Miller Magazine Issue: 132 December 2020

50 COVER STORY MILLER / december 2020 A good sampling technique should be applied to ob- tain correct laboratory results. Special device and an ap- propriate method of blending sub-samples, a composite representing the load average can be obtained. Trucks and train wagon can be sampled by using a manual sam- pling probe. Depending on the size of the load, sampling should take place at five or more different points (depth is also important to take deep sample). Automatic sampling usually is also used. A sampling device automatically takes the sample and pneumatically transfer to the laboratory for the analysis. 1.1.2. Dosing Equipment Scales, volumetric feeders, belt scales and flow rate dosers using load cells are among the dosing equipment used in receiving section. 1.1.3. Pitting hole (receiving pool) If raw material comes as bulk in a truck to plant area, it is discharged into a pitting hole. The pitting hole is under the ground level as open. There is a grid as a static screen to separate very big size foreign materials during the dis- charging of raw material. Dust formation occurs during the discharging therefore a vacuum air system should be used to collect this dust around the pitting hole. A spe- cial design cassettes (air channels) should be put near the pitting hole. Due to dust problem, the pitting hole should be closed. A special design roof (elevated) can be used to protect pitting hole and raw material against to rain and snow. The pitting holes are also potential rodent and insect entrance places, therefore traps and rodent traps can be used. In some pitting holes, a lift is used to discharge truck by inclined. Raw material is transferred from pitting hole to pre-cleaning system by elevators or pneumatic conveyor. Therefore the bottom design of the pitting holes should be made carefully by using angle of repose and sliding angle. İf not, the flow of raw material is not possible to feed the conveyors. 1.1.4. Conveying Equipment In receiving and cleaning section conveyors are very important. Therefore, their properties and design re- quirement should be known very-well. The properties of transport equipment/devices are given in Table 3 (Bren- nan, et. al., 1990). i) Bucket Elevator Bucket elevators are usually used to elevate grain to the storage facilities. The main advantages of bucket el- evators are their mechanical efficiencies of about 90%, low power and maintenance, and little damage to the grain. But, at the bottom section, if cleaning is not made periodically, the elevators cause rodent, microorganism and insect places, so they will be risk point for the food safety. In general, bucket elevators are suitable for dry product. If wet products are transported by using eleva- tors, buckets and bottom part of elevators cause mold- ing, smelling, insect growth, microorganism growth and food safety risk. The bucket elevator used for handling bulk materials consists of i) buckets to contain the material, ii) a belt to carry the buckets and transmit the pull, ii) a means to drive the belt (accessories: for loading the buckets or picking up the material, for receiving the discharge ma- terial, for maintaining belt tension, and for enclosing and protecting the elevator, for motion–detection devices, for belt–alignment monitoring devices, for fire-suppression system, and for belt–alignment monitoring devices, for fire-suppression system, and for an aspiration system to keep dust concentration inside the bucket elevator at least 25% below the lower explosion limit at all times during operation. If bucket elevators are used in a dusty area or to transport dust-having product, there is a dust explosion risk at high level. Therefore, an explosion ate, valve or vent should be used. Additionally, Atex/Exproof motors should be used for these kinds of elevators to prevent ignition and dust explosion. ii) Belt Conveyors Belt Conveyors have long been recognized as the most simple, reliable and economical handling materials in large or small capacities. A belt conveyor consists of a moving, endless belt, which supports material and by its motion, carries the material from one place to another. For dusty products, closed belt conveyors must be used. For ship ports, belt conveyors are good solution for big capacity loading and discharging. Additionally, belt con- veyors are known as hygienic conveyors. iii) Screw Conveyors The screw conveyor consists of a screw supported by bearings and rotating inside a throw. This conveyor can transfer dry materials at any angle as horizontal or in- clined. Use of the screw conveyor is declining today in grain industry because of high maintenance costs, re- maining product under screw, abrasion effect on screw, causing dust and hygienic problems. iii) Drag or Chain Conveyor The drag or chain conveyor can be used for the trans- fer of grain horizontally, vertically or in an inclined po- sition in the cleaning unit. It moves material more gen- tly than screw conveyors and is relatively self-cleaning, therefore it is useful for fragile grains (e.g. rice, beans etc.). The chain/drag conveyor consists of a series of spe- cially designed paddles or bars mounted on a drive chain that travels within a stationary through. It is also suitable for high capacity conveying and operations in the dusty places. It is easy to close to prevent the dust release to environment during the conveying. Recently, in the new plants, chain/drag conveyors are gaining acceptance in grain processing industry, replacing regular belt convey- ors. The following are some of the advantages of chain/