1. Product Introduction & Overview

The Bently Nevada 3500/34 module is a specialized relay / timing module within the 3500 Machinery Protection System. Its role is to provide redundant, high‑availability relay outputs (often in a Triple Modular Redundant, TMR, configuration), or in some variants to act as a Keyphasor / timing reference input module. It is a critical component when elevated reliability or precise timing signals are required in a rotating machinery protection system.

In the TMR relay version, the 3500/34 uses three parallel internal relay paths and applies 2-out-of-3 voting to drive each external relay output channel. This design is intended for applications requiring extremely high availability, similar to what is demanded in safety instrumented systems.

Depending on the installed variant, 3500/34 may serve as a 4-channel relay with TMR logic or as a Keyphasor input / timing reference input module.

It is installed in the 3500 rack in the relay output position (to the right of the TDI module) and works together with monitor modules, speed / keyphasor modules, and other relay modules in the system.

2. Technical Specifications

Below is a table of known / typical values for the 3500/34 (TMR Relay version) based on manufacturer / supplier data. For variants (Keyphasor style) some specs differ — this table reflects the TMR relay module variant.

Variant (Keyphasor / Timing) Notes:
Some descriptions of 3500/34 modules list them as Keyphasor input modules, which accept signals from Keyphasor / proximity probes and generate a clean pulse per revolution. In those variants, the relay output functionality is replaced by signal conditioning, timing diagnostics, and distribution of the keyphasor pulse to other modules.

For those versions, input voltage ranges, signal conditioning, frequency range, and output pulse characteristics differ from TMR relay versions. The table above is oriented toward the TMR relay module variant.

3. Applications & Use Cases

• High-Availability Relay Output
  In safety-critical applications, the TMR design ensures continued operation even if one internal path fails. It is used in power plants, turbines, compressors, critical pumps, etc.

• Fault Tolerant Protection Logic
  The module supports 2-of-3 voting internally, helping to prevent single-fault failures from causing incorrect trips or missed trips.

• Redundant Control Systems
  Integrated into architectures where redundancy and fault detection are mandatory (e.g. in API / ISA / SIL-level systems).

• Keyphasor / Timing Distribution (in variant versions)
  Provides a clean once-per-turn reference to other vibration monitoring or diagnostic modules for phase, order tracking, and synchronous analysis.

• Relay Interfacing to External Systems
  Drives external shutdowns, alarm circuits, interlocks, or control logic in plant DCS / safety systems.

• Upgrades / Retrofits
  Replacing simpler (single relay) modules with TMR modules to improve system reliability without redesigning the entire rack or wiring.

4. Advantages & Strengths

• Redundancy by Design
  Triple internal relays with voting logic provide fault tolerance and elevated availability compared to standard relay modules.

• Fault Isolation and Detection
  The design can detect individual internal path failures and continue to operate, improving maintainability.

• Flexible Alarm Logic
  Supports AND, OR logic combinations of alarm inputs, allowing customized interlock schemes.

• Compact Integration
  Fits in the standard 3500 rack form factor, with front and rear I/O modules as needed.

• Robust Industrial Performance
  Rated for wide temperature and humidity ranges, sealed contacts, and industrial electromagnetic compatibility.

• True Safety-Grade Option
  In systems requiring high safety / reliability, the 3500/34 TMR module offers redundancy suited for those demands.

• Seamless 3500 Ecosystem Compatibility
  Fully compatible with 3500 monitors, TDI, speed modules, and logic modules.

• Reduced Risk of Single-Point Failures
  By internal redundancy, reduces the risk that a single relay contact failure leads to an unintended machine trip or system failure.

5. Related / Companion Modules (Same Series / System)

Here are five modules in the 3500 protection system that naturally pair with, or are related to, the 3500/34:

These modules represent the sensing, logic, speed reference, and output layers of a complete 3500 system in which 3500/34 can serve as a high-reliability output or timing reference.

6. Popular / Notable Modules in Same Brand

Below are five other widely used or well-known modules in the Bently Nevada / 3500 ecosystem: