DOSING AND WEIGHING FACILITIES

In many productive processes, based on solid bulks, it is necessary to develop formulations, which require dosing of the different components involved.

According to the industrial process, the raw material used, the resulting final product and the quantities to be dosed, there are several techniques to perform the dosed weighing of the ingredients. These dosing processes can be carried out continuously or discretely (in batches), this will depend on how the process is designed.

Although in general the dosage is gravimetric, sometimes if the products are of very low density or precision in the dosage is not required, you can also perform the dosage in a volumetric way, but this one is unusual in solids dosage processes.

SOTECMA is specialist in bulk solids and dosing weighting systems.

At SOTECMA, we have extensive experience in both gravimetric and volumetric dosing processes regardless of whether the process is continuous or discrete.

Elements of a Concrete Dosing Plant and other dosing systems

In any dosing process, as well as in the manufacture of concrete and other construction materials, it is necessary to have at least three basic equipment:

1. The silo or warehouse where the material to be dosed is stored
2. The equipment that extracts the material
3. Continuous weighing scale

There is a fourth element that is practically essential, which is the automation system, this is what guarantees us that the adjustments will be precise, and that the product obtained will have constant characteristics in all manufacturing batches. In the continuous and gravimetric dosing processes, a system that is not controlled automatically is not conceived.

Types of solid and liquid dosing systems

They can be classified in two ways, depending on the way in which the measurement is carried out, they can be by weight (gravimetric) or volumetric, if we look at the type of process, they can be continuous or discontinuous (discrete).

Continuous gravimetric dosing

It is the most complex dosing process, it is generally only used for solids, for its execution it is required that the weighing equipment be dynamic, that is, the component is weighed as it is fed to the next process, which is usually mixing. Therefore the difficulty arises when designing this weighing element.

At SOTECMA, we have been developing continuous gravimetric dosing systems for more than 30 years, relying on dynamic weighing on a conveyor belt and the weighing dosing system with hopper. A utility model patented by SOTECMA more than 20 years ago and thanks to it is achieved greater precision. Due to its complexity, this type of dosage must always be carried out with an automatic control system.

We apply this type of dosage in our gravel-cement or cement soil plants, for the dosage of cement on the aggregate.

Discontinuous gravimetric dosing

It is the most used and precise dosing process since it allows us to weigh statically, thus allowing a good vein adjustment. It is easier to implement than the discontinuous one.

For any weighing system, the absence of vibrations and external actions that may interfere on the scale is essential, and more when it comes to dosing small quantities (below 10 kg), that’s why SOTECMA has developed and patented a high precision scale with a turning system for emptying and which is encapsulated to avoid the action of external agents.

In this case, the process can be carried out manually, starting and stopping the dosing equipment manually, but it is totally discouraged due to the risk of depending on the action of an operator who may forget to add a component, or repeating one or simply not stopping the dosing equipment in time by providing more of the component than required.

We apply this type of dosage in our dry mortar plants and concrete manufacturing plants, for the dosage of all the components that the mixture of this product requires.

Continuous volumetric dosing

It is used in both liquids and solids, for liquids the measurement can be quite precise in that the density is practically constant.

In the case of solids, the apparent density varies greatly depending on the granulometry and the degree of aeration of the product, and it is for this reason that this system is used only for processes where the proportion in weight of the various dosed components is not very precise.

We carry out this dosing system in our gravel-cement or soil-cement plants for dosing the water.

Discontinuous volumetric dosing

The only difference with the previous one is that the process is done in batches, but this does not mean more precision is achieved, the equipment used to measure is usually the same for both processes.

Dosing and weighing equipment

Within our range of equipment and the experience demonstrated in many years we highlight:

• Micro-dosage of additives by volume and by weight.
• Continuous cement and water dispenser for gravel-cement plant.
• Dynamic weighing on conveyor belt.
• Tipping precision scale weighing system. (Patented)
• Portable solid additive dispenser for asphalt plants. (Patented)
• Lime dosing silo for water treatment.
• Complete chemical additive dosing systems for dry mortar and glue cement manufacturing plants.