Bently Nevada 3500/50 Tachometer Module (Part No. 3500/50-01-00)

Description

Bently Nevada 3500/50 Tachometer Module (Part No. 3500/50-01-00)

1. Product Introduction

The 3500/50-01-00 is a dual-channel Tachometer Module part of the Bently Nevada 3500 Series Machinery Protection System. It is a sophisticated input module that provides the machinery monitoring system with essential rotational speed data. The module accepts input from various proximity probes or magnetic pickups (Keyphasor® inputs) and generates proportional outputs for speed, RPM, and rotor acceleration (overspeed).

Key features of the “-01” option include the ability to configure “Peak Hold” functionality and to process 2 out of 3 voting logic when used in redundant configurations (if supported by the specific firmware revision and application). It converts the raw signal from transducers into digital values that can be used for alarms, machine trips, and data acquisition.

350050 288062-02

2. Main Technical Specifications

• Model Number: 3500/50 (Tachometer Module)
• Option: 01 (Tachometer Module with Peak Hold and specific logic capabilities)
• Inputs:
  • Channels: 2 independent input channels.
  • Signal Types:
    • Proximitor (Non-contacting displacement sensors) -4 to -24 VDC signal.
    • Magnetic Pickup (Variable reluctance) – AC voltage signal.
    • Digital Input (TTL/CMOS levels).
• Frequency / Speed Range:
  • Input Frequency: 0.05 Hz to 20 kHz (covers very low to high-speed machinery).
  • Speed Range: Programmable (e.g., 0 to 20,000 RPM).
• Relay Outputs:
  • Configured via 3500/34 or 3500/33 Relay Modules (or 3500/32M) depending on rack configuration.
  • Supports Alarm Danger (Alert) and Danger setpoints.
• Accuracy: Typically ±0.01% of reading or 1 RPM (whichever is greater) within specified range.
• Power Requirements:
  • Powered via the 3500 Rack Internal Backplane (5 VDC).
• Time Base: Crystal-controlled oscillator for high precision.

3. Typical Applications

The 3500/50-01-00 is versatile and serves critical roles in rotating machinery management:

• Overspeed Protection: Critical protection for Steam Turbines, Gas Turbines, and Large Compressors. The module constantly monitors RPM and can trigger a machine shutdown if speed exceeds safe limits.
• Keyphasor® Reference: Providing a precise “once-per-revolution” trigger for the monitoring system to phase-reference vibration data (1X vector analysis).
• Speed Control: Feeding analog 4-20mA or relay outputs to control systems (DCS/PLC) for governor speed reference.
• Gearbox Monitoring: Monitoring multiple shaft speeds in gearboxes where different stages run at different speeds (using two channels).

4. Avoid Technical Pitfalls (Best Practices & Warnings)

• Input Signal Compatibility: The module can be configured for Proximitor or Magnetic Pickup, but you must configure the jumpers/software settings correctly. Applying a high-voltage magnetic pickup signal to a channel configured for a low-voltage Proximitor input (or vice versa) can result in no reading or damaged input circuits.
• Trigger Level Setup: If using a magnetic pickup, the trigger level (threshold) must be carefully adjusted in the software. If set too high, the module will miss teeth at low speeds; if set too low, electrical noise will be counted as “speed,” causing false alarms.
• Overspeed Voting Logic: If using this for overspeed protection, ensure it is integrated correctly with the voting logic (e.g., 2-out-of-3). The -01 module has specific firmware capabilities; verify if your application requires dedicated 3500/53 overspeed modules for safety-critical SIL-rated applications.
• Missing Pulse Detection: Ensure “Zero Speed” or “Missing Tooth” detection is disabled if not intended. A dirty probe or irregular gear surface can cause the module to interpret a missing tooth as a dangerous zero-speed or erratic RPM event.
• Backplane Compatibility: Ensure the rack firmware is compatible with the 3500/50-01-00. Older racks may require a firmware upgrade to recognize the module.

5. Related Product Recommendations

• Transducers:
  • 3300 XL 8mm Probes (e.g., 330103) + Proximitor (e.g., 330180) for high-accuracy Keyphasor signals.
  • Magnetic Pickups (e.g., 190950 or 77665) for general speed sensing in harsher environments.
• Relay Modules: 3500/34 (TMR Relay) or 3500/33 (Standard Relay) to execute the hardware trip contact outputs.
• Communication Modules: 3500/22M (Transient Data Interface) for transmitting RPM data to host software.
• Power Supply: 3500/15 (High Voltage Power Supply) to ensure stable rack operation.
• Software: 3500 System Configuration Software for setting RPM setpoints and trigger levels.