Product Description

The 3500/50M (Part Number 286566-02) is a high-precision, 2-channel Tachometer Module designed for the Bently Nevada 3500 Series Machinery Protection System. This module is engineered to accept input from proximity probes or magnetic pickups to provide continuous shaft speed monitoring, rotor acceleration data, and rotor direction detection. It acts as a critical component in the protection of turbines, compressors, and large industrial motors, where precise speed measurement is vital for both operational control and safety shutdown protocols.

Beyond simple RPM monitoring, the 286566-02 supplies conditioned Keyphasor® signals to the 3500 rack backplane, allowing other monitor modules (such as vibration and position monitors) to perform phase-locked data acquisition. The module features advanced programmable alarming, including zero-speed notification, speed band alarms, and reverse rotation detection. This ensures that any deviation from safe rotor dynamics is immediately identified, protecting high-value rotating assets from mechanical failure or catastrophic overspeed events.

Technical Specifications

• Model Number: 3500/50M

• Part Number: 286566-02

• Manufacturer: Bently Nevada (Baker Hughes)

• Channels: 2 Independent Tachometer Channels

• Input Signal Range: +10.0 V to –24.0 V (supports Proximitor* and Magnetic Pickups)

• Measurement Functions: Shaft Speed (RPM), Rotor Acceleration, Rotor Direction

• Alarm Types: Over/Under Speed, Speed Band, Zero Speed, Reverse Rotation

• Keyphasor® Output: Supplies conditioned signals to rack-resident modules

• Input Impedance: 20 kΩ (standard)

• Power Consumption: 5.8 Watts typical

• Operating Temperature: -30 °C to +65 °C (-22 °F to +149 °F)

• Physical Dimensions: 241 mm x 24.4 mm x 242 mm (Standard 3500 Rack Slot)

• Shipping Weight: 1.1 kg (Module and packaging)

• Compliance: API 670 Machinery Protection standard

System Role & Comparative Logic

In a standard machinery protection configuration, the 3500/50M plays a complementary role to vibration monitors like the 3500/42E. While vibration modules track the physical displacement and stability of the shaft, the 286566-02 provides the temporal reference (speed and phase) required for advanced diagnostics. It is typically installed in the rack alongside other I/O modules to ensure a complete picture of rotor dynamics. In petrochemical and power generation facilities, this synchronization is essential for accurate balancing and vibration analysis during machine startup and coast-down cycles.

Frequently Asked Questions

Can the 3500/50M detect if a shaft starts rotating in the wrong direction?Yes. When configured with two transducers monitoring the same gear or shaft, the 286566-02 can identify the phase sequence to trigger a reverse rotation alarm, preventing damage to pumps or compressors not designed for backward flow.

Does this module require a specific I/O module?Yes. The 286566-02 main module must be paired with a compatible 3500/50M I/O module (such as the 133442-01 or 133458-01) at the rear of the rack to facilitate physical sensor wiring and terminal connections.