3500/25 (128718-01) Monitoring System Module
Description:
The 3500/25, also known by the alternate part number 128718-01, is a Keyphasor Module for the Bently Nevada 3500 Machinery Monitoring System. This module is a fundamental component for providing a timing reference based on the rotation of a shaft.
Its primary function is to process the signal from one or two Keyphasor transducers (typically proximity probes or magnetic pickups). It generates a sharp electronic pulse for each revolution of the shaft. This Keyphasor pulse is the critical timing benchmark used by other modules in the 3500 system (like vibration monitors) to measure rotational speed (RPM) and vibration phase lag. Phase and speed information are essential for diagnosing rotor dynamics issues and performing field balancing.
Parameters & Specifications
The following table details the key parameters for this module.
| Parameter | Specification |
|---|---|
| Primary Part Number | 3500/25 |
| Alternate Part Number | 128718-01 |
| Module Type | Keyphasor Module |
| Compatibility | Bently Nevada 3500 Rack Frame |
| Slot Requirement | Single Slot |
| Typical Dimensions (H x W x D) | Approx. 193 mm x 27 mm x 170 mm (7.6 in x 1.06 in x 6.7 in) |
| Typical Weight | Approx. 0.3 kg (0.66 lbs) |
| Input Channels | 2 independent Keyphasor input channels |
| Input Types | Accepts signals from eddy current proximity probes and magnetic pickups. |
| Speed Measurement Range | From 0 RPM (standstill) to typically 60,000 RPM or higher, depending on the transducer. |
| Keyphasor Output | Provides a once-per-revolution pulse to other modules in the 3500 frame via the backplane. |
| Alarm Relays | Per-channel alarms for signal failure (OK Alarm) |
| Power Supply | Powered by the 3500 system backplane |
| Operating Temperature | -30°C to +65°C (-22°F to 149°F) |
| Primary Function | To provide a speed and phase reference for the monitoring system. |
*Note: The exact dimensions and weight are approximate. For precise mechanical and electrical specifications, always refer to the official Baker Hughes 3500/25 Keyphasor Module Documentation.*
Application Scenarios
The 3500/25 Keyphasor Module is deployed in virtually every application where the 3500 system is used to monitor turbomachinery. Its reference signal is the cornerstone for advanced diagnostics.
Vibration Phase Measurement: This is the most critical application. The Keyphasor pulse allows the system to measure the phase angle of vibration, which is indispensable for:
Field Balancing: Determining the magnitude and angular location of imbalance weights.
Diagnosing Rotor Faults: Identifying issues like misalignment, cracked shafts, and rotor rubs based on phase behavior.
Rotational Speed (RPM) Measurement: Provides an accurate and reliable measurement of shaft speed, which is a fundamental process variable for machine operation and protection.
Startup and Coast-down Analysis (Transient Analysis): The Keyphasor signal enables the capture of Bode plots (Amplitude vs. Speed, Phase vs. Speed) and Polar plots during machine start-ups and shutdowns. This is crucial for identifying critical speeds and understanding the rotor's dynamic response.
Synchronous Time Sampling: Provides a synchronous clock signal to vibration monitors, ensuring that vibration waveforms are captured consistently once per revolution. This allows for detailed analysis of the vibration shape and frequency.
Tachometer Reference for Control Systems: The Keyphasor signal often serves as the primary speed input for other plant systems, such as a Turbine Control System or a PLC.
Typical Machinery:
Steam Turbines & Gas Turbines
Centrifugal & Axial Compressors
Large Pumps and Fans
Turbo-generators and Expanders
Any critical rotating machine where knowledge of speed and phase is required for protection or diagnosis.
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