Bently Nevada 21505-00-20-10-02 Eddy Current Proximity Probe Product Specification
21505-00-20-10-02 is factory pre-calibrated front-mount 5 mm eddy current proximity probe designed for Bently Nevada 7200 series transducer system. Matched with 2155/00 proximitor preamplifier and original 75-ohm calibrated extension cable, it forms a complete non-contact measurement system complying with API 670 rotating machinery protection criteria. Based on eddy current induction principle, the probe converts clearance change between sensing tip and conductive metallic rotor target into linear analog voltage signals, which are transmitted to 7200 or 3500 rack monitor modules for continuous online measurement of rotor radial vibration, short-stroke axial displacement and Keyphasor rotational pulse signals. Widely deployed on steam turbines, gas turbines, centrifugal compressors and large turbo-generators in power, petrochemical and metallurgical sectors to realize over-limit alarm and emergency shutdown interlock protection. Every finished probe passes linearity calibration, high-low temperature cyclic aging and hermetic sealing inspection prior to factory delivery to sustain stable measuring accuracy under harsh working conditions with high bearing housing temperature, lubricant oil mist and complex electromagnetic interference from high-power motors and variable frequency drives.
Description
Bently Nevada 21505-00-20-10-02 Eddy Current Proximity Probe Product Specification
1. Product Overview
21505-00-20-10-02 is factory pre-calibrated front-mount 5 mm eddy current proximity probe designed for Bently Nevada 7200 series transducer system. Matched with 2155/00 proximitor preamplifier and original 75-ohm calibrated extension cable, it forms a complete non-contact measurement system complying with API 670 rotating machinery protection criteria. Based on eddy current induction principle, the probe converts clearance change between sensing tip and conductive metallic rotor target into linear analog voltage signals, which are transmitted to 7200 or 3500 rack monitor modules for continuous online measurement of rotor radial vibration, short-stroke axial displacement and Keyphasor rotational pulse signals. Widely deployed on steam turbines, gas turbines, centrifugal compressors and large turbo-generators in power, petrochemical and metallurgical sectors to realize over-limit alarm and emergency shutdown interlock protection. Every finished probe passes linearity calibration, high-low temperature cyclic aging and hermetic sealing inspection prior to factory delivery to sustain stable measuring accuracy under harsh working conditions with high bearing housing temperature, lubricant oil mist and complex electromagnetic interference from high-power motors and variable frequency drives.
2. Part Number Definition Breakdown
Each coded segment follows Bently’s standard part numbering rules for 7200 series front-install proximity probes. Base code 21505 stands for core series of standard front-mounted 5 mm proximity probe dedicated to 7200 transducer platform; segment 00 defines fixed internal coil structure, internal wiring layout and factory-locked original calibration parameters; segment 20 specifies medium short standard thread length of probe body for conventional front threading installation; segment 10 represents factory pre-molded integral cable fixed length of 1.0 meter permanently attached to probe body; final segment 02 indicates miniature coaxial terminal connector fitted at cable end for docking with certified matched extension cable. Probes with different code digits have inconsistent mechanical dimension or calibrated electrical parameters and cannot be randomly replaced on-site; improper substitution invalidates full-loop factory calibration and triggers measurement deviation or accidental protection trip.
3. Core Functional Characteristics
The probe threaded housing and sensing head are made of high-strength anti-corrosion stainless steel with excellent resistance against lubricating oil erosion and corrosive vapor inside closed bearing chambers. Internal induction coil is fully encapsulated with high-temperature epoxy potting compound to eliminate inner air gaps, effectively avoiding coil displacement and inter-turn short-circuit caused by long-term equipment continuous 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 restrain external electromagnetic noise during signal transmission. Field cutting, splicing or connector replacement on original integral cable is strictly prohibited, any physical modification permanently voids factory preset calibration data. Front thread mounting design enables direct screw-in installation from equipment outer surface, suitable for standard bearing pedestal reserved threaded hole layout. Open/short-circuit wiring faults can be rapidly identified via obvious output voltage drift to simplify daily field troubleshooting. The whole measuring system only maintains fixed linear conversion performance when fully matched with original extension cable and designated 2155/00 proximitor.
4. Electrical and Metrological Specifications
The matched 2155/00 proximitor provides regulated negative DC supply ranging from -17.5 VDC to -26 VDC, with typical field operating voltage at -24 VDC. Factory fixed calibrated sensitivity is 7.87 V/mm (200 mV/mil) referenced to standard AISI4140 carbon steel target, full-range linearity tolerance is controlled within ±5% per API 670 specification. Valid linear measuring range covers 0 mm ~ 1.27 mm for small-gap radial vibration and short-travel axial displacement monitoring of most industrial rotating shafts. Effective frequency response spans 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 midpoint of linear range to secure stable bias working point during long-time continuous unit operation.
5. Environmental Working Parameters
Permissible continuous operating temperature of probe sensing section ranges from -35°C to +120°C to adapt high-temperature installation near heated bearing housings and turbine casings. Spare storage temperature is kept between -55°C and +85°C under dry non-condensing storage environment; applicable working relative humidity is 5%RH~95%RH without dew condensation accumulating on probe housing and cable outer jacket. The probe withstands routine industrial vibration of 10 Hz ~ 2 kHz generated by adjacent running rotating equipment. Long-term continuous immersion in corrosive liquid, acid mist and sustained high-temperature steam is forbidden to prevent outer casing corrosion and inner insulation aging damage. For installation above 1000 meters altitude, shorten periodic inspection interval appropriately.
6. Installation and Routine Maintenance Guidance
Cut off power of entire monitoring loop before installation, screw the probe into reserved threaded hole of bearing pedestal or custom mounting fixture, adjust pre-set installation gap to rated design value and lock fastening nut to avoid loosening induced by long-term operational vibration. During cabling construction, separate probe signal cable routing away from high-current AC power cables and inverter output wiring to minimize cross electromagnetic coupling interference. Avoid sharp small-radius bending, overstretching and heavy squeezing on cable body to prevent internal core breakage and impedance shift. Within regular maintenance cycles, inspect cable outer jacket for oil corrosion, abrasion and cracking, and check connector locking tightness. When replacement is needed after probe failure, only spare with identical full part number 21505-00-20-10-02 is permitted for direct swap. All replacement probes complete impedance testing and calibration matching before factory outbound delivery to guarantee full interchangeability inside original measurement loops.
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