Complete Solutions to the Grain Value Chain
Understanding the dynamics of a silo project
– what does it entail?
a. Needs assessment, planning and preliminary design:
A silo project should start with an interpretation of customer needs assessed against the real requirements of a project with a service life of 30 to 50 years which may, over its lifespan, include many expansions, changes, handling capacity upgrades, subsequent cleaning and drying systems, intake design to accommodate changes in truck and rail logistics and many potential needs not necessarily apparent initially but which requires to be incorporated during the initial design.
An engineering team specialised in grain handling and storage with more than 50 years’ experience in grain handling and storage is available to our customers for this crucial phase of the project.
b. Costing and preliminary bill of quantities:
A free quotation, based on the needs assessment is supplied together with an estimate for quantities for civil works based on good soil conditions. These quantities are re-assessed once the customer or ABC Hansen conducts a proper soil stability study. The customer should in fact commission this study prior to obtaining quotations from service providers and suppliers to ensure a level competition field. ABC Hansen can either conduct the complete civil works if required or can furnish the selected contractor with all technical details to enable the customer to obtain competitive quotations.
c. Final Project Design, Costing, Bill of Quantities, Acceptance and Commencement
After assessment of the needs versus the costing and preliminary bill of quantities as final decision is made regarding the viability of the project – and costs are compared to savings and operational requirements. A final decision is made on the design, product flow diagrams, spouting and handling systems. The final stage of the planning process is the signoff of the final flowsheets and preliminary drawings and budgetary bills of quantities, and acceptance of the project by the customer, and the preparations for the financial aspects of the project such as loan approvements and building permit approvals based on the layout drawings – as well as payment term negotiations.
d. Commencement of project
After all approvals have been obtained, financial obligations have been finalized and detailed drawings have been approved, the project can commence. The first physical phase of the project is usually the civil works portion, and includes construction of dump pits and reception areas, silo, cleaner, dryer and elevator foundations, water run off contours and supply of bulk services to the site, such as stormwater drainage and main electrical supply to the site.
During this phase, the manufacturing, procurement and shipping to site of the grain storage and handling equipment is performed – in a timely manner, so that the equipment arrives as soon as the civil works are completed – and installation and erection of the handling equipment can commence without delay.
After months of hard work and planning – the project is completed on time and in budget and the first of many grain trucks deposits its load into your silo complex. Now you can start reaping the benefits of your project – for many years to come.
Equipment forming part of a grain storage system
1. Intake pits
- In concrete below ground with or without auger or chain conveyor moving product to a collection point for lifting to silo intake level.
- In concrete with ramps and built-in weighbridge and steel grain collection bin and auger or chain conveyor collection to unload point, usually used in conjunction with a grain pump.
- Above ground reception bins:
- In triangular execution for smaller scale operations with gravity flow or auger to silo load auger or elevator.
- Rectangular bins able to accommodate side tippers from 6 meters to 12 meters and with auger or chain conveyor to move grain to a silo loading collection point.
- Weigh bridges and axle weighers in single axle pads, 6 meter, 12 meter, 22 and 24 meter options.
- Structures over intake systems to allow work during rainy periods and to keep pits from water intake and flooding, thereby damaged below ground equipment is important and has to be considered and -planned well to allow back tippers, side tippers and other transport options to function.
- Aspiration of dust and other dust control during off-loading is sometimes a requirement for instance where offices are adjacent.
- Sampling systems at grain intake points, more or less automated.
intake + weighbridge
2. Conveyance of grain
- Elevator(s) to silo intake point or overhead conveyors. Elevators may also be used to load cleaners and dryers prior to loading overhead conveyors. Bucket elevators with steel or polyethylene or nylon or polyurethane buckets.
- Grain pumps may be loaded direct from the intake pit or after cleaners or dryers are loaded. The grain pump is a chin conveyor housed in a tube forming a loop over and below silos for both the load and unload functions. A system overwhelmingly supported and recommended by ABC Hansen who has brought this system to South Africa from the USA in the late 1990’s and with many in operation throughout Africa.
- Where bucket elevators are used, overhead chain conveyors often distribute the grain between silos and again reclaim the grain below silos for unloading via the load bucket elevator to load trucks. Special arrangements can be made for loading and unloading at the same time, especially for commercial silo operations.
- Auger loading and unloading of smaller silos are the lowest cost way to execute this function. A mobile auger can load and unload more than one silo while fixed installations are common with roof augers, overhead distribution augers and reclaim and truck loading augers.
- Capacities for intake systems can vary between 20 tons and 500 tons per hour.
- Sweep augers are used inside flat bottomless silos to convey the last grain to the centre of the silo for cleaning and unloading the entire contents of the bin.
Double Run Grainpump
- Flat bottomless silos for the storage of grain from 100 tons up to 20,000 tons per silo. Complete silos are imported from only major manufacturers in Europe, the USA and Turkey all with more than 20 years’ experience in the business and with certified quality standards for design, manufacture, steel quality and tensile strength traceability, galvanised coating and consistency and reliability for extreme accuracy, allowing for no additional drilling on site.
- Flat bottomless silos are often installed over a concrete hopper either above or below ground level for ease of unloading an entire bin.
- Hopper bottom silos are sometimes required for specific products or where industrial applications require bins to be completely unloaded. These bins are above ground level and has a capacity limit. These are also relatively expensive bins vs a. and b. above.
- Silo options:
- Aeration systems for maintaining grain quality over the long term.
- Fumigation systems.
- Automated Temperature control systems.
- Level measurement to allow monitoring of the exact volume of grain in a silo at any time and high-level indicators to avoid overloading.
Flat Bottom Silos
4. Towers, ladders, stairs and walkways
These may be requirements of construction or may be installed optionally for easing access for maintenance and inspection. Engineering determines the specifications and requirements. Galvanised or painted finish can be selected while standard supply from ABC Hansen would be galvanised.
Tower with staircase
5. Civil works:
Every silo supplied has a standard for foundations determined by the soil conditions. Often very poor soil conditions have to be improved to allow construction thereon. This may entail excavations and backfilling with appropriate materials and its compacting to a degree where foundations are stable. Civil works also includes slabs for towers, intake pits of various designs, ramps, weighbridge supports, water flow management at the site, aprons around silos to avoid ingress of moisture, roads, turning points, foundations for structures over intake systems etc.
Cleaning of grain can be accomplished in several fashions which will depend on the extend of cleaning (removals of under and oversized trash or only undersized or only oversized, whether special dust removal through aspiration is required, capacity of cleaning as determined by the handling equipment) and other considerations and preferences. The ABC Hansen program allows for the following types of cleaners:
- Rotary drum cleaners.
- Gravity cleaners.
Drying of grain is becoming more desirable especially for larger producers and those with irrigation fields to allow for faster harvest, better cashflow, lower risk, faster turnaround for the next crop. The ABC Hansen program allows for the following types of grain dryers, all normally diesel fired.
- Flow-through stacked section dryers.
- Tower dryers.
- In-bin batch drying.