Machinery must be safe and designed and built in such a way that it can be used, configured and maintained at all stages of its life cycle with minimal risk to people and the environment. In the European Union, the CE marking indicates that a machine has been tested by the manufacturer and meets all EU-wide safety, health and environmental protection requirements. All products manufactured worldwide that are marketed in the EU must bear a CE mark and meet the requirements of the European Machinery Directive.

If risks cannot be reduced or avoided through design measures, safety for machine-machine or human-machine collaboration can be ensured through functional safety. It offers the additional advantage that it often results in higher productivity and availability of the machine and consequently more efficient processes. To reduce risks, machines can be stopped quickly and safely, for example, or operated at a reduced, safe speed under certain conditions.

Functional safety in many areas

Functional safety is wide-ranging and plays a role in many areas - such as the paper industry, ski lifts, centrifuges and decanters, conveyor belts, woodworking machines, cranes, test benches, escalators, food and beverage, automated storage facilities, amusement parks and the plastics industry. The design of a safety system requires compliance with important functional safety standards. ABB offers both controllers and frequency inverters for safety functions. At the heart of the solution portfolio is the AC500 programmable logic controller, which can be upgraded with safety CPU and I/O modules to a fully integrated safety solution that meets the high requirements of Performance Level up to PL e according to ISO 13849 or Safety Integrity Level up to SIL 3 according to IEC 62061, IEC 61508 and IEC 61511.

Scaling to the safety PLC

A special feature of the AC500 is the module rack with up to six slots for communication and function modules as well as for a safety CPU, which allows the entire system to be scaled to the AC500-S safety PLC. Up to ten I/O modules, including safety I/Os, can be connected to one CPU. If this is not sufficient, there is the option of a decentralized solution with head stations, to which up to ten safety or non-safety modules can be docked. This allows particularly large or spatially extensive projects to be implemented. The ABB AC500 uses Profisafe for safe communication.

ABB offers various safety CPUs and I/Os for the AC500-S that meet different requirements. In addition to the non-safety portfolio, the safety CPUs and I/Os are also available as XC versions (extreme condition) for use in harsh environmental conditions, for example at minus 40 to plus 70 degrees Celsius, high vibration and acceleration forces and corrosive environments.

Automation Builder engineering tool

With the AC500-S, safety and non-safety I/Os are separated on the hardware side, but fully integrated on the software side. The exchange of safe and non-safe data is simple and takes place in a closed loop in the Automation Builder engineering tool. The Functional Safety Design Tool FSDT-01 is also integrated here, which can be used to evaluate the respective Performance Level and Safety Integrity Level. The Safety Code Analyzer is also integrated. It can be used to verify the safety programming rules or guidelines for programming PLC applications (FBD, LD, ST). With the help of the Automation Builder, even complex and scalable projects can be implemented; frequency inverters can be integrated at field level.

High level of safety and increased efficiency

An important safety application is tunnel automation, where personal safety within the system must be ensured at all times. The AC500 is a PLC system that is frequently used in Europe. Scalability and connectivity are decisive features in this segment. The AC500 enables redundant and highly available installations with up to 10,000 I/O signals.

Another relevant safety area is material handling with tower cranes. A system of crane networks that interact with each other in a movement circuit places great demands on the communication between the individual crane systems. The AC500-S safety PLC offers special features such as floating point and trigonometric calculation, programming in Structured Text and Profinet/Profisafe communication. The AC500 can also be used to increase the productivity and efficiency of crane systems. This is demonstrated by an example of fully automated RMG cranes (Rail Mounted Gantry). After automating the cranes with extended functional safety using the AC500 PLC and ACS880 frequency inverters from ABB, they work fully automatically in 24-hour operation. This has increased the terminal's container handling capacity by 20 percent, equipment utilization by 35 percent and its production capacity by 10 percent.

Integrated safety in the frequency inverter

Machine safety cannot only be guaranteed by separate external PLC systems. One example of the increasing integration of safety, control and monitoring are the modern frequency inverters from ABB's All-Compatible platform. All frequency inverters are characterized by the same look and feel as well as the same commissioning and parameterization. They have a common control panel with plain text display and share accessories such as fieldbus or I/O modules as well as tools such as the Drive Composer for drive commissioning, process optimization and monitoring.

All All-Compatible frequency inverters have the "Safe Torque Off" (STO) safety function as standard, which safely switches machines to a torque-free state or prevents them from starting up suddenly. This eliminates the need for a safety relay and two redundant contactors to implement this safety function, simplifies maintenance and reduces the amount of cabling required.

ABB offers the Profisafe safety function module FSPS-21 as an additional safety option for many applications, especially in the motion sector. FSPS-21 provides a safe Ethernet connection between the inverter and a safety PLC using the Profisafe over Profinet IO protocol and, in addition to the STO function, also supports the "Safe Stop" (SS1). Further functions such as "Safe Brake Control" (SBC) and "Safely Limited Speed" (SLS) are combined in the FSO-12 safety function module. With FSO-21 and FDE-31, a module for the feedback of encoder data, ABB also enables high-end functions such as SLS with encoder feedback. As an example of SLS functionality, the ACS880 all-compatible frequency inverter can be used together with the FSO-12 module in a gantry crane application. The safety function module can safely evaluate limit value or limit switches and use the SLS function to safely limit the speed in order to move to the end position. This ensures safety in the application even without a higher-level control system and also reduces engineering and material costs.