When it’s too little for the belt scale
MTS developed the CDW, the conveyor discharge weigher, for low and medium flow rates from 200 to 5,000 kg/h. Weighing is very accurate because it is static.
The recovery and recycling of valuable materials into raw materials is becoming increasingly important in order to conserve resources and reduce the final disposal of waste. Special weighing solutions are required in such applications in order to precisely record the individual recyclable materials with low flow rates.
Recyclable materials from waste should not only be separated by type, but also precisely recorded in terms of quantity. Belt conveyors are usually used to transport the waste. The use of a built-in belt scale for weighing the recovered recyclable materials during transport on the belts is an obvious solution - but often fails as a solution, especially in the area of slag processing and separation, due to the low flow rates.
The MAV Group operates plants at several locations in Germany for the processing of waste incineration grate ashes, which also contain valuable metals. These valuable materials are separated in several process stages and returned to the metal processing industry as recycled metal.
For precise balancing, the plant in Krefeld should now also record the quantities of the individual types of recyclable materials or metals. With this task, the company turned to MTS MessTechnik Sauerland GmbH.
During the inspection of the plant, it quickly became clear that, due to the low conveying quantities and the plant situation, no classic built-in belt scale could be used for this planned application. Nevertheless, the quantity of the recyclable materials was to be recorded exactly during the running production process. For this purpose, MTS developed a conveyor discharge weigher for installation directly at the discharge point of the selected belt conveyor.
The CDW conveyor discharge weigher consists of a weighing hopper with a pneumatically downward opening discharge flap and a robust subframe. The subframe is permanently installed at the discharge on the conveyor structure, while the actual weighing hopper is integrated into the frame by means of precise load cells.
The sorted recyclables are then transported away via the belt conveyor and fall into the closed weighing hopper at the discharge point - until a defined fill level or weight value is reached. The belt is then stopped briefly and the weighing hopper is weighed statically at the same time. Then the discharge flap opens and the hopper is emptied. The flap closes again, the hopper is tared and the infeed starts again for the next weighing cycle. Up to 50 weighing cycles can be carried out per hour.
Filling and emptying process as well as the load cell signals is controlled and evaluated by the powerful control unit ModWeigh Batch. On the one hand, the control unit records the weight value of the weighing hopper and accumulates the individual batch values in the totalizer. At the same time, the electronic also generates the flow rates in kg/h or t/h from the weight values of the individual batches and the time unit determined for a weighing. The flap is controlled self-sufficient via the ModWeigh. The measurement data can also be transmitted to the customer’s process control system via Profibus DP or Profinet.
The new scale was installed and commissioned by MTS at MAV in Krefeld in July 2020. Since then, the scale has been working reliably and safely, providing very accurate quantities of the secondary metal directly after the sorting process. As standard, the CDW conveyor discharge weigher is made of painted steel, optionally also in stainless steel. On the MAV, all heavily stressed components are made of Hardox. The flap is pneumatically controlled via powerful cylinders with additional electronic position monitoring.
Conclusion: The CDW conveyor discharge weigher is particularly suitable for recording low and medium flow rates from 200 to 5,000 kg/h. The CDW conveyor discharge weigher achieves very accurate measurement results because the weighing is static. The scale can be retrofitted into the customer’s existing system with little effort. Further conveyor discharge weighers have already been ordered by the MAV Group due to their good function and measuring accuracy.
