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Technique of weighing silos, reversers and hoppers

Sep 17, 2020 | News

The level measurement of a container whether liquid, solid or powder in a tank, silo, hopper is achieved by the addition of weighing sensor (weighs).


This technique makes it possible to obtain a high accuracy reliably provided you follow any rules you find in this article.

Choosing weighing sensors

Different sensor technologies exist depending on the constraints of use: bending sensor, single or double shear, compression, traction.

Determining weighing sensors
  • Compression, traction, shearing.
    Number of sensors and support points.
    Weighing range and sensor capacity.
    Precision.
  • Operating and functional mode:
    Easy assembly and maintenance.
    Transmission of the signal.
    Calibration
  • Environmental conditions:
    Climate, Wind.
    Temperature.
    Influence of rigid bonds
    Vibration
  • Risk control:
    Seismic risk.
    ATEX explosion risk.
Number of sensors and support points
It is important to ensure that the silo/hopper is based solely on stable, horizontal support points. For the support of a metal frame, this means having a maximum bending of 2/1000. Ducts, sheaths and all intermediate organs must be equipped with elastic bellows. Nevertheless, one can agree to leave fixed parts depending on the level of accuracy sought. Be careful, position the bellows so that there are no products in charge. The best accuracy (up; 0.5%) is obtained when the number of sensors is equal to the number of support points. In the case of a symmetrical tank containing liquid or very fluid product, it is only possible to partially equip the support points with sensors. For example: 4 feet 2 sensors, the accuracy then could not be better than 2% depending on the case.
Mechanical environment and assembly kit

Each sensor is equipped with a mechanical environment that facilitates assembly and ensures the mechanical safety of the silo and sensor. The 300 and 400 series has jack screws for the safety of the set during assembly or maintenance operations. Our mechanical environments are calculated and tested to resist parasitic forces in the 3 planes (refer to the technical sheet of each environment).

Precision

Weighing accuracy is the measurement error for a load, not to be confused with the display rung (multiple of 1, 2, 5). Accuracy depends on several factors:

  • Sensor errors < (0.01%).
  • Calibration error (automatic calibration of the indicator 0.1% or with standard masses < 0.01% ).
  • Mechanical error (mechanical stress of the ducts, bridge, cone supports …) of up to 1 t in practice.
  • Combined Sensor Error: E-N x Sensor.
Display and signal transmission

The LOCAL display allows signal processing and conditioning as close as possible to the source. In addition, the display is very practical for maintenance and diagnosis.
– Generally it is equipped with an analog output (4-20mA) or digital (ETHERNET, PROFINET, PROFIBUS, MODBUS…).

Weighing Indicator TMX100

Bending sensor


Flexion or simple shearing
Weighing range 10 to 5,000 kg
Series 300
Easy implementation
Integrated security
Accuracy < (0.05%)
– Limited in maximum capacity

Double shear sensor

Weighing range 5 to 100 t
Series 400
Easy implementation: effort is distributed and centered
Integrated security
Mechanical reliability (double supports)
– Accuracy ( < 0.1% )

Compression sensor

Weighing range 15 to 500 t
Series 700
Used for heavy loads > (100 t)
Load descents centered on a single axis, simplifying the design of the supports
– Very sensitive to misalignment of support
– No built-in sensor security.

Traction sensor
Weighing range 0.1 to 5 t Series 600 Self-centering forces Good accuracy (0.1%) – Complicated implementation – No built-in sensor security, provide security in case of a rupture  
Documentation: PDF weighing sensor mounting guide

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