Product No.: 3500/45 176449-04 + 135137-01 - General Introduction
This product is a complete Thrust Position (Axial Displacement) Monitoring Channel for the Bently Nevada 3500 Machinery Protection System. It is designed to continuously and accurately measure the axial movement of a rotor relative to its thrust bearing, a critical parameter for preventing catastrophic damage in rotating machinery.
3500/45: This is the Axial Position Monitor Module (a slot-in card for the 3500 rack). It conditions the signal from two opposing eddy current proximity probes to compute the rotor's axial position and differential expansion.
176449-04: This is the specific hardware revision part number for the monitor module. The "-04" suffix denotes a specific version with defined firmware, component set, and calibration.
135137-01: This is a high-quality, shielded, triaxial extension cable assembly. It is specifically designed to connect two eddy current probes (for differential measurement) to the single 3500/45 module channel, ensuring signal integrity and matched electrical characteristics.
Detailed Parameters
| Parameter Category | Specification | Details / Notes |
|---|---|---|
| System Function | Differential Axial Position (Thrust) Monitoring | Measures the dynamic and static axial position of a rotor using two probes observing opposite sides of a thrust collar or shaft shoulder. |
| Monitor Module (3500/45) | ||
| Module Type | 3500/45 - Axial Position Monitor | Typically a single-slot module in a 3500 rack. |
| Module Dimensions | H: 318.0 mm W: 20.0 mm D: 193.0 mm | Standard single-slot module size. |
| Module Weight | Approx. 0.5 - 0.7 kg | |
| Input Channels | One (1) Differential Channel | Accepts signals from two opposing eddy current probes via a single, dedicated cable assembly. |
| Measurement Range | Typically 0 to 2.0 mm (0 to 80 mils) of differential displacement. | Configurable via software. Can monitor both position and rate-of-change. |
| Keyphasor® Input | Required (from 3500/25). | Used to synchronize axial position data with rotational phase, helping diagnose tilt or thermal bow. |
| Outputs | • 4-20 mA analog output (proportional to position) • Danger & Alert Relay Outputs (for position and velocity) • OK Relay Output • Buffered Raw Signals | Relays can be set for excessive position (e.g., thrust bearing wear) or sudden velocity (e.g., shock). |
| Extension Cable (135137-01) | ||
| Cable Type | Triaxial, double-shielded, PTFE-insulated. | Contains three inner conductors: two for probe signals (+/- for each probe) and one for common power/signal return. Essential for noise immunity in differential measurement. |
| Cable Length | Defined by "-01" suffix (e.g., 5m, 7.5m, 10m). | Common standard length. Must be matched to probe cables to meet total system resistance requirements. |
| Connectors | One (1) module-end connector (to 3500/45) and Two (2) field-end connectors (to each probe). | Typically robust, threaded military-style (MS) connectors for vibration-proof connections. |
| Overall Loop Resistance | Precisely matched as part of the total transducer loop with the probes and monitor. | Critical for accurate calibration and scaling (mV/mil or mV/µm). |
| Probe System (Implied) | Two matched 8mm or 11mm Eddy Current Probes (e.g., 330101-00-XX-10-01-00 type). | Not included in this part number but required to complete the loop. Must be ordered separately. |
| System Scale Factor | Typically 200 mV/mil (7.87 mV/µm) for the complete loop (probes + cable + monitor). | Standard sensitivity. Verified during commissioning. |
| Primary Application | Thrust Bearing Wear Monitoring and Rotor Axial Clearance Protection. |
Primary Application Scenarios
This system is critical for protecting any machine with a significant axial load, where rotor axial movement must be strictly controlled.
Steam & Gas Turbine Thrust Bearing Protection:
Primary Application: Monitors the position of the turbine rotor relative to its thrust bearing to detect wear. A sustained movement in one direction indicates bearing wear, while a sudden large movement indicates a possible thrust bearing failure. The Danger relay typically initiates an emergency shutdown.
Centrifugal & Axial Compressor Surge Prevention:
Monitors axial rotor movement which can be a precursor to or a result of surge. Sudden axial displacement during a surge event can be detected to trigger anti-surge control responses or alarms.
Large Pump and Fan Monitoring:
Protects against axial thrust imbalance in single-stage, double-suction, or multi-stage pumps and fans. Detects rotor float due to hydraulic imbalance or impeller wear.
Hydroelectric Generator Thrust Bearing Monitoring:
Measures the axial position of the massive generator and turbine rotor under tremendous hydraulic thrust load, ensuring the thrust bearing is functioning correctly and the rotor is properly positioned.
Integrated Machinery Diagnostics:
By comparing axial position with radial vibration (3500/42) and differential expansion data, engineers can diagnose issues such as thermal binding, coupling misalignment, or casing distortion. The differential measurement cancels out common-mode effects like thermal growth of the stator, providing a true rotor-centric position.
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7×24 hours technical consultation, from selection guidance to installation and commissioning to provide full life cycle service (paid)
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