Flour milling is an ancient yet complex craft. Our food value chains rely as much today as they have for millennia on the miller’s ability to turn grain into a product that is healthy, nutritious, attractive, and safe for the consumer.
The grinding rollers are at the heart of the operation. Spinning at high speed, they must work in perfect harmony, accurately separating the bran from the endosperm, passage after passage, producing ever finer flour. Achieving clean sizing is a fine art.
It is not only the flour mill that relies on this process. It also plays a key role in the brewing and feed industries. In grist mills like the Maltomat 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 severe stress — stress they cannot withstand indefinitely. Constant use wears down the finely cut contours of fluted 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 the wheat kernel. Through each break the angles change, allowing a scraping action to accurately peel off the endosperm from the bran.
If the cutting angle begins to wear, it will not cut correctly and will inhibit the miller’s ability to set the rollers properly. The process will change from a cutting action to a crushing action. This not only requires more energy, it also fails to deliver the right kind of granular 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 2%, 4% or even 6% if the rollers are blunt. Both throughput and yield decline. An average 400-tonne-per-day capacity flour mill experiencing a drop in yield of only 0.1% will incur loss of revenue of approximately $12,000 a month (based on US market prices).
Energy consumption may rise by as much as 50%, while moisture 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. 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 people. The same principle applies for the brewing and feed plants. Keeping rollers in top condition means less waste and more profitability.
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. However, none of these is fully adequate. Some resort to generic 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 profile 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.
A 10-year track record
To address these concerns, Bühler launched rollDetect, which has revolutionized roller inspection and smart exchange planning. Today, rollDetect is in operation at more than 90 Bühler workshops around the world, improving operators’ bottom line.
Ten years ago, before the introduction of rollDetect, some customers were experiencing a huge drop in throughput and yields. With microscopic equipment, Bühler inspected third-party rollers at one of its workshops to get a better understanding of the situation. This sparked the development of rollDetect.
Initially, the measuring device was used to inspect refluted 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.
Ten years since its launch and with more than 90 rollDetect units in service worldwide, Bühler provides the tools, expertise and experience to precisely determine the right moment for a refit.
Truly cutting edge
The success of rollDetect rests on the unique precision of the rollDetect device in conjunction with analytical software — available in eight languages (English, German, Japanese, Spanish, Italian, Portuguese, Vietnamese and Russian) — and the expertise of Bühler’s experienced process engineers, who carry out the measurements and interpret the data on site at the customer’s plant, whether it is a flour mill, a feed mill or a brewing machine.
This is the main reason why rollDetect is offered as a service package rather than sold as a hardware and software bundle. It is also important to consider that measurement technologies continue to evolve at a rapid pace.
The rollDetect service package allows customers to benefit from the latest technological developments in this area.
The device is fitted with a precision contour red tracer stylus for fluted rollers or, for smooth rollers, a roughness blue tracer stylus equipped with a fine diamond tip.
All rollers can be accessed at a plant, which provides a full picture of the situation rather than fragmentary piecemeal information.
In addition, it features a positioner, the measuring system and a signal converter that is connected to a PC. The system is bundled with specifically designed software, developed and continuously optimized for accurate analysis and wear prediction. The rollDetect measuring device is portable and quickly installed by Bühler’s process engineers. The entire measuring procedure can be undertaken with minimal interruption to the operation.
Four types of reports
Are the rollers in working order and what is the absolute wear on the rollers? Comprehensive reports containing conclusive data and graphical representations equip operators with the information they need for objective decision making.
It’s a holistic approach, taking the entire process a step further.
The rollDetect software provides information on critical business figures and helps determine the best course of action.
There are four types of reports:
- tecReport for fluted and smooth rollers, available in field mode
- ecoReport for fluted rollers, available in field mode
- rollReport Summary, available in field mode
- rollReport for reconditioned fluted rollers, available in workshop mode
- Generated on-site, the tecReport features detailed graphic representations of actual and target corrugation profiles.
For smooth rollers, a graph displays roughness measurements. Roughness values are presented in Ra (average roughness) adhering to DIN EN ISO 4287.
A user-friendly traffic light system instantly answers the most pressing questions: Are the rollers in working order and what is the absolute wear on the rollers? Based on the measured values of the surface and corrugation edge condition, initial consultative advice can already be given on-site, keeping downtime to an absolute minimum. Customers are provided with the complete findings in the report.
The ecoReport provides customers with information on the economically optimal timing for examining rollers and a recommended date for the next roller change.
The measurement values are combined with customer-specific operational data. The results form the basis for a profitability analysis, showing detailed information about the customer’s service costs, energy loss due to non-optimal maintenance as well as the resulting loss in yield. The report forecasts data on the expected yield change, recommends a date for a roller revision and calculates the saving potential.
Customers will be able to request the comprehensive rollDetect service if findings suggest that further investigation is required.