Advanced Axial Position Monitoring for Industrial Machinery Protection
The Bently Nevada 991-25-XX-02-05 991 Thrust Sensor is a compact, loop-powered axial displacement transmitter designed to provide accurate and continuous monitoring of shaft thrust position in rotating equipment. Developed for OEM machinery builders and industrial operators, the 991 Series converts input signals from a compatible 3300 NSv proximity probe and extension cable system into a stable 4–20 mA proportional output for direct connection to PLC, DCS, SCADA, and machinery control platforms.
The 991-25-XX-02-05 configuration is designed with a 2.5 mm (25–0–25 mil) full-scale thrust measurement range, a configurable transducer system length, bulkhead screw mounting, and enhanced approval options. With integrated Proximitor® sensor electronics, the transmitter eliminates the requirement for a separate signal conditioning module while maintaining dependable performance in compact installation spaces.
Technical Specifications
| Parameter | Specification |
|---|
| Manufacturer | Bently Nevada |
| Model Number | 991-25-XX-02-05 |
| Product Type | 991 Thrust Sensor / Axial Position Transmitter |
| Measurement Function | Shaft Axial Displacement Monitoring |
| Measurement Range | 2.5 mm (25–0–25 mil) |
| Sensor Compatibility | Bently Nevada 3300 NSv Proximity Probe |
| System Length | XX (Selectable configuration) |
| Output Signal | 4–20 mA proportional analog output |
| Power Supply | +12 to +35 VDC |
| Electrical Design | Two-wire loop powered |
| Mounting Type | Bulkhead mounting screws |
| Signal Conditioning | Integrated Proximitor® Sensor |
| Diagnostic Output | PROX OUT and COM terminals |
| Loop Resistance | Up to 1000 Ω at 35 VDC |
| Zero / Span Adjustment | External non-interacting adjustment |
| Operating Temperature | -35°C to +85°C |
| Humidity Capability | Up to 100% condensing environment |
| Housing Design | Fully potted industrial enclosure |
| Dimensions | Approx. 82 × 35 × 75 mm |
| Weight | Approx. 0.44 kg |
Industrial Applications
The 991-25-XX-02-05 provides reliable thrust position feedback for machinery where continuous shaft movement monitoring is essential.
| Industry | Typical Equipment |
|---|
| Oil & Gas | Centrifugal compressors, process pumps |
| Petrochemical | Rotating process machinery |
| Power Generation | Turbine auxiliary systems |
| Manufacturing | Industrial motors and fans |
| Water Treatment | Large rotating pumps |
| OEM Equipment | Compressor and pump packages |
Common applications include:
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Thrust bearing condition monitoring
-
Axial shaft displacement measurement
-
Machinery protection systems
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Predictive maintenance programs
-
Process control integration
-
Rotating equipment diagnostics
Product Advantages
Reliable Thrust Position Measurement
The 991 Series is specifically designed to measure shaft axial displacement, helping operators identify abnormal thrust movement before it causes excessive bearing wear, rotor damage, or unexpected equipment shutdowns.
Integrated Proximitor® Sensor Technology
The built-in Proximitor electronics combine signal conditioning and transmitter functionality in one compact device. This reduces installation requirements, minimizes wiring complexity, and improves system reliability.
Flexible XX System Configuration
The XX designation allows selection of the required transducer system length to match different machine layouts and installation distances. The 991 family supports common 5 m and 7 m proximity probe system configurations.
Bulkhead Mounting Design
The 02 mounting option provides secure bulkhead screw installation, making the transmitter suitable for machinery skids, equipment panels, and OEM control enclosures where stable mechanical mounting is required.
Hazardous Area Support
The final 05 approval option provides enhanced certification capability for demanding industrial locations. Depending on ordering configuration, approvals may include CSA Division 2, ATEX Zone 0/2, and marine-related certifications.
Standard 4–20 mA Industrial Output
The widely accepted 4–20 mA signal allows simple integration with modern automation systems, providing operators with dependable thrust position data for alarms, monitoring, and control logic.
Technical FAQs
1. What is the Bently Nevada 991-25-XX-02-05 used for?
It is used for continuous measurement of shaft axial displacement (thrust position) on rotating machinery and provides a proportional 4–20 mA output to control systems.
2. What does the “25” option indicate?
The 25 designation represents a 25–0–25 mil (approximately 2.5 mm) full-scale thrust measurement range.
3. Which probe is compatible with this transmitter?
The transmitter is designed to operate with a Bently Nevada 3300 NSv proximity probe and matching extension cable system.
4. What does the “XX” code represent?
The XX section identifies the selectable transducer system length configuration required for the installation.
5. What does the “02” mounting code mean?
The 02 option indicates a bulkhead screw mounting configuration for secure equipment installation.
6. Does this model require an external Proximitor module?
No. The transmitter contains an integrated Proximitor® sensor, eliminating the need for a separate external module.
7. What output signal does the transmitter provide?
It provides a standard 4–20 mA DC proportional output representing measured shaft axial position.
8. What power supply is required?
The device requires a 12–35 VDC loop-powered supply.
9. Are diagnostic signals available?
Yes. The transmitter provides PROX OUT and COM terminals along with a diagnostic dynamic signal output for troubleshooting and verification.
10. What equipment commonly uses the 991 series?
The 991 series is commonly used on centrifugal compressors, pumps, motors, fans, and other OEM rotating equipment requiring axial position monitoring.
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