Triconex 4351B Communication Module

Technical Dossier

Product Details And Specifications

Triconex 4351B Series: Comprehensive Module Range and Technical Overview

The Triconex 4351B is a communication module deployed within the Tricon Triple Modular Redundant (TMR) Safety System platform, developed by Triconex — a brand under Schneider Electric. This module occupies a critical role in high-integrity industrial control architectures across global heavy industry sectors including petroleum refining, chemical processing, nuclear power generation, LNG terminals, and offshore platforms. The Tricon TMR architecture, of which the 4351B is a core communication component, is certified to IEC 61511 / IEC 61508 SIL 3, making it one of the most widely specified safety instrumented system (SIS) platforms in continuous process industries. Installed base counts in the tens of thousands of chassis worldwide, with operational lifespans routinely exceeding 20–30 years. The 4351B specifically handles high-speed serial communication between the Tricon main chassis and remote I/O expansion chassis or peer controllers, functioning as the physical and logical bridge in distributed Tricon network topologies.

The Evolution of Triconex 4351B Architecture

The Triconex TMR platform was introduced in the mid-1980s by Triconex Corporation, later acquired by Invensys and subsequently by Schneider Electric. The communication module lineage evolved through several distinct generations tied to the broader Tricon hardware platform revisions:

Early Generation (Tricon v1–v7, 1986–1998): Initial communication modules used proprietary Triconex Communication Protocol (TCP/IP predecessor) over RS-422/RS-485 serial links. Modules such as the 4351 (non-B revision) were the primary inter-chassis link devices. Backplane compatibility was limited to the original 7-slot and 14-slot Tricon main chassis.

Mid Generation (Tricon v8–v9, 1998–2008): The 4351B revision introduced enhanced noise immunity, extended temperature tolerance, and improved diagnostic coverage. This generation added support for Triconex Peer-to-Peer (TPTP) communication and expanded compatibility with the Tricon Enhanced Diagnostic Monitor (TEDM). The 4351B became the standard communication module for Tricon v8/v9 systems and remains the most widely deployed revision in the installed base.

Modern Transition (Tricon CX / Trident, 2008–present): Schneider Electric introduced the Tricon CX platform with fiber-optic inter-chassis communication, replacing copper serial links. The 4352 and 4353 modules represent the modern equivalents. However, the 4351B remains in active service across legacy Tricon v8/v9 installations where platform migration has not been executed. Compatibility between 4351B and Tricon CX chassis is not supported — migration requires full chassis and module replacement.

The 4351B is classified as a mature/end-of-active-production component. Schneider Electric no longer manufactures new 4351B units; however, long-term maintenance support (LTMS) agreements and third-party refurbished stock remain the primary sourcing channels for operators maintaining legacy Tricon systems.

Triconex 4351B Full Catalog & Functionalities (SKU List)

The following SKUs represent the verified Triconex Tricon TMR platform module range compatible with or directly related to the 4351B communication architecture. All models are classified by functional category:

Communication Modules

• 4351B: Tricon inter-chassis serial communication module, TMR architecture, RS-422 link, v8/v9 chassis compatible
• 4351: Original revision inter-chassis communication module, pre-v8 Tricon chassis, RS-422, non-enhanced diagnostics
• 4352: Enhanced communication module for Tricon v10+ / Tricon CX, fiber-optic inter-chassis link
• 4353: Dual-port fiber communication module, Tricon CX platform, extended distance inter-chassis link
• 4119A: Tricon network communication module (NCM), Ethernet TCP/IP, Modbus TCP gateway function
• 4119B: Enhanced NCM, dual Ethernet ports, TSAA protocol support, v9/v10 chassis

CPU / Controller Modules

• 4351A: Main processor module (MP), Tricon v8 platform, 32-bit TMR CPU, 1MB application memory
• 4110A: Tricon main processor, v9 platform, enhanced scan rate, 4MB application memory
• 4110B: Main processor module, Tricon v9.4+, extended memory, IEC 61131-3 LD/FBD support
• 4110C: Main processor, Tricon v10, dual Ethernet, USB configuration port

Digital Input (DI) Modules

• 3501E: 32-channel 24VDC digital input module, TMR voting, field diagnostics, v8/v9 chassis
• 3503E: 32-channel 120VAC digital input module, TMR, optical isolation, Tricon v8/v9
• 3664: 16-channel digital input, HART-capable, SIL 3 rated, Tricon v9/v10

Digital Output (DO) Modules

• 3601E: 16-channel 24VDC digital output module, TMR, solid-state relay, Tricon v8/v9
• 3603E: 16-channel 120VAC digital output module, TMR, supervised output diagnostics

Analog Input (AI) Modules

• 3700A: 8-channel 4–20mA analog input module, TMR, 12-bit resolution, HART pass-through
• 3703E: 16-channel analog input, 4–20mA / 1–5VDC, TMR, enhanced diagnostics, v9/v10

Power Supply Modules

• 8312: Tricon chassis power supply module, 24VDC input, TMR redundant power architecture
• 8110: AC/DC power supply, 120/240VAC input, Tricon main chassis, hot-swap capable

Sourcing Hard-to-Find & Obsolete Triconex 4351B Parts

The Triconex 4351B has been out of active production for over a decade. Operators running legacy Tricon v8/v9 systems face a constrained supply chain for this module. DriveKNMS maintains a dedicated inventory program for end-of-life Triconex components, with the following sourcing capabilities:

• Refurbished OEM Stock: Fully tested 4351B units sourced from decommissioned Tricon systems, inspected to original Triconex hardware revision specifications.
• Cross-Reference Verification: DriveKNMS engineers verify hardware revision compatibility (4351 vs. 4351B) before shipment to prevent backplane incompatibility failures.
• Emergency Dispatch: Critical spare orders for 4351B modules can be processed for same-day or next-business-day dispatch from stocked inventory.
• Long-Term Supply Agreements: For operators with multi-site Tricon v8/v9 installations, DriveKNMS offers annual supply agreements to reserve 4351B stock against future maintenance windows.
• Obsolescence Consulting: For sites evaluating migration from Tricon v8/v9 to Tricon CX or Trident platforms, DriveKNMS provides module-level cross-reference mapping and migration bill-of-materials support.

Quality Control for the Triconex 4351B Range

The 4351B communication module interfaces directly with the Tricon TMR backplane bus and executes time-critical inter-chassis synchronization. Standard refurbishment inspection protocols applied by DriveKNMS for this module include:

• Backplane Connector Inspection: Physical inspection of all backplane edge connector pins for oxidation, mechanical deformation, and contact resistance measurement per Triconex hardware maintenance specifications.
• Serial Link Loopback Test: RS-422 transmit/receive loopback verification at rated baud rates to confirm signal integrity of the inter-chassis communication link.
• TMR Voting Logic Verification: Functional test in a live Tricon v8/v9 chassis to confirm correct TMR voter behavior and absence of single-leg faults.
• Firmware Revision Audit: EPROM/firmware version identification and documentation to confirm compatibility with target system software revision.
• Thermal Burn-In: 48-hour powered burn-in at elevated ambient temperature to screen for latent component failures prior to shipment.
• Final Functional Acceptance Test: End-to-end communication test between two Tricon chassis using the 4351B under test, confirming inter-chassis data integrity at rated cycle times.