Table of Contents

Introduction

Why Silos are Important

Advantages of using Steel Silos for Grain Storage instead of Storing the Grain in Warehouses

Requirements to Store Grains Safely

How to Store Grain and Protect its Quality 

Introduction

Silo (from the Greek σιρός – Siros, "pit for holding grain") is a structure for storing bulk materials. They are essential in food processing and used in agriculture to store grain or fermented feed known as silage. Silos are important as they are commonly used for bulk storage of grain, coal, cement, carbon black, woodchips, food products, and sawdust. Three types of silos are in widespread use today: tower silos, bunker silos, and bag silos. a risk analysis must be done to define the requirements for the design and material of the silo. For free flow of the product along the silo wall and cleanability, it is advantageous to install only those fittings that are necessary inside a silo. The welding seams on the silo body should be smooth and easy to clean. This, of course, is a well-known requirement for hygienically designed containers.

Why Silos are Important

Silos are made of sheet metal, with a galvanized coating. And although it may seem otherwise, the increase in temperature of the sheet due to the heat of the sun is very superficial and does not affect the grain mass. The temperature variation that affects the grain mass is caused by the fermentation processes, that is when there is a moisture focus that begins to deteriorate the grain, and one of the consequences is the temperature increase.

Hence the importance of detecting moisture sources using tools allows one to measure the temperature inside the silos and set an alarm when there is an increase in temperature in any of the points, indicating that something serious is happening inside. Once the moisture has been detected, it is necessary to act, either by ventilating, that is to say, putting air at medium pressure inside the silo; or by recirculating and transferring the grain to another place, which is much safer.

The temperature control is only one of the processes of great importance for the future conservation of the grain, which normally has a much higher value than the silo where it is stored.

Advantages of using Steel Silos for Grain Storage instead of Storing the Grain in Warehouses

1. One advantage is lower assembling costs since this element is designed specifically for this purpose and weighs less than a storage facility.
2. Another advantage lies in how easy it is to keep the optimum storage conditions for the grain, by controlling the temperature, insects, mold, birds, which in long term storage facilities could result in an important economic loss.
3. 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.

Requirements to Store Grains Safely:

Compared to most other foodstuffs such as meats and vegetables, grains are relatively easy to store. If the grain is kept insect-free and below its safe moisture content, it will be safe for many years with minimal loss of quality or nutritional value.

Low temperature is an important factor in minimizing insect activity and in the maintenance of nutritional quality in general. Storage at or below the safe moisture content is essential for the prevention of deterioration caused by microorganisms and insects.

Where insects are present, temperatures are high, and most especially where moisture content is above safe levels, then storage of grain becomes both risky and difficult, and losses will be difficult to avoid. It is in these circumstances that the type of storage facility and its design become critical to the safety of the stored grain.

Whilst the choice of storage design is wide, the essential requirements needed to store grain safely remain the same.

They include:

• Sealing. The storage structure must keep the grain free from water ingress, insects, rodents, and birds.
• Cooling. If the grain is to be stored at a moisture content above ‘safe’ levels, provision should be made for cooling the grain.
• Easy disinfestation. The storage facility should also permit easy and economical disinfestation of grain in the event of insect infestation.

How to Store Grain and Protect its Quality

As a part of any grain quality maintenance program (usually customized by company or product), there is a good number of recommendations that go throughout the different phases of the grain storage process:

CLEANING: It is advisable to clean the grain before storing it. Farmers have the experience and they know what kind of impurities come with the grain. During the grain flow along with the cleaning phase, an aspiration system should be installed as well as the proper devices for disposal (impurities may have a value too).

DRYING: This comes after cleaning to reduce the moisture content to a level where grain is safe to be stored (a just harvested grain usually contains high moisture content). Without appropriate control of the natural respiration of the grain and the temperature. Leaving the harvested grain in the field to dry up should be avoided as well as using a sun drying system (lack of control over the drying process is the main limitation for these two ways). For heating air drying systems (either re-circulating batches or continuous flow dryers), we can find more advantages than disadvantages. Buffer Silos can be used when drying capacity is lower than cleaning capacity (a very common scenario): grain will be stored in Buffer Silos waiting to be dried. At this point in the process, the product is clean but still wet, that is the reason why we need to work on an appropriate ventilation system, exhaust fans, and over-head cones design for these silos. Same considerations for Tempering silos where, right after drying, the grain can cool down and get uniformity in terms of moisture content and temperature.

A customized VENTILATION system is a must: ventilation channels and grills, roof vents, exhaust, and centrifugal fans, and even cooling systems for tropical climates. A Temperature Monitoring System and some indicators such as the EMC (Equilibrium Moisture Content) will help to control both temperature and Moisture Content and, therefore, mold and insect development. This control is only possible when storing in silos.

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