June 05, 2026

Bently Nevada 21500-00-12-05-02 Eddy Current Proximity Probe Product Specification

21500-00-12-05-02 is factory pre-calibrated front-mounted 14 mm eddy current proximity probe exclusively developed 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 forms a full non-contact measurement system complying with API 670 industry standards for critical heavy-duty rotating machinery protection. Based on eddy-current induction principle, the probe converts minor clearance variations between its sensing tip and conductive metallic rotor target into linear analog voltage signals. These analog signals are transmitted to 7200 or 3500 rack-mounted monitoring modules to realize continuous online measurement of large-diameter shaft radial vibration, long-travel axial displacement and Keyphasor rotational pickup pulse signals. Widely deployed on heavy-duty steam turbines, large industrial gas turbines, oversized centrifugal compressors and big turbo-generators in power, petrochemical and metallurgical industries, it provides over-limit alarm trigger and emergency shutdown interlock signals to guarantee unit safe running. Every finished probe undergoes full-range linearity calibration, high-low temperature cyclic aging test and full hermetic epoxy encapsulation inspection before factory delivery to keep stable measuring accuracy under harsh field conditions including high internal temperature of bearing housings, pervasive lubricating oil mist and complex electromagnetic interference generated by high-current power cables and variable frequency drive equipment.

Description

Bently Nevada 21500-00-12-05-02 Eddy Current Proximity Probe Product Specification

1. Product Overview

2. Part Number Definition Breakdown

All coding segments follow Bently’s unified part coding specification for 7200 series front-installed proximity probes. Base code 21500 represents core product series of standard 14-millimeter diameter front full-thread proximity probe tailored for the 7200 transducer platform; segment 00 stands for zero exposed unthreaded tip length, fixed internal coil winding structure and factory locked original electrical calibration parameters without customized electrical modification; segment 12 specifies ultra-short full-threaded body dimension designed for ultra-shallow mounting holes on compact thin-wall heavy-duty bearing pedestals; segment 05 defines factory pre-molded integral coaxial cable fixed length of 0.5 meter permanently molded together with probe main body during original production; final suffix code 02 indicates standard miniature male coaxial terminal connector pre-mounted at cable tail for plug-type connection with original calibrated matched extension cable. Random replacement with non-same part number products will break the full-loop factory matching calibration, resulting in measuring deviation or unexpected protection trip of corresponding monitoring channel.

3. Core Functional Characteristics

The probe threaded housing and sensing head are precision machined from high-density anti-corrosion stainless steel material with outstanding resistance against lubricant erosion and weak corrosive vapor inside sealed bearing cavity. Internal induction coil is fully filled and fixed with high-temperature resistant epoxy potting adhesive to eliminate internal air gap, effectively avoid coil displacement and inter-turn short-circuit fault caused by long-term equipment running vibration and fluctuating ambient temperature. Attached 0.5-meter integral coaxial cable adopts standard 75-ohm controlled impedance structure with over 95% coverage dense tinned copper braided shielding layer to restrain external electromagnetic crosstalk during on-site signal transmission. Field cutting, joint splicing and arbitrary replacement of original cable and tail connector are strictly prohibited, all manual physical changes will permanently invalidate factory preset full-set calibration data of the whole transducer system. Ultra-short full-thread customized body design is exclusively optimized for ultra-shallow embedded installation environment of compact thin-wall heavy-duty bearing seat structure. Built-in open-circuit and short-circuit self-diagnosis function rapidly feeds back abnormal wiring state through obvious output voltage offset to simplify daily field circuit troubleshooting work. Complete measuring linearity of the whole system can only be maintained by original matching of this probe, designated calibrated extension cable and supporting 2155/00 proximitor preamplifier.

4. Electrical and Metrological Specifications

Matched supporting 2155/00 proximitor supplies regulated negative DC working voltage ranging from -17.5VDC to -26VDC, and -24VDC is the standard rated operating voltage adopted in practical industrial field. Factory fixed calibrated sensitivity is 7.87V/mm (200mV/mil) with standard AISI4140 carbon steel as calibration target material, full measuring range linearity error is controlled within ±5% complying with API670 specification requirement. Valid linear measuring range covers 0mm~2.54mm, which satisfies routine radial vibration and long-travel axial clearance detection of large industrial rotating shafts. Effective frequency response range covers DC to 10kHz, synchronously collecting low-frequency static thermal expansion drift signal and high-frequency dynamic shaft vibration signals. Recommended pre-installation gap is set at middle position of linear measuring range to ensure stable bias working point for long-time uninterrupted equipment operation.

5. Environmental Working Parameters

Permissible continuous operating temperature of probe sensing part ranges from -35°C to +120°C to adapt high-temperature installation surroundings near heated bearing housings and turbine cylinder casings. Spare part storage temperature is controlled between -55°C and +85°C under dry non-condensing storage environment; applicable working relative humidity ranges from 5%RH to 95%RH without dew accumulation on probe outer casing and cable outer jacket surface. The probe withstands routine industrial vibration of 10Hz~2kHz generated by adjacent running rotating equipment. Long-term continuous soaking in corrosive chemical liquid, acid mist and persistent high-temperature steam environment is forbidden to avoid outer casing corrosion and inner insulation aging damage. For installation location above altitude 1000 meters, shorten periodic inspection interval appropriately.

6. Installation and Routine Maintenance Guidance

Cut off total power supply of whole 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 gap to rated design value and lock fastening nut tightly to prevent installation looseness induced by long-term equipment running 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 squeezing on cable body to prevent inner core breakage and abnormal 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 replacement is needed after probe failure, only spare part with identical full part number 21500-00-12-05-02 is permitted for direct swap. All replacement probes complete impedance testing and calibration matching before factory outbound delivery to guarantee full interchangeability inside original vibration monitoring loops.

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