Its all about bunker storage like types, design and factors affecting.

1. Bunker storage of grains
Presented By
Shilpi
Dept. Of Agricultural And Food Engineering

2. CONTENTS
• Introduction
• Types of bunkers
• Design consideration of bunker
• Temperature and RH relationship inside bunkers
• Conclusions

3. INTRODUCTION
• Modern bunker storage in Australia derives
from pit storage developed by the
Commonwealth Industrial and Scientific
Research Organisation.
• Under Australian conditions pit storage was
too labor intensive and working conditions
too severe, therefore research moved to
above-ground bunker storage.
• This is a storage system built with structural
metal studs of galvanized steel and lateral
containment elements that form a rectangular
“tray”; having a base that could be its own
ground floor.
• Effective treatment of insect infestation is
difficult in sheds and bunkers.

4. Situations where bunkers can provide rapid, convenient
and inexpensive solutions are:
• At terminal silos when bins are filled to capacity.
• At collection sites and regional centers where incoming harvested
grain is bottle- necked due to transportation problems.
• When grain is to be held on a temporary basis in anticipation of
higher prices.
• For national grain reserves that require long-term storage.
• As buffer stocks for food-aid under emergency situations.

5. TYPES OF BUNKERS
Round bales
• Using round bales is a low cost,
effective method for smaller piles.
• Put the bales in a circle around
where you will pile your grain.
• Put a plastic barrier between the
bales and grain to prevent grain
from spilling out between cracks.
• Wrap a cable around the perimeter
of the of the bales to prevent them
from shifting outward under
pressure of grain. (with a 5ft grain
wall depth, there is a force of
115lbs per foot on the bales).

6. Plywood Bunkers
• Full 4’x 8’plywood sheets are nailed together using 2’x 4’s.
• Sheets are bent gradually to form a circle.
• Easy to alter.
• Cover & aerate like regular outdoor pile.
• Can easily disassemble & store when not in use.
• Should consider wrapping a cable around the diameter to prevent
joints from failing.

7. Open bin rings
• These rings can be set on the
ground, covered and aerated like a
regular outdoor pile.
• Rings need to be anchored
according to manufacturer speci..
• These rings can be ordered with
built in auger spouts or doors.
• Can significantly increase storage
if space is confined.

8. Wood Bunkers
• Relatively low cost.
• Usually constructed of plywood sheets with
a stick built frame.
• Shown at right is an oak board bunker.
• Bunkers are usually self supporting.
• Can be either purchased from a lumberyard
or constructed on your own.
• Easy to alter in order to add holes for
ventilation, augers, etc.
• Should be covered and aerated like other
outdoor piles.

9. • Most have a self supporting
design that does not need to be
anchored.
• Makes cleanup easier.
• Have a very long life.
• Not cost effective for a small
amount of bushels.
• Need to be set on a relatively
level surface to prevent gaps
between sections.
Cement Bunkers

10. Steel Bunkers
• These also have a self supporting design.
• Very long life.
• Need to be set on relatively level surface
to prevent gaps between sections.
• Not cost effective for a small number of
bushels.
• Cost estimation included bunkers, and
estimated tarp & aeration cost, no site
preparation.

11. Earthen Bunkers
• Need to choose a soil type that will pack
well.
• Create side and back barriers using soil.
• Base of the barrier should be four times
the height of the barrier. Width at the
top of the barrier should be half of the
base.
• Dig a trench on the barrier to insert the
liner into and cover with soil.
• The cover should at least go part way
down the outside of the barrier, and can
be anchored with dirt.
• This will prevent water from running
into the inside wall of the barrier.

12. • The bunker floor should be leveled and earth removed in this process
should be used to form the retaining ramps along one end and along the
two sides of the bunker.
• Soil types that permit compacting will enable ramp construction to
heights of one to two meters.
• Ramp cross section should be trapezoidal.
• For a 2 meter high ramp the base should be about 8 meters wide and the
top of the ramp 3-4 meters wide.
• The closed end-ramp should be shaped to the same dimensions as the
side ramps to form a radius equal to half the distance between the
parallel side walls.
• This semi-circular end-ramp eliminates the need to fill the corners with
grain.

13. Ultra hermetic bunker
• Ultra Hermetic Bunker can be made very
simply by spreading out low density PE sheets on
the bottom of a U- shaped compound consisting
of an earthen ramp.
• A better solution is to cover the ground with
asphalt or concrete and to replace the earthen
ramp with a concrete or metal support wall.
• The large pile of grain is made by a grain thrower
or grain pump, to be finally covered by large PVC
sheets which come partly assembled to the site.
• The sheets will be welded together on top of the
pile with a manual heat welder. Ends of PVC
sheet and LDPE sheet are rolled together and
buried in a surrounding trench to obtain ultra
hermetic sealing.

14. • The ramp is covered with plastic
sheeting to prevent being flushed
away by rain draining from the
bunker “roof”.
• When disassembling, PVC sheets
will be cut neatly and stored on
pallets for reuse in next season.
• The application of this technology is
subject to certain climates and low
MC’s of grain due to risk of
condensation.

15. DESIGN CONSIDERATION OF BUNKERS
• Site Selection
• The site should have a low water table;
• The site should slope between 1% and 5%;
• The soil should be well-drained sandy loam, but with sufficient clay to enable soil
to cover bunkers;
• The site should be on sufficiently high ground to prevent water accumulating on it;
• The site should be clear of flash floods;
• The site should not be on filled land;
• The site should be well away from nearby building drains, etc.;
• The site should be protected from strong winds.

16. Considerations
• Make sure that grain is at an appropriate moisture before
using any of these storage methods (13-15%).
• Grain should be clean to allow efficient & effective
aeration, reduce spoilage, and deteriotion by rodents.
• It is important to check grain for moisture, temperature,
sanitation, etc. at least once every two weeks.
• Consider whether short term expenses are justifiable
compared to adding permanent, long term storage.

17. Grain Handling Equipment
• Site preparation may be influenced by the nature of the in-
loading and out-loading equipment to be used.
• If the bunker is to be loaded from the side by means of screw
augers pneumatic conveyers or endless-belt conveyers, then
side access must be sufficient for both the loading equipment,
including loading hoppers, and dump trucks.
• If the grain bulk is in-loaded from the bunker floor itself, then
the access paths on each side of the bunker will be for
maintenance purpose only, but trucking access will be required
to allow vehicle entry into the bunker.

18. Bunker Dimensions
• The width of the bunker is dependent upon two
variables determined by the user, namely height at the
centre and height at the sides.
• Two variables determined by the grain, namely the
angle of repose for a given grain species, and the
specific gravity of the grain itself.
• Height At The Centre. This is limited by the height to
which the in-loader can raise the grain.
• Endless-belts that project the grain in an arc may reach
8 meters or more, while augers and conveyer belts may
only reach a maximum of 6 meters.

19. • Height At Sides. The higher the retaining side-walls the
greater the bunker capacity per unit length.
• Corrugated steel and concrete walls are usually 0.5 to 1 meter
high, earth ramps can be raised to 2 meters.
• Ramps require a broad base which adds considerably to the
total width of the bunker site.
• Experience has shown that bunker widths of the grain-bulk
greater than 25 meters are less convenient due to the quantity
of plastic liner that must be drawn over the grain during the
covering and uncovering process.

20. • Once the grain height at centre and sides has been decided
upon, the following simple equations may be used for roughly
calculating the length and width of a bunker:

21. • Decisions on bunker capacity will also determine the
amount of plastic liner to be used.
• The larger the bunker, the smaller the surface area per unit
volume of grain, and the smaller the capital investment per
tonne of grain stored.
• Calculation should be weighed against the convenience of
building a number of smaller bunkers with the inherent
convenience of handling and managing the smaller grain
bulks.

22. Drainage
• Proper drainage of run-off water from the overliner is essential.
• For this reason surrounding ground should be lower than the bunker
floor and sloping away from the bunker.
• Where earth ramps are constructed, earth from outside the bunker is
used to form the ramps and by so doing the level outside the ramps
is lowered.
• The access and maintenance paths around the bunker can then be
graded to ensure run-off.
• The bunker floor should be graded from the closed end to the open
end with a slope of at least 3%.

23. The Bunker Underliner
• Waterproof plastic sheeting should be laid across the floor and
over the retaining walls to prevent moisture migration and gas
exchange between the grain bulk and the ground.
• It is advised use of 200 to 250 micron polyethylene sheeting
laid progressively as loading advances, with an overlap of at
least 15 cm "tile fashion”.
• Each additional sheet should be laid as described above and
sealed with tape.

24. • An allowance of at least 2 meters of sheeting beyond the
retaining walls should be given to enable the underliner to
be sealed with the overliner.
• Care should be taken to avoid damage to the underliner
during loading, and walking or driving over the liner
should be minimized to prevent tears.
• The underliner should be discarded and replaced after
each storage period.

25. Permanent floor storage system

26. Temporary floor storage system

27. Ventilation And Aeration System
• Eliminates offensive odors at the source
• Environmentally controlled structure
• Air usually not recirculated
• Filtered ventilation systems supply clean well oxygenated
• Air Reduces odor at the source
• Depends on the design of bunkers

28. Different system of aeration

29. Temperature And Moisture
Relationships In Bunker Storage

30. Temperature Vs Time Of Storage

31. RH vs time of storage

33. CONCLUSIONS
• Bunker storage is still only recommended where the harvest period
coincides with the dry season of the year, since loading the grain may
take many days during which time the grain is exposed to the elements.
• The bunker over-liner does not provide protection from pilfering. Also
if animals are free roaming in the vicinity, fencing should be provided
to protect the bunker.
• The plastic may be damaged by mechanical punctures and by contact
with certain chemicals.
• Technique of passing air between the grain surface and the PVC liner
reduced temperature to a steady-state value in approximately three days
while a relative humidity stratification in the grain mass was not
achieved until after seven days.

34. REFERENCES
• ASAE Standards. 1987. D245.4:301-305. St. Joseph, MI:ASAE.
• Freer, M. W. et al. 1988. Modeling temperature and moisture content
changes in bunker-stored rice. ASAE Paper No. 88-6050. St. Joseph,
MI: ASAE.
• Gough, M. C. 1985. Physical changes in large-scale hermeticgrain
storage. Journal of Agricultural Engineering Research 31:55-65.
• Navarro, S., Donahaye, E. Kashanchi, Y., Pisarev, V. and Bulbul,
O. (1984) Airtight storage of wheat in a PVC covered bunker.
• Yates, C. J. and R. Sticka. 1984. Development and future trends in
bunker storage. In Developments in Agricultural Engineering 5: B.
E. Ripp et al, eds. New York: Elsevier Scientific Publishing Co.