Miller Magazine Issue: 117 September 2019

80 ARTICLE MILLER / SEPTEMBER 2019 taken into account during the planning stages the mill building. High humidity has the following effect on the milling process: i) Inefficient dressing of stocks resulting in: a) Increased colour. (high ash) b) Reduced extraction. c) Reduced output due to chokes. d) Possible increase in protein loss. e) fluctuations of the mill feed rate ii) Increased condensation at certain points in the process, resulting in poor hygiene and chokes in the system. 2) Accuracy of weighers: Weighing mechanisms can be divided into two categories: a) Internal and b) External Internal weighers refers to the B1; flour; byprod- ucts and screenings scales which are essential for accurate monitoring of the mills performance on a regular basis, (in modern mills, these are directly linked to yield calculators that are capa- ble of giving the miller flow rates and extraction values at a glance instead of having to calculate this on their own) care must be exercised in this case to ensure that the accuracy of these scales is verified at least once quarterly. Any fluctuations in the operation of the weighing equipment will give false information regarding the milling perfor- mance and often leads to unnecessary changes being made to the mill equipment. External weighers are those used to weigh incom- ing raw materials and outgoing finished products. Inaccuracies with these will lead to stock variances, affecting overall performance, and site losses. To ensure accuracy in this aspect of the milling process, it is critical that all weighing equipment have the following facilities: i) A means for accurate check weighing. ii) A means for accurate balancing. This being provided for by having a bag off point for a complete tip of the scale to a bag and for regular maintenance. 3) Exhaust and air movement To avoid an imbalance between the air pressure inside and outside the mill, and the possibility of stock losses and unhygienic conditions caused by escape of dust from machinery, it is essential that the incoming air into the system as a whole, balanc- es the outgoing air from the system. Pneumatic sys- tems provide for the exhausting of the main milling machinery (e.g. plansifters and rollermills). However, in an elevator mill, adequate and efficient exhaust must be applied to minimize atmospheric dust as well as maintaining cool and free flowing dressing of stocks and hygienic conditions throughout the mill. Losses in dust collection and exhaust to at- mosphere may occur should the dust/ air sep- aration mechanisms be incorrectly balanced or maintained. This resulting in loss of product and increased air pollution. 4) Mixing of chokes and returned products i) Records of all stocks mixed into the system are kept so that accurate stock control is maintained and allowances are made during calculation of extraction. 5) Losses in packing i) Packing machines must be set within fine tol- erances to ensure that packed products are not over or under weight. ii) Bags must be check-weighed at regular in- tervals to ensure that weighing equipment is set accurately. iii) Accurate records of each product packed must be kept to maintain stock control and to iden- tify any possible losses due to errors in loading. 6) Weighbridges i) Ensure that records of all vehicle tare mass and gross weights are cross checked and main- tained. ii) Check that vehicles are positioned correctly on weighbridges prior to weighing. 7) Other possible losses • Ensure that efficient security arrangements are maintained on site. • Correct recording of weight of incoming raw materials and care exercised during recycling op- erations in the silo. • Proper recording of all returns to the mills with correct weights of mix-backs from customers. • Accurate recording of all recons from silo to mill; mill to holding bins; holding bins through mixing and blending plants; mixing plants to bulk or packing facilities; packing bins to warehouses and warehouses to logistics and weighbridges.