Bently Nevada 21501-00-20-10-02 Eddy Current Proximity Probe Product Specification
21501-00-20-10-02 is factory pre-calibrated front-mounted 5 mm eddy current proximity probe exclusively engineered for Bently Nevada 7200 series transducer system. When paired with original 2155/00 proximitor preamplifier and factory-calibrated 75-ohm matched extension cable, the complete assembly forms a full non-contact measurement system complying with API 670 specification for critical rotating machinery protection. Based on eddy-current induction principle, the probe converts minor clearance variations between sensing tip and conductive metallic rotor target into linear analog voltage signals. These signals are transmitted to 7200 or 3500 rack-mounted monitoring modules for continuous online measurement of shaft radial vibration, short-travel axial displacement and Keyphasor rotational pickup pulses. Widely applied on small high-speed gas turbines, compact centrifugal compressors and miniature turbo-generators in power, petrochemical and metallurgical industries, it provides over-limit alarm and emergency shutdown interlock signals to secure reliable unit operation. Every finished probe undergoes full-range linearity calibration, high-low temperature cyclic aging test and full hermetic epoxy encapsulation inspection prior to factory shipment to retain stable measuring accuracy under severe field conditions including high bearing housing temperature, persistent lubricating oil mist and complex electromagnetic interference from high-current power cables and variable frequency drive equipment.
Description
Bently Nevada 21501-00-20-10-02 Eddy Current Proximity Probe Product Specification
1. Product Overview
21501-00-20-10-02 is factory pre-calibrated front-mounted 5 mm eddy current proximity probe exclusively engineered for Bently Nevada 7200 series transducer system. When paired with original 2155/00 proximitor preamplifier and factory-calibrated 75-ohm matched extension cable, the complete assembly forms a full non-contact measurement system complying with API 670 specification for critical rotating machinery protection. Based on eddy-current induction principle, the probe converts minor clearance variations between sensing tip and conductive metallic rotor target into linear analog voltage signals. These signals are transmitted to 7200 or 3500 rack-mounted monitoring modules for continuous online measurement of shaft radial vibration, short-travel axial displacement and Keyphasor rotational pickup pulses. Widely applied on small high-speed gas turbines, compact centrifugal compressors and miniature turbo-generators in power, petrochemical and metallurgical industries, it provides over-limit alarm and emergency shutdown interlock signals to secure reliable unit operation. Every finished probe undergoes full-range linearity calibration, high-low temperature cyclic aging test and full hermetic epoxy encapsulation inspection prior to factory shipment to retain stable measuring accuracy under severe field conditions including high bearing housing temperature, persistent lubricating oil mist and complex electromagnetic interference from high-current power cables and variable frequency drive equipment.
2. Part Number Definition Breakdown
All code segments follow Bently’s standard coding rules for 7200-series front-install proximity probes. Base code 21501 stands for standard 5 mm diameter front full-thread proximity probe series developed for the 7200 transducer platform; segment 00 means zero exposed unthreaded tip length, fixed internal coil layout and factory-locked original calibration parameters without customized electrical modification; segment 020 defines short full-threaded body dimension suitable for shallow standard mounting holes on thin and medium-thickness bearing pedestals; segment 10 represents factory pre-molded integral coaxial cable with fixed 1.0-meter length permanently bonded to probe main body during production; final suffix 02 indicates standard miniature male coaxial terminal connector mounted at cable tail for plug-in connection with certified original extension cable. Random substitution with probes of different part numbers changes mechanical dimensions or calibrated electrical parameters, invalidates factory full-loop matching calibration and may trigger measurement deviation or unexpected protective channel tripping.
3. Core Functional Characteristics
The probe’s threaded housing and sensing tip are precision machined from high-strength corrosion-resistant stainless steel with excellent resistance against lubricant erosion and corrosive vapor inside sealed bearing cavities. Internal induction coil is fully potted with high-temperature resistant epoxy resin to eliminate internal air gaps, effectively preventing coil displacement and inter-turn short-circuit faults induced by long-term equipment vibration and fluctuating ambient temperature. The attached 1.0-meter integral cable adopts standard 75-ohm controlled-impedance coaxial structure with over 95% coverage dense tinned copper braided shielding to suppress external electromagnetic crosstalk during on-site signal transmission. On-site cutting, splicing or arbitrary replacement of original cable and end connector is strictly prohibited; any physical damage permanently voids factory preset calibration data of the entire transducer set. Short full-thread front mounting design is optimized for conventional shallow pre-drilled holes and common thin-wall bearing pedestal structures. Built-in open/short-circuit fault diagnosis identifies abnormal wiring via obvious output voltage drift to simplify daily field troubleshooting. Stable linear measurement performance of the whole system can only be maintained by genuine original matching of this probe, certified extension cable and designated 2155/00 proximitor preamplifier.
4. Electrical and Metrological Specifications
The matching 2155/00 proximitor supplies regulated negative DC voltage ranging from -17.5 VDC to -26 VDC, with -24 VDC as standard nominal operating voltage for field usage. Factory-set calibrated sensitivity is 7.87 V/mm (200 mV/mil) referenced to standard AISI4140 carbon steel target, and full-range linearity error is controlled within ±5% as required by API 670. Valid linear measuring range covers 0 mm ~ 1.27 mm, satisfying routine radial vibration and short-stroke axial clearance measurement for small-diameter high-speed rotating shafts. Effective frequency response spans DC up to 10 kHz to synchronously collect low-frequency static thermal expansion drift and high-frequency dynamic shaft vibration signals. Recommended pre-installation gap is set near the midpoint of linear range to maintain stable bias working point for long-term uninterrupted equipment running.
5. Environmental Working Parameters
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 probe storage temperature is kept between -55°C and +85°C under dry non-condensing surroundings; applicable working relative humidity is 5%RH ~ 95%RH without dew accumulating on probe housing and cable outer sheath. The probe withstands regular industrial vibration of 10 Hz ~ 2 kHz generated by adjacent operating rotating machinery. Long-term continuous exposure or immersion in corrosive liquid, acid mist and persistent high-temperature steam is forbidden to avoid outer shell corrosion and premature aging of internal insulation materials. For installation locations above 1000 meters altitude, shorten regular inspection cycle appropriately.
6. Installation and Routine Maintenance Guidance
Cut off total power of the entire monitoring loop before field installation, screw the short full-thread probe into pre-reserved shallow threaded holes of bearing pedestal or custom mounting fixture, adjust installation clearance to rated design value and tighten lock nut firmly to prevent loosening caused by long-running operational 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 mechanical squeezing on cable body to prevent inner conductor breakage and abnormal impedance shift. Within regular maintenance cycles, periodically inspect cable outer sheath for oil corrosion, abrasion and cracking, and check fastening tightness of end terminal connector. When probe fails and needs replacement, only spare with identical full part number 21501-00-20-10-02 is allowed for direct swap. All replacement probes complete electrical performance testing and alternating temperature aging screening before factory delivery to guarantee full interchangeability inside original vibration monitoring loops.
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