Miller Magazine Issue 137 May 2021

66 COVER STORY MILLER / may 2021 The break system and stock distribution is one of the key factors that need to be well set for an effective mill performance. Millers must adjust the entire plant accord- ing to his intuition and ability, to obtain the best results in terms required by the expected quality of the finished product. Purification This is the separation and stratification of the interme- diate stock( mixture of semolina, bran particles and germ) into clean semolina/middlings particles, endosperm with bran attached, bran particles and germ, using the princi- ple of terminal air velocity. The terminal air velocity prin- ciple is influenced by factors such as; Density, shape and size of the stock particles. The purifier helps to improve the quality of the fin- ished product, especially in a situation where produc- tion of good yield with low ash flour is required. For an optimal purifier performance the following point must be achieved: • Uniform feeding of stock across the surface area of the sieves. • Proper air settings. • Good condition of the sieve mesh. • Efficient brush cleaning system. Reduction system The aim of the reduction system is to reduce the sem- olina of different sizes and ash content step by step into flour. During grinding the temperature in the grinding gaps are to reach a certain limit in order not to damage the gluten characteristics which could affect the baking characteristics of the flour. To achieve an efficient reduction of semolina and mid- dlings to flour the following important points need to occur: • Constant feeding of stock and distribution of stock over the entire length of the rolls. • Correct roll surface, differential speed and taper of the roll. • Appropriate flake detacher underneath the reduction rolls. To improve extraction and mill performance the above points need to be seriously put into consideration. CAPACITY UTILIZATION This is defined as the percentage of the equipment's capacity used during the milling process. This is based on the production in a steady state, and is strategical- ly pursued to maximize output and ensure the finished product is of the required standard. Milling equipment needs to be in its perfect state to achieve maximum uti- lization. The factors seriously influencing the final outcome of the finished product are ruled by three parameters: the processing capacity, the extraction and the type of fin- ished product. Any changes in one of the 3 factors will in- fluence the other two parameters as highlighted below: • Increasing the capacity is at the expense of ex- traction. It leads to overloading the milling machines with could affect the distribution of stocks. • Operation of the mill under-capacity conditions in- creases the extraction and alters the flour color, increas- ing their ash content and over sifting occurs. • Increasing capacity alters the granulation of flours, meaning it lowers the average diameter of flour fractions. FACTORS AFFECTING CAPACITY UTILIZATION AND MILLING PERFORMANCE • Maintenance Policies (Preventive and Predictive Maintenance) Maintenance is human activities conducted to maintain or take care of an object/hardware so that it can continue to be in use. A poor maintenance policy gradually affects the efficiency and performance of machines and equip-