High-Performance Thrust Monitoring for Critical Rotating Assets
The Bently Nevada 991-25-50-02-05 991 Thrust Sensor is a compact, loop-powered axial displacement transmitter developed to deliver continuous and accurate shaft thrust position monitoring in demanding industrial environments. Designed specifically for centrifugal compressors, pumps, motors, turbines, and other rotating machinery, the 991 Series converts the signal from a compatible 3300 NSv proximity probe system into a stable 4–20 mA analog output for direct connection to PLC, DCS, SCADA, and machinery protection systems. Integrated Proximitor® electronics reduce installation complexity while providing reliable long-term performance.
Configured with a 2.5 mm (25–0–25 mil) measurement range, 5-meter transducer system, bulkhead mounting, and hazardous-area approval option (05), the 991-25-50-02-05 is well suited for applications requiring dependable shaft position monitoring in harsh operating conditions. Its rugged industrial construction, simple commissioning, and industry-standard output make it an excellent solution for both OEM installations and retrofit machinery upgrades.
Product Specifications
| Parameter | Specification |
|---|
| Manufacturer | Bently Nevada |
| Model Number | 991-25-50-02-05 |
| Product Type | 991 Thrust Sensor / Thrust Transmitter |
| Measurement | Shaft Axial Displacement (Thrust Position) |
| Measurement Range | 2.5 mm (25–0–25 mil) Full Scale |
| Compatible Probe | 3300 NSv Proximity Probe |
| Transducer System Length | 5 m (16.4 ft) |
| Output Signal | 4–20 mA Linear Analog Output |
| Supply Voltage | 12–35 VDC |
| Wiring | Two-wire, Loop Powered |
| Mounting Style | Bulkhead Mount |
| Integrated Electronics | Proximitor® Signal Conditioner |
| Diagnostic Output | PROX OUT and COM |
| Loop Resistance | Up to 1000 Ω @ 35 VDC |
| Typical Accuracy | ±1.5% of Full Scale |
| Operating Temperature | -35°C to +85°C |
| Storage Temperature | -52°C to +177°C |
| Housing | Fully Potted Industrial Enclosure |
| Dimensions | Approx. 100 × 74 × 53 mm |
| Weight | Approx. 0.43 kg |
Typical Applications
The 991-25-50-02-05 is engineered to provide reliable thrust position monitoring across a wide variety of rotating equipment.
| Industry | Typical Equipment |
|---|
| Oil & Gas | Centrifugal compressors, pipeline pumps |
| Petrochemical | Compressors, process expanders |
| Power Generation | Steam turbines, generators |
| Chemical Processing | High-speed rotating machinery |
| Water Treatment | Large pumps and blowers |
| OEM Machinery | Compressor and pump packages |
Typical monitoring applications include:
-
Axial shaft displacement measurement
-
Thrust bearing protection
-
Machinery condition monitoring
-
Predictive maintenance programs
-
Process automation systems
-
Continuous equipment health monitoring
Key Advantages
Designed for Accurate Thrust Position Measurement
Unlike conventional vibration transmitters, the 991 Series is specifically optimized for shaft axial displacement monitoring, providing early warning of excessive thrust bearing wear and abnormal shaft movement.
Integrated Proximitor® Electronics
Built-in signal conditioning eliminates the need for an external Proximitor module, reducing wiring, installation time, and maintenance requirements while improving system reliability.
5-Meter Transducer System
The 50 configuration provides a 5-meter system length, allowing flexible installation between the sensor location and the control cabinet.
Bulkhead Mounting
The 02 mounting option enables secure installation on equipment panels, machinery skids, or custom enclosures, making it suitable for OEM and retrofit projects alike.
Standard 4–20 mA Process Signal
A linear 4–20 mA output ensures compatibility with virtually all modern industrial automation and control systems, simplifying integration and commissioning.
Hazardous-Area Certified Configuration
The 05 approval option is intended for installations requiring hazardous-area certifications, making this model suitable for demanding industrial environments where compliance and operational safety are essential. Specific approvals should be verified against the official ordering documentation.
Technical FAQs
1. What is the 991-25-50-02-05 used for?
It continuously measures shaft axial displacement (thrust position) and outputs a proportional 4–20 mA signal for machinery monitoring and protection.
2. Which probe works with this transmitter?
It is designed for use with the Bently Nevada 3300 NSv proximity probe and its matching extension cable.
3. What does the "25" option indicate?
It specifies a 2.5 mm (25–0–25 mil) full-scale thrust measurement range.
4. What does the "50" code represent?
It identifies a 5-meter transducer system length.
5. What does the "02" mounting option mean?
It designates a bulkhead-mounted transmitter configuration.
6. What does the final "05" option represent?
The 05 suffix identifies a hazardous-area approval configuration. The exact certification package depends on the manufacturer's ordering code and should be confirmed before procurement.
7. What power supply is required?
The transmitter operates from a 12–35 VDC loop-powered supply.
8. Does it require a separate Proximitor module?
No. The transmitter contains integrated Proximitor® electronics, eliminating the need for an external signal conditioner.
9. What diagnostic outputs are available?
The transmitter includes PROX OUT and COM terminals for dynamic signal and gap voltage diagnostics.
10. Which equipment commonly uses this model?
It is widely applied on centrifugal compressors, steam turbines, industrial pumps, electric motors, and other rotating machinery requiring continuous thrust position monitoring.
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