Published on February 18, 2014
Digital Re-print January | February 2014 Silos - Bulk storage special Grain & Feed Milling Technology is published six times a year by Perendale Publishers Ltd of the United Kingdom. All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies, the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis of information published. ©Copyright 2014 Perendale Publishers Ltd. All rights reserved. No part of this publication may be reproduced in any form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1466-3872 www.gfmt.co.uk
F SILO DESIGN AND CONSTRUCTION IN GEOGRAPHICALLY CHALLENGED AREAS by Bentall Rowlands Storage Systems Limited, UK S torage systems must be individually designed for each client. Each project must have a bespoke design that ensures it matches, if not exceeds client expectations,” says Kevin Groom, technical director of Bentall Rowlands Storage Systems Limited in the UK. “We are extremely proud of the projects that we have undertaken in geographically challenged areas, proving that whatever the specification, we are sure to provide the most suitable design necessary. “We have designed and installed silos worldwide in countries that include the UK, Kenya, Thailand, Holland, France, Ukraine, Malawi, New Zealand and many more. With over a century of experience in the design, quality and installation of grain storage systems, Bentall Rowlands have developed new technologies that have been applied to the manufacture as well as the installation of grain storage and processing equipment. Bentall Rowlands is a leading UK manufacturer in complete storage and processing equipment solutions for the agricultural and industrial markets. It offers a wide range of galvanised steel silos, flat bottom and hopper bottom, water tanks, catwalks and platforms, material handling equipment, cleaning and grading and weighing and drying systems that can be assembled worldwide. “Our engineering and technical expertise combined with continued focus on customer satisfaction places us in a strong position to capitalise on the expanding market in storage systems.” With capabilities to design, manufacture, supply and install storage systems from an extensive range of products, Bentall Rowlands provides a comprehensive end-toend solution which can be designed to any specific requirement. As the demand for bulk storage and handling equipment increases worldwide, volumes and competitive pricing in grain handling charges require efficient solutions. We manufacture the right quality of product to produce the efficiency savings required to justify the investment. Each project undertaken is designed differently and will need to take into account a number of factors. This includes geographical issues, including large temperature fluctuations, seismic activity, high winds and corrosion. Why do silos fail? On a number of occasions, the failure may only involve distortion or deformation, which doesn’t necessarily pose an immediate safety hazard. On the other hand, failure can mean complete collapse of the structure resulting in the loss of use and in some cases, the loss of life. The major causes of these failures are predominately down to design errors, construction errors and utilisation errors. “It is important that silos are built to meet the specifications set out in the design, eliminating any chance of silo failure. We work hard to #1 build the best relationships with our customers and spend time making sure that they receive the best possible service from the initial design concepts through to installation and completion of the project,” adds Mr Groom. Seismic activity “When we are tasked with the job of designing a new storage facility, there has to be a thorough inspection and survey of the site done prior to any work taking place. “The geology of the area is key to the design. For example we were chosen to design a site in New Zealand. “This country is known for its volcanic activity, earthquakes and geothermal areas because of its position on the boundary of the Australian Plate and Pacific Plates. We needed to know the area in great detail to make sure we designed the size and structure of the silos accordingly to dismiss any chances of collapse or damage if seismic activity does occur. “When designing a storage system for erection in a known earthquake region, they must be designed to the countries relevant seismic standards. All silos will need to be built a great deal stronger to cater for the horizontal loading at ground level. It is far better to keep the silos height down. “Silos that are shorter and wider are far better than those that are tall and thin. When seismic activity strikes, a structure that has a larger base area is more likely to withstand the pressures and remain intact. If you have a taller and thinner structure, this presents a huge amount of stress to the lower sections
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&Feed millinG technoloGy 20 | January - February 2014 of the silo which will ultimately result in the collapse of this structure. “Due to the fact that the magnitude of earthquakes varies greatly, all our silos are individually designed to suit each areas requirement. “The contract was originally built for the New Zealand Government to store oil seed rape. The stored grain would then be sent for crushing to be turned into biofuel. The silos were designed to hold the wet oil seed rape prior to going through a continuous flow drier,” he says. Dealing with high winds High winds can cause great problems for a number of structures, including our storage facilities. “We make sure that our silos are designed Grain to withstand gusts of 50m per second, which equates to 180km per hour. “During the recent storms that occurred in the North of England and Scotland, we had reports that all of the silos withstood the gale force winds, with no reported problems or damage.” In areas where silos could be prone to these high winds, the structure needs to be quite similar to that where seismic activity takes place. Silos will withstand these huge wind speeds when they are designed to cover a greater base area. This gives them the stability needed to remain intact once a storm has passed. Temperature change For countries that are prone to temperature fluctuations, the design of the storage system needs to be carefully thought out. More so for countries prone to high levels of moisture. In severe cold weather where snow can be quite extreme, it is the roof of the structure that needs to be one of the main focuses. Snow load is the reason for engineering changes. When designing the roof, it is important to know what depth of snow can be expected in a given area. “We designed a bespoke storage system for an area within the Ukraine where the snow can get extremely deep. “We specifically designed the roof on each silo to be able to withstand a pressure of 1kn/m2 which equates to one meter of snow,” he adds. Temperature changes within the actual stored prod- uct will affect the design of the silo, as does the moisture content of the stored product. “We look at the bulk solid that is being stored, and take into account the levels of moisture. Increased moisture within a storage system will affect the grain, causing expansion within the silo.” If this occurs when the materials are not being taken out, upward expansion is restrained. This means that the majority of the expansion will occur in the horizontal direction, resulting in increased lateral pressure, and hoop stresses in the silo walls. “In situations like this, we have to assess the area and the likelihood of significant moisture migration as this will affect the design of the system. Our silo roofs are designed with an area of overhang, meaning that in areas where rainfall will be a potential problem, we have that ‘run-off’ effect from the roof that protects the grain within the silos. “If our storage systems were designed differently, it would result in added moisture content within the silo, causing expansion and increased hoop stresses, but also the danger of losing the grain to mould.” The need for galvanising Galvanisation is the process of applying a protective coating of zinc to the silos in order to prevent rusting occurring. In areas where high levels of corrosion could be present, this is a necessity. “Compared to other companies, we use G600 as a standard whereas some companies may only use G90. This greatly increases the life expectancy of our silos.” For example, in tropical marine areas where storage systems are required, you can expect them to last somewhere around 35 years which is a huge advantage over other companies. Countries that have high levels of precipitation and humidity will rely on the galvanising of the silos in order to protect them from this corrosion. This is standard on all types of storage equipment, to add that extra bit of security on life expectancy. Getting the shipments right “Not only do we have to take into account the design of the silos in these geographically challenged areas, but the vast job of sorting the logistical side out. “All our shipments have to be correct at all times, especially the ones going to these challenged areas.” Getting it right first time is imperative. “To start shipping missing goods is not only a logistical nightmare, but can be a very expensive mishap, extremely time consuming and can hold up the project by a significant amount of time. “At Bentall Rowlands, when building large grain stores, it is common to agree a spares package that can be shipped with the main contract. More likely than not, some of the parts may become damaged or misplaced and parts that may only cost a few pounds could cost thousands if it has to be air freighted,” he notes.
F RECOMMNDATIONS FOR SOYBEANS AND SOYBEAN MEAL STORAGE by Pablo Fernández , Southeast Asia Area Manager Silos Cordoba S toring soybean and soybean meal leads to specific storage problems. That is why we need to know more about them. For example, the structure of the bean impacts its handling and: • Handling involves conveying and transporting from the farm to enduser. During this phase there are many different movements from harvest to the production into oil and meal • The structure of a soybean seed makes it susceptible to splitting and breakage during mechanical handling. The extent of breakage in soybeans during conveying varies with the impact force imposed on each individual seed. The least breakage occurs when soybeans are conveyed in a bucket elevator as compared to other conveying methods Figure 1 shows the extent of soya bean breakage with four methods of conveying: the first one represents the percentage of breakage of the grain in a free fall of 30, 21 and 12 meters. The storability of soybeans is affected by the degree of damage to the seed coat and by other factors such as mold or insect attack. It is therefore important to inspect soybeans for mechanical and other forms of damage prior to storage. If the amount of broken or split soybeans is very high, it may be prudent to separate the broken or split grains by sieving. This material can then be used first as opposed to long-term storage within the original stock. Soybean meal is difficult to handle because of its poor flowability and bridging characteristics. Soybean meal tends to settle or consolidate over time. This phenomenon occurs in most granular materials and becomes more severe with increased moisture, time and when particle sizes are small. Flow characteristcs The flow characteristics of bulk materials are dependent on individual particle shape, density, frictional property and moisture content. Granular materials have three typical flow patterns during discharge from hopper bottom bins: normal discharge pattern (there is no problem here), bridging and funneling. These two latter problems occur in grains containing high content of foreign material or moisture. Typical flow problems of meal products discharged from storage silos are hang-ups, dead pocket and piping (see figure 2). These are usually due to a combination of factors such as poor hopper design, high moisture content and storage time. External factors Beside all of the above soybean and soybean meal consideration, we have to keep in mind the most important external factors: moisture content, temperature and duration of temperature. The general condition of the product and amount of foreign materials also affect its #2 Table 1: Moisture content and safe storage durations Safe storage period Moisture content, % wet basis Market stock Seed stock 10-11 4 years 1 year 1-3 years 6 months 13-14 6-9 months Poor germination 14-15 6 months Poor germination 10-12,5 storability. By focusing on these three elements, we can assure the perfect storage of soya bean and soya bean meal: Moisture content: Depending on the percentage of moisture, the periods of storage change. Soybeans contain moisture ranging from 12 percent to 15 percent at harvest time. Above 13 percent should be dried to reduce the risk of deterioration due to seed respiration, mold attack, spontaneous heating and reduced germination. Temperature: Temperature is another very important factor influencing in soybean storage. Growth of fungi and chemical changes, such as oxidation, increased with temperature in both meal and whole beans. Moreover, it is really important to con-
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&Feed millinG technoloGy 24 | January - February 2014 Grain Figure 1 BREAKAGE IN SOYBEANS PERCENT BREAKAGE F 30m 21m 12m SPOUT THROW ELEV HANDLING METHOD TYPICAL PROBLEMS WITH MEAL PRODUCTS HANG UPS DEAD POCKETS sider the climate in the different regions of the world. Experience indicates that under hot and humid tropical conditions, grains stored in metal bins exhibit sweating. This problem arises with extreme high temperatures reached on the inner surface of the metal silo on a hot day, then, at night, the rapid cooling of the metal results in moisture condensation as the dew point is reached. Caking and charring in metal silos can be attributed to this phenomenon. Installing the proper devices of ventilation and cooling machines keep the correct temperature and avoid these problems. Time of storage: Shorter better! Fine foreign materials tend to segregate during bin loading and occupy void spaces in the central region of the grain mass. Meanwhile the large and lighter materials will accumulate close to the walls of the silo. Then, during aeration, the air will flow around spots with a higher concentration of Figure 2 PIPING fine foreign materials and through pockets of high concentration of large foreign materials. This condition creates a non-uniform flow of air during aeration, thus, making it an ineffective operation. Hence, cleaning soybeans prior to storage will minimise the risk of spoilage and economic loss. Detecting possible problems Here you have some indicators that will help you to detect any possible problems with the products storage inside the silos. Heating: Heating is the most common indicator of a problem in stored grains and oilseeds. High grain temperatures normally indicate either microbial or insect activity. If left unchecked, this may lead to heat-damaged or charred grains due to the phenomenon of stack burning. Because of this danger, hot spots in stored soybeans must be cooled or dissipated before they reach the critical level. If no action is taken when heating in soybeans occurs, either the product will be lost by stack burning (charring) or at worst, the entire facility will be lost through fire. Aerating soybeans when fire has already started makes the situation worse. A temperature monitoring system in soybean storage silos is essential. Immediate corrective measures for heating cannot be over-emphasised. Change in color and general appearance: In general, sound soybeans are plump with bright uniform tan with no trace of green colour and free from unusual spots and shriveled appearance. Discoloured soybeans usually indicate inferior quality and lower market value. The change in colour is usually associated with mold invasion accompanied by microbial respiration and subsequent heating. This deterioration process can be detected by periodic drawing of samples from the silos as part of an integrated approach of quality maintenance. Once detected, appropriate measures can then be taken such as cooling the grain either by aeration or use of a portable cooling unit. Another corrective measure is to transfer the grain to another silo thus breaking any hot spots present and cooling the soybeans during the conveying process. However, this should be done only as a last resort since it is costly and will increase the amount of broken or split soybean seed. Mustiness and off-odor condition: Musty odor usually indicates an advanced stage of insect or mold infestation and should be dealt with immediately. If this is detected, the soybean should be aerated to remove the bad odor and cool the material. Seeds should then be used at the earliest opportunity. The grain should be fumigated immediately if insects are present. A sharp odor may indicate rancidity due to chemical changes in the oil component. Lumping and caking: Lumping and caking indicate a very advanced stage of fungi invasion in soybeans and soybean meal. In metal bins, caking usually occurs on the bin walls as a result of sweating or moisture condensing on the inner surface of the cold bin wall. The condensing moisture is absorbed by the adjacent grains resulting in either sprouting or mold growth. Useful tips for soybean and soybean meal storage For all of this, low product moisture, low temperature and short storage periods are desirable. After this brief analysis we can give some tips for those who need to store either soybean meal or soya bean: The proper devices for storing soybean and soybean meal are: 1. Hydraulic sweep auger (for soybean meal). This sweep auger effectively reclaims meal products from silos because it is able to work with full silos. One full rotation of the screw once a day is mandatory to prevent the mentioned discharge problems.
F &Feed millinG technoloGy 26 | January - February 2014 Grain 2. Smoother wall ring+washer outside the silos and head-round bolts inside the silos. Different silos manufacturers using different wall ring waves. We have to be careful and choose a long wave. 3. Pre-cleaner. “Fine foreign materials tend to segregate during bin loading and occupy void spaces in the central region of the grain mass. Meanwhile the large and lighter materials will accumulate close to the walls silos”. That fact effects the ventilation, “the air will flow around spots with higher concentration of fine foreign materials and through pockets of high concentration of large foreign materials. This condition will create a non-uniform flow of air during aeration, thus, making it an ineffective operation.” Cleaning the product prior to storage will minimise the risk of spoilage and economic loss. Moreover, if the product has to be dried it is totally necessary to avoid the burn of the waste (fine foreign materials like straw, dust, etc) inside the dryer. 4. Dryer. Soybean moisture above 13 percent should be dried to reduce the risk of deterioration due to seed respiration, mold attack, spontaneous heating and reduced germination. 5. Ventilation. Centrifugal fans. The primary purpose of aeration is to make the temperature of the grain bulk uniform. This prevents moisture migration in the grain mass due to natural convection. Aeration may also be used to hold partially dried soybean for a few days to prevent spoilage before proper drying. It should be noted that aeration is not intended to dry grains. 6. Cooling machines. Strongly recommended in tropical climates with high heat and high humidity. Soybean, even after harvested, still keeps on breathing. The grain once chilled, keeps its low temperature for a long time, without the need for a continuous cooling. Direct consequences of non-controlled storing of wet grain are the appearance of fungi and toxins, which are very dangerous for the health of humans and animals. The proper storing of grain by means of chilled and dry air fix completely or widely minimise the problem. 7. Temperature monitoring system. This device is essential to control and correct any deviation of the optimum. 8. Belt conveyors. To prevent the breakage of the grain. This kind of conveyor can move grains for great distances without damage. 9. Periodic drawing of product samples and accurately testing them. By following all these steps you can be assured of avoiding change in color, risk of deterioration due to seed respiration, mold attack, spontaneous heating, reduced germination, mustiness and off-odor conditions, presence of insects, lumping and caking and finally economic loss. Answering your questions What flat bottom silos are suitable for storing soybean meal? In order to avoid long storage in soymeal silos, we of course recommend our model: Silo model: 12.22/12 Silo diameter: 12.22m Eave height: 13.73m Total capacity: 1.749m3 (1120T) Discharge capacity: 50T/h approx Please note that few silos in the same site can share the same hydraulic unit, and therefore the unitary price decreases. With several silos they can rotate the product between them; that is especially useful for long storage. What extraction screws do you deliver together with above flat bottom silos? We have worked with hydraulic sweep augers from Morillon. According to the capacity required they can be single arm or double arm. What hopper silos are suitable for storing soybean meal? Due to the poor flow characteristics of the soy, hopper silos with a reinforced cone of 60º are suitable. These silos should be equipped with screw discharge conveyors The biggest hopper silo model we have installed so far for this product is our model 60º hopper silo 6.88/9, with the 467m3. More inforMation: www.siloscordoba.com STORAGE SYSTEMS WORLDWIDE We take looking after grain very seriously Stand No. D109 Hall EH104 and EH103 Bentall Rowlands Storage Systems Limited Dragonby Vale Enterprise Park, Mannaberg Way, Scunthorpe, North Lincolnshire, DN15 8XF, UK T: +44 (0)1724 282 828 E: email@example.com W: www.bentallrowlands.com SITE 6 SITE 5 SITE 4 SITE 3 SITE 2 SITE 1
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LINKS January - February 2014 This digital Re-print is part of the January | February 2014 edition of Grain & Feed Milling Technology magazine. Content from the magazine is available to view free-of-charge, both as a full online magazine on our website, and as an archive of individual features on the docstoc website. Please click here to view our other publications on www.docstoc.com. first published in 1891 • • Having no choice is not reasonable The quest for a healthier snack Design of an efficient intake pit dedusting system Silos special: Bulk storage challenges • Contact the GFMT Team • Subscribe to GFMT NIR: • Keep running costs down the state-of-the-art in technology • Visit the GFMT website In this issue: • • • See the full issue Production control in rapeseed processing using NIR technology operating en-masse chain conveyors • Getting your dies and rolls re-worked locally to global standards INCORPORATING PORTS, DISTRIBUTION AND FORMULATION A subscription magazine for the global flour & feed milling industries - first published in 1891 To purchase a paper copy of the magazine, or to subscribe to the paper edition please contact our Circulation and Subscriptions Manager on the link adove. INFORMATION FOR ADVERTISERS - CLICK HERE Article reprints All Grain & Feed Milling Tecchnology feature articles can be re-printed as a 4 or 8 page booklets (these have been used as point of sale materials, promotional materials for shows and exhibitions etc). If you are interested in getting this article re-printed please contact the GFMT team for more information on - Tel: +44 1242 267707 - Email: email@example.com or visit www.gfmt.co.uk/reprints www.gfmt.co.uk
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