 tonnes per day, PeriCom compact mills can be used as a supplement to an existing mill or as a stand-alone unit. Arriving on site in containers, all parts are keyed to detailed drawings. The facility can be quickly assembled by engineers using Satake supervision or a full installation and commissioning service.