Yokogawa ALF111-S50 Fieldbus Comm Module

Description

The Yokogawa ALF111-S50 is a Foundation Fieldbus H1 communication module designed for Yokogawa's CENTUM VP and CS 3000 distributed control systems (DCS) . It mounts on field control units (AFV30, AFV40, A2FV50, A2FV70) and ESB bus node units (ANB10, ANB11), enabling seamless integration between the Field Control Station (FCS) and fieldbus-compliant devices such as transmitters, valve positioners, and actuators . The module features four independent H1 ports, each operating as a separate fieldbus segment at 31.25 kbps. It acts as the Link Active Scheduler (LAS) for its segments, managing deterministic data exchange—a critical requirement for time-sensitive control loops . The -S50 suffix indicates ISA Standard G3 conformal coating, providing protection against corrosive gases and harsh industrial environments typical of refineries and chemical plants .

Features

· 4 Independent H1 Segments: Each of the four ports operates as a separate Foundation Fieldbus H1 segment at 31.25 kbps, allowing flexible field device distribution

· Dual-Redundancy Support: Two ALF111 modules can be installed in the same node unit for redundant configuration, enabling automatic failover and bumpless transfer without process interruption

· High Isolation Voltage: 1500 V AC withstand voltage between field signals and system logic, protecting sensitive electronics from electrical noise and surges

· Control in the Field (CiF) Support: Enables PID loops to execute directly at the device level, reducing central controller load and improving overall system integrity

· Low Power Consumption: Consumes 0.5 A or less at 5 V DC, making it energy-efficient for dense I/O configurations

Application

· Petrochemical and Refining Industries: Manages communication with critical field devices such as ESD valves, fire and gas detectors, and key process transmitters in high-availability redundant configurations

· Chemical Processing Plants: The ISA G3 conformal coating provides protection against corrosive atmospheres commonly found in chemical manufacturing environments

· Power Generation Facilities: Deployed for boiler control and turbine monitoring, where reliable communication in redundant configurations is critical for maintaining grid stability

· Pharmaceutical Manufacturing: Supports precise control over sensors, pumps, and valves in batch processing, where product consistency and regulatory compliance are paramount

· Water and Wastewater Treatment: Connects distributed field devices to the central DCS for monitoring and control of treatment processes

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FAQ

Q: What is the communication speed of the ALF111-S50?
A: The module communicates at 31.25 kbps per H1 segment, complying with the Foundation Fieldbus H1 specification .

Q: Can the ALF111-S50 be used in a redundant configuration?
A: Yes. The module supports dual-redundancy by installing two units in annexed slots of the same node unit. The system provides automatic failover and bumpless transfer of control if a module or segment fails .

Q: How many fieldbus devices can be connected per segment?

A: Up to 32 devices per segment, with the ALF111 module counting as one unit. Each segment supports a maximum of 48 control I/O points .

Q: Does the ALF111-S50 provide power to field devices?
A: No. The module functions only as a communication master (LAS). A separate Foundation Fieldbus power supply and proper terminators are required to power field devices on each segment .

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