A. DIFFERENCES AND BENEFITS OF A GALVANIZED STEEL SILO AND A CARBON STEEL SILO WITH FOOD PAINT ?
For those trying to choose an appropriate silo, it may be useful to understand the differences between a galvanized steel silo and a carbon steel silo with food paint.
Galvanization is the process of applying a protective zinc coating to steel in order to prevent rusting. That means that a thicker coating gives the steel a longer useful life.
In the market, you will find silo manufacturers using different Zinc coatings: Z-275, Z-375, Z-450, Z-600. The number represents the grams of zinc per square meter that steel has on both sides (inner and outer faces).
Silo Masters supplies high resistance galvanized steel S450GD (according to EN 10346), with a high elastic limit and a minimum Z-600 coating in all its silos. This coating contains 600 gr/m2 of Zinc and is equivalent to a thickness of 42 microns per side which makes it longer-lasting even in the most aggressive of atmospheres (as established in Standard ISO 9223).
The high resistance steel S450GD and the Z600 coating reduce the weight of the silos, providing advantages in logistics, handling of the components during assembly, as well as extending their useful life. High elastic limit steels have the same performance as conventional steels but with less thickness and therefore less weight. They are ideal for the manufacturing of structural elements and parts subjected to high dynamic and static stresses.
Painted carbon Steel silo
There are several solutions in the market, but basically we can see:
- Plastic paint.
- Epoxy paint.
Although the second one has a high zinc content, both solutions are not as strong as galvanized steel.
Due to the high investment involved in a storage silo project, the high cost of painting the entire surface (labor, raw materials, longer installation time), the difficulty of applying a multilayer paint, lower final quality and lower service life of painted steel, we do not recommend this solution.
Painting should only be used as a maintenance system in case any rust appear.
B. WHY USE METAL SILOS INSTEAD OF WAREHOUSE STORAGE ?
Grain storage in silos is vertical, while the storage of grain in warehouses is horizontal.
Using steel silos to store the grain instead of using warehouses provides many advantages:
- The first advantage lies in the occupied ground surface. This method requires less ground space, which is important if space is not available or if its cost is high like at ports.
- Another advantage lies in how easy it is to keep the optimum storage conditions for the grain, by controlling the temperature, insects, mould, birds, which in long term storage facilities could result in an important economic loss.
- The third advantage consists of lower costs than that incurred from using warehouses, which entails the automation of the grain transport equipment. The loading as well as the unloading can be completely automated using a SCADA system and at a lower cost.
- Handling the product stored in silos is simple, quick, less damaging to the grain and does not require investment in additional machinery for handling.
- Another advantage is lower assembling costs since this element is designed specifically for this purpose and weighs less than a storage facility.
- Finally, we have the fact that it is less expensive overall, and this is probably the main advantage in comparison to grain warehouses.
C. WHY USE METAL SILOS INSTEAD OF CONCRETE SILOS?
Whilst the choice of grain storage methods is wide, the most popular ones are steel silos, concrete silos, storage warehouses and bag silos among others. Through this article we’ll analyze the difference between steel silos and concrete silos.
A common question that almost all the companies ask themselves before planning a new storage project is: What kind of storage system should I choose? Warehouse, concrete silos, steel silos…? As an answer to these questions here we point out the key differences between Steel Silos and Concrete Silos.
All steel silo parts are manufactured in a factory, so the quality can be totally controlled, whereas cast in place concrete silos involve more variables such as concrete delivery and weather. The customer must bear in mind that useful life of concrete before use is less than 2-3 hours. After this period, concrete start losing its optimal characteristics
- The slip frame concrete process is further complicated by the fact it is a dynamic or continuous process. Rebar placement, concrete quality, etc., all affect the final product. Also, field supervision plays a really serious role in concrete silos: more people working on site, longer period of commissioning (due to weather conditions) and, ultimately, higher costs.
- Concrete silos can be taller than steel silos but these ones have bigger diameters, so the total capacity is highest. For this reason, concrete silos are only more suitable when the space is really limited.
- It is easier to erect steel silos and to install accessories like doors, ladders, samplers, etc.
- Steel structure is more flexible, so steel silos have better behavior in case of earthquake.
- Regarding airtight, both structures are normally airtight if the openings are properly sealed.
- Steel silos generally give you greater storage capacity per dollar. They tend to be more cost-effective because of the higher storage capacity.
- It is easier and more effective to do aeration in steel silos. Aeration horsepower is a non-linear function of grain depth. It is often impossible or impractical to provide the same airflow in tall concrete silos that could be obtained in shorter and wider silos (the case of steel silos). A higher grain depth also leads to a higher heat of compression in the aeration system. This means it takes a lower outside temperature to achieve the same grain temperature, making early aeration more difficult.
- Steel silos do not require the soil to be as firm to support the weight of the structure. Sometimes steel silos can be built on land that doesn’t have the higher load-bearing capacity needed for concrete.
There are many details and variables in silo projects and every type of grain storage has pros and cons. The right choice is the one that fits in your infrastructure strategy.