Safety networks are communication networks designed to support high-integrity applications. Integrity is typically specified using a qualitative and quantitative index called the safety integrity level (SIL), specified by SIL1 to SIL4. Each incremental level corresponds to an order of magnitude increase in integrity.
The new Allen-Bradley Guard-Logix controller from Rockwell Automation features a two-processor safety architecture and is rated up to a SIL 3 functionality. The SIL 2 and SIL 3 are the most common safety integrity levels required in machinery and process safety applications, making GuardLogix ideal for a range of safety applications.
GuardLogix safety controllers are based on the same Logix control engine, networking, and input/output (as other Rockwell Automa- tion Integrated Architecture control systems.
This design commonality, along with using the standard RSLogix 5000 software, allows for better information sharing, reduced training costs and faster programming and commissioning.
Rockwell Automation Integrated Architecture features multidisciplined control across process, discrete, motion, drive and safety applications, as well as connectivity to plantwide information sys- tems.
The breakthrough in safety networking came with the introduction of safety communication over a single medium. These first safety networks were closed proprietary networks, built either on available commercial networks or purpose-built communication networks. The next advancement was the coexistence of safety and standard communications on the same wire.
Media independence has been one of the most recent advancements in safety networking. Functional partitioning of the safety application and the message transmission mechanism provides an additional benefit, and the underlying communications stacks can be interchanged.
“As the first safety control solu- tion for integrated architecture, GuardLogix is a leap forward for machine safety,” explains Rockwell Automation integrated architecture commercial engineer for sub- Saharan Africa and the Middle East, Vusi Sithole.
GuardLogix uses Rockwell Soft-ware RSLogix 5000 programming software – the same development tool used by all Logix program- mable automation controllers.
RSLogix 5000 software also helps manage safety memory, so users do not have to manually manage the separation of standard and safety memory, or worry about partitioning logic to isolate safety-related data.
During a GuardLogix system development, safety control is managed in the same way as standard control. Also, with online editing, the development and debug environment is simpler. Safety memory is locked to a SIL 3 state and logic is protected, but the standard side of GuardLogix continues to operate like a regular Logix controller.
Standard logic and external devices, such as human machine interfaces and other controllers, can read safety memory. Users have systemwide integration and the ability to easily display safety status on displays.