Bently Nevada 3500/34 TMR Relay Module: Triple Modular Redundant Voting for Safety-Critical Machinery Protection
Overview
The Bently Nevada™ 3500/34 TMR (Triple Modular Redundancy) Relay Module is a high-integrity safety interface designed for applications demanding the highest levels of reliability and availability, comparable to Safety Instrumented Systems (SIS). As a cornerstone of the 3500 Machinery Protection System, this module translates critical machinery data into reliable alarm and shutdown signals, employing a 2-out-of-3 voting architecture to eliminate single-point failures and ensure uninterrupted protection even in the event of internal component faults.
Description
For applications requiring the extremely high reliability standards of ISA S84.01-1996 for Safety Instrumented Systems, the 3500 Machinery Protection System supports the TMR Relay Module configuration. The 3500/34 TMR Relay Module operates in conjunction with a special TMR Rack Interface Module and three monitor modules to provide 2-out-of-3 voting for inputs.
The TMR Relay Module system comprises two key components: two TMR Relay Modules and one TMR Relay I/O Module. When programmed, both TMR Relay Modules perform identical functions in parallel, effectively providing redundant support. Each relay within the module includes Alarm Drive Logic, programmed using AND/OR logic based on alarming inputs (Alert and Danger statuses), Not-OK signals, or individual Measured Variables from any monitor channel or combination of channels in the rack. The Alarm Drive Logic is configured using the Bently Nevada 3500 Rack Configuration Software.
Key Features and Benefits
Triple Modular Redundant Architecture: Three independent relay channels operate in parallel with majority voting logic, ensuring that a single channel fault does not affect output. Only when two or more channels agree on an abnormal condition does the relay actuate, eliminating false shutdowns in critical industrial applications.
2-out-of-3 Voting: The TMR Relay I/O Module contains 12 relays divided into four channel groups of three relays each, providing 2-out-of-3 relay voting for four relay channels.
Fault-Tolerant Design: If any data channel's OK status becomes NOT OK, the alarm contact signals associated with that channel are invalidated. If a TMR Relay Module is in a NOT OK state, its alarm contact signals are not detected, ensuring fault tolerance without compromising safety.
Programmable Alarm Drive Logic: Each relay channel's Alarm Drive Logic is programmed using AND and OR logic combinations, incorporating Alert, Danger, Not-OK, and individual Measured Variables from any monitor channel.
Epoxy-Sealed Relays with Arc Suppressors: Relays are epoxy-sealed and feature arc suppressors installed as standard. Relays can be programmed for normally energized or de-energized operation.
Rapid Response: Response time is under 15 ms from input signal to relay actuation, ensuring quick action to mitigate risks.
Technical Specifications
Parameter Specification
Model 3500/34 TMR Relay Module
Module Type: TMR (Triple Modular Redundancy) Relay Module
Power Consumption: 9.6 Watts typical
Relay Type: Three DPDT relays connected as SPST per channel
Number of Relay Channels: 4
Voting Logic 2-out-of-3
Operating Temperature -30°C to +65°C (-22°F to +150°F)
Storage Temperature -40°C to +85°C (-40°F to +185°F)
Humidity: 95%, non-condensing
Contact Life 100,000 operations @ 5A, 24 Vdc or 120 Vac
Relay Module Dimensions: 120.4 mm x 24.6 mm x 241.8 mm
Relay Module Weight: 0.34 kg (0.74 lb.)
I/O Module Dimensions 241 mm x 24.4 mm x 99.1 mm
I/O Module Weight: 0.5 kg (1.0 lb.)
Part Number Configuration
The 3500/34 TMR Relay Module system consists of:
Two TMR Relay Modules (3500/34)
One TMR Relay I/O Module (125696-01 or equivalent)
The module is designed for use in TMR racks and must be configured with a TMR Rack Interface Module and three monitor modules to function properly.
Applications
The 3500/34 TMR Relay Module is indispensable in industries where safety and reliability are paramount:
Nuclear Power Plants: Protect reactor coolant pumps by processing vibration and temperature data, triggering shutdowns only when all three TMR channels confirm critical conditions—preventing unnecessary reactor trips.
Offshore Oil and Gas Platforms: Safeguard subsea compressors where a single fault could lead to catastrophic consequences. ATEX certification ensures safe operation in hazardous zones.
Chemical Processing Facilities: Manage safety interlocks for agitators and reaction vessels handling toxic or flammable materials.
Steam and Gas Turbines: Provide reliable overspeed protection and emergency shutdown logic for critical turbomachinery.
High-Availability Machinery Protection: Support ISA S84.01-1996 compliant safety instrumented systems requiring extremely high reliability.
Installation and Configuration Notes
TMR Rack Requirement: The 3500/34 TMR Relay Module can only be configured to drive relays from channels in a TMR group and must be used with a TMR Rack Interface Module.
Module Composition: A complete 3500/34 TMR Relay Module consists of two half-height Monitors and one full-size I/O module. The two monitors are configured identically and perform the same monitoring function redundantly.
Alarm Drive Logic Programming: Use the Bently Nevada 3500 Rack Configuration Software to program AND/OR logic for each relay channel, selecting inputs from Alert, Danger, Not-OK, and individual Measured Variables as required.
Redundancy Configuration: Both TMR Relay Modules must be programmed to perform identical functions to provide effective redundant support.
3500/34-01
3500/34-01-00
3500/34-01-01
125696-01
125704-01
04425545
132317-01
00580438
129771-01
