June 05, 2026

Bently Nevada 21501-00-08-05-02 Eddy Current Proximity Probe Product Specification

21501-00-08-05-02 is factory pre-calibrated front-mounted 5 mm eddy current proximity probe specially designed for Bently Nevada 7200 series transducer system. Together with original 2155/00 proximitor preamplifier and factory-calibrated 75-ohm matched extension cable, the complete set forms a full non-contact measurement system conforming to API 670 standards for critical rotating machinery protection. Based on the eddy-current induction principle, the probe converts tiny clearance variations 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 continuously measure shaft radial vibration, short-travel axial displacement and Keyphasor rotational pickup pulses. This probe is widely fitted on compact high-speed gas turbines, miniature centrifugal compressors and small turbo-generators in power, petrochemical and metallurgical industries to provide over-limit alarm and emergency shutdown interlock signals for equipment safe operation. Each finished probe undergoes full-range linearity calibration, high-low temperature cyclic aging test and full hermetic epoxy encapsulation inspection before factory delivery to retain stable measuring accuracy under harsh field conditions including high bearing housing temperature, continuous lubricating oil mist and complex electromagnetic interference from high-current power cables and variable frequency drive devices.

Description

Bently Nevada 21501-00-08-05-02 Eddy Current Proximity Probe Product Specification

1. Product Overview

2. Part Number Definition Breakdown

Each coding segment follows Bently’s unified part coding specification 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 indicates zero exposed unthreaded tip length, fixed internal coil structure and factory-locked original calibration parameters without customized electrical modification; segment 08 represents ultra-short full-threaded body dimension made for ultra-shallow mounting holes on thin-wall standard bearing pedestals; segment 05 means factory pre-molded integral coaxial cable with fixed 0.5-meter length permanently bonded to probe main body during production; final suffix 02 refers to standard miniature male coaxial terminal connector pre-installed at cable tail for plug-in connection with certified original extension cable. Random replacement with probes of different part numbers will change mechanical dimensions or calibrated electrical characteristics, invalidate full-loop factory matching calibration and cause measurement deviation or unexpected protective tripping of the corresponding monitoring channel.

3. Core Functional Characteristics

The probe’s threaded housing and sensing tip are precision machined from high-strength corrosion-resistant stainless steel with superior resistance against lubricant erosion and corrosive vapor accumulated inside sealed bearing compartments. The internal induction coil is fully potted with high-temperature resistant epoxy resin to eliminate inner air gaps, effectively avoiding coil displacement and inter-turn short-circuit faults caused by long-term equipment vibration and fluctuating ambient temperature. The attached 0.5-meter integral coaxial cable adopts standard 75-ohm controlled-impedance coaxial design 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, as any physical alteration permanently voids factory preset calibration data of the entire transducer assembly. Ultra-short full-thread front mounting design is optimized for ultra-shallow pre-drilled holes and thin-wall bearing pedestal structures unsuitable for longer threaded probes. Built-in open-circuit and short-circuit fault diagnostics identify abnormal wiring via obvious output voltage drift to facilitate daily field troubleshooting. Consistent linear measurement performance of the whole system can only be secured by genuine original matching of this probe, calibrated extension cable and designated 2155/00 proximitor preamplifier.

4. Electrical and Metrological Specifications

The matched 2155/00 proximitor supplies regulated negative DC supply ranging from -17.5 VDC to -26 VDC, with -24 VDC as the standard nominal operating voltage for 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 controlled within ±5% per API 670 specification requirements. Valid linear measuring range spans 0 mm to 1.27 mm, satisfying routine radial vibration and short-travel axial clearance measurement for small-diameter high-speed industrial rotating shafts. Effective frequency response covers 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 positioned near the midpoint of linear range to maintain a stable bias operating point for long-term uninterrupted equipment service.

5. Environmental Working Parameters

The sensing section 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 probes 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 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 sites above 1000 meters altitude, shorten regular inspection cycle appropriately.

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 prevent 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 the end terminal connector. In case of probe failure requiring replacement, only spare parts with identical full part number 21501-00-08-05-02 are allowed for direct swap. All replacement probes complete full electrical performance testing and alternating temperature aging screening before factory delivery to guarantee full interchangeability within the original vibration monitoring measurement loop.

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