Past Reliability Aids Future Flexibility

How General Electric's TMR Controllers Helped Maximize Process and Plant Uptime in More Than 10,000 Critical Applications

There's no substitute for experience, especially in generating new innovations. For instance, General Electric has been in the controller business for decades. It started making its Mark series high-availability controllers in the 1960s for industries requiring extreme reliability and availability, and since the 1980s, its triple-modular-redundant (TMR) controllers have helped maximize process and plant uptime in more than 10,000 critical applications.

However, while Mark controllers were widely deployed, they were typically used only by GE's internal customers. Even the most recent, Mark VIe intelligent controller and Mark VIeS intelligent safety controller, were only released internally in 2005.

SEE ALSO: Control Simplicity, Flexibility

Fortunately, the consolidation of GE Intelligent Platforms with GE's Controls Center of Excellence for power and water six to eight months ago allows the converged organization to release a newly updated version its Mark VIeS control system.

"We looked at all of GE's businesses, and industrial controls are needed at all levels, but now we're making a consistent controls experience for all of them," says Rebecca Boll, product line leader for Intelligent Platforms' control and communications systems. "This is also part of GE's effort to invest in the Industrial Internet and make it easy to use as the regular Internet is for mainstream consumers."

As a result, MarkVIeS consists of a main control processor, Ethernet drivers for communicating with its I/O and control networks, and simplex-, dual- or TMR-configurable I/O modules. Its control logic is programmed in a combination of function block diagrams (FBDs), relay ladder diagram (RLD) and sequential function charts (SFCs), which are executed by a real-time operating system (RTOS). The controller's I/O network is a dedicated, full-duplex, point-to-point protocol, and it supports a deterministic, 100-Mbps communications network suitable for local or distributed I/O modules.

"This I/O architecture provides the flexibility needed to meet specific requirements and allows users to apply and optimize them quickly," says Ashok Acharya, product manager for GE's Mark safety controllers. "Safety systems typically have multiple loops, but not all of them need redundancy. MarkVIeS allows users to customize each loop with the right safety integrity levels (SILs) and modify them easily if needed." 

To serve in the same mission-critical applications as its predecessors, Mark VIeS is exida-certified for SIL 3 applications in compliance with the IEC 61508 standard and implements redundancy for safety based on its SIL requirements. It also holds an Achilles Level I cybersecurity certification from Wurldtech.

While much of its hardware is the same, MarkVIeS's software and networking are streamlined. For example, a couple of years ago it added OPC UA networking protocol for communicating between its Control ST-based Workstation software and PLCs and DCSs, and last year it integrated a shared I/O communications concept between its safety and non-safety controllers by using GE's Ethernet Global Data (EGD) protocol.

In addition, MarkVIeS's Workstation software uses other sections of GE's ControlST software, including ToolboxST for configuration and maintenance; Trender data collection for time-based signal plotting; and Alarm View to display and manages alarm and event information in accordance with the ISA 18.2 standard.

Also, because simulation of processes and associated control can be essential for training and validation, the controller has Virtual Mark VIeS, which provides a PC-based form of itself. "This allows users to test and examine different data without having to connect to a physical system," Acharya explains.

Finally, MarkVIeS uses exida's exSILentia software to help analyze safety instrumented functions (SIFs), verify that it's meeting safety requirements and demonstrate compliance. "Users employ this tool to calculate their SIL functions and decide on the architecture and SIL level for specific applications," Acharya adds.