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 Classified , it becomes particularly interesting with regards 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 is composed of the Latin ?gravitas? for ?gravity? and the Greek ??? ??????? for ?measure?. In gravimetric measurement, therefore, the heaviness of the mass is combined with weight force to create 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 specially suitable when uneven distribution may appear within the vessels.
Gravimetric level measurement: Advantages
This kind of weighing has several advantages. Possibly the greatest advantage is that the force transducers used for gravimetric level measurement are located beyond your vessel. Thus, they don’t touch the product. Neither is it necessary to open or modify the vessels. Contamination can thus be eliminated. Cleaning can be much easier. Furthermore, very precise measurement is possible ? 0.02 % of the rated load isn’t uncommon with regard to relative linearity error. This makes dosing possible when, for instance, food is filled into bags ? not to mention the packaging must support the amount specified.
Another advantage is that the merchandise does not influence the measurement. The level could be determined gravimetrically for all contents ? solids, liquids, viscous substances, foaming substances ? even toxic or aggressive contents can be viewed as. Furthermore, the measurement isn’t falsified even if voids or uneven contents distribution occur inside the silo or tank, because the entire contents are weighed.
Suitable mounting modules not only ensure that the weight force is properly led in to the force transducers, they also make installation super easy. The module and force transducer have a low height and a small installation volume. However, it is usually problematic if the vessels are already permanently installed and may only be positioned on modules with significant amounts of effort. Then it is probably advisable to bolt strain transducers to the supports. Any risk of strain transducers determine the compression of the supports caused by the weight of the contents. They thus make it possible to weigh immovable vessels gravimetrically.
Gravimetric level measurement: Disadvantages
The disadvantages of gravimetric level measurement vary in significance depending on the application. Results 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 instance, struts are essential. Then it depends on what great their supporting effect is. Similar problems 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 could be affected by natural factors. For example, if wind pushes or snow results in a significant increase in weight.
Typical force transducers for the weighing of vessels
Single point load cells are classically useful for scales. These not only have a low price and high accuracy, however the weight is also determined reliably, no matter where it is placed on the platform. For optimal force introduction, bending or shear beams with the corresponding weighing modules are usually installed under tanks, silos or vessels that stand on supports. To look for 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 utmost capacity of which reaches around 300 t. With Interesting , vessels as high as 1,200 t can be weighed with the best accuracy. Alternatively, vessels could be suspended from S-type force transducers or fitted with strain transducers.
Note
Level can be measured in many different ways. Whether gravimetric as described, or with a submersible pressure sensor, float switch or pressure sensor ? WIKA has the right sensor for every application. Would you like to buy the products? In our WIKA online-shop you will find a few of our standard designs. If you have any questions, your contact will gladly help you.
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Bending beam and shear beam in weighing technology
Request of strain transducers

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