Dependable Axial Position Measurement for Critical Machinery
The Bently Nevada 991-25-70-02-01 991 Thrust Sensor is a rugged, loop-powered thrust transmitter engineered to provide continuous shaft axial displacement monitoring for rotating equipment operating in demanding industrial environments. Designed for centrifugal compressors, pumps, turbines, motors, and similar machinery, the 991 Series accepts signals from a compatible 3300 NSv proximity probe system and converts them into a precise 4–20 mA analog output for direct connection to PLC, DCS, SCADA, and machinery protection systems. Integrated Proximitor® electronics simplify installation by eliminating the need for a separate signal conditioning module while delivering reliable long-term performance.
The 991-25-70-02-01 configuration features a 2.5 mm (25–0–25 mil) full-scale measurement range, 7-meter transducer system, bulkhead mounting, and a CSA Division 2 approval configuration, making it well suited for industrial applications that require dependable thrust position monitoring and regulatory compliance.
Technical Specifications
| Parameter | Specification |
|---|
| Manufacturer | Bently Nevada |
| Model Number | 991-25-70-02-01 |
| 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 | 7.0 m (23 ft) |
| Output Signal | 4–20 mA linear analog output |
| Power Supply | 12–35 VDC |
| Wiring | Two-wire, loop powered |
| Mounting Method | Bulkhead mounting |
| Signal Conditioning | Integrated Proximitor® electronics |
| Diagnostic Outputs | PROX OUT and COM |
| 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 | -52°C to +177°C |
| Dimensions | Approx. 100 × 74 × 53 mm |
| Weight | Approx. 0.43 kg |
Typical Applications
The 991-25-70-02-01 is designed for continuous thrust position monitoring across a broad range of industrial rotating equipment.
| Industry | Typical Equipment |
|---|
| Oil & Gas | Centrifugal compressors, process pumps |
| Petrochemical | Compressors and expanders |
| Power Generation | Steam turbines, generators |
| Chemical Processing | High-speed rotating machinery |
| Manufacturing | Industrial motors, blowers, fans |
| OEM Equipment | Compressor and pump packages |
Typical applications include:
-
Shaft axial displacement monitoring
-
Thrust bearing protection
-
Machinery condition monitoring
-
Predictive maintenance programs
-
Equipment health diagnostics
-
PLC, DCS, and SCADA integration
Product Advantages
Optimized for Thrust Position Monitoring
The 991 Series is specifically developed to monitor shaft axial movement, enabling maintenance teams to detect excessive thrust bearing wear before it leads to unplanned equipment downtime.
Integrated Proximitor® Electronics
Signal conditioning electronics are built directly into the transmitter housing, reducing wiring complexity, lowering installation costs, and improving overall system reliability.
Extended 7-Meter System Length
The 70 configuration provides a 7-meter transducer system, offering greater flexibility when control cabinets are located farther from the monitored machine.
Bulkhead Mounting Design
The 02 mounting option allows secure bulkhead installation on machinery skids, enclosures, or OEM control panels, supporting both new installations and retrofit projects.
CSA Division 2 Configuration
The 01 approval option is supplied with a CSA Division 2 configuration suitable for industrial installations where this certification is required. Approval requirements should always be verified against the project specification.
Standard 4–20 mA Output
The industry-standard 4–20 mA analog output allows straightforward integration with modern industrial automation and machinery protection systems.
Technical FAQs
1. What is the 991-25-70-02-01 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 proximity probe is compatible?
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 "70" configuration represent?
It identifies a 7-meter (23 ft) transducer system length.
5. What does the "02" mounting option mean?
The 02 configuration specifies bulkhead mounting.
6. What does the final "01" option represent?
The final 01 designates the CSA Division 2 approval configuration in the ordering code.
7. What power supply is required?
The transmitter operates from a 12–35 VDC two-wire loop-powered supply.
8. Does the transmitter require an external Proximitor?
No. It incorporates integrated Proximitor® electronics, eliminating the need for an external signal conditioner.
9. What diagnostic outputs are available?
The transmitter provides PROX OUT and COM terminals for dynamic vibration and gap voltage diagnostics.
10. Which equipment commonly uses this model?
It is commonly installed on centrifugal compressors, steam turbines, industrial pumps, electric motors, and other rotating machinery requiring continuous thrust position monitoring.
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