Product Description
The AFG84D-H4123 from Yokogawa is a duplex Field Control Unit engineered for continuous, high-availability operation in CENTUM VP and CS 3000 distributed control systems.
It combines redundant processing architecture, dual Vnet/IP communication paths, and flexible power input options to ensure stable control execution in critical plant environments.
This FCU serves as the central controller for Yokogawa Field I/O (FIO) nodes, handling real-time control logic, I/O scanning, and network communication with deterministic performance.
By integrating hardware redundancy at multiple levels, the unit minimizes single-point failures and supports seamless operation during component faults or maintenance.
Core Architecture and Capabilities
The AFG84D-H4123 is built around a duplex control configuration, allowing two synchronized control paths to operate simultaneously.
Automatic switchover mechanisms ensure uninterrupted control if one path experiences failure.
Dual Vnet/IP interfaces provide fault-tolerant communication with higher-level systems, while the CP461 processor module delivers high-speed execution of control strategies, interlocks, and sequence logic.
The unit is designed for long-term deployment in demanding industrial environments, supporting stable operation across extended temperature ranges and continuous duty cycles.
Key Functional Features
Supports fully redundant Vnet/IP network communication for high system availability
Implements dual power supply inputs to eliminate power-related single points of failure
Integrates CP461 control processor for fast and deterministic control execution
Native compatibility with Yokogawa FIO modules and remote I/O architectures
Designed for continuous operation in safety-critical and mission-critical processes
Technical Specifications
Model
AFG84D-H4123
Manufacturer
Yokogawa Electric Corporation
Control Architecture
Duplexed Field Control Unit
Processor Module
CP461
Network Interface
Dual-redundant Vnet/IP
Supported Systems
CENTUM VP
CENTUM CS 3000
Power Input Options
100–120 V AC
220–240 V AC
24 V DC
Power Consumption
Approx. 200 VA at 100–120 V AC
Approx. 230 VA at 220–240 V AC
Approx. 5.5 A at 24 V DC
Mounting Method
19-inch standard control rack
System Integration and Reliability
The AFG84D-H4123 is optimized for integration within Yokogawa’s distributed control architecture.
It supports seamless communication with operator stations, engineering stations, and higher-level plant networks through Vnet/IP, while maintaining deterministic control at the field level.
Redundant power and communication design significantly reduce downtime risk, making this FCU suitable for plants with strict uptime and safety requirements.
Typical Application Areas
Oil and gas production and refining facilities
Petrochemical and chemical processing plants
Thermal and combined-cycle power generation
Metals, pulp and paper, and large-scale manufacturing
Utilities and infrastructure systems requiring 24/7 control availability
Frequently Asked Questions
Can the AFG84D-H4123 operate with single power input if redundancy is not required?
Yes. While designed for redundant power supply operation, the unit can function with a single power input depending on system design.
Is this FCU compatible with legacy CENTUM systems?
The AFG84D-H4123 is primarily intended for CENTUM VP and CS 3000. Compatibility with older systems depends on system configuration and migration strategy.
Does the unit support online maintenance and module replacement?
Yes. The duplex architecture allows maintenance activities to be performed without stopping control execution when properly configured.
