Miller Magazine Issue: 132 December 2020

52 COVER STORY MILLER / december 2020 drag conveying: i) can move material vertically, horizon- tally and at any slope up to angle of repose, ii) requires simple methods of loading and unloading, iii) handles more than one materiel at a time, and self-cleaning pass- ing from one product to another, iv) produces minimal dust emission because it is completely enclosed, v) is au- tomated (remote-controlled) and process controlled, vi) is safe because it has no fast-moving parts, vii) is hy- gienic. iv) Pneumatic Conveying Equipment The benefits of pneumatic conveying of grain are the small space occupied by the conveying lines, improved sanitation and the increased flexibility of diverting flow of material to any point, as compared with other means of conveying grain, which is closed system, hygienic, and started to widely used in the industry. The main disad- vantages is the relatively high energy consumption com- pared to other means. High dense and low dense phases are available. High-dense phase system is used to con- vey fragile product, but its investment cost is high. Low- dense phase pneumatic conveyors are also two types as negative and positive pneumatic. Elbows in pneumatic conveying equipment are usually the points that wear and tear. So, to overcome this abrasion, they are lined with ceramics or wide radius can be used. Pneumatic conveyors are highly suitable for horizontal conveying when compared to vertical position. Aspiration of equip- ment and pneumatic conveying generate a relatively large volume of air mixed with product. At the end of the pneumatic line, cyclone or bag-filter are used. If the conveying particle is fine, performance of bag-filter is better than cyclone. Filter fabrics vary in weight, thick- ness, permeability, strength, specific gravity, pore size, temperature limitations and surface finish, additionally the cleaning the fabric bags of the filter is important for keeping the filter at top performance efficiency. A ma- nometer is used to the dirty and clean air parts of the filter. Protection systems monitor volume and pressure of airflow in and out of dust collectors. Such suppression systems include venting and isolation to prevent incipient fires and subsequent dust explosions. Therefore, dust ex- Table 3. Applications of materials-handling equipment