Introduction to the 991-06-70-03-05
When axial shaft position monitoring demands reliability, the 991-06-70-03-05 from Bently Nevada delivers precise thrust measurement. This probe vibration transmitter converts proximity probe signals into a standard 4-20 mA output, simplifying integration with existing control systems.
Engineered for continuous operation, the 991-06-70-03-05 accepts one non-contacting 3300 NSv proximity probe and extension cable. Its DIN rail mounting option (option 03) with clips and screws ensures secure installation in industrial cabinets.
Key Features and Technical Specifications
The 991-06-70-03-05 offers a full-scale range of 0.6-0-0.6 mm, suitable for axial thrust measurements. With a system length of 7.0 meters (23.0 feet), it accommodates typical machine train layouts.
- Power Requirement: +12 to +35 Vdc input at the transmitter terminal.
- Output Signal: 4-20 mA in a 2-wire configuration.
- Linear Range: 0.25 to 1.65 mm for Prox Out, supporting 0.6-0-0.6 mm or 25-0-25 mils current loop linear ranges.
- Loop Accuracy: Within ±1.5% over specified full scale (typical), measured from TEST signal input to voltage across a 250 Ω loop resistance.
- Maximum Loop Resistance: 1,000 Ω including cable at 35 Vdc.
- Current Limiting: 23 mA typical.
- Not OK/Signal Defeat: Output goes to less than 3.6 mA within 100 µs after a Not OK condition, restored within 0.1 seconds after removal.
- Environmental Limits: Operating temperature -35°C to +85°C (-31°F to +185°F); storage -51°C to +100°C (-60°F to +212°F).
- Weight: 0.43 kg (0.9 lbm).
Zero and span adjustments are non-interacting external controls, simplifying calibration. The transmitter's current limiting protects the loop, while the fast Not OK response enhances system safety.
Applications and Use Cases
Commonly used in turbomachinery, the 991-06-70-03-05 monitors axial shaft position to prevent thrust bearing damage. Its 4-20 mA output interfaces directly with PLCs, DCS, and SCADA systems, making it a versatile choice for retrofits or new installations.
For example, in a steam turbine, the transmitter provides continuous thrust position data, enabling early detection of abnormal axial movement. This proactive approach reduces unplanned downtime and extends machine life.
Installation and Mounting
Mount the 991-06-70-03-05 on a standard DIN rail using the provided clips and screws. Ensure the transmitter is positioned within the specified system length (7.0 m) from the probe. Connect the 3300 NSv probe and extension cable, then wire the 4-20 mA loop to the control system.
Power the transmitter with +12 to +35 Vdc at the terminal. Verify loop resistance does not exceed 1,000 Ω to maintain accuracy. Adjust zero and span as needed using the external potentiometers.
Maintenance and Reliability
Regularly inspect the transmitter for signs of environmental stress, as operating temperatures range from -35°C to +85°C. Check that the DIN rail mounting remains secure and that all connections are tight.
Because the 991-06-70-03-05 has no moving parts, maintenance is minimal. However, periodic verification of loop accuracy and Not OK functionality is recommended. Follow the manufacturer's manual for detailed procedures.
Troubleshooting Common Issues
If the output signal is erratic, first verify the input power is within +12 to +35 Vdc. Next, confirm the probe and extension cable are properly connected and that the system length does not exceed 7.0 meters.
Should the output drop below 3.6 mA, the transmitter may be in a Not OK state. Check the probe gap and target condition. If the issue persists, consult the Bently Nevada documentation or contact AutoDCSTech for support.
Compatibility and Integration
The 4-20 mA output is universally compatible with most industrial control systems, including PLCs and DCS platforms. The transmitter works with Bently Nevada 3300 NSv proximity probes, ensuring a matched system.
For new installations, the 991-06-70-03-05 can replace older thrust transmitters with similar output requirements. Its DIN rail mounting simplifies panel integration.
Support and Availability
The 991-06-70-03-05 is available through AutoDCSTech. Contact us for current stock and lead times. We provide genuine Bently Nevada parts and technical support.
