Bently Nevada 21504-00-60-10-02 Eddy Current Proximity Probe Product Specification
21504-00-60-10-02 is factory pre-calibrated front-mounted 8 mm eddy current proximity probe developed for Bently Nevada 7200 series transducer system. Combined with original 2155/00 proximitor preamplifier and 75-ohm factory-calibrated matching extension cable, it forms a complete non-contact measuring system complying with API 670 rotating machinery protection specifications. Based on eddy current induction principle, the probe converts tiny 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 monitor modules to realize 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 industries for over-limit alarm trigger and emergency shutdown interlock protection to guarantee unit safe operation. Every finished probe passes linearity calibration, high-low temperature cyclic aging test and full hermetic epoxy encapsulation inspection before factory delivery to maintain stable measuring accuracy under harsh field conditions including high bearing housing temperature, pervasive lubricant oil mist and complex electromagnetic interference from high-current power cables and variable frequency drives.
Description
Bently Nevada 21504-00-60-10-02 Eddy Current Proximity Probe Product Specification
1. Product Overview
21504-00-60-10-02 is factory pre-calibrated front-mounted 8 mm eddy current proximity probe developed for Bently Nevada 7200 series transducer system. Combined with original 2155/00 proximitor preamplifier and 75-ohm factory-calibrated matching extension cable, it forms a complete non-contact measuring system complying with API 670 rotating machinery protection specifications. Based on eddy current induction principle, the probe converts tiny 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 monitor modules to realize 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 industries for over-limit alarm trigger and emergency shutdown interlock protection to guarantee unit safe operation. Every finished probe passes linearity calibration, high-low temperature cyclic aging test and full hermetic epoxy encapsulation inspection before factory delivery to maintain stable measuring accuracy under harsh field conditions including high bearing housing temperature, pervasive lubricant oil mist and complex electromagnetic interference from high-current power cables and variable frequency drives.
2. Part Number Definition Breakdown
Each coded segment follows Bently’s standard coding rules for 7200 series front-install proximity probes. Base code 21504 represents core series of standard front-thread 8 mm proximity probe exclusively designed for the 7200 transducer platform; segment 00 defines fixed internal coil winding layout, internal wiring structure and factory-locked original electrical calibration parameters without special customized modification; segment 60 specifies extra-long threaded body dimension for deep-hole mounting on thick bearing pedestals; segment 10 stands for factory pre-molded integral coaxial cable fixed length of 1.0 meter permanently attached to probe main body; final segment 02 denotes standard miniature coaxial terminal connector equipped at cable end for plug-in connection with certified original matched extension cable. Probes with altered code digits have different mechanical dimensions or calibrated electrical characteristics and cannot be randomly replaced on-site; improper substitution invalidates full-loop factory preset calibration and results in measurement deviation or unexpected protection trip of the monitoring channel.
3. Core Functional Characteristics
The probe threaded housing and sensing tip are precision fabricated from high-strength corrosion-resistant stainless steel with outstanding resistance against lubricant erosion and weak corrosive vapor 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 or inter-turn short-circuit caused by long-term continuous equipment vibration and ambient temperature fluctuation. The attached 1-meter integral cable adopts standard 75-ohm controlled-impedance coaxial structure with dense tinned copper braided shielding over 95% coverage to suppress external electromagnetic crosstalk during long-distance signal transmission. Field cutting, splicing or manual replacement of original integral cable and end connector is strictly prohibited; any physical modification permanently voids factory preset calibration data. Front screw-in mounting design with extra-long thread is optimized for deep reserved mounting holes and thick-wall bearing pedestal structures unavailable for short-body probes. Built-in open/short-circuit fault diagnosis identifies abnormal wiring via obvious output voltage drift to simplify daily field troubleshooting. Stable linear conversion performance of the whole measuring system can only be retained by full original matching of this probe, designated calibrated extension cable and corresponding 2155/00 proximitor preamplifier.
4. Electrical and Metrological Specifications
The matched 2155/00 proximitor provides regulated negative DC power ranging from -17.5 VDC to -26 VDC, with -24 VDC as standard field operating voltage. 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 standard. Valid linear measuring range covers 0 mm ~ 2.0 mm for regular small-gap radial vibration and short-travel axial displacement measurement of 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 the midpoint of linear range to secure stable bias working point during long-term uninterrupted 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 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 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 immersion in corrosive liquid, acid mist and persistent high-temperature steam is forbidden to avoid 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 supply of entire monitoring loop before installation, screw the extra-long threaded probe into deep reserved threaded hole of bearing pedestal or custom mounting fixture, adjust pre-set installation gap to rated design value and lock fastening nut tightly to prevent 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, periodically inspect cable outer sheath for oil corrosion, abrasion and cracking, and check locking tightness of terminal connector. When probe breakdown requires replacement, only spare part with identical full part number 21504-00-60-10-02 is allowed for direct swap. All replacement probes complete impedance testing and calibration matching before factory outbound delivery to guarantee full interchangeability inside original vibration monitoring loops.
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