CELMI srl (Italy) - When we talk about static weighing systems we can mean different types of weighing, such as a simple weighing system, a dosing system, an object weigher or a truck weighing platform. For each of these specific areas, Celmi Srl offers a product suitable for guaranteeing maximum and extreme weighing precision.
In this article we see together and in detail two particular types of static weighing: simple weighing and dosage.
By simple weighing we mean all those systems whose primary and fundamental function is to indicate the weight value and / or alarm signals.
This macro-category includes, for example, the level meter of the silos, complete with high and low level signaling and equipped with any “attach / detach” control of the feeding machine. Furthermore, the weighing platforms for internal use can also be defined as a simple weighing system, as well as the control instrument for the anti-overload of the lifting means, or the measuring system of the breaking load with peak signaling (of response speed of the instrument is often important).
Modern systems always encounter new and different needs, so modern weighing instruments must be able to perform a very wide range of functions to be effectively functional. Even if it is not a strictly necessary factor, the trend is to design and create more and more simple weighing systems that can make all the functions required by the systems coexist; moving in this direction it will be easier to proceed with the standardization of production volumes.
An example of simple weighing, also proposed by Celmi S.rl., Is the T-DASC. This digital weight transmitter with analogue output is a repeater of the weight value deriving from one or more load cells. A peculiarity of the T-DASC devices is the fact that they can be connected in pairs, so as to be able to view the total of the weighs; it is also possible to connect a single device to an external panel, which will continuously receive the detected weight value.
This tool is usually applied for weighing systems in general, to indicate the level of hoppers or silos, to control the overload of lifting machines or to signal any process variation via an mV signal.
An automatic dosing system has the function of producing a batch of one or more ingredients or materials, which are called “ components ” in jargon, with a predetermined weight (also called set-point) and in a given time. During this time, which must not exceed a specific error or "tolerance" for each component, a series of mixtures of specific products, also called "recipes", which are part of the production process, must be memorized.
With respect to the operating principles, it is possible to establish the existence of two basic types of dosage: the dosage in charge and the dosage in discharge. In charge dosage is the most common type and consists in feeding a hopper, or any other weighing container, with individual materials in an established sequence. This feeding will be stopped when the weight of the material being loaded reaches the value set in the recipe; in this way, the mixture obtained is discharged in one or more solutions. Dosing in discharge, on the other hand, consists in the extraction of a defined quantity of material from a weighed storage silo. When this silo reaches a specific and determined minimum weight, then it is reloaded to the maximum of its own containment capacity.
Generally, these two types of dosage correspond to separate applications. In fact, the batching in charge prepares the mixtures necessary for the production, while the batching in discharge is normally used for loading the trucks. In the case of particularly complex systems, dosing cycles may be required including in the same recipe both batching in charge and dosage in discharge.
In any case, in addition to the two types of dosage described above, there are other types of dosage, certainly of rarer use but which are part of the most modern programs. Some examples are timed dosing and pulse dosing , which come from a volumetric meter and whose material does not enter the weighing hopper, but is part of the same recipe as the weighed materials. In general, and in conclusion, each dosing program performs different and varied functions thanks to the tabular setting of the information, which each operator must fill in in advance.