Application Scenarios
In a large utility power station, steam turbine generators operate at 3,600 RPM with rotor-to-stator clearances measured in fractions of a millimeter. The BENTLY NEVADA 81725-01 functions as the primary measurement element within the turbine protection system, mounted on bearing housings to continuously monitor shaft relative vibration and axial thrust position. When a turbine experienced a gradual increase in radial vibration due to bearing wear during a high-load operating period, the 81725-01 sensor detected the subtle displacement changes and transmitted the signal to the 7200 series monitor, which triggered an alarm before the vibration reached destructive levels. The 14mm probe diameter and 100mV/mil sensitivity of the 81725-01 provided the signal resolution necessary to distinguish between normal operational vibration and developing mechanical degradation, enabling the plant to schedule bearing replacement during a planned outage rather than facing an unplanned forced shutdown .
Parameter
| Parameter | Value/Description |
|---|---|
| Product Model | BENTLY NEVADA 81725-01 (81725-XX, 155875-01) |
| Manufacturer | Bently Nevada |
| Product Category | Proximitor Sensor / Eddy Current Proximity Probe |
| Probe Diameter | 14 mm |
| Sensitivity | 100 mV/mil |
| Operating Voltage | 24 VDC |
| System Compatibility | 7200 Series Machinery Protection Systems |
| Measurement Applications | Shaft vibration, axial position (thrust), eccentricity |
| Standard Compliance | API 670 |
| Signal Output | DC voltage proportional to displacement |
| Mounting | Rack-mounted within 7200 series chassis |
Technical Principles and Innovative Values
- Innovation Point 1 – Eddy Current Measurement Principle: The BENTLY NEVADA 81725-01 operates on the eddy current principle, generating a high-frequency RF signal that creates eddy currents in the conductive target surface. As the shaft moves relative to the probe, the eddy current losses vary, producing a DC voltage output proportional to displacement. This non-contact method eliminates wear and enables continuous measurement in high-speed rotating machinery .
- Innovation Point 2 – 14mm Probe Geometry with 100mV/mil Sensitivity: The 81725-01‘s 14mm probe diameter provides a larger sensing area than smaller probes, delivering stable signal output across the measurement range. Combined with 100mV/mil sensitivity, this configuration ensures that minute displacement changes generate measurable voltage variations, enabling early detection of bearing degradation and rotor instability .
- Innovation Point 3 – 7200 Series System Integration: The 81725-01 is purpose-engineered for the Bently Nevada 7200 series chassis, where it functions as both signal conditioner and monitor. The module converts high-frequency RF probe signals into precise DC voltage outputs that the protection system evaluates against alarm and trip thresholds, providing a complete measurement chain from probe to protective action .
- Innovation Point 4 – API 670 Compliance for Safety-Critical Applications: The 81725-01 meets the requirements of API 670, the recognized industry standard for machinery protection systems. This compliance ensures that installations using the 81725-01 satisfy the reliability and performance benchmarks demanded by petrochemical, power generation, and other safety-critical industries .
