Advanced Thrust Position Monitoring for Critical Rotating Equipment
The Bently Nevada 991-25-70-01-05 991 Thrust Sensor is a compact and dependable axial position transmitter engineered for continuous monitoring of shaft thrust movement in rotating machinery. Designed for OEM machinery builders and industrial operators, the 991 series converts displacement measurements from a 3300 NSv proximity probe system into a reliable 4–20 mA proportional output signal for direct connection with PLC, DCS, SCADA, and machinery protection systems.
Featuring a 25–0–25 mil (approximately 2.5 mm) thrust measurement range, 7-meter transducer system length, 35 mm DIN-rail mounting clips, and enhanced hazardous-area approval capability, the 991-25-70-01-05 provides a practical solution for compressors, pumps, motors, fans, and other rotating assets where accurate axial position feedback is essential. The integrated Proximitor® Sensor eliminates the need for an external signal conditioning module, reducing installation complexity and improving system reliability.
Technical Specifications
| Parameter | Specification |
|---|
| Manufacturer | Bently Nevada |
| Model Number | 991-25-70-01-05 |
| Product Type | 991 Thrust Sensor / Thrust Transmitter |
| Measurement Function | Shaft axial displacement / thrust position |
| Measurement Range | 25–0–25 mil (≈ 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 current output |
| Power Supply | 12–35 VDC loop powered |
| Electrical Configuration | Two-wire transmitter |
| Mounting Type | 35 mm DIN-rail clips |
| Electronics | Integrated Proximitor® Sensor |
| Diagnostic Output | PROX OUT and COM terminals |
| Hazardous Area Approval | CSA Division 2, ATEX Zone 0/Zone 2, ABS marine approval options |
| Operating Temperature | -35°C to +85°C |
| Storage Temperature | Approx. -51°C to +110°C |
| Dimensions | Approx. 73 × 50 × 100 mm |
| Weight | Approx. 0.43–0.44 kg |
Application Areas
The 991-25-70-01-05 is designed for applications requiring continuous shaft thrust monitoring and reliable machine protection feedback.
| Industry | Typical Equipment |
|---|
| Oil & Gas | Centrifugal compressors, process pumps |
| Petrochemical | Rotating process machinery |
| Power Generation | Turbine auxiliary systems |
| Manufacturing | Motors, fans, blowers |
| Water & Utilities | Industrial pump systems |
| OEM Machinery | Compressor packages and skid equipment |
Typical applications include:
-
Axial shaft position monitoring
-
Thrust bearing protection
-
Rotating equipment condition monitoring
-
Machinery alarm and shutdown systems
-
Predictive maintenance programs
-
Industrial automation feedback
Product Advantages
Integrated Proximitor® Sensor Technology
The 991 transmitter combines proximity signal conditioning and transmitter functions into one compact unit. This integrated design removes the requirement for a separate Proximitor module, helping reduce cabinet space, wiring requirements, and installation time.
Extended 7-Meter Transducer System
The 70 configuration provides a 7-meter proximity measurement system, offering additional installation flexibility when the sensing location is separated from the control cabinet or monitoring panel.
DIN-Rail Mounting Convenience
The 01 mounting option uses 35 mm DIN-rail clips, allowing quick installation inside electrical cabinets and OEM control panels. This compact mounting style is ideal for machinery packages with limited available space.
Hazardous Environment Capability
The final 05 approval option supports demanding industrial environments and may include certifications such as CSA Division 2, ATEX Zone 0/Zone 2, and ABS marine approval, depending on the ordered configuration.
Reliable 4–20 mA Industrial Output
The transmitter converts shaft axial displacement into a standard 4–20 mA signal, enabling easy integration with modern control systems for monitoring, alarm logic, and machinery protection applications.
Compact Design for OEM Integration
The small enclosure size makes the 991 series especially suitable for centrifugal air compressors, small pumps, motors, and fans where reliable thrust feedback is required without large monitoring hardware.
Technical FAQs
1. What is the Bently Nevada 991-25-70-01-05 used for?
It is used for measuring shaft axial displacement and monitoring thrust position in rotating machinery applications.
2. What does the “25” option represent?
The 25 code indicates a 25–0–25 mil thrust measurement range, approximately equivalent to a 2.5 mm axial displacement measurement system.
3. What does the “70” configuration mean?
The 70 option identifies the 7-meter (23 ft) transducer system length.
4. What does the “01” mounting option specify?
The 01 option indicates 35 mm DIN-rail clip mounting for installation inside industrial control cabinets.
5. What does the final “05” indicate?
The 05 suffix identifies the enhanced approval configuration, including hazardous-area and marine certification options depending on the supplied version.
6. Which probe is compatible with this transmitter?
The transmitter works with the Bently Nevada 3300 NSv proximity probe and matching extension cable system.
7. Does the 991-25-70-01-05 require an external Proximitor module?
No. The Proximitor® Sensor electronics are integrated inside the transmitter housing.
8. What output signal does this model provide?
It provides a standard 4–20 mA proportional output representing shaft axial position.
9. What power supply is required?
The transmitter operates from a 12–35 VDC loop-powered supply.
10. Which machines commonly use the 991 series?
Typical installations include centrifugal compressors, small pumps, motors, fans, and OEM rotating machinery requiring continuous thrust monitoring.
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