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- Bently Nevada
- 21504-000-040-10-02
- 7200 Series 8 mm Standard Mount Proximity Probe
- USA
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Product Overview
The Bently Nevada 21504-000-040-10-02 is a 7200 Series 8 mm Standard Mount Proximity Probe used for non-contacting measurement of shaft vibration and displacement in rotating machinery. It operates as the sensing element of an eddy-current proximity transducer system, detecting changes in the distance between the probe tip and a conductive target, typically a rotating machine shaft.
The probe features an 8 mm sensing tip and a standard threaded mounting configuration. Its 3/8-24 UNF mounting thread allows it to be installed in a suitable threaded mounting point near the monitored shaft. The probe has a 1-meter total length and a miniature male coaxial connector for connection to the associated transducer electronics.
In a steam turbine installation, for example, the probe can be positioned near a journal bearing to measure radial shaft vibration. As the shaft rotates, small changes in the distance between the probe tip and shaft surface produce corresponding changes in the electrical measurement signal. The monitoring system uses this information to evaluate shaft movement and identify abnormal vibration conditions.
The 21504-000-040-10-02 belongs to the Bently Nevada 7200 Proximity Transducer Systems family. It works with a compatible extension cable and Proximitor driver to form a complete measurement circuit. The probe itself performs the sensing function, while the associated driver processes the signal and supplies the output required by the monitoring equipment.
For replacement applications, particular attention should be paid to the 8 mm probe diameter, standard mounting arrangement, 3/8-24 UNF thread, overall case length, cable length, and connector configuration. These details determine whether the probe can be installed correctly and operate with the existing 7200 measurement system.
Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Bently Nevada |
| Model | 21504-000-040-10-02 |
| Product Series | 7200 Series |
| Product Family | 7200 Proximity Transducer Systems |
| Product Type | 8 mm Standard Mount Proximity Probe |
| Probe Part Number | 21504 |
| Probe Tip Diameter | 8 mm |
| Mounting Configuration | Standard Mount |
| Mounting Thread | 3/8-24 UNF-2A |
| Cable Armor | No |
| Unthreaded Length Code | 000 |
| Overall Case Length Code | 040 |
| Total Length | 1 meter |
| Connector Type | Miniature Male Coaxial Connector |
| Measurement Technology | Eddy Current |
| Measurement Principle | Non-contacting proximity measurement |
| Calibrated Range | 2.0 mm (80 mils) |
| Starting Measurement Distance | Approximately 0.25 mm (10 mils) |
| Scale Factor | 7.87 V/mm (200 mV/mil) |
| Frequency Response | 0 to 10 kHz |
| Supply Requirement | -17.5 to -26 V DC (system driver) |
| Maximum System Current Consumption | 12 mA |
| Weight | 0.22 kg |
Product Features
- 7200 Series 8 mm Probe: Suitable for non-contacting shaft vibration and displacement measurement.
- Standard Mount Configuration: Uses a 3/8-24 UNF-2A threaded mounting arrangement.
- 8 mm Probe Tip: Provides the sensing interface for eddy-current measurement.
- 1-Meter Total Length: Suitable for installations requiring the specified probe length.
- Miniature Male Coaxial Connector: Connects the probe to the compatible transducer cable arrangement.
- Unarmored Cable: Uses a non-armored probe cable configuration.
- 2.0 mm Calibrated Range: Supports shaft displacement measurement within the specified calibrated range.
- 7.87 V/mm Scale Factor: Provides the nominal measurement sensitivity for the compatible 7200 system.
- Wide Frequency Response: Supports dynamic shaft vibration measurement up to 10 kHz.
- Non-Contacting Operation: Measures shaft movement without physical contact with the rotating component.
- Industrial Machinery Monitoring: Suitable for compatible turbine, compressor, pump, and generator installations.
Product Working Principle
The 21504-000-040-10-02 operates through the eddy-current measurement principle. It detects changes in the distance between its sensing tip and a conductive target without requiring direct contact with the rotating component.
The probe is normally installed near a shaft surface using its standard threaded mounting arrangement. When connected to a compatible 7200 Proximitor driver, the probe forms part of an electromagnetic measurement circuit.
The measurement process follows this sequence:
Rotating Shaft → 21504 Proximity Probe → Extension Cable → Proximitor Driver → Machinery Monitoring System
The probe generates an electromagnetic field around its sensing tip. When the probe is positioned near a conductive shaft, eddy currents develop within the target material. Changes in the distance between the probe and shaft affect the electrical characteristics of the sensing circuit.
The associated Proximitor driver processes these changes and converts them into a proportional electrical output. Within the calibrated range, the output voltage varies according to the distance between the probe tip and the target surface.
During machine operation, shaft vibration causes continuous changes in the probe gap. These variations appear as changes in the output signal, allowing the monitoring equipment to calculate shaft vibration and evaluate the mechanical condition of the rotating assembly.
The same measurement arrangement can also be used for static displacement monitoring. For example, probes installed near a turbine thrust bearing can track axial shaft movement relative to the stationary machine structure.
This measurement method is particularly useful in machinery where conventional contact-based sensors cannot be used because of shaft rotation, operating speed, or installation requirements.
Role in Bently Nevada 7200 Proximity Transducer System Architecture
The 21504-000-040-10-02 serves as the sensing component within a Bently Nevada 7200 proximity measurement system.
Unlike a complete proximity transducer assembly, the probe does not independently provide the final monitoring output. It must operate with the corresponding extension cable and Proximitor driver. The driver processes the probe signal and supplies the measurement output to the connected monitoring equipment.
Rotating Shaft → 7200 Series 8 mm Probe → Extension Cable → Proximitor Driver → Monitoring Equipment
| System Component | Function |
|---|---|
| Rotating Shaft | Conductive measurement target |
| 21504-000-040-10-02 | Detects changes in the probe-to-shaft distance |
| 21747 Extension Cable | Connects compatible 7200 proximity probes to the driver |
| 18745 Proximitor Driver | Processes the proximity probe signal |
| Monitoring Equipment | Receives and evaluates the conditioned measurement signal |
| Machinery Protection System | Uses vibration and displacement information for monitoring and protection |
| Condition Monitoring Software | Supports machinery condition evaluation and diagnostics |
The probe, extension cable, and driver must be treated as a matched transducer system. Cable compatibility, total electrical system length, and driver configuration should be checked when replacing an individual component.
Industrial Applications
The 21504-000-040-10-02 is suitable for machinery installations requiring non-contacting shaft vibration and displacement measurements.
| Industrial Application | Typical Monitoring Purpose |
|---|---|
| Steam Turbines | Monitoring radial shaft vibration and axial displacement |
| Gas Turbines | Measuring shaft movement during operation |
| Centrifugal Compressors | Monitoring shaft vibration near bearing assemblies |
| Industrial Pumps | Detecting shaft displacement and vibration |
| Electric Generators | Monitoring rotor movement and bearing-related vibration |
| Power Generation Plants | Supporting rotating machinery condition monitoring |
| Petrochemical Facilities | Measuring shaft vibration in critical process equipment |
| Refinery Equipment | Monitoring compressors and rotating machinery |
| Industrial Motors | Measuring shaft movement in compatible installations |
| Mechanical Drive Systems | Tracking rotating shaft displacement and vibration |
Installation and Maintenance
- Verify the Complete Model Reference: Confirm the 21504-000-040-10-02 identification before installation or replacement.
- Check Probe Diameter: Verify that the existing measurement arrangement requires an 8 mm proximity probe.
- Inspect Mounting Threads: Confirm that the mounting point matches the standard 3/8-24 UNF-2A thread configuration.
- Verify Overall Case Length: Check the 040 case-length configuration against the available installation depth and mounting arrangement.
- Confirm Total Probe Length: Verify that the 1-meter total length matches the required installation configuration.
- Inspect the Connector: Check the miniature male coaxial connector for damaged contacts, contamination, or mechanical wear.
- Check Cable Condition: Examine the unarmored cable for cuts, damaged insulation, crushing, or other physical deterioration.
- Verify Driver Compatibility: Confirm that the associated Proximitor driver is compatible with the 7200 Series 8 mm probe.
- Check Electrical System Length: Verify the complete probe and extension cable arrangement against the driver requirements.
- Adjust the Probe Gap: Position the sensing tip according to the applicable 7200 system specifications and required measurement range.
- Verify Measurement Output: Check the electrical output at the Proximitor driver and compare the reading with the expected probe gap.
- Record Installation Information: Document the probe model, mounting configuration, total length, driver identification, initial gap setting, and monitoring channel assignment.
If the monitoring signal becomes unstable or produces an unexpected reading, inspect the probe connector, cable condition, probe gap, and Proximitor driver before replacing the sensing element.
Compatible System Components
| Component | Function |
|---|---|
| Bently Nevada 21504 Series Probe | 7200 Series 8 mm standard-mount sensing element |
| 21747 Extension Cable | Connects compatible 7200 proximity probes to the driver |
| 18745 Proximitor Driver | Processes the proximity probe signal |
| 7200 Proximity Transducer System | Complete non-contacting proximity measurement arrangement |
| Machinery Monitoring Equipment | Receives and evaluates proximity measurement outputs |
| Vibration Monitoring Channels | Processes shaft vibration information |
| Machinery Protection System | Uses measurement signals for machinery protection |
| Industrial Control System | Receives relevant monitoring information for equipment operation |
Recommended Related Models
| Model / Product Family | Product Type | Typical Application |
|---|---|---|
| Bently Nevada 21504 | 7200 Series 8 mm Standard Mount Probe | Shaft vibration and displacement measurement |
| Bently Nevada 21505 | 7200 Series 8 mm Armored Probe | Proximity measurement with armored cable configuration |
| Bently Nevada 21508 | 7200 Series 8 mm Reverse Mount Probe | Reverse-mounted proximity measurement |
| Bently Nevada 21747 | 7200 Series Extension Cable | Probe-to-driver signal connection |
| Bently Nevada 18745 | 7200 Series Proximitor Driver | Proximity signal conditioning |
| Bently Nevada 7200 Series | Proximity Transducer System | Rotating machinery vibration and displacement monitoring |
Key Advantages
- 8 mm sensing element for non-contacting shaft measurement.
- Standard threaded mounting configuration.
- 1-meter total probe length.
- Miniature male coaxial connector.
- 2.0 mm calibrated measurement range.
- Suitable for dynamic shaft vibration and static displacement monitoring.
- Compatible with the corresponding 7200 Series transducer arrangement.
- Applicable to turbines, compressors, pumps, and generators.
Technical FAQs
1. What is the difference between the 21504 and 21505 proximity probes?
Both belong to the Bently Nevada 7200 Series 8 mm proximity probe family. The 21504 is the unarmored standard-mount configuration, while the 21505 is the armored version. The selection depends on the installation environment and the required cable protection.
2. Can the 21504-000-040-10-02 connect directly to a monitoring module?
No. The probe requires a compatible 7200 Proximitor driver to process its electrical response. The driver generates the conditioned measurement output that can then be connected to suitable monitoring equipment.
3. What does the 040 code represent in the model number?
The 040 code identifies the overall case length option in the probe configuration. For this model, it corresponds to the specified case-length code of 040. This parameter should be checked when matching the probe to an existing mounting arrangement.
4. Does the 1-meter total length include the associated extension cable?
The 1-meter option refers to the probe’s specified total length configuration. It should not be confused with the complete electrical system length, which also depends on the extension cable used between the probe and Proximitor driver. The total transducer system configuration must be checked separately.