TWINKAM

The  TWINKAM system for measuring the potassium concentration with two detectors is used for the current measurement of the surface mass of the material transported by the conveyor belt and for determining the mass fraction of potassium (KCl or K2O) in the transported material.

The  determination of the mass fraction of potassium uses the detection of the natural isotope K-40, which is part of the transported material.

Since  the radiation intensity depends on the absolute amount of the K-40 isotope, to determine the mass fraction (in percent) it is necessary to either provide a constant "amount" of the material or to compensate / correct changes in the amount of material.

The  potash content measurement system TWINKAM offers this correction by using two PD125 detectors. The measured values ​​are determined on the basis of the differentiation of the measured values ​​of the detectors, which measure the same “material sample” under different external conditions: Between one of the detectors and the material to be transported (e.g. a box with NaCl), a radiation source is created between the other Detector and the material to be transported installed (e.g. box with high KCl content).

The  measurement of the potassium salt content is the measurement of the radioactive decay per unit of time. The accuracy achieved is subject to the statistical laws of the so-called chaotic process.

The  parameters used in the calculation formulas vary depending on:
● the specific conditions and location of the measurements,
● the sensitivity of the sensor,
● the average intensity of the background radiation,
● the distance of the sensor from the measured substance,
● the shape and properties of the container
etc.

The  transport speed is the necessary parameter for determining the mass. The speed determination in the TWINKAM measuring system can be carried out by a rev counter, which is transmitted from the "upper" level of the ACS (Profibus) to the measuring system and is controlled by a digital signal.

The  K-40 content is measured by measuring the radiation intensity of natural radioactivity, usually γ-radiation with an energy of 1.47 MeV.

The  detector can determine the intensity, but cannot distinguish on which side the radiation source is located. The detector thus determines the total intensity without distinguishing between reflected radiation, radiation from a distributed source and radiation from a point source.

Different  intensities are determined for different amounts of material (different loads). Different loads are measured during calibration and are reflected in the calibration curves depending on the amount of material and intensity.

It  is important that the radiation intensity is the same for the same load and the same potassium content. To illustrate this, we will replace the distributed source with a point source that is in the center of gravity of the load profile.

Determining  the load profile does not solve the problem, since the dependence of the intensity profile can still be determined and this is only possible with considerable effort. In addition, this dependency will vary from sponsor to sponsor.

It  is therefore important that the load profile does not change when measuring on a tape for the same load, since it is possible that the profile is shifted to the left, for example, for light loads and to the right for high loads. It is then important that the profile is always shifted to the left for small loads and to the right for large loads - the profile should remain unchanged with the same load.

This  is particularly important when calibrating. With static calibration, the conveyor is filled manually and it is not easy to form a profile that is identical to the working profile. When calibrating, it is important to form a profile that reproduces the profile as accurately as possible during normal operation on the conveyor.

Inaccuracies  in the calibration ultimately result in measurement inaccuracies.