TRICONEX 4351B

Description

Product Overview

The TRICONEX 4351B is a high-density, 120V AC digital input module designed for the Triconex Tricon v9, v10, and v11 safety instrumented systems (SIS), now part of Schneider Electric. This module serves as a critical interface for reading the status of field devices operating at standard North American line voltage, such as switches, relays, and circuit breaker auxiliary contacts. The primary function of the TRICONEX 4351B is to provide safe, reliable, and diagnosed acquisition of 120V AC signals, converting them into triple-redundant digital data for the TMR (Triple Modular Redundant) safety logic solvers.

Product Parameters and Specifications

• Function: 120V AC Digital Input Module for Tricon TMR Safety System.
• Safety Standard: Compliant with IEC 61508 and designed for use in Safety Instrumented Systems up to SIL 3.
• Architecture: Triple Modular Redundant (TMR). Each of the 32 input points is independently processed by three isolated input circuits, with mid-value voting performed in the main processor.
• Number of Channels: 32 isolated input channels per module.
• Input Voltage: Rated for 120V AC nominal, with a defined operational range (e.g., 79-132V AC).
• Input Type: Designed for dry contact or active (sourcing) 120V AC inputs.
• Diagnostics: Continuous online diagnostics include field power monitoring, channel comparison, and internal circuit fault detection.
• Isolation: High-voltage isolation between the field side (120V AC) and the internal low-voltage TMR logic.
• Connection: Uses a removable front connector with screw terminals for efficient field wiring.
• Response Time: Fast, deterministic response time suitable for critical safety functions.

Advantages and Key Features

The TRICONEX 4351B offers distinct advantages for safety-critical applications involving high-voltage AC signals. Its core feature is its TMR hardware architecture, which provides true fault tolerance; the system can tolerate a fault in any single channel or component and continue to operate correctly, ensuring extremely high availability. The high channel density (32 points) makes it a space and cost-effective solution for plants with many high-voltage status points to monitor. The module provides robust isolation that protects the sensitive TMR electronics from transients and faults on the 120V AC field side. It supports hot-swappable replacement in online systems, allowing for maintenance without a process shutdown. The TRICONEX 4351B is fully integrated with the TriStation 1131 programming and diagnostic software, enabling clear configuration, real-time monitoring, and detailed fault analysis.

Application Cases in Industry

This module is a standard component in TMR-based SIS and ESD (Emergency Shutdown) systems across high-hazard industries, particularly where 120V AC control circuits are standard. In Oil & Gas Refineries and Offshore Platforms, the TRICONEX 4351B reads status from 120V AC powered limit switches on valves, pump run-status contacts, and emergency stop circuits. Within Power Generation plants, it monitors breaker auxiliary contacts (52a/52b), turbine lube oil pressure switches, and other critical protective device contacts. For Chemical and Petrochemical facilities, it interfaces with high-voltage interlock systems and safety relay outputs. It is also used in LNG liquefaction and regasification terminals for critical equipment monitoring.

Comparison with Competing Products

Compared to standard PLC AC input modules, the TRICONEX 4351B is in a different class, being specifically designed and certified for safety functions with TMR redundancy. Its most direct competitors are other safety system vendors’ high-voltage input modules, such as those from ICS Triplex (Trusted) or HIMA. Compared to the ICS Triplex T8431 (a 120V AC TMR input module), both offer TMR architecture and SIL 3 capability. Key differentiators often lie in the specific system architecture (Triconex uses a single-chassis TMR versus distributed TMR), diagnostic methods, module density, and the proprietary engineering toolset. Triconex’s long-standing market presence in oil & gas and its integrated TMR chassis are significant factors for users.

Selection Suggestions and Precautions

• Selection Advice:
  1. Voltage Compatibility: Ensure your field devices provide a dry contact or an active 120V AC signal. Do not use this module for DC or other voltage levels.
  2. Tricon System Compatibility: Verify the TRICONEX 4351B is compatible with your specific Tricon chassis model (v9, v10, v11) and main processor.
  3. Fusing and Protection: Each group of inputs typically requires external fusing on the field power supply. Adhere to the manual’s specifications for fuse ratings and wire gauges.
  4. Point Density Planning: With 32 points per module, plan your rack configuration efficiently. Consider mixing with other I/O types (DC, analog) in the same chassis.
• Important Precautions:
  1. Safe Wiring Practices: 120V AC poses a shock hazard. Ensure all power is locked out during installation. Follow all applicable electrical codes for high-voltage wiring, including proper strain relief and separation from low-voltage cables.
  2. Use of External Field Power: The module typically requires an external, isolated 120V AC field power supply to power the input circuits. This supply must be reliable and suitably rated for the total load of all connected devices.
  3. Grounding: Follow the system grounding instructions meticulously. Improper grounding can create noise, cause diagnostics faults, or compromise safety.
  4. Configuration and Testing: After installation, the module must be correctly configured in the TriStation software. Conduct a thorough loop check, verifying each input point with the actual field device to ensure proper operation and voting logic.

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