Reliable Shaft Thrust Monitoring for Critical Rotating Machinery
The Bently Nevada 991-25-70-02-00 991 Thrust Sensor is a high-performance axial position transmitter designed to provide continuous monitoring of shaft thrust displacement in rotating equipment. As part of the Bently Nevada 991 Thrust Transmitter family, this device converts proximity probe measurements into a proportional 4–20 mA output signal, allowing direct integration with PLC, DCS, SCADA, and machinery control systems.
Designed primarily for OEM and industrial applications, the 991-25-70-02-00 combines a 25–0–25 mil (approximately 2.5 mm) thrust measurement range, 7-meter transducer system length, bulkhead screw mounting, and a standard approval configuration. The integrated Proximitor® Sensor electronics provide signal conditioning inside the transmitter housing, eliminating the need for an external Proximitor module while simplifying installation and maintenance.
Technical Specifications
| Parameter | Specification |
|---|
| Manufacturer | Bently Nevada |
| Model Number | 991-25-70-02-00 |
| Product Type | 991 Thrust Sensor / Thrust Transmitter |
| Measurement Function | Shaft axial displacement (thrust position) |
| Full Scale Range | 25–0–25 mil (approximately 2.5 mm) |
| Compatible Probe | Bently Nevada 3300 NSv Proximity Probe |
| Transducer System Length | 7.0 m (23 ft) |
| Output Signal | 4–20 mA proportional analog output |
| Power Supply | +12 to +35 VDC |
| Electrical Configuration | Two-wire loop powered |
| Mounting Type | Bulkhead mounting screws |
| Signal Conditioning | Integrated Proximitor® Sensor |
| Diagnostic Output | PROX OUT and COM terminals |
| Loop Resistance | Up to 1000 Ω at 35 VDC |
| Accuracy | ±1.5% of full-scale range (typical) |
| Operating Temperature | -35°C to +85°C |
| Storage Temperature | -52°C to +177°C |
| Humidity Rating | Up to 100% condensing, non-submerged |
| Housing Design | Sealed potted industrial enclosure |
| Dimensions | Approx. 82 × 35 × 75 mm |
| Transmitter Weight | Approx. 0.43 kg |
| Total System Weight | Approx. 0.82 kg typical |
Industrial Applications
The 991-25-70-02-00 provides dependable thrust position feedback for equipment where accurate axial movement measurement is essential.
| Industry | Typical Equipment |
|---|
| Oil & Gas | Centrifugal compressors, process pumps |
| Petrochemical | Rotating process machinery |
| Power Generation | Turbines and auxiliary systems |
| Manufacturing | Motors, blowers, industrial fans |
| Water & Utilities | Large rotating pumps |
| OEM Machinery | Compressor packages and skid systems |
Common applications include:
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Axial shaft displacement monitoring
-
Thrust bearing protection
-
Rotating equipment condition monitoring
-
Machinery protection alarm systems
-
Predictive maintenance programs
-
Control system feedback applications
Engineering Advantages
Integrated Proximitor® Sensor Design
The 991 transmitter integrates proximity signal conditioning electronics directly into the transmitter assembly. This eliminates the requirement for a separate Proximitor unit, reducing cabinet space requirements and simplifying field wiring.
Extended 7-Meter Transducer System
The 70 option provides a 7-meter proximity measurement system, allowing flexible installation where the sensing location and control cabinet are separated by greater distances.
Bulkhead Mounting Configuration
The 02 option provides bulkhead screw mounting, making the transmitter suitable for OEM machinery panels, equipment skids, and industrial enclosures requiring secure mechanical installation.
Standard 4–20 mA Industrial Output
The transmitter delivers an industry-standard current signal proportional to shaft axial position, allowing easy connection to automation systems without additional signal conversion hardware.
Compact Design for Limited Installation Space
The 991 Series is designed for applications where installation space is limited. Its compact construction allows use on smaller compressors, pumps, motors, and fans while maintaining reliable thrust measurement performance.
Enhanced Diagnostic Capability
Additional diagnostic connections including PROX OUT and COM terminals provide access to dynamic signals and gap voltage information for troubleshooting and system verification.
Technical FAQs
1. What is the Bently Nevada 991-25-70-02-00 used for?
The transmitter is used for continuous measurement of shaft axial displacement and thrust position on rotating machinery.
2. What does the “25” option mean?
The 25 designation indicates a 25–0–25 mil measurement range, equivalent to approximately 2.5 mm axial displacement.
3. What does the “70” option represent?
The 70 code identifies the 7-meter (23 ft) transducer system length.
4. What does the “02” mounting code indicate?
The 02 option specifies a bulkhead screw mounting configuration for secure installation.
5. What does the final “00” approval code mean?
The 00 option indicates that no additional agency approval option is selected in the ordering configuration.
6. Which proximity probe is compatible with this transmitter?
The unit is designed to operate with the Bently Nevada 3300 NSv proximity probe and matching extension cable system.
7. Does this model require an external Proximitor module?
No. The 991 transmitter includes an integrated Proximitor® Sensor, eliminating the need for an external signal conditioner.
8. What type of output signal does it provide?
It provides a proportional 4–20 mA analog output representing shaft axial position.
9. What power supply is required?
The transmitter requires a 12–35 VDC loop-powered supply.
10. Which machines commonly use the 991 Series?
Typical applications include centrifugal compressors, pumps, motors, fans, and other rotating equipment requiring continuous thrust monitoring.
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