Bently Nevada 21504-000-024-10-02 Eddy Current Proximity Probe Product Specification
21504-000-024-10-02 is factory pre-calibrated front-mounted 8 mm eddy current proximity probe designed exclusively for Bently Nevada 7200 series transducer system. Matched with original 2155/00 proximitor preamplifier and factory-calibrated 75-ohm extension cable, the complete set forms a non-contact measuring system fully compliant with API 670 specifications for critical rotating machinery protection. Following the eddy-current induction principle, the probe converts tiny clearance changes between its sensing tip and conductive metal rotor target into linear analog voltage signals. These signals are fed to 7200 or 3500 rack monitoring modules to continuously measure shaft radial vibration, short-travel axial displacement and Keyphasor rotational pulse signals. Widely used on steam turbines, gas turbines, centrifugal compressors and large turbo-generators in power, petrochemical and metallurgical industries, it provides over-limit alarm and emergency shutdown interlock signals to secure unit running safety. Each finished probe passes full-scale linear calibration, high-low temperature cycling aging test and fully sealed epoxy encapsulation inspection before shipment to sustain stable accuracy under harsh field conditions including high bearing housing temperature, pervasive lube oil mist and electromagnetic interference from high-current cables and variable frequency drives.
Description
Bently Nevada 21504-000-024-10-02 Eddy Current Proximity Probe Product Specification
1. Product Overview
21504-000-024-10-02 is factory pre-calibrated front-mounted 8 mm eddy current proximity probe designed exclusively for Bently Nevada 7200 series transducer system. Matched with original 2155/00 proximitor preamplifier and factory-calibrated 75-ohm extension cable, the complete set forms a non-contact measuring system fully compliant with API 670 specifications for critical rotating machinery protection. Following the eddy-current induction principle, the probe converts tiny clearance changes between its sensing tip and conductive metal rotor target into linear analog voltage signals. These signals are fed to 7200 or 3500 rack monitoring modules to continuously measure shaft radial vibration, short-travel axial displacement and Keyphasor rotational pulse signals. Widely used on steam turbines, gas turbines, centrifugal compressors and large turbo-generators in power, petrochemical and metallurgical industries, it provides over-limit alarm and emergency shutdown interlock signals to secure unit running safety. Each finished probe passes full-scale linear calibration, high-low temperature cycling aging test and fully sealed epoxy encapsulation inspection before shipment to sustain stable accuracy under harsh field conditions including high bearing housing temperature, pervasive lube oil mist and electromagnetic interference from high-current cables and variable frequency drives.
2. Part Number Definition Breakdown
Each code segment follows Bently’s standard coding rule for 7200 series front-install proximity probes. Base code 21504 stands for standard 8 mm diameter front-thread probe series developed for the 7200 transducer platform; segment 000 indicates zero exposed unthreaded tip length with fixed internal coil structure and factory-locked original calibration parameters without custom electrical modification; segment 024 defines medium-short full-threaded body dimension applicable for regular shallow to medium-depth mounting holes on standard bearing pedestals; segment 10 represents factory pre-molded integral coaxial cable with fixed 1.0-meter length permanently attached to probe body during production; final suffix 02 refers to standard miniature male coaxial connector installed at cable end for plug connection with original certified extension cable. Replacing with probes of different part codes will alter mechanical dimensions or calibrated electrical characteristics, which invalidates factory matching calibration and leads to measurement error or unintended protection trip of monitoring channels.
3. Core Functional Characteristics
The threaded housing and sensing tip are precision machined from high-strength anti-corrosion stainless steel with outstanding resistance against lubricant erosion and corrosive vapor inside sealed bearing chambers. The internal induction coil is fully potted with high-temperature epoxy resin to eliminate internal air gaps and effectively avoid coil displacement or inter-turn short-circuit caused by long-term equipment vibration and ambient temperature fluctuation. The attached 1-meter integral coaxial cable adopts standard 75-ohm controlled impedance design with over 95% coverage tinned copper braided shielding to suppress external electromagnetic crosstalk during signal transmission. Any field cutting, splicing or replacement of original cable and end connector is strictly forbidden, as physical damage will permanently void factory preset calibration data. Medium-short full-thread front mounting structure is optimized for conventional shallow mounting holes and common thin-to-medium thickness bearing seat structures. Built-in open/short-circuit fault diagnosis identifies abnormal wiring via obvious output voltage offset to facilitate daily on-site troubleshooting. Stable linear measurement performance can only be guaranteed by full original matching of this probe, matched extension cable and designated 2155/00 proximitor preamplifier.
4. Electrical and Metrological Specifications
The supporting 2155/00 proximitor supplies regulated negative DC voltage from -17.5 VDC to -26 VDC, and -24 VDC is the nominal standard operating voltage for field application. Factory calibrated sensitivity is 7.87 V/mm (200 mV/mil) based on AISI4140 carbon steel target material, with full-range linearity deviation controlled within ±5% in accordance with API 670 requirements. Valid linear measuring range covers 0 mm to 2.0 mm, meeting routine radial vibration and short-stroke axial clearance measurement of most industrial rotating shafts. Frequency response ranges from DC to 10 kHz to capture both low-frequency static thermal drift and high-frequency dynamic vibration signals synchronously. The recommended pre-install gap is set near the midpoint of linear range to maintain a stable bias working point for long-term continuous equipment operation.
5. Environmental Working Parameters
Continuous operating temperature for the sensing part is from -35°C to +120°C, adapting high-temperature installation near heated bearing housings and turbine casings. Storage temperature for spare probes is kept between -55°C and +85°C within dry non-condensing surroundings; applicable working relative humidity ranges from 5%RH to 95%RH without dew forming on probe housing and cable outer jacket. The probe can withstand regular equipment vibration of 10 Hz to 2 kHz from adjacent rotating machinery. Long-term immersion or exposure to corrosive liquid, acid mist and continuous high-temperature steam is prohibited to prevent shell corrosion and internal insulation aging. For installation sites above 1000 meters altitude, shorten routine inspection cycle appropriately.
6. Installation and Routine Maintenance Guidance
Cut off full power of the entire monitoring loop before installation, screw the medium-short full-thread probe into pre-reserved shallow threaded holes of bearing pedestal or customized mounting fixture, adjust installation clearance to rated design value and tighten lock nut to prevent loosening induced by long-running vibration. During wiring construction, separate probe signal cable routing away from high-current AC cables and inverter output wires to reduce cross electromagnetic coupling interference. Avoid sharp small-radius bending, overstretching and heavy compression on cable to prevent inner conductor breakage and abnormal impedance shift. Within regular maintenance cycles, regularly inspect cable sheath for oil corrosion, abrasion and cracking, and check fastening tightness of end connector. When probe fails and needs replacement, only spare with identical part number 21504-000-024-10-02 is allowed for direct replacement. All replacement probes complete electrical testing and temperature aging screening before factory delivery to ensure full interchangeability inside original vibration monitoring loops.
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