Compact Axial Position Transmitter for Continuous Machinery Protection
The Bently Nevada 991-25-70-01-00 991 Thrust Transmitter is a high-performance axial displacement monitoring transmitter developed for continuous shaft thrust measurement in rotating machinery. Designed specifically for OEM equipment manufacturers and industrial process applications, the 991 Series converts signals from a compatible 3300 NSv proximity probe system into a standard 4–20 mA proportional output, allowing seamless integration with PLC, DCS, SCADA, and machinery control systems. It is widely used on centrifugal compressors, pumps, motors, and fans where reliable thrust position monitoring is essential.
The 991-25-70-01-00 configuration features a 25–0–25 mil (approximately 2.5 mm) measurement range, 7-meter transducer system length, 35 mm DIN-rail mounting, and the 00 agency approval option. Its integrated Proximitor® Sensor electronics simplify installation by eliminating the need for an external signal conditioner while maintaining excellent measurement stability and long-term reliability.
Technical Specifications
| Parameter | Specification |
|---|
| Manufacturer | Bently Nevada |
| Model Number | 991-25-70-01-00 |
| Product Type | 991 Thrust Transmitter |
| Measurement Function | Shaft axial displacement (thrust position) |
| Measurement Range | 25–0–25 mil (≈ 2.5 mm) |
| Compatible Probe | Bently Nevada 3300 NSv Proximity Probe |
| System Length | 7.0 m (23 ft) |
| Output Signal | 4–20 mA proportional analog output |
| Power Supply | 12–35 VDC |
| Electrical Configuration | Two-wire loop powered |
| Mounting Method | 35 mm DIN-rail clips |
| Signal Conditioning | Integrated Proximitor® Sensor |
| Diagnostic Connections | PROX OUT and COM terminals |
| Agency Approval | 00 (No agency approval required) |
| Operating Temperature | -35°C to +85°C |
| Storage Temperature | -52°C to +177°C |
| Relative Humidity | 100% condensing (non-submerged) |
| Dimensions | Approx. 82 × 35 × 75 mm |
| Transmitter Weight | Approx. 0.43 kg |
| Typical System Weight | Approx. 0.82 kg |
Typical Industrial Applications
The 991-25-70-01-00 is designed for rotating equipment that requires accurate thrust position monitoring to enhance machinery protection and operational reliability.
| Industry | Typical Equipment |
|---|
| Oil & Gas | Centrifugal compressors, process pumps |
| Petrochemical | Process compressors and rotating machinery |
| Power Generation | Steam turbine auxiliary equipment |
| Manufacturing | Industrial motors, blowers and fans |
| Water Treatment | High-capacity pumps |
| OEM Machinery | Compressor and pump packages |
Typical applications include:
-
Shaft axial displacement monitoring
-
Thrust bearing protection
-
Rotating equipment health monitoring
-
Predictive maintenance systems
-
PLC and DCS process feedback
-
Machinery shutdown and alarm systems
Performance Highlights
Integrated Signal Conditioning
The transmitter incorporates Proximitor® Sensor electronics within the housing, reducing installation complexity and eliminating the need for a separate external Proximitor module. This compact design minimizes wiring while improving system reliability.
Flexible 7-Meter System Length
The 70 configuration includes a 7-meter transducer system, making it suitable for installations where the probe location is positioned farther from the control cabinet or monitoring equipment.
Easy DIN-Rail Installation
The 01 mounting option utilizes 35 mm DIN-rail clips, allowing quick installation inside industrial control panels and OEM cabinets while reducing installation time.
Reliable Industrial Output
A stable 4–20 mA output provides accurate shaft thrust information for automation systems, enabling dependable monitoring, alarm generation, and machine protection.
Compact Design for OEM Equipment
Its compact construction makes the transmitter particularly suitable for compressors, pumps, motors, and fans where available installation space is limited but dependable monitoring is required.
Proven Machinery Protection Solution
The 991 Series has become a trusted choice for OEM manufacturers and maintenance engineers seeking long-term reliability, straightforward installation, and consistent performance in demanding industrial environments.
Technical FAQs
1. What is the 991-25-70-01-00 used for?
It continuously measures shaft axial displacement and converts the measurement into a 4–20 mA signal for machinery monitoring and protection.
2. What does the "25" option indicate?
It specifies a 25–0–25 mil full-scale thrust measurement range, approximately equal to 2.5 mm.
3. What does the "70" code mean?
The 70 designation indicates a 7-meter (23-foot) transducer system length.
4. What does the "01" mounting option represent?
It identifies the 35 mm DIN-rail clip mounting configuration.
5. What does the "00" approval option mean?
The 00 option indicates that no additional agency approval is specified for this ordering configuration.
6. Which proximity probe is compatible?
The transmitter is designed for use with the Bently Nevada 3300 NSv proximity probe and matching extension cable system.
7. Does this transmitter require an external Proximitor?
No. The Proximitor® electronics are fully integrated into the transmitter housing.
8. What power supply is required?
The transmitter operates from a 12–35 VDC loop-powered supply.
9. What diagnostic features are available?
The unit includes PROX OUT and COM terminals, providing access to dynamic signals and gap voltage for troubleshooting and verification.
10. Which machines commonly use the 991 Series?
The transmitter is widely installed on centrifugal compressors, pumps, motors, industrial fans, and other rotating machinery requiring continuous thrust monitoring.
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