Precision Thrust Position Monitoring for Industrial Rotating Machinery
The Bently Nevada 991-25-50-02-00 991 Thrust Sensor is a compact, loop-powered thrust transmitter designed to provide continuous monitoring of shaft axial displacement on critical rotating equipment. Built for OEM machinery manufacturers and industrial users, the 991 Series accepts signals from a compatible 3300 NSv proximity probe system and converts them into a linear 4–20 mA output, allowing seamless integration with PLC, DCS, SCADA, and machinery protection systems. Integrated Proximitor® electronics eliminate the need for a separate signal conditioning module, reducing installation time and simplifying system architecture.
The 991-25-50-02-00 configuration features a 2.5 mm (25–0–25 mil) full-scale axial displacement range, a 5-meter transducer system, bulkhead mounting, and the standard approval configuration, making it an excellent choice for compressors, turbines, pumps, motors, and other rotating machinery where reliable thrust bearing monitoring is essential.
Engineering Specifications
| Parameter | Specification |
|---|
| Manufacturer | Bently Nevada |
| Model Number | 991-25-50-02-00 |
| Product Type | 991 Thrust Sensor / Thrust Transmitter |
| Measurement Type | Shaft Axial Displacement (Thrust Position) |
| Full Scale Range | 2.5 mm (25–0–25 mil) |
| Compatible Probe | 3300 NSv Proximity Probe |
| Transducer System Length | 5.0 m (16.4 ft) |
| Output Signal | 4–20 mA proportional output |
| Power Supply | 12–35 VDC |
| Loop Configuration | Two-wire, loop-powered |
| Mounting Method | Bulkhead mounting |
| Signal Conditioning | Integrated Proximitor® electronics |
| Diagnostic Outputs | PROX OUT and COM terminals |
| Maximum Loop Resistance | Up to 1000 Ω at 35 VDC |
| Typical Accuracy | ±1.5% of full scale |
| Operating Temperature | -35°C to +85°C |
| Storage Temperature | -51°C to +177°C |
| Dimensions | Approx. 100 × 74 × 53 mm |
| Weight | Approx. 0.43 kg |
Typical Applications
The 991-25-50-02-00 is designed for continuous shaft thrust monitoring in demanding industrial environments where reliable machinery protection is required.
| Industry | Typical Equipment |
|---|
| Oil & Gas | Centrifugal compressors, process pumps |
| Petrochemical | Compressors, expanders |
| Power Generation | Steam turbines, generators |
| Chemical Processing | High-speed rotating machinery |
| Manufacturing | Motors, fans, blowers |
| OEM Equipment | Compressor and pump skids |
Typical applications include:
-
Axial shaft displacement monitoring
-
Thrust bearing protection
-
Predictive maintenance programs
-
Machinery condition monitoring
-
Equipment health diagnostics
-
PLC, DCS, and SCADA integration
Performance Advantages
Extended 2.5 mm Measurement Range
The 25 measurement option provides a 2.5 mm full-scale axial displacement range, making it suitable for machinery requiring a larger thrust travel measurement than standard 0.6 mm versions.
Integrated Proximitor® Electronics
Signal conditioning electronics are built directly into the transmitter, reducing external hardware requirements while improving installation efficiency and long-term reliability.
Flexible 5-Meter Transducer System
The 50 configuration incorporates a 5-meter transducer system, offering installation flexibility for machines with moderate cable routing distances.
Bulkhead Mounting Configuration
The 02 mounting option is supplied for bulkhead installation, allowing secure attachment to machinery skids, enclosures, or custom control panels.
Standard 4–20 mA Process Output
The transmitter delivers an industry-standard 4–20 mA analog output, ensuring compatibility with virtually all modern industrial automation and monitoring systems.
Rugged Industrial Construction
Designed for continuous operation in demanding industrial environments, the 991 transmitter features a sealed, fully potted construction capable of withstanding vibration, humidity, and wide operating temperatures.
Technical FAQs
1. What is the 991-25-50-02-00 used for?
It continuously measures shaft axial displacement (thrust position) and converts the measurement into a 4–20 mA process signal for machinery monitoring.
2. Which proximity probe is compatible?
It is designed for use with the Bently Nevada 3300 NSv proximity probe and matching extension cable system.
3. What does the "25" option indicate?
It specifies a 2.5 mm (25–0–25 mil) full-scale axial displacement measurement range.
4. What does the "50" option represent?
It indicates a 5-meter (16.4 ft) transducer system length.
5. What does the "02" mounting option mean?
The 02 configuration specifies bulkhead mounting rather than DIN-rail mounting.
6. What does the final "00" code indicate?
The 00 option represents the standard product configuration without additional agency approvals.
7. What output signal does this transmitter provide?
It provides a linear 4–20 mA output proportional to measured shaft axial position.
8. Does the transmitter require an external Proximitor?
No. The transmitter incorporates integrated Proximitor® electronics, eliminating the need for an external signal conditioning module.
9. What power supply is required?
The unit operates from a 12–35 VDC loop-powered supply.
10. Which machines commonly use this model?
It is commonly installed on centrifugal compressors, turbines, pumps, motors, blowers, and other rotating machinery that require continuous thrust position monitoring.
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