Intelligent wiring helps make control solution smarter

30 May 2017

An aging barrel feeding system, which forms part of a polyurethane production process, has been brought up to date with the addition of new operator panels connected back to a central PLC control via an intelligent wiring system. 

An aging plant handling system at BASF’s Lemförde plant is a crucial element in the barrel transportation chain around the facility. The barrel feeding system transports 200l drums filled with raw materials or finished products to and from the two production halls to the barrel warehouse. 

The 25-year-old system was recently upgraded with the installation of SmartWire-DT and motor protection switches, supplied by Eaton, which has enabled simple power measurement of each individual drive, supporting precautionary maintenance. In the event of a fault, the drives affected can now be deactivated in a controlled manner before the motor protection switch triggers.

“There is a whole chain of processes behind the system, with no buffer stock between the individual process steps. If the feeder system fails, the production process can run into problems,” said Claus Buhrmester, a specialist in the plant's maintenance systems team.

After 25 years in operation, the barrel transportation system was no longer able to fulfil the company’s requirements.  Thomas Büch, a member of Site Engineering Lemförde’s technical team, takes up the story: “The system was controlled by three PLCs that had to be replaced as spare parts were no-longer manufactured. The safety levels were not state-of-the-art and we had no plant visualisation. Manual operation to rectify faults in the event of failure was also not possible.” 

Within the framework of the upgrade project, it was decided to update the automation and safety technology. During this process, a total of 50 three-phase motors needed to remain operational for the feed route and the five integrated vertical feeders.

As part of the modernisation project, the barrel transportation system is now controlled centrally from a PLC instead of from three autonomously controlled systems. “This simplified the structure of the automation architecture and the consolidation of the three control cabinets allowed us to save valuable panel space,” said Büch. 

In addition, operator panels were installed at the critical points of the system to aid visualisation. Now the operator is able to identify any barrels not removed from the transport system and can see when congestion occurs. The operator panels are also important for preventive maintenance. “The system displays the type of error that has occurred. We can, for example, distinguish whether it is a runtime error due to an overcurrent or frequent switching on and off,” explained Buhrmester. As a result, the maintenance team is provided with valuable information in order to act early and proactively test the drives or mechanics.

To enable this error detection, the BASF team paid close attention to the current measurements on the drives. “This was the main reason for us to wire the control cabinet with the SmartWire-DT intelligent wiring system,” said Büch. It connects the individual switchgear and drives not via point-to-point wiring with the control, but all devices are connected via the SmartWire-DT eight-pole flat cable. This now supplies all the devices connected with power and simultaneously takes care of data communication. 

“By using system tools and components, wiring errors are virtually eliminated,” said Thomas Gern, head of the Industrial Systems Technology department at Elektro-Anlagen-Technik EAT, the electro-technical service provider built the control cabinets for the BASF plant. “Routine testing of the cabinet can, therefore, take place within a very short time. After a brief system introduction at our end, our control cabinet makers were able to complete wiring in half the time in comparison with conventional point-to-point wiring.” The system also saves space in the control cabinet. For the control of the contactors and the feedback from contactors and motor circuit breakers, no inputs or outputs of the PLC are needed. All input signals are collected via SmartWire-DT and transferred to the PLC. 

During the plant modernization project, BASF was able to divide the plant into different security areas. In the past, if an emergency-stop button was pressed, the entire system stopped and confirmation for a re-start was only possible from a central location. To optimise this outdated condition, via the power-feed modules that supply the switchgear with power in the SmartWire-DT system, safety zones have been created – one module supplies the power to the drives within its safety zone. In the event of an emergency stop, the relevant power-feed module and the high-level, redundant group contactor are switched off. This means that the system only shuts down in this particular zone. Re-start authorisation can be given via the corresponding operator panel on site. 

“In general, we mainly retrofitted the safety technology we had,” said Büch. Many safety-light barriers and fence elements were installed. In addition, the system was fitted with a hand-held control panel with ‘dead-man’ function. This allows the operator to control the system manually for routine maintenance tasks. The entire safety technology communicates with the controller via PROFINET.  For that reason, Büch connected the SmartWire-DT system with a corresponding PROFINET gateway. 

“Thanks to the upgrade of the system, we have avoided the need to call in electricians during the night time or over weekends,” said Büch. “Furthermore, the system is back up and running much faster after an overload situation. Slightly increased current levels, for example in the event of mechanical faults, can be identified more quickly and can be rectified in good time. In particular, for drives that are usually in operation for only a couple of minutes during a conveying cycle, an early identification by a conventional motor-protection switch would be virtually impossible.” Buhrmester adds: “With the information of each individual drive, the cause of a fault can be found and rectified easily.” 

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