ICS Triplex T8402 TMR (Triple Modular Redundancy) Safety Control System Dual 24VDC Digital Input Module

ICS Triplex T8402 TMR Dual 24VDC Digital Input Module (Trusted T8000 SIL3 Safety System)

1、 Product basic positioning

T8402 is a high-density digital input card for Rockwell ICS Triplex Trusted T8000 triple redundancy security platform, with TMR 3-to-2 voting architecture and T Ü V IEC 61508 SIL3 certification. It is designed to collect on-site switch, contact, and proximity switch signals for ESD emergency shutdown, FGS fire and gas, and boiler/unit safety interlock circuits, commonly known as the dual 24VDC DI module.
Differentiation: T8402 (60 channel DI); T8403/T8403C (40 channel DI, same series alternative)

2、 Core hardware architecture (TMR triple redundancy)

1oo2D dual channel measurement+the third mock examination voting
Each on-site input is equipped with two independent sets of sigma delta voltage acquisition circuits, and the module has three independent slicing hardware voting channels; The single slice fault module continues to operate, and the dual slice fault safety reports a fault, meeting SIL3 fault tolerance requirements.
Dual circuit line monitoring: Each channel has an independent voltage threshold judgment, and can enable separate disconnection/short circuit diagnosis. It is compatible with dry contacts and active PNP/NPN 24V sensors.
Backplane triple data exchange, controller triple processor cross check input status, to prevent single point erroneous acquisition.

3、 Electrical and channel specifications

1. Channel configuration
Total input channel: 60 channels of 24VDC TMR digital input
Grouping: 12 groups, 5 channels per group, independent loop monitoring for each group
Rated input voltage: 24VDC, on-site withstand range 18~32VDC
Single channel typical input current: 6mA; minimum detection current for line diagnosis: 2mA
Support signals: passive dry contact, active 24V PNP/NPN proximity switch, limit switch, pressure/temperature switch
2. Isolation and anti-interference
channel ↔ Backboard: 2500V pulse optoelectronic isolation
Channel isolation, group independent power supply, suppress crosstalk and common mode interference
Built in 50/60Hz configurable digital filter to filter out frequency converter and motor induced noise
3. System power supply and performance
Backplane power supply: 20~32VDC
Whole machine power consumption: ≤ 18W
Channel response time:<10ms
SOE event sequence recording: 1ms high-precision time scale, automatic timing log for switch displacement, used for accident traceability
Periodic hardware self inspection of the whole machine: automatic verification of the third mock examination voltage and acquisition circuit, and early warning of hidden fault
4. Environmental mechanical parameters
Working temperature: -20 ℃~+60 ℃ (inside the rack); Storage -40~+85 ℃
Humidity: 0~95% RH, no condensation
Size: 125 × 84 × 35mm, weight approximately 480g
Seismic resistance: Complies with IEC 60068 industrial vibration impact standard
Installation: T8100/T8300 Trusted Safety Rack, equipped with a dedicated T8 series terminal base

4、 Core functional characteristics

Full channel line diagnosis (switchable channel by channel)
Real time detection: line open circuit, cable short circuit, sensor loss, circuit undervoltage/overvoltage; Panel LED direct fault alarm, fault code uploaded to TriStation configuration software.
Online hot swappable maintenance
Support non-stop replacement of spare slots/paired adjacent slots, with no interruption of safety circuit signals during the replacement process and no triggering of interlock misoperation.
Panel status indicator light
60 independent channel LED: green=conductive, red=line fault
Module overall status light: Active running/Standby/Fault three color indicator
Periodic safety testing
Cooperate with TriStation to achieve mandatory channel verification and loop testing, meeting the annual testing standards for SIL safety loops.
Compatible with explosion-proof accessories
The module body does not have explosion-proof certification, and the explosion-proof area signal needs to be connected in series with intrinsic safety isolation barriers.

5、 Security certification and compliance

Functional safety: T Ü V Rheinland IEC 61508 SIL3, can be used for SIL3 level safety instrumented systems SIS
EMC: IEC 61000-6-2 (Industrial General Immunity), IEC 61000-6-4 (Heavy Industry Strong Electromagnetic)
Compliance: CE, UL, CSA, IECEx certification (with matching terminal base)

6、 Adaptation system and software

Compatible rack: Trusted T8100, T8300 security controller backplane
Supporting CPU: T810B, T8111, T8151B and other T8000 series triple redundant processors
Configuration software: TriStation 1131, supports channel threshold, filtering SOE、 Diagnostic function configuration
Supporting terminal: Dedicated T8 series 60 channel terminal base, divided into ordinary zone/intrinsic safety zone versions

7、 Lifecycle and Supply Status (2026)

Original factory status: EOL completely discontinued (Discontinued)
Rockwell has stopped the production of T8402 complete machine, and the original factory has no new product order channels; The original factory only retains limited paid maintenance services, which have long cycles and high costs.
Market supply: There is very little new inventory, and the mainstream is disassembled and refurbished spare parts, with a warranty period ranging from 3 to 12 months.
Alternative models: T8403/T8403CX (40 channel 24VDC TMR DI), new optimized drive and diagnostics, T8403CX is preferred for new projects.

8、 Typical application scenarios

Oil and gas industry: wellhead pressure switch, liquid level switch, compressor ESD interlock contact
Thermal power/thermal power: turbine trip signal, boiler furnace safety monitoring FSSS, auxiliary equipment protection switch
Fine Chemicals/Refinery: Reaction kettle over temperature and over pressure switch, toxic medium cut-off feedback, fire and gas detector contacts
Collection of safety switch signals for offshore platforms and pharmaceutical explosion-proof workshops

9、 Precautions for use

The dry contact circuit must enable line monitoring, otherwise cable breakage cannot be detected;
The total current of each group of 5 channels should not exceed the rated value to avoid group power overload;
The front end of the explosion-proof hazardous area must be equipped with intrinsic safety barriers and cannot be directly connected to on-site explosion-proof equipment;
It is recommended to enable 50Hz digital filtering for on-site long cables to eliminate erroneous displacement caused by induced voltage;
The new project directly uses T8403CX to avoid the risk of spare parts supply interruption in the later stage of T8402 shutdown.