Just don’t spill anything

Article of 25 October 2019 

Schuettgut

Bulk materials such as sugar, sand or carbon are often poured into different containers during processing. At first glance, this is a simple process, but it also involves risks. Accidentally released dust can jeopardise the health of employees or contaminate products. Dust-tight docking and undocking systems ensure that the bulk material stays where it belongs.

In the pharmaceutical industry as well as in the food and chemical industries, the handling of bulk material is the order of the day. For further processing and conveying, it is often filled into mobile vessels such as containers or barrels. It sounds easy – but it’s not.

For the filling process, the containers, also known as target containers, dock to a fixed dosing point. Then the dosing device – a kind of funnel – opens and the target container is filled. The challenge is that, before docking on and after undocking, no residues that are in the lead pipe of the funnel can be allowed to escape. In addition, no dust should be released into the ambient atmosphere.

Tightly sealed

The solution is CleanDock, a docking system with integrated, decentralised control from Festo. The system ensures that the bulk material does not escape into the atmosphere – both the dosing device and the target container are tightly sealed before and after filling. CleanDock was developed by AZO in cooperation with Festo as a specialist for automation technology.

Festo linear drives pull the flexible plastic tubing of the target container through which the bulk material flows close to the CleanDock. Only when there is no more gap do the plug closures of the container and dosing point open.
Festo linear drives pull the flexible plastic tubing of the target container through which the bulk material flows close to the CleanDock. Only when there is no more gap do the plug closures of the container and dosing point open.

At the beginning of the filling process, the mobile container moves under the funnel. The Festo linear drives then pull the container cover upwards by retracting. As soon as the container cover is in contact with the CleanDock, a latching mechanism is activated by pressure, whereby the container lid and station are firmly connected to each other. A further linear drive now opens the plug valves of the cover and dosing unit simultaneously. As soon as the correct amount of bulk material has been dosed, it closes the valves again. Finally, the locking mechanism is depressurised again and released, the drives remove the cover and the target container moves on.

Fast commissioning thanks to decentralised control

Many different raw materials are often stored in bulk-material depots. The demand for docking systems can be correspondingly high. AZO has already built plants with up to 60 CleanDocks.

The CPX/MPA with integrated CEC control system controls the linear drives, a pneumatic knocker to loosen possible residual bulk material in the CleanDock and the pneumatic locking of the dosing point and target container.
The CPX/MPA with integrated CEC control system controls the linear drives, a pneumatic knocker to loosen possible residual bulk material in the CleanDock and the pneumatic locking of the dosing point and target container.

With such a large number of filling stations, the effort for programming and commissioning has been relatively high up to now and there was a risk of errors. The system ran centrally via a higher-order controller (process control system). In the new version of CleanDock, the process control system only gives the command for docking and undocking. The CleanDock itself takes over all detail processes via decentralised controls (PLC) in the individual modules of the system. The process control system therefore only retrieves one function from the PLC, but does not need to know the process steps stored for it in detail. This is taken care of by the intelligent modules – in this case the CPX electrical terminal with integrated CEC controller and MPA valve terminal.