Miller Magazine Issue: 131 November 2020

73 ARTICLE MILLER / November 2020 tomat III MDBA and in feed mills like the multi-stage grinding DFZL, grinding rollers are equally central to operations. However, the grinding process subjects rollers to se- vere stress – stress they cannot withstand indefinitely. Constant use wears down the finely cut contours of flu- ted rollers and decreases the required level of roughness on smooth rollers. “When they are properly serviced, the rollers’ cutting angles act like a filet knife. In a flour mill, that is how they open up the wheat kernel. Through each break the ang- les change, allowing a scraping action to accurately peel off the endosperm from the bran,” says Bill Ritchie, Technical Sales and Service, North America. “If the cut- ting angle begins to wear, it will not cut correctly and will inhibit the mil- ler’s ability to set the rollers properly. The process will change from a cut- ting action to a crushing action. This not only requires more energy; it also fails to deliver the right kind of gra- nular product.” The consequences are significant for the flour miller. In the case of fluted rollers, the yield of pure flour extracted during sifting can drop by two, four or even six percent if the rollers are blunt. Both throughput and yield decline. An average 400t flour mill experiencing a drop in yield of only 0.1 percent will incur loss of revenue of approximately 12,000 USD a month (based on US market prices). Energy con- sumption may rise by as much as 50 percent, while mois- ture content declines and the quality of the end product suffers. “This is significant in terms of the economics involved but also a question of sustainability,” says Roman Inauen, Customer Service Sales Support, Milling Solutions, Büh- ler Switzerland. “If you can maintain a maximum yield, that means there is less waste of precious resources, like water, and more flour that is made into bread to feed pe- ople. The same principle applies for the brewing and feed plants. Keeping rollers in top condition means less waste and more profitability.” TOO COSTLY FOR GUESSWORK Worn out rollers are costly and compromise product quality. To maintain the profitability of a milling plant, timely replacement is essential. How can plant operators evaluate wear and determine the right moment for an exchange of rollers? Plants deploy several strategies and techniques. Howe- ver, none of these is fully adequate. Some resort to ge- neric maintenance schedules or a set volume of material processed as a marker for impending replacement. Some exchange the rollers frequently, even when they are still in working order. Some inspect rollers by scratching the surface with a fingernail without seeing if the fluting pro- file is intact. Others try to determine the right moment of exchange by sampling the granulation of sifted product Increased power consumption may give clues, but it does not provide any information on which passage and roller is responsible for decreased efficiency Moisture detection and ash curve checks may provide more accurate results but require lab tests. Some of these methods are highly subjective, others deliver objective data but lack detailed and complete analysis resulting in ill-informed decisions with a detrimental effect to the bottom line and quality. KNOWING RATHER THAN GUESSING Bühler has more than 160 years of experience in the milling industry and roller technology. As technologists we understand the commercial context our customers operate in. When rollDetect was launched it revolutioni- zed roller inspection and smart exchange planning. Today rollDetect is in operation at more than 90 Bühler works- hops around the world improving operators` bottom line. “Ten years ago, before the introduction of rollDetect, we really felt the pain of our customers experiencing a huge drop in throughput and yields. With microscopic equipment we inspected third party rollers at one of our workshops to get a better understanding of the situati- on,” says Ritchie. “This sparked the development of rol- lDetect.” Initially, the measuring device was used to inspect reflu- ted rollers before they left the Bühler workshops. Today, the device can be used in the workshop or out in the field, and the same device can be used for smooth or fluted rollers. Figure 1: rollDetect’s analysis of worn out fluted rollers.