Bently Nevada 21504-000-012-10-02 Eddy Current Proximity Probe Product Specification
21504-000-012-10-02 is factory pre-calibrated front-mounted 8 mm eddy current proximity probe specifically designed for Bently Nevada 7200 series transducer system. When combined with original 2155/00 proximitor preamplifier and factory-calibrated 75-ohm matched extension cable, the entire assembly forms a complete non-contact measurement system compliant with API 670 specification for critical rotating machinery protection. Based on eddy-current induction working principle, the probe converts minor clearance variations between its sensing tip and conductive metallic rotor target into linear analog voltage signals. These output signals are transmitted to 7200 or 3500 rack-mounted monitoring modules to realize continuous online measurement of shaft radial vibration, short-stroke axial displacement and Keyphasor rotational pickup pulse signals. This probe is widely applied on steam turbines, gas turbines, centrifugal compressors and large turbo-generators within power generation, petrochemical and metallurgical industries to provide over-limit alarm and emergency shutdown interlock signals for unit safe operation. Every finished probe undergoes full-range linear calibration, high-low temperature cyclic aging test and full hermetic epoxy encapsulation inspection prior to factory delivery to sustain stable measuring accuracy under harsh field conditions including high bearing housing temperature, persistent lubricating oil mist and complicated electromagnetic interference from high-current power cables and variable frequency drive equipment.
Description
Bently Nevada 21504-000-012-10-02 Eddy Current Proximity Probe Product Specification
1. Product Overview
21504-000-012-10-02 is factory pre-calibrated front-mounted 8 mm eddy current proximity probe specifically designed for Bently Nevada 7200 series transducer system. When combined with original 2155/00 proximitor preamplifier and factory-calibrated 75-ohm matched extension cable, the entire assembly forms a complete non-contact measurement system compliant with API 670 specification for critical rotating machinery protection. Based on eddy-current induction working principle, the probe converts minor clearance variations between its sensing tip and conductive metallic rotor target into linear analog voltage signals. These output signals are transmitted to 7200 or 3500 rack-mounted monitoring modules to realize continuous online measurement of shaft radial vibration, short-stroke axial displacement and Keyphasor rotational pickup pulse signals. This probe is widely applied on steam turbines, gas turbines, centrifugal compressors and large turbo-generators within power generation, petrochemical and metallurgical industries to provide over-limit alarm and emergency shutdown interlock signals for unit safe operation. Every finished probe undergoes full-range linear calibration, high-low temperature cyclic aging test and full hermetic epoxy encapsulation inspection prior to factory delivery to sustain stable measuring accuracy under harsh field conditions including high bearing housing temperature, persistent lubricating oil mist and complicated electromagnetic interference from high-current power cables and variable frequency drive equipment.
2. Part Number Definition Breakdown
Each coding segment follows Bently’s standard part coding rules for 7200-series front-install proximity probes. Base code 21504 stands for core series of standard 8 mm diameter front full-thread proximity probe exclusively developed for the 7200 transducer platform; segment 000 represents zero exposed unthreaded tip length, fixed internal coil winding layout and factory-locked original calibration parameters without customized electrical modification; segment 012 refers to ultra-short full-threaded body dimension optimized for ultra-shallow mounting holes on thin-wall standard bearing pedestals; segment 10 defines factory pre-molded integral coaxial cable with fixed 1.0-meter length permanently bonded to probe main body during production; final suffix code 02 indicates standard miniature male coaxial terminal connector pre-installed at cable tail for plug-in connection with certified original extension cable. Random substitution with probes of different part numbers will alter mechanical dimensions or calibrated electrical parameters, invalidate factory full-loop matching calibration and trigger measurement deviation or unexpected protective shutdown of the monitoring channel.
3. Core Functional Characteristics
The probe’s threaded housing and sensing tip are precision manufactured from high-strength corrosion-resistant stainless steel with superior anti-corrosion performance against lubricant erosion and corrosive vapor inside sealed bearing compartments. Internal induction coil is fully potted with high-temperature resistant epoxy resin to eliminate inner air gaps, effectively preventing coil displacement and inter-turn short-circuit faults caused by long-term equipment vibration and ambient temperature fluctuation. The attached 1.0-meter integral coaxial cable adopts standard 75-ohm controlled-impedance structure with dense tinned copper braided shielding over 95% coverage to suppress external electromagnetic crosstalk during field signal transmission. On-site cutting, splicing or arbitrary replacement of original cable and end connector is strictly prohibited; any physical modification will permanently void factory preset calibration data of the complete transducer set. Ultra-short full-thread front mounting design is specially tailored for ultra-shallow pre-drilled mounting holes and thin bearing pedestal structures where longer threaded probes cannot be assembled properly. Built-in open-circuit and short-circuit fault diagnosis identifies abnormal wiring via obvious output voltage drift to simplify daily field troubleshooting. Consistent 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 matched 2155/00 proximitor supplies regulated negative DC power ranging from -17.5 VDC to -26 VDC, with -24 VDC as the standard nominal operating voltage for industrial field application. Factory fixed calibrated sensitivity is 7.87 V/mm (200 mV/mil) referenced to standard AISI4140 carbon steel target material, and full-range linearity error is controlled within ±5% in accordance with API 670 requirements. Valid linear measuring range covers 0 mm to 2.0 mm to meet regular radial vibration and short-travel axial clearance measurement of most industrial 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 keep a stable bias working point for long-term uninterrupted equipment running.
5. Environmental Working Parameters
Permissible continuous operating temperature of the probe sensing section ranges from -35°C to +120°C to adapt high-temperature installation near heated bearing housings and turbine casings. Storage temperature for spare probes is kept between -55°C and +85°C under dry non-condensing surroundings; applicable working relative humidity is 5%RH ~ 95%RH without dew condensation on probe housing and cable outer jacket. The probe can withstand regular industrial vibration of 10 Hz ~ 2 kHz generated by adjacent running rotating equipment. Long-term continuous exposure or immersion in corrosive liquid, acid mist and persistent high-temperature steam is forbidden to avoid outer casing corrosion and premature aging of internal insulating materials. For installation locations above 1000 meters altitude, shorten regular inspection cycle appropriately.
6. Installation and Routine Maintenance Guidance
Disconnect total power of the entire monitoring loop before field installation, screw the ultra-short full-thread probe into pre-reserved ultra-shallow threaded hole of bearing pedestal or custom mounting fixture, adjust pre-set installation clearance to rated design value and tighten lock nut securely to prevent loosening induced by long-running operational vibration. During cabling work, 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, excessive stretching and heavy mechanical extrusion on cable body to prevent inner conductor fracture and abnormal impedance shift. Within scheduled maintenance cycles, periodically inspect cable outer sheath for oil corrosion, abrasion and cracking damage, and verify locking tightness of the end terminal connector. In case of probe failure requiring replacement, only spare parts with identical full part number 21504-000-012-10-02 are allowed for direct swap. All replacement probes complete full electrical performance testing and alternating temperature aging screening before factory outbound delivery to guarantee full interchangeability inside original vibration monitoring loops.
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