Johan Sterrenburg, Technical Manager at Chemours Netherlands, was impressed by the simple connection of the SafetyBridge modules to the S7 controller, among other things.

© Phoenix Contact

Johan Sterrenburg, technical manager for electrical systems and measuring equipment at the Dordrecht site, explains the project approach: "Right from the start of the activities, it was clear that our main focus was on separating the safety system from the main control system. After examining and evaluating all possible solution concepts, we ultimately opted for the I/O system Inline from Phoenix Contact with the TÜV-certified SafetyBridge Technology (SBT). This is because the solution can be easily connected to the S7 standard controller and also includes its own safety CPU. The solution can therefore be fully integrated into the existing network and still be operated independently of the standard controller."

The facilities for finishing and packaging with their numerous control cabinets are spread over a large area at Chemours Netherlands. The safety sensors and position switches of all processes could now be integrated into the automation solution for the first time via the decentralized safety I/O system. Specifically, the chemical producer uses version 3 of the so-called LPSDO module (Logic Programmable Safe Output Device) from the SafetyBridge portfolio in the two lines. In the current configuration, up to 16 safe input or output terminals are controlled remotely via the network. In principle, the SBT system is designed so that it can be easily configured like a safety module. Nevertheless, it offers the functionality and flexibility of a programmable logic controller with safe I/O modules that can be used in an extensive automation network - independently of the controller and the automation network.

In addition to the so-called logic module, the system consists of safe input and output modules. The I/O modules monitor the signals from the safety sensors and switch off the control components. The logic module generates and controls the safety-related SBT transmission protocol and also processes the user-defined safety logic. It also has eight additional safety outputs.

Should Chemours Netherlands require further safety signals in the future, additional I/O modules can simply be added or a new LPSDO module with the associated I/Os can be integrated into the solution. This option offers the chemical company exactly the flexibility that those responsible for the project had set as their goal.

Modules for implementing the safety functions

Using the Safeconf configuration software, the user can assign up to 16 different safety I/O modules, each with a unique address, to the central logic module. To implement the individual safety functions, the configuration software offers corresponding modules that are based on the PLCopen specification and cover all common types of safety sensors and sensor-based functions - for example muting.

The assigned hardware sensor inputs can be set accordingly to the sensor type, for example to record specific test pulse filter widths or discrepancy times. Depending on the control components used, the user can also select SBT output modules with semiconductor outputs or potential-free relay contacts. Depending on the configuration and wiring, the SafetyBridge modules are generally suitable for safety applications up to PLe in accordance with EN ISO 13849-1 or SIL 3 in accordance with EN IEC 62061.

Programming errors excluded

Once the safety logic has been implemented, the distribution and the respective installation location of the I/O modules in the network are irrelevant, as neither of these influences the safety logic. To implement or retrofit the safety logic in an existing standard controller, the programmer requires neither special experience nor training in the field of functional safety. From the perspective of the standard PLC, the SafetyBridge system is an ordinary I/O module for the transmission of safety packages, the content of which is not accessible or visible to it. The content of the safety packets is continuously monitored by the safety modules themselves. If they detect a deviation, the logic module immediately puts the system into a safe state.

It was also particularly important for the application at Chemours Netherlands that the status data is transmitted to the central control room - another advantage offered by a safety solution integrated into the network. Due to the safety measures integrated into the safety system, errors or impairments to functional safety caused by the programmer of the standard PLC are ruled out. All in all, with the Safety Bridge concept implemented, Chemours has now installed a TÜV-certified safety system in the Dordrecht plant that works independently of the S7 standard controller and yet is fully integrated into the existing plant network.

Author:
Simon Davis works for Phoenix Contact Electronics in Bad Pyrmont.

The Chemours Group

The American chemical group 'The Chemours Company' is one of the international market leaders in the field of titanium dioxide technologies, fluorine products and other chemical-based solutions. The company was spun off from Dupont's High Performance Chemicals division in 2015 and today supplies customers in the automotive, coatings, plastics, electronics, energy and telecommunications industries in over 130 countries. Although it has only been operating independently for two years, The Chemours Company can look back on 200 years of history. The Group now employs several thousand people at 45 production sites, laboratories and branches worldwide.