GRAIN BUNKER STORAGE COVERS

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1 A: Massey Ave, Leeton NSW 2705 PO Box 860, Leeton NSW 2705 P: F: E: W: GRAIN BUNKER STORAGE COVERS PRODUCT APPLICATION SHEET The application of woven poly/pvc grain bunker storage systems which can be constructed under farm conditions has become an accepted method in providing on-farm temporary storage of grain. Initial experiments conducted by Grain Handling Authorities throughout Australia in conjunction with Rheem Australia Limited, proved that technology, developed by Bulk Grain Queensland in constructing large-scale bunker storages, could be supplied successfully to scaled-down on-farm versions to provide reliable and cost effective grain storage protection Circumstances which can impose the need to save grain quickly and independently of traditional facilities can include: Silos filled to capacity Delays in turnaround time at grain storage depots Lack of, or delays in available transport The threat of adverse weather conditions Retention of crop in anticipation of better selling prices or greater export opportunities Having determined the need for on-farm grain storage it is important to consider the type of construction materials required and how long it will be expected to provide reliable protection. THE BUNKER A bunker storage consists of three retaining walls which are lined with plastic & filled with grain. A suitable cover sheet is placed over the grain pile and sealed to keep out water, insects and other containments. SITE SELECTION AND POSITIONING The bunker must be sited on a well drained area where the water table is well below the surface. Surface vegetation needs to be removed and the bunker should not be placed too close to trees (which could drop limbs onto the top cover during storms). It is advisable to face the closed end of the bunker into the prevailing wind to reduce problems when placing the top cover. Otherwise, run the bunker north-south for even exposure of the cover to UV radiation from sunlight Good access to the site for vehicles and handling equipment is also important of course. BUNKER DIMENSIONS The first factor to consider when determining a bunker dimension is the height to which your grain handling equipment can form a stack of grain. This height, together with side retaining wall height, determines the distance required between each side (see tables 1-6). When assessing your stack height remember that a particular type of grain will form a heap relevant to its angle of repose: 23 to horizontal for wheat, 26 for barley, 30 for oats (as illustrated in diagram 1). The auger must also be positioned far enough back to prevent the under-carriage being excessively buried by grain during filling. It may be desirable in some instances to attach an extension piece to the auger outlet to achieve greater bunker height (see diagram 6). Once the grain height has been determined, the dimension of a bunker to store a particular quantity of grain can be arrived at from table 1-6. Note: this table refers to bunkers with a wall height of either.5 of a metre or 1 metre. The width increase by approximately 1 metre if bags of grain are used to form the retaining walls.

2 It is advantageous to spread your total storage requirements over several small bunkers rather than confine storage to one very large bunker. For example, two 400t storages could be constructed rather than a single 800t unit. By doing this, the cover sheets will be kept to a manageably size and bunkers can be located at several convenient sites. LINING THE BUNKER A waterproof plastic lining laid across the floor and over the walls of a bunker prevents moisture entering the grain from below as well as avoiding grain from being contaminated by soil. In addition, the completed bunker can be effectively sealed once the top cover is in place and permit fumigation of the entire storage for effective insect control. A large prefabricated lining sheet similar to the top cover can be used as a liner, its main advantage being speed of application in addition to greater security and complete removal of uncontaminated grain when emptying. Alternatively, lining of 200 micron polyethylene can be laid across the bunker and sealed with tape. Additional widths are progressively laid as the bunker is filled and are lapped 150mm over the previous width. Tape each overlay to prevent grain from pushing laps up and to prevent insect migration allow 1 metre of sheeting to extend beyond the walls to be sealed later with the cover sheet. An alternative lining arrangement using bags filled with grain is shown in diagram 5. FILLING THE BUNKER Grain should not be stored at greater than 12% moisture content; otherwise losses are likely to occur. Bunkers are simply filled by dumping grain from a truck into an auger (or grain thrower) located midway between the side wall. As the bunker fills, the auger is progressively moved towards the open end, taking care not to tear the ground sheet. The grain peak should be a uniform height along its full length and correct height to suit the distance between your walls (refer to tables 1-6). Hand trimming of the stack before covering is necessary to avoid depressions where rainfall may collect.

3 FITTING THE COVER The bunker does not have to be completely full before starting to cover the grain. The cover is fitted by hand with a team of men dragging the concertina fabric from the filled end across the top of the stacks. Apply the cover as filling progresses to avoid possible damage by sudden storms. A temporary, easily removed cover can be placed over grain at night. Do not attempt to handle large areas of cover sheet during windy conditions as it will quickly become unmanageable, even for a team of men. The cover is tensioned over the banks of the bunker to protect from erosion by water, and the end and edges are finally sealed. SEALING Bunker covers must be effectively sealed around the walls and ends of the bunker in order to: Anchor the top covers to prevent wind lift Prevent water and insects from entering Allow fumigation if required Protect earthen banks from erosion by water Several methods for achieving a good seal are available. One of the simplest and more successful in practice requires both top and bottom covers to extend about 1 metre beyond the base of the walls. These edges are buried in a previously dug trench about 250mm deep at the base of the wall as shown in diagram 7. Used tyres, soil-filled wheat bags or other suitable ballast can be placed on and around the top cover to hold it down and reduce wind flap. Avoid objects with sharp projections that may puncture the cover, or abrade holes from movement in the wind wear patches are recommended under the tyres or bags. It is advisable to provide a fence, perhaps a temporary electric fence, around the bunker if there is any likelihood of animals foraging near the bunker. A well constructed and effectively sealed bunker can also be fumigated to control grain insects. REMOVING THE GRAIN The top cover is progressively removed and folded in the reverse manner to which it was applied. Careful removal and storage of good quality top covers should allow them to be re-used. The unexposed side of the cover must be faced out next time it is used. A mobile auger fitted with a cross sweep is ideal for unloading a bunker storage. Shovels and brooms complete the job. Pneumatic grain conveyors are also effective in unloading this type of storage and front-end loaders could be used. Ensure that covers still on the stack during unloading are held down against the wind. A bunker can be resealed after partial unloading. NOTE: At all times care must be taken not to damage the cover. Whilst reinforced fabrics are much more robust than plastic film they can be damaged by sharp objects, abrasion, some chemicals etc. avoid all contamination of fabrics from machinery and contamination from herbicides, oil and other chemicals as these can attack the UV stabilizers in the fabric, reduce the life of the cover and negate the warranty. Also, do not clean the cover with harsh, strong cleaning compounds, as these also have a negative effect on cover life.

4 Tables 1 6 Bunker Dimensions BANK HEIGHT.5 Metre Wheat Height, BARLEY & SORGHUM Repose Angle 26º 650kg per cubic metre OATS Repose Angle 30º 400kg per cubic metre Oats Height, BANK HEIGHT 1 Metre Wheat Height, BARLEY & SORGHUM repose Angle 26º 650kg per Cubic Metre OATS repose Angle 30º 400kg per Cubic Metre Oat Height,

5 Tables 7 12 Cover Dimensions BANK HEIGHT.5 Metre Wheat Height, BARLEY & SORGHUM Repose Angle 26º 650kg per cubic metre OATS Repose Angle 30º 400kg per cubic metre Oats Height, 200t 300t 400t 500t Lengt h BANK HEIGHT 1 Metre Wheat Height, BARLEY & SORGHUM repose Angle 26º 650kg per Cubic Metre OATS repose Angle 300º 400kg per Cubic Metre Oat Height,

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