Bently Nevada 21505-00-28-10-02 Eddy Current Proximity Probe Product Specification
21505-00-28-10-02 is factory pre-calibrated front-mounted 5 mm eddy current proximity probe designed for Bently Nevada 7200 series transducer system. When matched with 2155/00 proximitor preamplifier and original 75-ohm calibrated extension cable, it forms a complete non-contact measuring system conforming to API 670 rotating machinery protection standards. Based on eddy-current induction principle, the probe converts clearance variation between sensing tip and conductive metallic rotor target into linear analog voltage signals. Output signals are fed into 7200 or 3500 rack monitoring modules to realize continuous measurement of rotor radial vibration, short-stroke axial displacement and Keyphasor pulse signals. Widely applied on steam turbines, gas turbines, centrifugal compressors and large turbo-generators in power, petrochemical and metallurgical industries for alarm setup and emergency shutdown interlock control. Every finished probe undergoes linearity calibration, high-low temperature cyclic aging and hermetic encapsulation inspection before factory delivery to retain stable measuring accuracy under harsh field conditions including high bearing housing temperature, lubricant oil mist and complex electromagnetic interference from high-current cables and variable frequency drives.
Description
Bently Nevada 21505-00-28-10-02 Eddy Current Proximity Probe Product Specification
1. Product Overview
21505-00-28-10-02 is factory pre-calibrated front-mounted 5 mm eddy current proximity probe designed for Bently Nevada 7200 series transducer system. When matched with 2155/00 proximitor preamplifier and original 75-ohm calibrated extension cable, it forms a complete non-contact measuring system conforming to API 670 rotating machinery protection standards. Based on eddy-current induction principle, the probe converts clearance variation between sensing tip and conductive metallic rotor target into linear analog voltage signals. Output signals are fed into 7200 or 3500 rack monitoring modules to realize continuous measurement of rotor radial vibration, short-stroke axial displacement and Keyphasor pulse signals. Widely applied on steam turbines, gas turbines, centrifugal compressors and large turbo-generators in power, petrochemical and metallurgical industries for alarm setup and emergency shutdown interlock control. Every finished probe undergoes linearity calibration, high-low temperature cyclic aging and hermetic encapsulation inspection before factory delivery to retain stable measuring accuracy under harsh field conditions including high bearing housing temperature, lubricant oil mist and complex electromagnetic interference from high-current cables and variable frequency drives.
2. Part Number Definition Breakdown
Each segment of the part number follows Bently’s standard coding rules for 7200 series front-install proximity probes. Base code 21505 stands for core series of standard front-mounted 5 mm proximity probe exclusively developed for the 7200 transducer platform. Segment 00 defines fixed internal coil structure, inner wiring layout and factory-locked calibration parameters. Segment 28 specifies customized length of probe threaded body for standard medium-length thread installation. Segment 10 represents factory pre-molded integral cable fixed length of 1.0 meter permanently attached to probe body. Final segment 02 means miniature coaxial connector equipped at cable terminal for connecting matched extension cable. Probes with different digit combinations have different mechanical dimensions or calibrated electrical characteristics and cannot be arbitrarily replaced on-site; improper replacement invalidates full-loop factory calibration and causes measurement deviation or unexpected protection trip.
3. Core Functional Characteristics
Probe threaded body and sensing tip are processed from high-strength corrosion-resistant stainless steel with excellent oil and vapor resistance to adapt long-term working inside closed oil-filled bearing compartments. Internal induction coil is fully potted with high-temperature epoxy resin to eliminate inner air gaps, effectively preventing coil displacement or inter-turn short-circuit caused by long-period equipment vibration and ambient temperature fluctuation. The attached 1-meter integral cable adopts 75-ohm controlled-impedance coaxial structure with dense tinned copper braided shielding over 95% coverage to suppress external electromagnetic noise during signal transmission. Field cutting, splicing or connector replacement of original integral cable is strictly forbidden; any physical modification permanently voids factory preset calibration data. Front thread mounting structure allows direct screw-in installation from equipment outer side, convenient for conventional bearing pedestal mounting layout. Open/short-circuit wiring faults can be quickly identified via obvious output voltage drift to simplify on-site troubleshooting. Stable linear performance of the entire measurement system is only guaranteed by full original matching of probe, extension cable and designated 2155/00 proximitor.
4. Electrical and Metrological Specifications
The supporting 2155/00 proximitor provides regulated negative DC power ranging from -17.5 VDC to -26 VDC, and -24 VDC is the commonly used field operating voltage. Factory fixed calibrated sensitivity is 7.87 V/mm (200 mV/mil) tested with standard AISI4140 carbon steel target, with full-span linearity tolerance controlled within ±5% complying with API 670 specification. Valid linear measuring range covers 0 mm ~ 1.27 mm for small-gap radial vibration and short-travel axial displacement measurement of industrial rotating shafts. Effective frequency response ranges DC up to 10 kHz to collect both low-frequency static thermal expansion drift signals and high-frequency dynamic shaft vibration signals simultaneously. Recommended pre-installation gap is set near the midpoint of linear range to keep a stable working bias voltage for continuous long-term operation.
5. Environmental Working Parameters
Continuous permissible operating temperature of probe sensing part ranges from -35°C to +120°C to fit high-temperature installation nearby heated bearing housings and turbine casings. Spare storage temperature is maintained between -55°C and +85°C under dry non-condensing storage environment; applicable working relative humidity is 5%RH~95%RH without dew condensation on probe housing and cable surface. The probe can withstand regular industrial vibration of 10 Hz to 2 kHz generated by adjacent running rotating equipment. Long-term continuous immersion in corrosive liquid, acid mist and persistent high-temperature steam is prohibited to avoid outer casing corrosion and inner insulation aging damage. For installation positions above 1000 meters altitude, shorten periodic inspection cycle appropriately.
6. Installation and Routine Maintenance Guidance
Cut off power supply of the whole monitoring loop before field installation, screw the probe into reserved threaded hole of bearing housing or customized mounting fixture, adjust pre-set installation gap to design value and lock fastening nut to prevent loosening caused by long-term equipment running vibration. During cabling construction, separate probe signal cable routing away from high-current AC power cables and inverter output wiring to reduce cross electromagnetic coupling interference. Avoid sharp small-radius bending, overstretching and heavy squeezing on cable body to prevent internal core damage and impedance shift. Within regular maintenance cycles, periodically inspect cable outer sheath for oil corrosion, abrasion and cracking, and check locking tightness of terminal connector. When probe breakdown requires replacement, only spare part with identical full part number 21505-00-28-10-02 is allowed for direct swap. All replacement probes complete full electrical performance testing and alternating temperature aging screening before factory shipment to guarantee complete interchangeability inside original vibration monitoring loops.
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