Bently Nevada 21505-00-08-10-02 Eddy Current Proximity Probe Product Specification
21505-00-08-10-02 is a factory pre-calibrated front-mounted 5 mm eddy current proximity probe for Bently Nevada 7200 series transducer system. Combined with matched 2155/00 proximitor preamplifier and certified 75-ohm extension cable, it forms a complete non-contact measuring system compliant with 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, which are transmitted to 7200 or 3500 rack monitoring modules for continuous measurement of rotor radial vibration, short-stroke axial displacement and Keyphasor pickup signals. Widely applied on steam turbines, gas turbines, centrifugal compressors and large turbo-generators across power, petrochemical and metallurgical industries for over-limit alarm and emergency shutdown interlock control. Every finished probe passes linearity calibration, high-low temperature cyclic aging and hermetic encapsulation inspection before factory shipment to maintain stable measurement accuracy under harsh on-site conditions with high bearing housing temperature, lubricating oil mist and complex electromagnetic interference from high-current power cables and variable frequency drives.
Description
Bently Nevada 21505-00-08-10-02 Eddy Current Proximity Probe Product Specification
1. Product Overview
21505-00-08-10-02 is a factory pre-calibrated front-mounted 5 mm eddy current proximity probe for Bently Nevada 7200 series transducer system. Combined with matched 2155/00 proximitor preamplifier and certified 75-ohm extension cable, it forms a complete non-contact measuring system compliant with 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, which are transmitted to 7200 or 3500 rack monitoring modules for continuous measurement of rotor radial vibration, short-stroke axial displacement and Keyphasor pickup signals. Widely applied on steam turbines, gas turbines, centrifugal compressors and large turbo-generators across power, petrochemical and metallurgical industries for over-limit alarm and emergency shutdown interlock control. Every finished probe passes linearity calibration, high-low temperature cyclic aging and hermetic encapsulation inspection before factory shipment to maintain stable measurement accuracy under harsh on-site conditions with high bearing housing temperature, lubricating oil mist and complex electromagnetic interference from high-current power cables and variable frequency drives.
2. Part Number Definition Breakdown
Each segmented code follows Bently’s standard coding rules for 7200-series front-install proximity probes. Base code 21505 represents core series of standard front-mounted 5 mm proximity probe dedicated to the 7200 transducer platform; segment 00 defines fixed internal coil layout, body structural parameters and factory-locked calibration parameters; segment 08 specifies ultra-short threaded body dimension for shallow-hole front installation; segment 10 stands for factory pre-molded integral cable fixed length of 1.0 meter permanently attached to probe body; final segment 02 indicates miniature coaxial connector fitted at cable terminal for plugging into original matched extension cable. Probes with different digit combinations have different mechanical dimensions or calibrated electrical characteristics and cannot be replaced arbitrarily on-site; improper substitution invalidates full-loop factory calibration and leads to measurement drift or unexpected equipment protection trip.
3. Core Functional Characteristics
The probe threaded housing and sensing tip are fabricated from high-strength corrosion-resistant stainless steel with outstanding resistance against lubricant erosion and corrosive vapor inside confined 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-term 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 replacement of original integral cable and end connector is strictly forbidden, as any physical modification permanently voids factory preset calibration data. Short-thread front mounting design is ideal for shallow reserved holes on bearing pedestals with limited installation depth. Built-in open/short-circuit fault diagnosis identifies abnormal wiring via obvious output voltage offset to simplify on-site troubleshooting. Consistent linear performance of the whole measuring system is only retained with full original matching of probe, extension cable and designated 2155-series proximitor.
4. Electrical and Metrological Specifications
The matched 2155/00 proximitor provides regulated negative DC power ranging from -17.5 VDC to -26 VDC, and -24 VDC is the standard field operating voltage. Factory fixed calibrated sensitivity is 7.87 V/mm (200 mV/mil) referenced to standard AISI4140 carbon steel target, with full-range linearity error controlled within ±5% per API 670 standard. Valid linear measuring range covers 0 mm to 1.27 mm for small-gap radial vibration and short-travel axial displacement measurement. 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 clearance is set near the midpoint of linear range to secure a stable operating bias point during long-term continuous equipment running.
5. Environmental Working Parameters
Permissible continuous operating temperature of probe sensing part ranges from -35°C to +120°C to adapt high-temperature installation close to hot bearing housings and turbine casings. Spare storage temperature is kept between -55°C and +85°C under dry non-condensing storage surroundings; applicable working relative humidity ranges 5%RH~95%RH without dew condensation on probe housing and cable outer jacket. The probe withstands routine industrial vibration of 10 Hz ~ 2 kHz generated by adjacent running rotating machinery. Long-term continuous soaking in corrosive liquid, acid mist and persistent high-temperature steam is prohibited to avoid outer casing corrosion and inner insulation aging damage. For installation locations above 1000 meters altitude, shorten regular inspection cycle appropriately.
6. Installation and Routine Maintenance Guidance
Cut off power supply of the whole monitoring loop before installation, screw the short-thread probe into shallow reserved threaded hole of bearing pedestal or custom mounting fixture, adjust pre-set installation gap to design value and lock fastening nut against operational loosening. During cabling construction, separate probe signal cable routing away from high-current AC power cables and inverter output lines 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 deviation. Within regular maintenance cycles, periodically inspect cable outer sheath for oil corrosion, abrasion and cracking, and check locking tightness of terminal connector. When probe failure requires replacement, only spare part with identical full part number 21505-00-08-10-02 is allowed for direct swap. All replacement probes complete full electrical performance testing and alternating temperature aging screening before factory delivery to guarantee complete interchangeability inside original vibration monitoring loops.
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