Bently Nevada 3500/50-04-00 3500 Series Tachometer Module

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

• Comprehensive Speed Metrics: Continuous monitoring of machine RPM, zero-speed detection, rotor acceleration, and reverse rotation indicators.
• Integrated Intrinsic Safety: Equipped with internal barriers that isolate field wiring, eliminating the footprint and cost of external isolation barriers.
• Multi-Transducer Compatibility: Direct interface capability with Bently Nevada Proximitor sensors, magnetic pickups, and active shaft-speed encoders.
• Flexible Alarm Logic: Dynamic alarm configuration (Alert and Danger) via 3500 configuration software, supporting latching or non-latching parameters.
• 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

Technical Specifications

Connections and Interfaces

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