World Grain - June 2012 - 60

MILLINGOPERATIONS

and cause undersized product to carry over with the tailings. The sifter checklist will also help to prevent incorrect sieve installation. Material may back up if a smaller micron size sieve is installed incorrectly or if sieves are placed out of order in the sifter section. The operator must also be careful not to accidentally turn a sieve

90 or 180 degrees from the proper position. In all of these scenarios, the sifter may work for a while, but eventually the incorrect separations will cause the section to ﬁll or send product to the wrong location downstream in the process. The operator must check and double-check that the sieves are placed in the correct order and are properly oriented.

The new “Giotto” wheat sterilizer main feature is its ability
to remove various outer bran layers whilst purifying the grain. The PLC operated adjustable peeling process lowers the grain’s bacteria count by removing crease dirt, the wheat beard and some of the pericarp. Even with dirtiest wheat the removal of fungi and mycotoxins results in highly puriﬁed cereals. The Giotto features hardened steel hand tools, with the tempering in excess of 750 Brinell Units and Inox steel shell ensuring reliability and extended life. Decrease bacteria, fungus and mycotoxins by making

“Giotto” your partner in wheat sterilization.

Another variable to be aware of is how replacing one sieve clothing type with another may affect the performance of the sifter. The sieve size and material originally speciﬁed for the sifter matched the stock application requirements, with the correct type (wire or synthetic), open area and mesh size. Replacing the original screen with one that has less open area will restrict the sifter, causing a change in the product to exit with the tailings. Be sure the proper changes are made. Consult the sifter or sieve clothing manufacturer to help determine which sieve clothing is most appropriate to meet the required changes. Finally, when you inspect the sifter, also check the head press mechanism to ensure that the sieves will be properly secured during operation and the sleeves connecting the top and bottom of the sifter to product spouts. A worn head press clamp may result in leakage around the sieve, impacting product quality. Dirty or worn sleeves should be replaced as a good sanitation practice to avoid stock from dusting out onto the ﬂoor. KEEPING THE SEPARATIONS When a sifter is properly designed and maintained, it can be the most overlooked machine in the mill. The rolls need adjusted regularly, but a sifter simply gyrates slowly and does its job. However, it is critical not to overlook the importance of checking the performance of the sifter regularly as well. The sieves, sieving material and the moving parts of a sifter wear just like any other machine and require a preventive maintenance plan to ensure they continue to operate as designed. The sifters are relied upon to grade and distribute the ground material throughout the mill to maximize ﬂour extraction and to maintain high quality product.
Mark Fowler is associate director of the International Grains Program at Kansas State University. He may be reached at mfowler@k-state.edu.

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World Grain - June 2012

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