Depending on the application, dispersion powder must be manufactured in different grain sizes. To ensure and document this process, Wacker in Burghausen has for the past year been identifying the mesh width of its tumbler screens with Turck’s BL ident RFID system which is also approved for use in dust hazardous areas. In the light of the company’s good experience, the next project is already under way.
The author: Holger Anders Key account manager, Turck
Wacker has 25 production facilities, 20 technical centers of excellence and 53 sales offices worldwide with a total of 17,200 staff. The chemical company’s most important production site is the plant in Burghausen, idyllically situated on the Austrian border in the so-called Bavarian chemical triangle. Around 10,000 people are employed on this site at some 150 facilities, where thousands of different products are manufactured in a three-quarters of a square mile area.
Among these products are dispersion powders that are added to tile adhesives, plasters, screeds and other building materials to give them specific properties. To obtain the end product, a liquid is dried in a drying tower at the end of the production process. The resulting powder then has to be vibrated through a screen before it can be packaged, to ensure that it has the required grain size.
In order to increase transparency and traceability in the manufacture of dispersion powder, the Production department expressed a wish for the screen size used in the tumbler screens to be detected automatically. “The correct screen size was previously measured manually by colleagues in the plant”, explains Michael Holzapfel, the engineer responsible for electrical planning in the Construction Polymers division. “In order to exclude the possibility of human error, the screen used for each batch now has to be measured automatically. This not only enables us to guarantee 100 % quality in the ongoing process; we also have a retrospective record of screening accuracy.” Continuous vibration calls for a wireless solution. Holzapfel soon discarded his initial idea of using a code in conjunction with inductive sensors: “The screen vibrates almost non-stop throughout the entire year and so wired solu-tions are simply not feasible. We already have first-hand experience of this. Every month we have to replace the earthing cables of the screens to make sure they don’t break, even though highly flexible wiring is used.” An RFID solution was gradually considered as an alternative for this reason. Owing to the particular environmental conditions prevailing in Burg-hausen, however, the solution had to be approved for dust hazardous areas. “Turck was the only manufacturer that could offer us an RFID system with Ex approval for Zone 22 (dust)”, says Holzapfel when asked to describe the original reason for choosing this system from the Mülheim automation specialist.
So far, Wacker has fitted four tumbler screens with a type TNLR-Q80-H1147-Ex read/write head that is approved for Ex Zones 2 and 22. All the screens used there have been provided with a TW-R50-B128-Ex tag on which the mesh width is stored. This disc-shaped tag is mounted at the edge of the screen, directly underneath a strap with the optical ID for the mesh width. The read/write head reads the mesh width and transfers the data to the process control system over a Profibus line via one of three BL20 I/O stations.
There was one other hurdle that had to be overcome during the installation phase: “The function block supplied with the RFID system is programmed for a Siemens S7 PLC and not a Siemens PCS7 process control system like the one we use here”, Holzapfel continues. “However, our software specialists collaborated closely with Turck Support to adapt the S7 function block as quickly as possible, so that it now also runs on the PCS7.”
New project: coupling station
The system has been in operation at Wacker for the past year to the customer’s satisfaction. Encouraged by the good experience with his supplier, Holzapfel has already started to tackle the next project: “The RFID system works so well in the tumbler screens that we are now extending it for use in our coupling stations, where dust Ex approval is also required.” Around twenty targets and nine sources need to be recorded via RFID in order to guarantee a reliable and transparent process. For this purpose, each of the twenty DN 80 hoses will be provided with a tag containing the individual hose number. Each target will be fitted with a read/write head. When a hose is connected, the system will read the appropriate number and enable operation if everything is connected correctly. Turck will supply a ready-to-connect solution – featuring a customised male connector and fully encapsulated – for the coupling station project via its mechatec subsidiary.
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