Miller Magazine Issue: 125 May 2020

55 COVER STORY MILLER / MAY 2020 respiration. A decrease in temperature slows down the res- piration rates in grains like many other foods. Grain Storage All storage systems must be designed to adequately pro- tect and preserve the quality of the grain. Whole grain can sprout under certain conditions and will also attract moulds, insects and rodents. In addition, the storage of grain pres- ents several safety issues. Grain storage systems come in a range of shapes and sizes, design of a grain storage facility should be based on • Length of time for storage – temporary or long-term. • Degree of segregation of different types of grain. • Identity preservation requirements. • Expected useful life of the structure. Long Term Storage In general, grain in long term storage should be held cool and dry. Options include smooth wall steel silos, corrugated steel silos bins, concrete silos and underground pits. Steel silos are the most common method of long term storage for grain at feedlots, but underground pit storage is an alterna- tive for longer term storage. Silos Silos are available in a variety of sizes, configurations and materials, including flat bottom or cone base, gas-tight sealable or non-sealed, aerated and non-aerated. Silos can be built on site or transported fully constructed and ready to stand. The size of fully constructed, transportable silos is limited by road transport regulations. As a general guide, fully constructed silos can be up to 140t capacity. Most small (50–70t) cone-bottom silos are generally prefabricat- ed and transported. Cone-bottom silos are self-emptying, but are limited to capacities of less than 300t. Feedlots may require air-tight/gas-tight storage facilities of higher capac- ity. But the increased surface area of a larger silo requires more sheet metal joins, providing more opportunity for air or gas to escape. Capacity is commonly quot- ed in tones, but may also be quoted as cubic meters (m3). To determine tonnage capacity, multiply the cubic capacity by the bulk density of the grain. Silo Foundations Foundations for elevated silos are differ- ent to those for general building construc- tion because of the large loads involved. The first step in establishing a silo is to construct a good quality pad. These structures are en- gineered to support grain in a vertical plane, with pressure exerted and distributed evenly around the base support frame. If the pad is not level, the weight of the grain will place ex- cessive stresses on the lower sheets of the silo and possibly twist the base frame - deforming the silo. The soil engineering requirements for most elevated silos should be determined by a consulting geotechnical engineer. Silo Safety Safety issues associated with grain stor- age and handling include working at heights, working in confined spaces, entering grain silos while being emptied (grain entrapment) and dust explosions. Silo designs now incorporate ground operated lids, caged ladders, platforms and top rails to minimize the risk of operators falling. Facil- ities for harness attachments, which should be worn by all operators who are climbing and entering silos, should also be fitted. Silos are classified as confined spaces and correct procedures need to be followed prior to entry. Grain Storage Management Good hygiene in grain handling and storage premises will maintain the quality of the products handled. Problems with grain caking on silo walls, being damp and mouldy in the base of the store and sprouting in the headspace are caused by poor grain management or poor maintenance of the grain store. Other problems have been reported with lu- pins or peas stored in old silos, where walls have buckled or compressed from the greater pressure exerted by the round seeds. In extreme cases, the silo has collapsed. Good hygiene can be achieved by ensuring that storages facilitate are • Easily inspected. • Regularly serviced for equipment maintenance. • Cleaned of grain residues, particularly in sheds, around silos, in augers and in silos after emptying. Good storage design should be complemented by • Correct training of people in safety and hygiene-related issues. • Regular monitoring. • Establishing a system for recording and checking hygiene procedures.