Component Description
The part number 3500/32 125720-02+125712-01 refers to a specific configuration of modules for the Bently Nevada 3500 Monitoring System.
3500/32: This designates a Dual-Channel Displacement/Position Monitor Module. This module is designed to monitor the DC (static) gap voltage from eddy current proximity probes to measure the relative position of a machine's rotor. Key measurements include axial thrust position and radial position (eccentricity).
125720-02: This is a specific hardware revision or assembly number for the Displacement/Position Monitor Module.
125712-01: This is a Relay Module. This module provides physical relay outputs that are actuated based on alarm statuses received from the monitoring modules within the 3500 rack.
In summary, this part number represents a Dual-Channel Displacement/Position Monitor Module paired with a Relay Module. This combination provides continuous monitoring of critical rotor positions (like thrust bearing wear) and the ability to execute immediate protective actions (like tripping the machine) through relay outputs if the rotor moves to a dangerous position.
Key Parameters
The following table outlines the key parameters for this module configuration.
| Parameter | Specification |
|---|---|
| System | Bently Nevada 3500 |
| Primary Function | Rotor Position Monitoring & Protective Relay Output |
| Channels | Two independent displacement/position channels. |
| Input Signal | Conditioned DC voltage from a Proximitor Module (e.g., 3500/40) representing probe gap. |
| Measurement Capabilities | Axial Thrust Position, Radial Position (Eccentricity), Differential Expansion, Valve Position, etc. |
| Alarm Functions | Per channel: Two programmable alarm setpoints (usually Alert and Danger) for each direction of movement. |
| Relay Outputs | Typically 4 or 6 independent, configurable Form-C relays (dependent on the specific relay variant). |
| Relay Contacts | SPDT (Single Pole Double Throw), often rated for 2A @ 30VDC or 250VAC. |
| Mounting | Slides into dedicated slots in a 3500 rack. |
| Dimensions (H x W x D) | Approx. 193 mm x 55 mm x 200 mm (7.6 in x 2.16 in x 7.87 in) per module |
| Weight | Approx. 0.5 - 0.7 kg (1.1 - 1.5 lbs) per module |
Application Scenarios
This module configuration is critical for protecting machinery from severe damage caused by excessive rotor movement in the axial or radial plane.
Thrust Bearing Monitoring:
Application: Steam Turbines, Centrifugal Compressors.
Function: Monitors the axial position of the rotor within its thrust bearings. The module will trigger alarms and, via the relay module, initiate a machine shutdown if the rotor moves beyond safe limits, preventing catastrophic thrust bearing failure and rotor-stator rubs.
Rotor Eccentricity Monitoring:
Application: Large Steam Turbines.
Function: Measures shaft bow or sag when the machine is on turning gear (at low speeds). High eccentricity can indicate a bent rotor or thermal bow. The system can prevent a high-speed startup if the eccentricity is too high, avoiding potential vibration damage.
Differential Expansion Monitoring:
Application: Steam Turbines.
Function: Monitors the difference in thermal growth between the rotor and the stator (casing) during startup, shutdown, and load changes. Excessive differential expansion can lead to damaging internal rubs. The relay module can trip the turbine if clearances become too small.
Valve Position Monitoring:
Application: Various industrial processes.
Function: Can be used to monitor the precise position of critical valves by using a proximity probe to track the valve stem position, providing feedback and alarm capability to the control system.
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