Bently Nevada 3500/34 TMR Relay Module – API 670 Compliant Protection

Brand ABB

Model Bently 3500/34

Product Overview

The Bently Nevada 3500/34 is a Triple Modular Redundant (TMR) Relay Module engineered for the most demanding machinery protection applications within the 3500 Monitoring System. Unlike conventional relay modules that rely on a single output path, the Bently Nevada 3500/34 employs a fundamentally different architecture: each of its four relay channels is driven by three independent relays, creating a 3-out-of-2 (3oo2) voting scheme that ensures a trip signal is generated only when at least two of the three redundant channels agree . This design philosophy directly addresses the stringent reliability requirements of Safety Integrity Level 3 (SIL 3) applications, where a failure to trip during a dangerous event could result in catastrophic equipment damage or personnel injury.

The Bently Nevada 3500/34 operates in conjunction with a TMR Rack Interface Module and three monitor modules configured as a TMR set, ensuring that alarm signals from the monitoring channels are delivered through three independent data paths . Within this architecture, the TMR Relay Module evaluates each data path separately, generating three discrete alarm contact signals that are then routed to the TMR Relay I/O Module. The I/O module houses twelve relays organized into four channel groups of three, where each group performs the 3oo2 voting function that defines the module’s safety character .

A critical operational safeguard built into the Bently Nevada 3500/34 is its handling of data path integrity. If any single data channel reports a NOT OK status, the alarm contact signals associated with that channel are automatically invalidated, preventing a single faulty channel from compromising the voting logic . The module is also designed for hot-swappability within the 3500 rack, allowing maintenance personnel to replace a Bently Nevada 3500/34 without interrupting the operation of unrelated modules—though external trip circuits must be bypassed beforehand to prevent unintended shutdowns .

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Description

Technical Specifications

Parameter Name	Parameter Value
Product Model	Bently Nevada 3500/34
Manufacturer	Bently Nevada (Baker Hughes)
Product Type	Triple Modular Redundant (TMR) Relay Module
Relay Channels	4 Channels (each with 3oo2 voting)
Relay Type per Channel	3 × DPDT relays connected as SPST
Voting Logic	3-out-of-2 (3oo2)
Contact Life	100,000 operations @ 1.5 A, 24 VDC or 1 A, 120 VAC
Arc Suppression	Not supported
Alarm Drive Logic	Programmable AND/OR logic via 3500 Rack Configuration Software
LED Indicators	6 LEDs: OK, TX/RX, CH ALARM (per channel)
Rack Compatibility	3500 Series Full-Size and Mini Racks
Operating Temperature	-30°C to +65°C (-22°F to +149°F)
Storage Temperature	-40°C to +85°C (-40°F to +185°F)
Humidity	5% to 95% Non-Condensing
Compliance	API 670, SIL 3 Capable
Hot-Swap Support	Yes (with external trip bypass)
Contact Sealing	Epoxy Sealed

Main Features and Advantages

The Bently Nevada 3500/34 distinguishes itself through a safety architecture that prioritizes reliability above all else, making it the definitive choice for applications where a missed trip is not an option.

Triple Redundant 3oo2 Voting Architecture: The defining feature of the Bently Nevada 3500/34 is its use of three independent relays per channel to drive a single output. This 3-out-of-2 voting scheme means that the module tolerates the failure of any single relay or data path without compromising its ability to trip when a genuine dangerous condition exists. The Bently Nevada 3500/34 thus eliminates the single point of failure inherent in conventional relay modules, delivering the fault tolerance required for SIL 3 safety instrumented functions .

Automatic Channel Invalidation on Fault: When any of the three data channels feeding the Bently Nevada 3500/34 reports a NOT OK condition, the alarm contacts associated with that specific channel are automatically invalidated. This intelligent diagnostic behavior prevents a degraded channel from contributing to the voting logic, ensuring that the 3oo2 decision remains valid even during partial system degradation .

Programmable Alarm Drive Logic: The Bently Nevada 3500/34 supports user-programmable alarm drive logic that can combine alarm signals from any monitor channel or multiple monitor channels within the 3500 rack. Using AND/OR logic programmed through the 3500 Rack Configuration Software, engineers can define complex trip conditions that reflect the specific protection requirements of the machinery being monitored .

Hot-Swappable Rack Integration: Like all modules in the 3500 platform, the Bently Nevada 3500/34 supports removal and insertion while the rack remains powered. This capability minimizes downtime during maintenance or module replacement, though proper procedures—including external trip circuit bypass—must be followed to prevent spurious shutdowns .