Description
The part number 3674 (referred to as TRICON 3674) specifies a 24 VDC 32-Point Dual Digital Output (DDO) Module designed for the Triconex Tricon Safety Instrumented System (SIS) by Schneider Electric (Invensys).
Technical Specifications
| Feature | Specification |
| Manufacturer | Triconex (Schneider Electric / Invensys) |
| Product Type | Dual Digital Output (DDO) Module |
| Nominal Voltage | 24 VDC |
| Voltage Range | 16 to 30 VDC (Maximum: 36 VDC withstand) |
| Number of Output Signals | 32 points, commoned |
| Current Rating | 2.0 A max continuous per point (10 A surge for 10 ms) |
| Point Isolation | 1,500 VDC minimum |
| Safety Integrity Level | TÜV Certified up to SIL 3 applications (IEC 61508) |
| Architecture | Dual-redundant output paths with internal 2-out-of-3 (2oo3) voting |
Product Overview
The Triconex 3674 is a dual-redundant digital output module built for safety-critical applications where reliable shutdown logic is critical. Unlike full Triple Modular Redundancy (TMR) modules like the 3625, the dual-redundant 3674 series provides a cost-optimized safety configuration while maintaining strict fault-tolerant standards. It is optimized for de-energize-to-trip (fail-safe) architectures commonly used in emergency shutdown systems.
Key Features:
-
Internal 2oo3 Voting: Applies a 2-out-of-3 voting process internally to output switches to guarantee high integrity and safe operation even when handling component degradation.
-
Built-In Voltage Loopback: Continuously monitors and independently verifies output switch states to instantly catch faults like stuck-ON or stuck-OFF conditions.
-
Comprehensive Diagnostics: Features active front-panel status indicators (PASS, FAULT, ACTIVE, LOAD/FUSE, and individual point ON/OFF states) for fast local troubleshooting.
-
Hot-Swap Support: Fully compatible with online module replacement (hot-swapping) via an External Termination Panel (ETP), allowing maintenance without interrupting active plant processes.
3674
Core Functional Features
▪ Full TMR triple independent circuit design, majority voting logic; single channel fault will not trigger incorrect output
▪ Total 32 channels 24VDC sinking digital outputs, commoned terminal layout
▪ Per channel continuous current: 2 A; supports 10 A short surge within 10 ms
▪ Built-in comprehensive loopback diagnosis: detect open circuit, load loss, short circuit on field wiring
▪ Hardware self-protection for each channel, no external fuses required on module side
▪ Response speed optimized, faster than the earlier 3664 model
▪ Supports hot-swap replacement under running rack conditions, no system shutdown
▪ Front panel LED array visually displays channel status, module fault and communication activity
▪ Communicates with main processor via TriBus high-speed internal rack bus
▪ PCB conformal coating option available, suitable for environments with vibration, temperature fluctuation and dust
Installation & Commissioning Guidelines
Classify wiring reasonably: separate field power cables and TriBus communication cables; use shielded wiring for long-distance transmission and implement standardized single-point shielding grounding.
After wiring inspection, power on the rack. Use TriStation 1131 engineering software to download safety logic and verify output action.
Carry out fault simulation test: verify open-circuit and short-circuit alarms can be captured accurately. For safety interlock loops, test emergency shutdown output reliability.
After commissioning acceptance, implement periodic inspection: check connector tightness, LED status and clear accumulated dust.
