Bailey Controls remains an important name in the history of distributed control systems, particularly for plants operating Network 90, INFI 90 and Harmony control platforms. Although Bailey Controls is now part of ABB’s broader automation heritage, many industrial facilities continue to operate Bailey-based systems, creating an ongoing need for lifecycle management, hardware replacement and gradual DCS modernization.

Recent developments in industrial automation are placing greater emphasis on modernizing legacy control systems without unnecessarily replacing field wiring, I/O infrastructure and proven control strategies.

From Network 90 to INFI 90 and Harmony

Bailey Controls introduced the Network 90 distributed control system in the 1980s. The platform subsequently evolved into INFI 90 and later became part of the Harmony family of industrial control technologies.

These systems were widely adopted in industries where continuous and reliable process control was essential, including power generation, chemical processing and other large industrial facilities.

For plants with decades of operational history, the challenge is not simply replacing an old controller. A legacy DCS can contain thousands of configured control loops, I/O points, graphics, alarms, engineering configurations and field connections.

Consequently, modernization often needs to be approached as a staged engineering project rather than a complete replacement.

INFI 90 Modernization

Modernization options for Bailey INFI 90 systems can include controller upgrades, communication improvements, operator workstation modernization and integration with newer automation platforms.

ABB provides evolution paths connecting Harmony INFI 90 with System 800xA, allowing plants to add modern operator interfaces, asset optimization, information management and other extended automation functions while maintaining parts of the existing control environment.

This approach can be particularly useful for facilities where a complete DCS replacement would require extensive rewiring and a lengthy production shutdown.

Protecting Existing Field Infrastructure

One of the most important considerations in a Bailey DCS migration is the existing field infrastructure.

Replacing controllers does not necessarily mean replacing every field termination. Modern migration architectures can allow existing I/O and wiring arrangements to remain in service while newer control technologies are introduced.

This is significant for large plants because field wiring represents a substantial engineering and commissioning workload.

The same principle is now being applied across the wider DCS industry. Modern migration solutions increasingly focus on preserving existing field wiring while upgrading controllers, engineering tools and operator environments.

Bailey DCS and PLC Integration

Another important aspect of legacy Bailey systems is their ability to interact with other industrial automation equipment.

Many plants have added PLCs, motor control systems, instrumentation, analyzers and specialized equipment over the years. As a result, a modern migration project often needs to consider both the original DCS architecture and newer automation systems.

This makes communication infrastructure an important part of modernization planning.

A properly engineered migration can help connect legacy Bailey control functions with modern PLC, SCADA, DCS and industrial networking technologies without unnecessarily disturbing established process control strategies.

A Step-by-Step Modernization Strategy

For an operating plant, a staged approach can reduce migration risks.

Typical activities include:

• Inventorying existing Bailey controllers and I/O modules
• Reviewing INFI 90 and Network 90 communication architecture
• Evaluating operator and engineering workstations
• Checking spare-part availability
• Identifying obsolete hardware and software
• Mapping existing field wiring and I/O
• Planning controller and communication upgrades
• Introducing modern operator interfaces
• Testing new and existing systems before final cutover

This approach allows plant operators to prioritize the most critical components rather than replacing the entire system at once.

The Continuing Importance of Bailey Controls

The Bailey name remains relevant because thousands of industrial automation components and legacy control architectures were built around its technology.

For automation engineers working with Bailey INFI 90, Network 90, Harmony DCS, controllers, I/O modules and communication boards, understanding the original architecture is still valuable when planning system upgrades.

The broader trend is clear: legacy DCS modernization is increasingly moving toward step-by-step evolution rather than complete replacement. By combining existing Bailey infrastructure with newer control, networking, monitoring and digital technologies, industrial facilities can extend the useful life of established automation investments while preparing for future requirements.