Description

Application Scenarios

At a liquefied natural gas (LNG) export terminal in Australia, a high-integrity ESD system was required to monitor 200+ critical valve limit switches and compressor trip signals. Legacy systems suffered from undetected wiring faults that delayed shutdown responses. After deploying TRICONEX 3721 modules across redundant Tricon chassis, the facility achieved:

Continuous wire-off/short-circuit detection on every channel

Sub-100 ms response to emergency inputs

Full audit trail via Sequence of Events (SOE) with 1 ms resolution

Zero spurious trips over 3 years of operation

During a simulated pipeline rupture test, all 16 channels on a single 3721 module correctly detected closure feedback from block valves within 12 ms, triggering a full plant isolation. Regulators approved the system under SIL 3 without reservation—thanks to the proven reliability of the TRICONEX 3721.

Technical Principles & Innovation Highlights

True TMR at I/O Level: Unlike “2oo3” software voting, the 3721 implements hardware-level triple redundancy—each input is physically read by three independent circuits before voting.

Zero Latency Voting: Input data is synchronized across all three main processors using Tricon’s patented SyncLink technology, ensuring deterministic timing.

Advanced Diagnostics: Detects not only open wires but also degraded signals (e.g., 18 V instead of 24 V), preventing latent failures.

No External Relays Needed: Direct connection to field devices reduces cost, footprint, and failure points compared to relay-based safety interfaces.

Seamless Integration with Tricon Tools: Fully supported in TriStation 1131 for configuration, diagnostics, and SOE analysis.

Typical Use Cases

Emergency shutdown (ESD) button and switch monitoring

Valve position feedback (open/close limit switches)

Pump and compressor running status

Fire and gas detector alarm inputs

Pressure/temperature switch trip signals

Turbine overspeed interlock confirmation

Compatible System Components

Main Processors: MP3008. MP3009. MP3009A (Tricon v10/v11)

Chassis: 4329A, 4329B, 4329C (Standard, Extended, or XP)

Power Supplies: 8312. 8312E, 8312H

Communication Modules: 4351B (for Modbus, Ethernet/IP)

Engineering Software: TriStation 1131 v4.1+

Safety Applications: Burner Management (BMS), HIPPS, F&G, Turbine Protection

Installation & Lifecycle Support

The TRICONEX 3721 installs in seconds—simply slide into any I/O slot in a powered Tricon chassis. No jumpers or DIP switches are required; configuration is done entirely in TriStation 1131. Wiring uses standard screw terminals with optional removable connectors for rapid maintenance.

For lifecycle management:

Firmware and diagnostics are updated via TriStation

Failed modules can be replaced online (hot-swap) without system shutdown

Full diagnostic logs support predictive maintenance and regulatory audits

✅ Note: The 3721 is not interchangeable with non-TMR modules (e.g., 35xx or 36xx series). It requires a full Tricon TMR system to operate.

Summary

The TRICONEX 3721 remains a cornerstone of high-integrity safety systems worldwide—trusted where failure is not an option. By combining hardware TMR, continuous diagnostics, and proven field reliability, it delivers the highest level of functional safety for digital input monitoring in the most demanding industrial environments.

Need a quote, compatibility check, or lifecycle migration plan? Contact us for genuine, tested TRICONEX 3721 modules with full warranty and technical support—ensuring your safety system stays online, compliant, and certified.