Logix SIS integrates basic control and process safety

One of the most important jobs of any distributed control system (DCS)—if not the most important—is process safety. However, process safety is different than machine safety that immediately stops and powers down devices. Process safety is trickier because process applications must typically go through predefined steps to reduce high temperatures and pressures—and fail safely.

The good news is that failing safely is getting simpler and easier. “Process safety used to require a control system that was separate and redundant from the basic process control system (BPCS), but some of those regulations like IEC 61508 have relaxed slightly in recent years,” explained Kris Dornan, commercial marketing manager at Rockwell Automation, who hosted a press conference at Rockwell Automation Fair 2024 last week in Anaheim, Calif. “This enabled us to look at using ControlLogix as a safety instrumented system (SIS) function, and now we’ve developed Logix SIS, which lets users employ a common system for their BPCS and SIS.”

Launched in September, Logix SIS is a modern, integrated safety solution with safety-integrity level (SIL) 2 and SIL 3 certifications for enhanced process and hybrid safety. It provides all the components of an SIS, including process logic-solver and I/O. Logix SIS is engineered to provide high availability with Rockwell Automation hardware, including the latest 1756-L85E controller, FLEX 5000 I/O platform, and Studio 5000 Logix Designer application for an integrated user experience.

“Logix SIS is a step towards a fully integrated control system because it uses the same BPCS, but is built with SIS capabilities. This lets it provide highly available safety for regular and hybrid systems,” explained Liz Bahl Prosak, commercial portfolio manager at Rockwell. “Logix SIS uses an L85 controller for routine and redundant tasks. Plus, it’s TÜV-certified as SIL 2 and 3 compliant.”

Dornan added that Logix SIS was developed by reexamining how Rockwell’s longtime ControlLogix PLC platform was applied in baggage handling and other industries. Prosak added that Logix SIS has already been applied successfully by several beta-test users operating tunnel systems and other processes. Logix SIS presently works with Rockwell’s GuardLogix 5580 safety controller, but it’s also expected to dovetail with the upcoming GuardLogix 5590 that’s expected to launch in 2025.

Other key capabilities of Logix SIS include:

• High-availability safety delivers continuous operation for critical processes.
• Streamlined implementation by leveraging familiar hardware and software.
• Reduce engineering time to maximize efficiency through simplified design and configuration.
• System upgrades without requiring planned downtime.
• Available through Rockwell Automation distribution channels, providing convenient access to users worldwide. 

Prosak reported Logix SIS performs all its functions in ControlLogix, Version 37, firmware, which also enables its redundancy and other safety capabilities. This also means users no longer have to develop custom code for SIS capabilities. 

“In the past, users could use many of the checkboxes in Logix Designer software, but they still needed custom code to comply with IEC 61508 requirements,” explained Prosak. “Now, Version 37 lets users deploy safety functions and controllers in redundant arrangements. They can just set up and add a new checkbox in Logix Designer, click on it, and they’re done.”