TMR Relay Module

For applications requiring extremely high availability, comparable to Safety Instrumented Systems (SIS) as defined in ISA S84.01-1996, the Bently Nevada 3500 Machinery Protection System supports a Triple Modular Redundant (TMR) Relay Module.

The TMR Relay Module employs three independent relays to drive a single logical relay output. Operating in conjunction with a dedicated TMR Rack Interface Module and three monitor modules, the system implements 2-out-of-3 (2oo3) voting on input signals to achieve high reliability and fault tolerance.

Alarm Drive Logic

Each relay on the TMR Relay Module incorporates Alarm Drive Logic, which is user-programmable using AND / OR logic.

Alarm Drive Logic can utilize:

Alert and Danger signals from any monitor channel, or

Combinations of multiple monitor channels within the rack

Logic configuration is performed using the 3500 Rack Configuration Software, allowing customization to meet specific application and safety requirements

TMR Relay I/O Module

The TMR Relay I/O Module contains 12 relays, organized into four relay channels, with three relays per channel.

Relay Channel Architecture

Each 4-channel group provides 2-out-of-3 relay voting

For each relay channel:

The TMR Relay Module supplies three Alarm Contact Signals

Each Alarm Contact Signal drives one relay within the channel group

The voting arrangement ensures that a valid output is generated only when at least two of the three relays are energized

Module Health Monitoring

Each TMR Relay Module continuously reports an OK status, which is evaluated by the TMR Relay I/O Module.

If a TMR Relay Module is NOT OK:

The TMR Relay I/O Module excludes Alarm Contact Signals from that module

Voting logic continues using the remaining healthy modules, maintaining system integrity

Key Benefits

High availability through Triple Modular Redundancy (TMR)

2oo3 voting for both inputs and relay outputs

Flexible, software-configurable alarm logic

Fault tolerance with automatic exclusion of failed modules

Designed for critical machinery protection applications

BENTLY 3500/34 TMR Relay Module