Belt scales: Interview with Ivo Mewes

What are the challenges of weighing bulk solids?

Weighing bulk material becomes a challenge when the quantity is so large that it can no longer be recorded on a conventional static scale. Of course, you could still divide the quantity into portions and weigh them on a truck scale, for example, and add them up. This is certainly not practically feasible or efficient. Where, for example, a ship has to be loaded with grain from a silo, this is not an option. Here, the bulk material must be weighed without delay on its way to the loading point.

The ability to integrate into higher-level production and logistics processes is also frequently required. Adverse environmental conditions are the rule - so the weighing electronics must be robust if the belt weigher is used in ports, in gravel pits, in open-cast mining or in truck, ship and railcar loading facilities.
But also in hygienically very demanding environments, such as in the food sector, bulk materials are occasionally weighed with belt weighers . The SysTec weighing terminals are also ideally suited here due to their IP69K protection class and highest processing quality.

What is the characteristic of a belt weigher?

Unlike a static scale, the weight of a belt scale is recorded dynamically, i.e. in motion. In addition to evaluating the load cell signal, the belt speed must also be measured. For this purpose, a rotary encoder is mounted on the deflection pulley or on a specially installed impeller, which precisely records the movement of the belt.

The load cell signal provides the so-called belt load in kilograms per meter related to the length of the weighing distance. The rotary encoder provides the belt speed in meters per second over time. After conversion of the units, the two together then result in the conveying capacity - e.g. in tons per hour - as well as the quantity recorded at any given time.

What must be observed during parameterization and calibration?

The parameterization is slightly different from that of a static scale. In addition to the load cell signal, the speed sensor must also be parameterized here and the inclination sensor calibrated if necessary. In addition, there is a wealth of belt scale-specific parameters to set, such as the weighing length and zeroing belt length.
We are aware that calibration with material places high demands on logistics at the point of use and is already a demanding process. Therefore, SysTec has placed great emphasis on simple and unambiguous operability in the calibration dialog. Calibration is usually performed at regular intervals - or when recalibration is due.

When must a belt scale be legal for trade and which weighing terminals are suitable?
Calibration is a prerequisite for trading goods. If trading is done on the basis of the quantity of bulk material, the quantity must be determined with the help of a calibrated scale. Our weighing terminals IT3 BELT, IT6000E BELT and IT8000E BELT are legal for trade and therefore perfectly suitable. Our approval allows different accuracy classes for custody transfer applications. Ultimately, however, the system accuracy of all components used determines the accuracy class of the belt scale. The weighing terminal should not be the "bottleneck". The approval allows a flexible design of the belt scale and leaves a lot of freedom in the choice of load cells, force application and speed transducers.

Why does flexibility in weighing electronics play a major role for partners and customers? And what do SysTec weighing terminals offer?
Our partners, the scale manufacturers and the plant engineers, design the beltweighers and appreciate it when the weighing terminals offer them as much flexibility as possible so that they, in turn, can adapt the scale precisely to the wishes of the end customer. As a manufacturer of weighing terminals , the only option for us was therefore to connect analog load cells across manufacturers in order to offer our users maximum flexibility. The free programmability with RTC WIN also offers flexibility to our users.
Furthermore, SysTec weighing terminals allow easy integration into modern control systems via the fieldbus interfaces PROFINET, PROFIBUS DP, Ethernet/IP or Modbus TCP. Of course, the analog signal and pulse output is just as possible.
Many SysTec partners are located abroad or deliver abroad. Multilingual user guidance was therefore the focus of development from the very beginning.
Last but not least, SysTec relies on know-how transfer with partners. We train the special belt scale knowledge regarding the weighing electronics in a seminar and offer telephone support during commissioning.