Gravimetric level measurement in vessels

In the pharmaceutical, building materials and food industries, on vessels and silos, on platforms and dosing systems, right around kitchen and bathroom scales ? weight is measured everywhere. In industry, it becomes particularly interesting when it comes to the level in vessels. There are several possibilities for weight measurement or weighing. The filling level could be determined optically, hydrostatically, by ultrasound, microwaves and radar, mechanically, capacitively, by heat dissipation, by displacement and resistance or, what this short article is about, gravimetrically.
The term gravimetric comprises the Latin ?gravitas? for ?gravity? and the Greek ??? ??????? for ?measure?. In gravimetric measurement, therefore, the heaviness of the mass is combined with the weight force to form a meaningful value and thus the level is determined by weighing vessels (the filling level results from the density of the medium and the geometry of the vessel). This makes gravimetric level measurement a part of weighing technology.
Gravimetric level measurement is particularly suitable when uneven distribution can occur within the vessels.
Gravimetric level measurement: Advantages
This type of weighing has several advantages. Possibly the greatest advantage is that the force transducers useful for gravimetric level measurement can be found beyond your vessel. Thus, they do not touch the product. Neither is it necessary to open or modify the vessels. Contamination can thus be eliminated. Cleaning is also much easier. Furthermore, very precise measurement can be done ? 0.02 % of the rated load isn’t uncommon with regard to relative linearity error. This makes dosing possible when, for example, food is filled into bags ? not to mention the packaging must support the amount specified.
Another advantage is that the product will not influence the measurement. The particular level could be determined gravimetrically for all contents ? solids, liquids, viscous substances, foaming substances ? even toxic or aggressive contents can be considered. Furthermore, the measurement isn’t falsified even though voids or uneven contents distribution occur inside the silo or tank, because the entire contents are weighed.
Suitable mounting modules not merely make sure that the weight force is properly led in to the force transducers, they also make installation very easy. The module and force transducer have a minimal height and a little installation volume. However, it usually is problematic if the vessels already are permanently installed and can only be placed on modules with a great deal of effort. Then it really is probably advisable to bolt strain transducers to the supports. The strain transducers determine the compression of the supports caused by the weight of the contents. They thus be able to weigh immovable vessels gravimetrically.
Gravimetric level measurement: Disadvantages
The disadvantages of gravimetric level measurement vary in significance according to the application. Email address details are mainly distorted when force shunts cannot be prevented. Ideally, the vessel ought to be mechanically decoupled. Used, however, it could always happen that, for example, struts are essential. Then it depends on how great their supporting effect is. Unjustified may appear if the measurement is influenced by a high bearing weight. The lower the weight of the vessel compared to the product, the more accurate the gravimetric measurement. Finally, free-standing outdoor vessels can be suffering from natural factors. For example, if wind pushes or snow leads to a significant increase in weight.
Typical force transducers for the weighing of vessels
Single point load cells are classically useful for scales. These not merely have a low price and high accuracy, but the weight can be determined reliably, regardless of where it is positioned on the platform. For optimal force introduction, bending or shear beams with the corresponding weighing modules are often installed under tanks, silos or vessels that stand on supports. To determine the rated load of these force transducers, divide the total weight of the vessel by the number of supports. If the rated load exceeds 10 t, you’ll be able to switch to compression force transducers, the maximum capacity of which reaches up to 300 t. With four supports, vessels as high as 1,200 t can be weighed with the highest accuracy. Alternatively, Report could be suspended from S-type force transducers or fitted with strain transducers.
Note
Level can be measured in many various ways. Whether gravimetric as described, or with a submersible pressure sensor, float switch or pressure sensor ? WIKA gets the right sensor for every application. Do you want to buy the products? Inside our WIKA online-shop you will find some of our standard designs. Assuming you have any questions, your contact will gladly help you.
Also read our posts
Bending beam and shear beam in weighing technology
Request of strain transducers

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