The Bently Nevada 991-25-70-01-01 is a 2-wire, loop-powered thrust transmitter that converts signals from a 3300 NSv proximity probe into a 4-20 mA output proportional to axial shaft position. Designed for general-purpose machinery like centrifugal air compressors, pumps, and fans, it eliminates the need for external signal conditioning and provides reliable thrust monitoring in tight installation spaces.
Item No :
991-25-70-01-01Order(MOQ) :
1 PiecePayment :
EXWProduct Origin :
USAShipping Port :
WuhanLead Time :
3~5 daysWeight :
3kg| Feature | Description |
|---|---|
| Manufacturer | Bently Nevada (Baker Hughes) |
| Product Family | 991 Series Thrust Transmitter |
| Model / Order Code | 991-25-70-01-01 |
| Core Function | Converts axial displacement (thrust) to a 4-20 mA signal |
| Full-scale Range | ±25 mils (0.6 mm total) |
| Output Signal | 4-20 mA DC, loop-powered (2-wire) |
| Compatibility | 3300 NSv proximity probe and extension cable |
| System Length | 7.0 meters (23.0 feet) |
| Mounting Option | 35 mm DIN-rail clips |
| Power Supply | 12 to 35 Vdc at transmitter terminal |
| Agency Approval | CSA Division 2 |
| Operating Temp. | -35°C to +85°C |
| Construction | Potted for operation in 100% condensing humidity |
| Diagnostics | Non-isolated PROX OUT and COM terminals for gap verification; Not OK/Signal Defeat circuit |
| Weight | Approx. 0.43 kg |
| Category | Model | Description |
|---|---|---|
| 5m System Length | 991-25-50-01-01 | Same transmitter, ±25 mils range, but with 5.0m system length |
| Metric Range | 991-06-50-01-01 | Same features with 0.6-0-0.6 mm full-scale range |
| Bulkhead Mounting | 991-25-70-02-01 | Same specs, but bulkhead mounting instead of DIN-rail |
| Proximity Probe | 3300 NSv Series | Required narrow side-view proximity probe for system compatibility |
| Extension Cable | 330930 Series | Matching extension cable (5m or 7m options) |
| Vibration Transmitter | 990 Series | Vibration version for general-purpose vibration monitoring (not thrust) |
Q1: What is the primary application of the 991-25-70-01-01?
It is used to continuously monitor axial shaft position (thrust) on general-purpose machinery such as centrifugal air compressors, pumps, motors, and fans, providing a 4-20 mA signal to the control system for protection alarming and logic .
Q2: What does the model number suffix "25-70-01-01" mean?
The suffix defines configuration: 25 = ±25 mils full-scale range; 70 = 7.0m system length (probe + extension cable); 01 = 35mm DIN-rail mounting; 01 = CSA Division 2 agency approval .
Q3: Does the 991 transmitter require an external proximity sensor or driver?
No. The 991 integrates the proximity sensor conditioning circuitry (Proximitor) internally. It accepts the 3300 NSv probe and extension cable directly, eliminating the need for a separate driver unit .
Q4: What are the diagnostic features of the 991 transmitter?
It includes non-isolated PROX OUT and COM terminals for verifying probe gap voltage during setup, and a "Not OK/Signal Defeat" circuit that prevents false high outputs from faulty probes or loose connections . It also has a test input pin for simulating probe movement to verify the 4-20 mA loop without physically moving the rotor .
Q5: Is the 991 transmitter suitable for critical machinery like large turbines?
No. The 991 is designed for non-critical, general-purpose machinery. For critical turbine or compressor protection, Bently Nevada recommends the 3500 series monitoring system.
The Bently Nevada 330105-02-12-05-02-00 is an 8 mm reverse-mount proximity probe from the 3300 XL series, engineered for non-contact vibration and position monitoring in space-constrained machinery.
The Bently Nevada 330130-085-00-00 is an 8.5-meter standard extension cable for the 3300 XL 8 mm Proximity Transducer System. It connects a 3300 XL proximity probe to its Proximitor® sensor, transmitting eddy-current displacement signals for vibration, axial position, and Keyphasor measurements on critical rotating machinery.
The Bently Nevada 21000-00-00-15-030-04-00 is a Proximity Probe Housing Assembly from the 21000 series, designed to provide a secure, environmentally sealed mounting interface for reverse-mount proximity probes on critical rotating machinery.
The Bently Nevada 330780-50-00 is a 5.0-meter Proximitor® Sensor for the 3300 XL 11 mm Proximity Transducer System. It receives signals from a 3300 XL 11 mm probe and its extension cable, conditioning them into a linear voltage output proportional to shaft displacement for radial vibration, axial thrust position, and Keyphasor measurement.
The Bently Nevada 21747-040-00 is a 4-meter Proximitor probe extension cable designed for the 3300 and 7200 Series Proximity Transducer Systems. It connects a proximity probe to its Proximitor sensor, transmitting high-frequency eddy-current displacement signals for vibration and shaft position monitoring on critical rotating machinery.
The Bently Nevada 330710-00-060-10-02-00 is a 3300 XL 11 mm Proximity Probe designed for non-contact vibration and position measurement on large, fluid-film bearing machinery. Its 11 mm tip provides a longer linear range compared to the standard 8 mm system, making it ideal for applications requiring greater measurement span, such as axial thrust position, differential expansion, and radial vibration on steam turbines, centrifugal compressors, and large pumps.
The Bently Nevada 330103-00-11-50-02-00 is a 3300 XL 8 mm proximity probe with a metric M10×1 thread and a 5.0-meter integral cable terminated with a miniature coaxial ClickLoc™ connector. This extended-reach configuration features a 110 mm overall case length and connects directly to a Proximitor® sensor without requiring an extension cable for short-run installations.
The Bently Nevada 990-10-XX-01-00 (MOD 165353-01) is a two-wire, loop-powered Vibration Transmitter designed for OEMs of centrifugal air compressors, small pumps, motors, and fans. It accepts input from a 3300 NSv proximity probe and its matching extension cable, conditioning the signal into a 4–20 mA output proportional to peak-to-peak vibration amplitude.
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