Safety logic advances with relay, PLC


Discrete Control

Allen-Bradley Guardlogix safety memory can be read by standard logic and external devices, such as human machine interfaces (HMI) and other controllers, saving time by eliminating the need to set up or condition safety data from a dedicated safety device, says Rockwell Automation.

Several advances in safety logic were announced recently. Panasonic Electric Works Corp. of America (formerly Aromat) touts fast response time from a slim safety relay. Rockwell Automation introduced a safety controller rated to SIL 3 that allows integration of controls and safety, with appropriate design.


Slim safety relay features forcibly guided contacts, complying with EN50205 Type A. The SFS relay from Panasonic Electric Works (nee Aromat) has a built-in LED indicator, eliminating design and mounting of a separate LED circuit, cutting costs and saving labor. The 4-pole SFS measures 40 x 13 x 24 mm (L x W x H). SFS has fast response time (8 ms max.), high shock resistance, and is available in 2a2b, 3a1b, 4a2b, 5a1b, and 3a3b contact arrangements. PC board sockets are available. Applications include machine tools, elevator/escalator control, factory automation, and automotive manufacturing lines. SFS2 is priced at $11.40 each in quantities of 1,000.


Combine standard and safety control functions to lower cost, increase productivity. Rockwell Automation introduced a new safety controller. Allen-Bradley GuardLogix controller features two-processor safety architecture and is rated up to a Safety Integrity Level (SIL) 3 functionality. SIL 2 and SIL 3 are the most common safety levels required in machinery and process-safety applications, making GuardLogix ideal for a wide range of safety applications, Rockwell Automation says. The controllers are based on the same Logix control engine, networking, and I/O as other Rockwell Automation Integrated Architecture control systems. This design commonality, along with using the standard RSLogix 5000 software, allows reduced training costs, faster programming and commissioning, and better information sharing across process, discrete, motion, drive, and safety applications, and seamless connectivity to plant-wide information systems.


RSLogix 5000 software also helps manage safety memory, eliminating manual management of the separation of standard and safety memory or worries about partitioning logic to isolate safety-related data. Once the project is tested and ready for final validation, the user sets the safety task to SIL 3, which is then enforced by the GuardLogix controller. Safety memory is locked to a SIL 3 state, logic is protected, but the standard side of GuardLogix continues to operate like a regular Logix controller.


GuardLogix controllers leverage Common Industrial Protocol (CIP) Safety on DeviceNet for safety I/O connectivity, and EtherNet/IP for safety interlocking between GuardLogix processors. Multiple GuardLogix controllers can share safety data for safe interlocking between cells/areas.

—Edited by Mark T. Hoske, editor-in-chief, Control Engineering

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