Product Description

The 3500/25 (Enhanced Keyphasor Module) is a half-height, two-channel module designed to provide critical phase reference signals to the Bently Nevada 3500 Machinery Protection System. This specific assembly includes the main module 149369-01 paired with the 125800-01 I/O module, featuring internal terminations for simplified wiring. It accepts inputs from proximity probes or magnetic pickups and converts them into digital Keyphasor signals, which are essential for synchronous vibration measurements and vector analysis.

Unlike standard monitors, the 3500/25-01-05-05 acts as the system’s primary timing reference. It distributes conditioned pulses across the rack backplane, allowing vibration monitors—such as the 3500/42M or 3500/40M—to calculate phase angles (1X, 2X, etc.) and perform precise "once-per-turn" tracking. This is foundational for identifying rotor imbalances, misalignments, and other dynamic mechanical faults. The enhanced version offers improved signal processing capabilities over legacy Keyphasor cards, supporting a vast frequency range from 0.016 Hz up to 100 kHz for high-speed aero-derivative turbines and low-speed hydro-generators.

Technical Specifications

• Model Number: 3500/25

• Ordering Code: 3500/25-01-05-05 (Enhanced Version)

• Main Module PN: 149369-01

• I/O Module PN: 125800-01

• Manufacturer: Bently Nevada (Baker Hughes)

• Channel Configuration: 2-Channel (Dual independent inputs)

• Termination Type: Internal Terminations (Option 01 I/O)

• Input Signal Acceptance: Proximity probes (Non-contacting) or Magnetic Pickups

• Frequency Range: 0.001 to 1,200,000 cpm (0.016 Hz to 20 kHz) standard; up to 100 kHz

• Signal Conditioning: Raw signal to TTL-compatible digital pulse conversion

• Redundancy Support: Keyphasor signals can be shared across multiple racks

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

• Dimensions: 228 mm x 50 mm x 289 mm

• Weight: 0.9 kg (2 kg shipping weight)

• Compliance: API 670 Machinery Protection standard

• Certifications: CE, CSA, ATEX, and country-specific approvals (CN option)

Application & Comparative Logic

The 149369-01 + 125800-01 assembly is a staple in petrochemical plants and power stations where synchronous data acquisition is mandatory for critical rotating machinery. While the 3500/50M Tachometer focuses on displaying and alarming on RPM, the 3500/25 is the "heartbeat" provider for phase-locked analysis. Without the Enhanced Keyphasor Module, advanced diagnostics like Bode plots and polar plots—necessary for assessing machine startup and coast-down behavior—would be impossible. The Enhanced version ensures higher signal integrity and noise immunity in complex electromagnetic environments.

Frequently Asked Questions

Can one 3500/25 module drive multiple racks?Yes. Keyphasor signals generated by the 3500/25-01-05-05 can be "daisy-chained" or distributed to other 3500 racks using the buffered outputs on the I/O module, ensuring all racks share the same phase reference.

What is the benefit of the Internal Termination I/O module (125800-01)?The internal termination option allows field wiring to be connected directly to the module’s terminal blocks at the rear of the rack, eliminating the need for external termination blocks and reducing cabinet space requirements.