Bently Nevada 21504-000-008-10-02 Eddy Current Proximity Probe Product Specification
21504-000-008-10-02 is factory pre-calibrated front-mounted 8 mm eddy current proximity probe designed exclusively for Bently Nevada 7200 series transducer system. When matched with original 2155/00 proximitor preamplifier and factory-calibrated 75-ohm matched extension cable, the complete assembly constitutes a full non-contact measurement system compliant with API 670 standards for critical rotating machinery protection. Based on eddy-current induction principle, the probe converts tiny clearance fluctuations between its sensing tip and conductive metallic rotor target into linear analog voltage signals. These analog outputs 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. Widely deployed on steam turbines, gas turbines, centrifugal compressors and large turbo-generators across power, petrochemical and metallurgical sectors, it delivers over-limit alarm triggers and emergency shutdown interlock signals to secure reliable unit operation. Each finished unit undergoes full-range linearity calibration, high-low temperature cyclic aging test and complete hermetic epoxy encapsulation inspection prior to factory shipment to sustain stable measuring accuracy under rigorous field environments including high bearing housing temperature, continuous lubricating oil mist and complex electromagnetic interference from high-current power cables and variable frequency drive equipment.
Description
Bently Nevada 21504-000-008-10-02 Eddy Current Proximity Probe Product Specification
1. Product Overview
21504-000-008-10-02 is factory pre-calibrated front-mounted 8 mm eddy current proximity probe designed exclusively for Bently Nevada 7200 series transducer system. When matched with original 2155/00 proximitor preamplifier and factory-calibrated 75-ohm matched extension cable, the complete assembly constitutes a full non-contact measurement system compliant with API 670 standards for critical rotating machinery protection. Based on eddy-current induction principle, the probe converts tiny clearance fluctuations between its sensing tip and conductive metallic rotor target into linear analog voltage signals. These analog outputs 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. Widely deployed on steam turbines, gas turbines, centrifugal compressors and large turbo-generators across power, petrochemical and metallurgical sectors, it delivers over-limit alarm triggers and emergency shutdown interlock signals to secure reliable unit operation. Each finished unit undergoes full-range linearity calibration, high-low temperature cyclic aging test and complete hermetic epoxy encapsulation inspection prior to factory shipment to sustain stable measuring accuracy under rigorous field environments including high bearing housing temperature, continuous lubricating oil mist and complex electromagnetic interference from high-current power cables and variable frequency drive equipment.
2. Part Number Definition Breakdown
All coding segments comply with Bently’s standardized part coding specification for 7200-series front-install proximity probes. Base code 21504 represents standard 8 mm diameter front full-threaded proximity probe series developed for the 7200 transducer platform; segment 000 indicates zero exposed unthreaded tip length together with fixed internal coil structure and factory-locked original calibration parameters without customized electrical modification; segment 008 stands for ultra-short full-threaded body dimension engineered for ultra-shallow mounting holes on thin-wall standard bearing pedestals; segment 10 refers to factory pre-molded integral coaxial cable with fixed 1.0-meter length permanently bonded to the probe main body during original production; final suffix 02 specifies standard miniature male coaxial terminal connector fitted at cable tail for plug-and-play connection with certified original extension cable. Random replacement with differently coded probes changes mechanical dimensions or calibrated electrical characteristics, invalidates full-loop factory matching calibration and may cause measurement drift or undesired protective tripping of the corresponding monitoring channel.
3. Core Functional Characteristics
The probe’s threaded housing and sensing tip are precision fabricated from high-strength corrosion-resistant stainless steel, featuring outstanding resistance against lubricant erosion and corrosive vapor accumulated inside sealed bearing compartments. 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-duration equipment vibration and fluctuating ambient temperature. The attached 1.0-meter integral cable adopts standard 75-ohm controlled-impedance coaxial construction with dense tinned copper braided shielding exceeding 95% coverage to suppress external electromagnetic crosstalk throughout field signal transmission. On-site cutting, splicing or arbitrary replacement of original integral cable and end connector is strictly prohibited, as any physical alteration permanently voids factory preset calibration data of the complete transducer set. The ultra-short full-thread front mounting design is optimized for ultra-shallow pre-drilled holes and thin-wall bearing pedestal structures incompatible with longer threaded probes. Built-in open-circuit and short-circuit fault diagnostics identify abnormal wiring via noticeable output voltage deviation to streamline routine field troubleshooting. Consistent linear measurement performance of the entire system can only be preserved through genuine original matching of this probe, calibrated extension cable and designated 2155/00 proximitor preamplifier.
4. Electrical and Metrological Specifications
Matching 2155/00 proximitor provides regulated negative DC supply ranging from -17.5 VDC to -26 VDC, with -24 VDC defined as standard nominal operating voltage for industrial field application. Factory-set calibrated sensitivity is 7.87 V/mm (200 mV/mil) referenced against standard AISI4140 carbon steel target material, and full-range linearity deviation is restricted within ±5% per API 670 specification requirements. Valid linear measuring range spans 0 mm to 2.0 mm, satisfying routine radial vibration and short-travel axial clearance measurement for most industrial rotating shafts. Effective frequency response covers DC up to 10 kHz, enabling synchronous acquisition of low-frequency static thermal expansion drift and high-frequency dynamic shaft vibration signals. Recommended pre-installation gap is positioned near the midpoint of linear range to maintain a stable bias operating point for prolonged uninterrupted equipment service.
5. Environmental Working Parameters
The sensing portion supports continuous operating temperature from -35°C to +120°C to accommodate high-temperature installation adjacent to heated bearing housings and turbine casings. Storage temperature for spare units is maintained between -55°C and +85°C under dry non-condensing conditions; applicable operating relative humidity ranges from 5%RH to 95%RH without dew condensation on probe housing and cable outer jacket. The probe withstands regular industrial mechanical vibration of 10 Hz ~ 2 kHz generated by nearby operating rotating equipment. Long-term continuous immersion or exposure to 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 sites above 1000 meters altitude, regular inspection frequency shall be properly increased.
6. Installation and Routine Maintenance Guidance
Disconnect full power of the entire monitoring loop before field installation, screw the ultra-short full-threaded probe into pre-reserved ultra-shallow threaded holes of bearing pedestals or custom mounting fixtures, adjust pre-set installation clearance to rated design value and fasten lock nut securely to eliminate loosening triggered by long-running operational vibration. During cabling work, route the probe signal cable separately away from high-current AC power lines and inverter output wiring to minimize cross electromagnetic coupling interference. Avoid sharp small-radius bending, excessive stretching and heavy mechanical squeezing 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, and verify locking tightness of end terminal connector. Upon probe failure requiring replacement, only spare parts with identical full part number 21504-000-008-10-02 are permitted for direct swap. All replacement probes complete full electrical performance testing and alternating temperature aging screening before factory delivery to guarantee full interchangeability within original vibration monitoring measurement loops.
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