Description
Processing rotational speed signals within the 3500 machinery protection architecture, the Bently Nevada 3500/50-04-00 operates as a high-precision tachometer module designed to accept input from proximity probes or magnetic pickups. This module measures shaft rotational speed, rotor acceleration, and reverse rotation, conditioning these inputs to drive alarms and provide critical overspeed protection. The 3500/50-04-00 model variant features an I/O module with internal barriers and internal terminations, providing built-in intrinsic safety for transducers located in hazardous industrial environments without requiring external barrier cabinets.
Features
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Comprehensive Speed Metrics: Continuous monitoring of machine RPM, zero-speed detection, rotor acceleration, and reverse rotation indicators.
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Integrated Intrinsic Safety: Equipped with internal barriers that isolate field wiring, eliminating the footprint and cost of external isolation barriers.
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Multi-Transducer Compatibility: Direct interface capability with Bently Nevada Proximitor sensors, magnetic pickups, and active shaft-speed encoders.
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Flexible Alarm Logic: Dynamic alarm configuration (Alert and Danger) via 3500 configuration software, supporting latching or non-latching parameters.
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On-Board Diagnostics: Real-time self-test functions that continuously monitor transducer loop integrity and point out circuit faults.
Applications
- Overspeed protection and RPM monitoring of utility steam turbines.
- Critical speed and reverse rotation tracking in large centrifugal compressors.
- Hydroelectric generator speed sensing and start-up sequence interlocking.
- High-speed turboexpander and industrial gas turbine protection systems.
Ordering Information
| Option Code |
Description |
| 3500/50 |
Tachometer Module (Main Monitor Board) |
| -04 |
I/O Module with Internal Barriers and Internal Terminations |
| -00 |
Agency Approval: None / Pending |
Technical Specifications
| Parameter |
Specification Value |
| Manufacturer |
Bently Nevada |
| Part Number |
3500/50-04-00 |
| Module Type |
Tachometer Module with Internal Barriers |
| I/O Configuration |
Internal Terminations, Internal Safety Barriers |
| Main Board Dimensions |
241.3 mm x 24.4 mm x 241.8 mm |
| I/O Module Dimensions |
241.3 mm x 24.4 mm x 163.1 mm |
| Module Weight |
1.28 kg |
| Shipping Weight (Calculated) |
3.00 kg |
| Country of Origin |
United States |
Connections and Interfaces
| Terminal Group |
Function Assignment |
| Ch 1 / Ch 2 / Ch 3 / Ch 4 |
Independent speed/proximity probe input channels |
| PWR / COM / SIG / SHLD |
Transducer power supply (-24 Vdc), common return, input signal, and shield ground |
| REC OUT |
Buffered transducer analog output signals for external diagnostic recorders |
Empirical Engineering Insights
Alternative Models & Compatibility
The 3500/50-04-00 with internal barriers cannot be hot-swapped into a backplane slot configured for non-barrier I/O (such as the standard 3500/50-01-00) without first updating the rack configuration. Attempting to run a mismatch between physical I/O type and software definitions triggers a configuration fault in the 3500 Rack Interface Module (RIM).
Application Pitfalls & Engineering Notes
Internal barrier loops introduce a fixed, series current-limiting resistance. When pairing this module with long field cable runs (exceeding 300 meters), calculate the total loop resistance to ensure the signal voltage does not drop below the minimum trigger threshold of the tachometer input circuitry, especially at high rotational frequencies.
Commissioning & Wiring Tips
Always verify the transducer type (Proximitor vs. Magnetic Pickup) using the 3500 Configuration Software before applying power to the field loop. Selecting the incorrect sensor type can cause the internal barrier to trip or limit current, leading to persistent "Not OK" status indications on the tachometer front panel.
Installation Guidelines
CRITICAL WARNING
Isolate and de-energize the entire 3500 instrument rack and all associated field loops before inserting or removing the 3500/50-04-00 module. Failure to de-energize can damage sensitive internal barrier circuitry and compromise explosive-area safety ratings.
1
Verify that the physical keying pegs on the rear of the 3500 rack correspond to the correct option slots for the Tachometer Module and its I/O baseboard.
2
Slide the main monitor board into the front guide rails of the rack, and secure it firmly using the captive chassis screws.
3
Mount the internal barrier I/O module into the corresponding slot on the rear panel of the rack, securing the module with its mounting fasteners.
4
Connect field wiring to the screw terminal blocks, ensuring that transducer shields are terminated according to Bently Nevada grounding standards.