Gravimetric level measurement in vessels

In the pharmaceutical, building materials and food industries, on vessels and silos, on platforms and dosing systems, right up to kitchen and bathroom scales ? weight is measured everywhere. In industry, it becomes particularly interesting when it comes to the level in vessels. There are Jumpstart for weight measurement or weighing. The filling level can 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 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 specially suitable when uneven distribution may appear within the vessels.
Gravimetric level measurement: Advantages
This type of weighing has several advantages. Perhaps 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 essential to open or modify the vessels. Contamination can thus be eliminated. Cleaning is also easier. Furthermore, very precise measurement can be done ? 0.02 % of the rated load is not 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 does not influence the measurement. The particular level can be determined gravimetrically for several contents ? solids, liquids, viscous substances, foaming substances ? even toxic or aggressive contents can be viewed as. Furthermore, the measurement is not 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 into the force transducers, they also make installation very easy. The module and force transducer have a low height and a little installation volume. However, it can be problematic if the vessels already are permanently installed and may only be positioned on modules with a great deal 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 application. Email address details are mainly distorted when force shunts cannot be prevented. Ideally, the vessel should be mechanically decoupled. Used, however, it can always happen that, for instance, struts are absolutely necessary. Then it depends on how great their supporting effect is. Similar problems can occur if the measurement is influenced by way of 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 suffering from natural factors. For example, if wind pushes or snow results in a significant upsurge in weight.
Typical force transducers for the weighing of vessels
Single point load cells are classically useful for scales. Depraved have a low price and high accuracy, however 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 the force transducers, divide the total weight of the vessel by the amount of supports. If the rated load exceeds 10 t, it is possible to switch to compression force transducers, the utmost capacity of which reaches around 300 t. With four supports, vessels of up to 1,200 t could be weighed with the highest accuracy. Alternatively, vessels can be suspended from S-type force transducers or fitted with strain transducers.
Note
Level could 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 each and every application. Do you want to buy the products? Inside our WIKA online-shop you will discover a few of our standard designs. In case you have any questions, your contact will gladly assist you to.
Also read our posts
Bending beam and shear beam in weighing technology
Practical application of strain transducers

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