Bently Nevada 27890-1-00-20-50-2 Eddy Current Proximity Probe Product Specification
27890-1-00-20-50-2 is a factory pre-calibrated integrated armored eddy current proximity probe belonging to Bently Nevada’s classic 3300XL sensor series, fully compliant with API 670 turbomachinery protection standards. The probe features an integral construction with sensing head and stainless steel armored coaxial cable sealed as one finished assembly, calibrated entirely at the factory to form a complete measurement loop when paired with matching proximitor and designated 2789 series calibrated extension cable. Widely used across power generation, petrochemical and metallurgical industries, it is deployed on steam turbines, turbo-generators, centrifugal compressors and large industrial blowers to conduct non-contact continuous monitoring of radial shaft vibration, thrust bearing axial displacement and once-per-revolution Keyphasor pickup for phase reference. Every finished unit passes linearity calibration, insulation resistance testing, alternating high-low temperature cycling aging and anti-vibration durability inspection before factory dispatch, ensuring stable signal output under severe field conditions including high operating temperature, persistent lubricant oil mist and complex electromagnetic interference within bearing housings. Converted gap-proportional analog voltage signals are transmitted to 3300 or 3500 rack monitor modules to support real-time condition monitoring, pre-alarm indication and critical safety shutdown interlock for rotating equipment protection.
Description
Bently Nevada 27890-1-00-20-50-2 Eddy Current Proximity Probe Product Specification
1. Product Overview
27890-1-00-20-50-2 is a factory pre-calibrated integrated armored eddy current proximity probe belonging to Bently Nevada’s classic 3300XL sensor series, fully compliant with API 670 turbomachinery protection standards. The probe features an integral construction with sensing head and stainless steel armored coaxial cable sealed as one finished assembly, calibrated entirely at the factory to form a complete measurement loop when paired with matching proximitor and designated 2789 series calibrated extension cable. Widely used across power generation, petrochemical and metallurgical industries, it is deployed on steam turbines, turbo-generators, centrifugal compressors and large industrial blowers to conduct non-contact continuous monitoring of radial shaft vibration, thrust bearing axial displacement and once-per-revolution Keyphasor pickup for phase reference. Every finished unit passes linearity calibration, insulation resistance testing, alternating high-low temperature cycling aging and anti-vibration durability inspection before factory dispatch, ensuring stable signal output under severe field conditions including high operating temperature, persistent lubricant oil mist and complex electromagnetic interference within bearing housings. Converted gap-proportional analog voltage signals are transmitted to 3300 or 3500 rack monitor modules to support real-time condition monitoring, pre-alarm indication and critical safety shutdown interlock for rotating equipment protection.
2. Part Number Definition Breakdown
Each dash-separated segment of 27890-1-00-20-50-2 represents fixed factory configuration parameters. The prefix 27890 designates the integrated armored proximity probe base product series with flexible stainless steel spiral armor for the integral lead; the digit 1 stands for standard 8mm tip size with fixed factory calibrated sensitivity and corresponding standard linear measurement range; 00 indicates standard non-customized mechanical structure including standard mounting thread and encapsulation without special mechanical modification; 20 defines the total length of factory pre-molded integral armored cable measured in inches; 50 specifies the cable tail connector mechanical specification and interface form; the final digit 2 denotes standard output connector design to match 2789-series extension cables and compatible Bently proximitor units. All length and capacitance parameters are locked during factory calibration, and substitution with non-matching cables or sensors will invalidate original calibration accuracy of the whole measuring circuit.
3. Core Functional Characteristics
Operating on high-frequency eddy current induction principle, the probe converts variable clearance between probe tip and conductive metal target surface into linear analog electrical output with zero mechanical contact, eliminating component abrasion and wear problems found on contact-type displacement sensors. Its primary onsite applications include long-term radial vibration monitoring of rotating shafts, thrust pad axial position tracking and Keyphasor pulse collection to supply phase benchmark data for vibration spectrum analysis. The attached integral cable is wrapped with flexible stainless steel spiral armor, which effectively shields internal coaxial core from mechanical squeezing, sharp scratching and long-term lubricant corrosion inside confined bearing housing space. When assembled with original matched proximitor and factory-calibrated extension cable, the complete transducer system outputs voltage linearly corresponding to actual gap value, enabling backend monitoring modules to set multi-stage alert and trip thresholds. Once measured displacement exceeds preset safety limits, the system activates alarm or emergency interlock to avoid costly catastrophic mechanical damage of core turbomachinery components. High-temperature resistant epoxy encapsulation at probe head guarantees stable performance under continuous high heat and oil contamination inside bearing compartments.
4. Electrical and Metrological Specifications
The full probe-cable-proximitor measuring loop receives regulated negative DC supply ranging from -17.5VDC to -26VDC from matching Bently proximitor, following universal 3300XL series power specification. This standard 8mm probe maintains fixed factory-set calibrated sensitivity and defined effective linear measurement range per original Bently design criteria. Premium high-temperature insulation materials inside encapsulated probe head and coaxial cable ensure high insulation resistance to minimize signal drift caused by ambient moisture or oil infiltration into internal wiring. Double-layer full shielded coaxial layout of armored integral cable suppresses external electromagnetic interference from adjacent high-voltage power cables and variable-frequency drive equipment during signal transmission. Only factory-approved matching proximitor and corresponding calibrated 2789 model extension cables can be combined with this probe to preserve original factory calibration and measuring precision.
5. Environmental Working Parameters
The continuous permissible operating temperature of probe body ranges from -40°C up to +177°C, well suited for high-temperature installation near turbine and compressor bearing pedestals and confined equipment enclosures. Spare storage temperature is maintained between -55°C and +95°C under dry non-condensing storage conditions. Applicable working relative humidity spans 5%RH to 95%RH, and surface or internal condensation is strictly prohibited to prevent insulation degradation and internal short-circuit faults. The armored probe assembly withstands regular industrial operating vibration of 10Hz~2kHz generated by running rotating machinery. Long-term continuous exposure to heavily corrosive gas and sustained hot steam immersion is forbidden to extend service lifespan of internal sensing coil and insulating structures. For installation at elevations over 1000 meters above sea level, shortening routine inspection cycle is recommended for improved thermal management.
6. Installation and Routine Maintenance Guidance
The probe is equipped with standard external mounting thread for threaded bore installation on bearing supports or user-designed mounting brackets. Field commissioning staff fine-tunes screwing depth during installation to set required initial gap between probe tip and target metal surface as specified in project technical documents. During periodic maintenance cycles, inspectors regularly check probe mounting tightness, outer armor integrity, cable sheath condition and connector locking tightness to rule out intermittent signal loss triggered by loose terminals or cable aging deterioration. When field replacement becomes necessary due to probe damage, only spare part with identical part number 27890-1-00-20-50-2 is allowed for direct replacement; mismatched alternative sensors will result in linearity shift and inaccurate measurement readings. All replacement probes complete full factory recalibration and alternating high-low temperature aging test prior to shipment to ensure full interchangeability during unit overhaul and system maintenance.
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