Discrete solutions without expensive safety PLC
Virtually any larger machine represents a potential hazard for its users, due to movements of the robot arms or hydraulic cylinders, for example. Flexible options for add-on functional safety solutions therefore form an integral part of Weidmüller’s remote I/O solution.
“In an industrial context, the terms 'Safety' and 'Security' have closely related but nonetheless distinct meanings. Security means protection of the machine from people, whereas safety, i.e. functional safety is the protection of people from the machine,” says Gorm Rose, Weidmüller electronics developer with a focus on functional safety. “In order to reliably pre-empt hazards emanating from the machine, we have extended our u-remote product range to include safe power-feed modules. With a safety level of SIL 3 CL as per DIN EN IEC 62061 and Category 4, PL e as per DIN EN ISO 13849-1, we achieve the highest possible degree of protection in the area of machinery.”
Safety-driven shutdown with standard modules
Per safe power-feed module, two independent safety circuits can be created. These circuits can
With u-remote, protection against hazards comes inclusive
also differ technically: for example, taking the form of an emergency stop chain with mechanical contacts and a contactless protective device with OSSD outputs, such as a laser scanner or light curtain.
Integrated safety without a security control – no problem thanks to the safe power-feed modules as integral part of the u-remote system
There is also the possibility of providing functional safety in complex automation solutions by cascading several modules. The switching output of a u-remote station thereby serves as the input for the next module, meaning that two stations are linked together and that linked protection zones can be created within one application.
“A load current up to 8 A can be safely shut down by a single u-remote safe power-feed module actuated by sensors,” says Rose. “And it is cost-effective: Standard output modules can be used. Our customer can thus operate both a DC motor drive with speed control and safely shut it down as well as switch the doubly redundant motor contactors. Even failsafe control of proportional valves with 4-20 mA input is possible. There is a choice between immediate and delayed disconnection.”
Fully designed with safety in mind
Using a standard PLC, machine operators achieve a maximum degree of safety and complete control. All input sensors are independently supplied via separate voltage paths and report the current machine or system status to the control unit. Restart is performed either manually or via the auto-start function. All modules are certified by TÜV Nord (German Technical Inspectorate) and bear the “TÜV type test approved” symbol.
“Users receive complete status information about the inputs and outputs thanks to the complete integration of the safe power-feed modules in the u-remote system. In a solution relying on external devices this would not be possible in this form,” says product manager Andreas Hoffmann. “Configuration is also at least as easy as in a solution with safety switching devices – and with respect to wiring, it is definitely easier.”
You might also be interested in:
Safely control complex systems using modern fieldbus technology
Project examples for the use of solutions without a safety control:
Industrial cleaning: Servicing Europe NDT, Netherlands
Food industry: ANSELMO S.p.a., Italy