Intelligent Axial Position Monitoring for Critical Rotating Machinery
The Bently Nevada 991-06-70-03-EN 991 Thrust Sensor is a compact, two-wire, loop-powered thrust transmitter designed to provide continuous monitoring of shaft axial displacement (thrust position) in rotating equipment. Engineered for OEM machinery and industrial process applications, the 991 series converts signals from a compatible 3300 NSv proximity probe system into a precise 4–20 mA output, enabling direct integration with PLC, DCS, SCADA, and machinery protection systems. The integrated Proximitor® electronics simplify installation by eliminating the need for an external signal conditioner while maintaining reliable measurement accuracy.
The 991-06-70-03-EN configuration offers a 0.6 mm (24 mil) full-scale axial displacement range, a 7-meter transducer system, bulkhead mounting, and the EN regional configuration, making it an ideal solution for monitoring thrust bearing condition and shaft movement in demanding industrial environments.
Technical Specifications
| Parameter | Specification |
|---|
| Manufacturer | Bently Nevada |
| Model Number | 991-06-70-03-EN |
| Product Type | 991 Thrust Sensor / Thrust Transmitter |
| Measurement Type | Axial Displacement (Thrust Position) |
| Full Scale Range | 0–0.6 mm (24 mils) |
| Compatible Probe | 3300 NSv Proximity Probe |
| Transducer System Length | 7.0 m (23 ft) |
| Output Signal | 4–20 mA proportional axial displacement |
| Power Supply | +12 to +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 | 1000 Ω at 35 VDC |
| Accuracy | ±1.5% of full scale |
| Operating Temperature | -35°C to +85°C |
| Storage Temperature | -51°C to +177°C |
| Relative Humidity | Up to 100% condensing (non-submerged) |
| Dimensions | Approx. 100 × 74 × 53 mm |
| Weight | Approx. 0.45 kg |
Typical Applications
Designed for continuous shaft position monitoring, the 991-06-70-03-EN is widely used in industries where thrust bearing protection is essential.
| Industry | Typical Equipment |
|---|
| Oil & Gas | Centrifugal compressors, process pumps |
| Petrochemical | Compressors and expanders |
| Power Generation | Steam turbines and auxiliary machinery |
| Chemical Processing | High-speed rotating equipment |
| Manufacturing | Motors, blowers, industrial fans |
| OEM Equipment | Compressor and pump packages |
Typical applications include:
-
Axial shaft position monitoring
-
Thrust bearing protection
-
Machinery condition monitoring
-
Predictive maintenance
-
Equipment health diagnostics
-
PLC and DCS integration
Performance Highlights
Dedicated Thrust Position Measurement
Unlike vibration transmitters that monitor radial shaft movement, the 991 series is specifically designed to measure axial displacement, providing early warning of excessive thrust bearing wear and abnormal shaft travel.
Integrated Proximitor® Electronics
The built-in Proximitor® circuitry combines signal conditioning and transmitter functions into a single compact housing, reducing installation costs and simplifying maintenance.
7-Meter Transducer System
The 70 configuration includes a 7-meter transducer system, providing installation flexibility when the control cabinet is positioned away from the monitored machine.
Bulkhead Mounting Design
The 03 configuration utilizes bulkhead mounting, offering a secure installation method for machinery skids, equipment enclosures, and custom OEM control panels.
Standard 4–20 mA Output
A linear 4–20 mA output enables straightforward connection to industrial automation systems while supporting reliable machinery protection and condition monitoring.
Rugged Industrial Construction
The transmitter features a fully potted industrial design capable of operating in harsh environments with high humidity, vibration, and wide temperature variations, ensuring dependable long-term performance.
Technical FAQs
1. What is the 991-06-70-03-EN used for?
It continuously measures shaft axial displacement (thrust position) and converts it into a 4–20 mA signal for machinery monitoring systems.
2. Which probe is compatible with this model?
The transmitter is designed for use with a Bently Nevada 3300 NSv proximity probe and its matching extension cable.
3. What does the "06" option indicate?
It specifies a 0.6 mm (24 mil) full-scale axial displacement measurement range.
4. What does the "70" configuration represent?
It identifies a 7-meter (23 ft) transducer system length.
5. What does the "03" option mean?
The 03 configuration designates bulkhead mounting instead of DIN-rail mounting.
6. What does the "EN" suffix indicate?
The EN suffix identifies a specific regional ordering or certification configuration. The exact regional configuration should be verified using the official Bently Nevada ordering guide.
7. What output signal does this transmitter provide?
It delivers a 4–20 mA proportional output corresponding to shaft axial position.
8. Does it require an external Proximitor module?
No. The transmitter incorporates integrated Proximitor® electronics, eliminating the need for an external signal conditioner.
9. What supply voltage is required?
The transmitter operates from a 12–35 VDC loop-powered supply.
10. Which machines commonly use the 991-06-70-03-EN?
Typical applications include centrifugal compressors, steam turbines, pumps, motors, and other rotating machinery requiring continuous thrust position monitoring.
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