Introduction
The component with part number 990-04-70-01-00 is a Proximity Transducer System, commonly known as a probe and extension cable assembly, manufactured by Bently Nevada* (a Baker Hughes company). This part number represents a complete kit for measuring the relative vibration and position of a rotating shaft.
This system is a fundamental component for machinery condition monitoring and protection. It typically includes an 8mm proximity probe, a matching extension cable, and often a connector. The system works by generating a DC voltage proportional to the distance between the probe tip and the shaft (position) and an AC voltage representing the dynamic motion (vibration). It is a critical input for monitoring systems like the 3500 series.
*Bently Nevada is a part of Baker Hughes.
Parameters
The following table outlines the key technical parameters for a typical 990-04-70-01-00 assembly.
| Parameter | Specification |
|---|---|
| Part Number | 990-04-70-01-00 |
| System Type | Proximity Transducer System (8mm) |
| Components | Typically includes an 8mm Proximity Probe (e.g., 330104-00-00-10-02-00), an Armored Extension Cable (e.g., 5m or 10m), and necessary connectors. |
| Probe Diameter | 8 mm (0.31 inches) |
| System Scale Factor | 200 mV/mil (7.87 V/mm) |
| Linear Range | Approximately 0.25 to 2.3 mm (10 to 90 mils) |
| Recommended Target | ASTM A284 Steel or equivalent |
| Operating Temperature | Probe: -34°C to 177°C (-29°F to 350°F) Cable: -34°C to 177°C (-29°F to 350°F) |
| Power Requirement | Typically -24 VDC from the proximitor driver/monitor. |
| Output Signal | The gap-to-voltage signal containing both DC (position) and AC (vibration) components. |
| Dimensions & Weight (Approx.) | Probe: Diameter ~8mm, length ~60mm. Cable: Diameter ~6.4mm. Total Weight (for a 5m system): ~1.2 kg (2.65 lb) |
Application Scenarios
The 990-04-70-01-00 proximity transducer system is a workhorse for measuring key parameters on rotating machinery. Its primary application scenarios include:
Radial Vibration Monitoring:
Mounted perpendicular to the shaft at bearing housings to measure the dynamic motion (vibration) of the rotor. This is essential for detecting conditions like unbalance, misalignment, and oil whirl.
Axial (Thrust) Position Monitoring:
Mounted parallel to the shaft axis to monitor the position of the thrust collar. This prevents catastrophic damage by ensuring the rotor remains within its designed axial clearance.
Differential Expansion Monitoring:
Used to measure the difference in thermal growth between the rotor and the stator (casing) during startup and shutdown of large turbines.
Eccentricity (Slow-Roll) Monitoring:
Measures shaft bow or bend when the machine is at low speeds or on turning gear, helping to prevent high vibration during startup.
Keyphasor® Reference Signal:
Used to provide a once-per-revolution timing mark for measuring phase angle, which is critical for machine balancing and diagnosing specific faults.
Typical Machinery Monitored:
Steam Turbines & Gas Turbines
Centrifugal & Axial Compressors
Large Pumps & Motors
Generators
Gearboxes
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