Digital Re-print -
January | February 2014
Silos - Bulk storage special
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SILO DESIGN AND
by Bentall Rowlands Storage Systems Limited, UK
torage systems must be individu- capitalise on the expanding market in storage build the best relationships with our customers
ally designed for each client. Each systems.” and spend time making sure that they receive
project must have a bespoke design With capabilities to design, manufacture, the best possible service from the initial design
that ensures it matches, if not exceeds supply and install storage systems from concepts through to installation and comple-
client expectations,” says Kevin Groom, an extensive range of products, Bentall tion of the project,” adds Mr Groom.
technical director of Bentall Rowlands Rowlands provides a comprehensive end-to-
Storage Systems Limited in the UK. end solution which can be designed to any Seismic activity
specific requirement. “When we are tasked with the job of
“We are extremely proud of the projects As the demand for bulk storage and designing a new storage facility, there has to
that we have undertaken in geographically handling equipment increases worldwide, be a thorough inspection and survey of the
challenged areas, proving that whatever the volumes and competitive pricing in grain site done prior to any work taking place.
specification, we are sure to provide the handling charges require efficient solutions. “The geology of the area is key to the
most suitable design necessary. We manufacture the right quality of product design. For example we were chosen to
“We have designed and installed silos to produce the efficiency savings required to design a site in New Zealand.
worldwide in countries that include the UK, justify the investment. “This country is known for its volcanic
Kenya, Thailand, Holland, France, Ukraine, Each project undertaken is designed dif- activity, earthquakes and geothermal areas
Malawi, New Zealand and many more. ferently and will need to take into account because of its position on the boundary of
With over a century of experience in a number of factors. This includes geo- the Australian Plate and Pacific Plates. We
the design, quality and installation of grain graphical issues, including large temperature needed to know the area in great detail
storage systems, Bentall Rowlands have fluctuations, seismic activity, high winds and to make sure we designed the size and
developed new technologies that have been corrosion. structure of the silos accordingly to dismiss
applied to the manufacture as well as the any chances of collapse or damage if seismic
installation of grain storage and processing Why do silos fail? activity does occur.
equipment. On a number of occasions, the failure “When designing a storage system for
Bentall Rowlands is a leading UK manu- may only involve distortion or deformation, erection in a known earthquake region, they
facturer in complete storage and processing which doesn’t necessarily pose an immediate must be designed to the countries relevant
equipment solutions for the agricultural and safety hazard. seismic standards. All silos will need to be
industrial markets. On the other hand, failure can mean built a great deal stronger to cater for the
It offers a wide range of galvanised steel complete collapse of the structure resulting horizontal loading at ground level. It is far
silos, flat bottom and hopper bottom, water in the loss of use and in some cases, the better to keep the silos height down.
tanks, catwalks and platforms, material han- loss of life. “Silos that are shorter and wider are far
dling equipment, cleaning and grading and The major causes of these failures are better than those that are tall and thin. When
weighing and drying systems that can be predominately down to design errors, con- seismic activity strikes, a structure that has a
assembled worldwide. struction errors and utilisation errors. larger base area is more likely to withstand
“Our engineering and technical expertise “It is important that silos are built to meet the pressures and remain intact. If you have
combined with continued focus on customer the specifications set out in the design, eliminat- a taller and thinner structure, this presents a
satisfaction places us in a strong position to ing any chance of silo failure. We work hard to huge amount of stress to the lower sections
grain silos hoppered silos
tech expo Grain
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O ces and Factory:
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13210 Villarta de San Juan • Ciudad Real- Spain
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20 | January - February 2014 Grain &Feed millinG technoloGy
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 pres-
sure, 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.
of the silo which will ultimately result in the to withstand gusts of 50m per second, which Our silo roofs are designed with an area
collapse of this structure. equates to 180km per hour. of overhang, meaning that in areas where
“Due to the fact that the magnitude “During the recent storms that occurred rainfall will be a potential problem, we have
of earthquakes varies greatly, all our silos in the North of England and Scotland, we that ‘run-off’ effect from the roof that pro-
are individually designed to suit each areas had reports that all of the silos withstood the tects the grain within the silos.
requirement. gale force winds, with no reported problems “If our storage systems were designed
“The contract was originally built for the or damage.” differently, it would result in added moisture
New Zealand Government to store oil seed In areas where silos could be prone to these content within the silo, causing expansion
rape. The stored grain would then be sent high winds, the structure needs to be quite and increased hoop stresses, but also the
for crushing to be turned into biofuel. The similar to that where seismic activity takes place. danger of losing the grain to mould.”
silos were designed to hold the wet oil seed Silos will withstand these huge wind speeds
rape prior to going through a continuous when they are designed to cover a greater base The need for galvanising
flow drier,” he says. area. This gives them the stability needed to Galvanisation is the process of applying
remain intact once a storm has passed. a protective coating of zinc to the silos in
Dealing with high winds order to prevent rusting occurring.
High winds can cause great problems for Temperature change In areas where high levels of corrosion
a number of structures, including our storage For countries that are prone to tempera- could be present, this is a necessity.
facilities. ture fluctuations, the design of the storage “Compared to other companies, we use
“We make sure that our silos are designed system needs to be carefully thought out. G600 as a standard whereas some compa-
More so for nies may only use G90. This greatly increases
countries prone to the life expectancy of our silos.”
high levels of mois- For example, in tropical marine areas
ture. In severe cold where storage systems are required, you
weather where can expect them to last somewhere around
snow can be quite 35 years which is a huge advantage over
extreme, it is the other companies. Countries that have high
roof of the structure levels of precipitation and humidity will rely
that needs to be one on the galvanising of the silos in order to
of the main focuses. protect them from this corrosion. This is
Snow load is the standard on all types of storage equipment,
reason for engineer- to add that extra bit of security on life
ing changes. expectancy.
ing the roof, it is Getting the shipments right
important to know “Not only do we have to take into
what depth of snow account the design of the silos in these geo-
can be expected in a graphically challenged areas, but the vast job
given area. of sorting the logistical side out.
“We designed “All our shipments have to be correct at
a bespoke storage all times, especially the ones going to these
system for an area challenged areas.”
within the Ukraine Getting it right first time is imperative.
where the snow can “To start shipping missing goods is not
get extremely deep. only a logistical nightmare, but can be
“We specifically a very expensive mishap, extremely time
designed the roof consuming and can hold up the project by a
on each silo to be significant amount of time.
able to withstand a “At Bentall Rowlands, when building large
pressure of 1kn/m2 grain stores, it is common to agree a spares
which equates to package that can be shipped with the main
one meter of snow,” contract. More likely than not, some of the
he adds. parts may become damaged or misplaced
Temperature and parts that may only cost a few pounds
changes within the could cost thousands if it has to be air
actual stored prod- freighted,” he notes.
SOYBEANS AND SOYBEAN MEAL
by Pablo Fernández , Southeast Asia Area Manager Silos Cordoba
toring soybean and soybean meal material can then be used first as opposed to Table 1: Moisture content and safe storage
leads to specific storage problems. long-term storage within the original stock. durations
That is why we need to know more Soybean meal is difficult to handle
Moisture Safe storage period
about them. because of its poor flowability and bridging
content, % Market Seed
characteristics. Soybean meal tends to settle
wet basis stock stock
For example, the structure of the bean or consolidate over time. This phenom-
impacts its handling and: enon occurs in most granular materials and
10-11 4 years 1 year
• Handling involves conveying and becomes more severe with increased mois-
transporting from the farm to end- ture, time and when particle sizes are small. 10-12,5 1-3 years 6 months
user. During this phase there are many 6-9 Poor
different movements from harvest to Flow characteristcs 13-14
the production into oil and meal The flow characteristics of bulk materials
• The structure of a soybean seed makes are dependent on individual particle shape, 14-15 6 months
it susceptible to splitting and breakage density, frictional property and moisture con-
during mechanical handling. The tent. Granular materials have three typical flow storability. By focusing on these three ele-
extent of breakage in soybeans during patterns during discharge from hopper bottom ments, we can assure the perfect storage of
conveying varies with the impact force bins: normal discharge pattern (there is no soya bean and soya bean meal:
imposed on each individual seed. The problem here), bridging and funneling. These
least breakage occurs when soybeans two latter problems occur in grains containing Moisture content:
are conveyed in a bucket elevator as high content of foreign material or moisture. Depending on the percentage of mois-
compared to other conveying methods Typical flow problems of meal products ture, the periods of storage change. Soybeans
Figure 1 shows the extent of soya bean discharged from storage silos are hang-ups, contain moisture ranging from 12 percent to
breakage with four methods of conveying: dead pocket and piping (see figure 2). 15 percent at harvest time. Above 13 per-
the first one represents the percentage of These are usually due to a combination cent should be dried to reduce the risk of
breakage of the grain in a free fall of 30, 21 of factors such as poor hopper design, high deterioration due to seed respiration, mold
and 12 meters. moisture content and storage time. attack, spontaneous heating and reduced
The storability of soybeans is affected germination.
by the degree of damage to the seed coat External factors
and by other factors such as mold or insect Beside all of the above soybean and soy- Temperature:
attack. It is therefore important to inspect bean meal consideration, we have to keep Temperature is another very impor-
soybeans for mechanical and other forms of in mind the most important external factors: tant factor influencing in soybean storage.
damage prior to storage. moisture content, temperature and duration Growth of fungi and chemical changes, such
If the amount of broken or split soybeans of temperature. as oxidation, increased with temperature in
is very high, it may be prudent to separate The general condition of the product and both meal and whole beans.
the broken or split grains by sieving. This amount of foreign materials also affect its Moreover, it is really important to con-
The right storage solution starts with the right advice.
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F 24 | January - February 2014 Grain &Feed millinG technoloGy
by stack burning (charring) or at worst, the
BREAKAGE IN SOYBEANS
Figure 1 entire facility will be lost through fire.
PERCENT BREAKAGE Aerating soybeans when fire has already
started makes the situation worse. A temper-
ature monitoring system in soybean storage
silos is essential. Immediate corrective meas-
ures for heating cannot be over-emphasised.
Change in color and general
30m 21m 12m SPOUT THROW ELEV appearance:
HANDLING METHOD In general, sound soybeans are plump
with bright uniform tan with no trace of
green colour and free from unusual spots
TYPICAL PROBLEMS WITH MEAL PRODUCTS Figure 2 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 micro-
bial 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
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.
HANG UPS DEAD POCKETS PIPING
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:
sider the climate in the different regions fine foreign materials and through pockets of Lumping and caking indicate a very
of the world. Experience indicates that high concentration of large foreign materials. advanced stage of fungi invasion in soybeans
under hot and humid tropical conditions, This condition creates a non-uniform and soybean meal. In metal bins, caking usually
grains stored in metal bins exhibit sweat- flow of air during aeration, thus, making it occurs on the bin walls as a result of sweating
ing. This problem arises with extreme high an ineffective operation. Hence, cleaning or moisture condensing on the inner surface
temperatures reached on the inner surface soybeans prior to storage will minimise the of the cold bin wall. The condensing moisture
of the metal silo on a hot day, then, at risk of spoilage and economic loss. is absorbed by the adjacent grains resulting in
night, the rapid cooling of the metal results either sprouting or mold growth.
in moisture condensation as the dew point Detecting possible problems
is reached. Here you have some indicators that will Useful tips for soybean and
Caking and charring in metal silos can be help you to detect any possible problems soybean meal storage
attributed to this phenomenon. Installing the with the products storage inside the silos. For all of this, low product moisture, low
proper devices of ventilation and cooling temperature and short storage periods are
machines keep the correct temperature and Heating: desirable. After this brief analysis we can
avoid these problems. Heating is the most common indicator give some tips for those who need to store
of a problem in stored grains and oilseeds. either soybean meal or soya bean:
Time of storage: High grain temperatures normally indi- The proper devices for storing soybean
Shorter better! Fine foreign materials cate either microbial or insect activity. If left and soybean meal are:
tend to segregate during bin loading and unchecked, this may lead to heat-damaged 1. Hydraulic sweep auger (for soybean
occupy void spaces in the central region of or charred grains due to the phenomenon meal). This sweep auger effectively
the grain mass. of stack burning. Because of this danger, hot reclaims meal products from silos
Meanwhile the large and lighter materials spots in stored soybeans must be cooled or because it is able to work with full silos.
will accumulate close to the walls of the dissipated before they reach the critical level. One full rotation of the screw once
silo. Then, during aeration, the air will flow If no action is taken when heating in soy- a day is mandatory to prevent the
around spots with a higher concentration of beans occurs, either the product will be lost mentioned discharge problems.
F 26 | January - February 2014 Grain &Feed millinG technoloGy
2. Smoother wall ring+washer outside soybean for a few days to prevent spoilage storing soybean meal? In order to avoid
the silos and head-round bolts inside before proper drying. It should be noted long storage in soymeal silos, we of course
the silos. Different silos manufacturers that aeration is not intended to dry grains. recommend our model:
using different wall ring waves. We have 6. Cooling machines. Strongly recommended Silo model: 12.22/12
to be careful and choose a long wave. in tropical climates with high heat and high Silo diameter: 12.22m
3. Pre-cleaner. “Fine foreign materials humidity. Soybean, even after harvested, Eave height: 13.73m
tend to segregate during bin loading and still keeps on breathing. Total capacity: 1.749m3 (1120T)
occupy void spaces in the central region The grain once chilled, keeps its low Discharge capacity: 50T/h approx
of the grain mass. Meanwhile the large temperature for a long time, without the Please note that few silos in the same site
and lighter materials will accumulate need for a continuous cooling. Direct can share the same hydraulic unit, and there-
close to the walls silos”. consequences of non-controlled storing fore the unitary price decreases. With several
That fact effects the ventilation, of wet grain are the appearance of fungi silos they can rotate the product between
“the air will flow around spots with and toxins, which are very dangerous them; that is especially useful for long storage.
higher concentration of fine foreign for the health of humans and animals.
materials and through pockets of high The proper storing of grain by means What extraction screws do you
concentration of large foreign materials. of chilled and dry air fix completely or deliver together with above flat
This condition will create a non-uniform widely minimise the problem. bottom silos?
flow of air during aeration, thus, making 7. Temperature monitoring system. This We have worked with hydraulic sweep
it an ineffective operation.” Cleaning the device is essential to control and correct augers from Morillon. According to the
product prior to storage will minimise any deviation of the optimum. capacity required they can be single arm or
the risk of spoilage and economic loss. 8. Belt conveyors. To prevent the double arm.
Moreover, if the product has to be breakage of the grain. This kind of
dried it is totally necessary to avoid the conveyor can move grains for great What hopper silos are suitable for
burn of the waste (fine foreign materials distances without damage. storing soybean meal?
like straw, dust, etc) inside the dryer. 9. Periodic drawing of product samples Due to the poor flow characteristics of
4. Dryer. Soybean moisture above 13 and accurately testing them. the soy, hopper silos with a reinforced cone
percent should be dried to reduce By following all these steps you can be of 60º are suitable. These silos should be
the risk of deterioration due to seed assured of avoiding change in color, risk of equipped with screw discharge conveyors
respiration, mold attack, spontaneous deterioration due to seed respiration, mold The biggest hopper silo model we have
heating and reduced germination. attack, spontaneous heating, reduced germi- installed so far for this product is our model
5. Ventilation. Centrifugal fans. The primary nation, mustiness and off-odor conditions, 60º hopper silo 6.88/9, with the 467m3.
purpose of aeration is to make the presence of insects, lumping and caking and
temperature of the grain bulk uniform. This finally economic loss.
prevents moisture migration in the grain More inforMation:
mass due to natural convection. Aeration Answering your questions www.siloscordoba.com
may also be used to hold partially dried What flat bottom silos are suitable for
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: firstname.lastname@example.org W: www.bentallrowlands.com
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