Crushing, Grinding and Reduction in Flour Milling

02 November 20168 min reading

“It is necessary to create a good control system at the factory to ensure the stability at the product quality.  It must be studied meticulously in all stages of production so that the quality of product is good.”

Sinan AYBAKAR Member of the Board Aybakar Dış Ticaret A.Ş.


More functional and useful features have been added compared to the former ones with the development of electronics and automation in roller mills. Torque motors are used which we have made the R&D work for the years especially in the area of product supply. The product level is determined via sensor or loadcell integrated into the roller mill bottle and the feeding speed can be set according to the incidence rate. This provides a continuous product flow. Also the possible damage to the machine is minimized if there is any impaction through the sensors which can be put in different places, and the failure can be identified and rectified before the growth of failure. Lubrication systems are not on bearings one by one in the new generation of CERES II roller mills, they have been taken at a central point with easy access. Thus the lubrication is provided easily and in a short time. We can provide to lubricate in a stable form by controlling the centralized lubrication systems with the PLC system.

The front of the roller mills is made openable to make the roll changing operation more quickly and easily in roller mills and two rolls can be easily taken out along with the bearings. Thus, the changing of rolls can be made in a short time and production will have to stop for long periods.

THE EFFECT OF ROLLER MILL ROLLS TO GRINDING There are two types of roller mill rolls as Crushing roller mill rolls and reduction roller mill rolls; 1. Crushing roller mill rolls make an angle on rollers in order to fulfill the wheat cutting-opening, excavating- eroding and crushing and spliting missions, to do so, it has extending threads. Their numbers, angles, and heights in centimeters vary depending on how these threads will destroy and cut the product. Unless appropriate selection of roller threads, there will be problem related to efficiency and quality.

2. Reduction roller mill rolls are straight roller mill rolls. The task of reduction roller is gradually to convert semolina obtained in the crushing system into the flour and to make flake by crushing bran and germ particles. They make the compress, crushing and shredding tasks. Expansion occurs at the edges because of heat released due to compression and crushing in these rolls; A little camber is given to the middle part in order to ensure crushing in parallel and equally while running the rolls. This camber varies depending on the density and structure of the product to passage. If appropriate camber is not selected, a complete crushing can not be provided and thus quality defects with yield losses are seen.

ENERGY CONSUMPTION IN ROLLER MILLS Thanks to the advancement and the good use of technology today, the effort to make optimum production has increased with the minimum energy in the mill. Because the competition is increasing day by day. Therefore, machine manufacturers put in effort to make machines that can operate at maximum capacity by spending less energy. Also the selection of machine and the preparation of diagram according to the feature, capacity of raw materials to be processed and of product to be produced in making the factory projects directly affects the energy consumption. As a result of the development of machines, energy consumption has reduced rather than the former.

GRINDING GAP AND PARTICLE SIZE Grinding gap and particle size are reduced towards the end from roller mills which the grinding begins. The reason for this is that each process has disintegration and contraction while making gradually cutting, sorting and scraping actions during the separation of endosperm and bran. Therefore the grinding gap will be less in the next crushing process. This range varies depending on the chracteristics of the desired product, the performed diagram, tonnage and the humidity of the milled product.

TEMPERATURE CONTROL IN ROLLER MILL AND ROLL BEARINGS Temperature control is very important in especially reduction (liso) in other words straight roller mills. While making crushing and blasting operation in these roller mills, it may occur more heat. The crushing and blasting operation performed here should be applied so as not to impair the gluten and strach features of the flour. The roller mill rolls temperature should not be more than 40 to 45 degrees. If this remperature is more, there would be deterioration in the bread value of flour, also it begins to appear the deformations on the roller mill rolls and this temperature spreads to the bearings. The oil used in the bearings become thinner and exudes outward, in this case the life of the bearings is reduced.

STABILITY OF PRODUCT QUALITY It is necessary to create a good control system at the factory for ensuring the stability in the product quality. It must be studied carefully in all phases of production so that product quality is good. Things to pay attention are as follows: • The supply of the right raw materials according to the product to be produced, the classification and storage of these raw materials, • The making of the right wheat blending according to the product to be produced, • Routine checks on time cleaning machines for cleaning of wheat in a good way, • The wheat humidity is important for a standard milling. To be done right the quenching operation required to the wheat, • After quenching according to the physical properties of wheat, the rest time is very important for coming to ideal humidity of the wheat. To rest at the right time. • To maintain the tonnage constantly at the grinding part, • Routin controls are made so that roller mill settings are stable.

FEEDING IN ROLLER MILLS The roller mill supply settings must be done in good way to obtain the maximum efficiency in the roller mills. Because if the product to rolls comes in the form of curtain and continuously among the roller mill rolls, grinding and milling process will be stabil; thereby the product coming to the sieves will be continuous and homogeneous. The feeding process is very important for the stability of product quality. Sensor and load cell system faciliates fairly in adjusting the product coming to the roller mills and the product given to the roller mill rolls. If the product to roller mill is thicker, the closeness of the roller mill rolls to each other is not importance, a shortage is seen in performing the crushing. So grain curtain setting and speed setting should be adjusted very well.

GRINDING CAPACITY Grinding capacity is calculated according to the factory's capacity. Crushing roller mill rolls should be up to approximately 40 percent of the total roller mill length, Reduction (liso) roller mill rolls are up to 60 percent of the total roller mill lenght. The average lenght of the roller mill is based on the account of12mm / 100kg /24 hours. This account is valid for standard flour mills. It varies according to the ratio of the products in the passages.

ROLLER MILL SETTINGS Roller mill settings can be adjusted according to three basic principles. • The first is a setting done by hand. When the product is squeezed equally by keeping from both ends of the roller mill rolls, the decision is taken by touching • The second is a setting done by eyes. Flaking and fragmentation of the milled product at both ends are looked with eye. • The third is based on heat; the temperature in the roller mill rolls is synchronized with the heat meters from the both ends of the roller mill rolls and manually if there is no heat meter. It is effective to find the healthy setting to use these three method together while the roller mills are set. Also the product received from two sides of the roller mill rolls in the crushing roller mills can be adjusted, and can be adjusted according to the rate of product under the sieve by passing through laboratory sieve. For example about 30-35 percent of the particles must pass below 1000 microns sieve in B1 roller mills.

ROLLER MILL CARE AND MAINTENANCE PERIOD Maintenance and repair is a system that we still are forced to fix nowadays. As Aybakar, we committed to provide the necessary training on maintenance and repair to our customers. Our customers' technical teams are trained at our factory and in customers' factories prior to delivery of the machine.

The necessary maintenance intervals to be performed are as follows: Weekly maintenance • Control of air supplies • Control of roller mill rolls belt • Control of the belt roller mills • Cleaning of the roller engines • Combining and opening the roller mill rolls

Monthly maintenance • Aspiration system control in crushing roller mill • Brush control • Temperature control of rollers and roller mill rolls bearings

3rd month maintenance • Control and cleaning of motor fans • Tension of roller mill rolls and roller belt

15.000 hours maintenance • Changing of the roller mill rolls belts • Change of roller bearings and controls

25.000 hours maintenance • Changing of the roller belts

LUBRICATION Lubrication process may vary depending on operating speed and ambient temperature. Aybakar's proposal is that lubrication is made from the central system per 1000 hours. By a single point lubrication with 8 bearing of 4 roller in our single storey CERES II roller mills, central system has been designed and approximately 640-800 grams of oil should be pressed. Double storey CERES II roller mills has been designed by lubricating of 8 roller from 16 single point and approximately 2560-3200 grams of oil should be pressed.

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