Bently Nevada 21508-02-12-05-02 Proximity Probe Product Specification
21508-02-12-05-02 is an 8 mm reverse-mounted eddy current proximity probe belonging to Bently Nevada 7200 and 3300XL proximity transducer product family, specially developed for non-contact real-time measurement of shaft radial vibration, axial thrust displacement and rotational shaft position on critical rotating equipment. As the core sensing component of a complete proximity measurement system, it cooperates with matched proximitor preamplifier and calibrated extension cable to convert metal target clearance variation into proportional analog voltage signal, then transmits measured data to 3300, 7200 or 3500 series rack monitoring modules for machinery condition monitoring and interlock protection control. This probe is widely deployed on steam turbines, gas turbines, centrifugal compressors, large generators and high-speed pumps within power generation, petrochemical, metallurgy and offshore energy industries, fully complying with API 670 industrial machinery protection specification requirements. Every single probe completes factory full-set calibration with designated proximitor and extension cable before delivery to guarantee consistent linear measurement performance under complicated industrial operating surroundings including high bearing housing temperature, oil mist corrosion and strong electromagnetic interference from high-current power equipment.
Description
Bently Nevada 21508-02-12-05-02 Proximity Probe Product Specification
1. Product Overview
21508-02-12-05-02 is an 8 mm reverse-mounted eddy current proximity probe belonging to Bently Nevada 7200 and 3300XL proximity transducer product family, specially developed for non-contact real-time measurement of shaft radial vibration, axial thrust displacement and rotational shaft position on critical rotating equipment. As the core sensing component of a complete proximity measurement system, it cooperates with matched proximitor preamplifier and calibrated extension cable to convert metal target clearance variation into proportional analog voltage signal, then transmits measured data to 3300, 7200 or 3500 series rack monitoring modules for machinery condition monitoring and interlock protection control. This probe is widely deployed on steam turbines, gas turbines, centrifugal compressors, large generators and high-speed pumps within power generation, petrochemical, metallurgy and offshore energy industries, fully complying with API 670 industrial machinery protection specification requirements. Every single probe completes factory full-set calibration with designated proximitor and extension cable before delivery to guarantee consistent linear measurement performance under complicated industrial operating surroundings including high bearing housing temperature, oil mist corrosion and strong electromagnetic interference from high-current power equipment.
2. Part Number Coding Definition
The five-segment part number 21508-02-12-05-02 strictly follows Bently Nevada standard probe coding specification. The base code 21508 represents 8 mm reverse-installed proximity probe core series for 7200/3300XL transducer platform; the second segment 02 stands for standard probe body thread specification and internal coil winding configuration for 8 mm sensing tip; the third segment 12 defines standard probe mounting thread dimension and installation mechanical structure; the fourth segment 05 indicates fixed integral coaxial cable length of 0.5 meter pre-attached to probe body; the final suffix 02 denotes miniature male coaxial connector equipped at the cable terminal for plugging with corresponding extension cable end. Any modification of single code digit changes probe electrical characteristic or total calibrated loop length, cross replacement with probes carrying different part numbers will invalidate original factory calibration data and trigger measurement drift or unexpected equipment protection trip.
3. Core Functional Characteristics
Adopting high-stability eddy current induction working principle without physical contact between probe tip and measured metal target surface, effectively eliminating mechanical abrasion and zero drift induced by friction during long-term continuous equipment running. Internal built-in high-precision enameled copper induction coil with strict impedance matching design ensures stable inductance parameter and excellent signal linearity across full rated measuring range. Outer probe housing is constructed from high-strength anti-corrosion alloy material to resist lubricant oil erosion, chemical vapor corrosion and occasional mechanical collision in bearing compartment space. The attached 0.5-meter integral coaxial cable features 75-ohm controlled impedance structure with dense tinned copper braided shielding over 95% coverage to restrain external electromagnetic noise interference during signal transmission. Field cutting, splicing or connector replacement on integral cable is prohibited entirely, any physical damage on cable or connector will void factory calibration and product warranty. Each probe is calibrated with standard AISI4140 steel target at factory to secure uniform sensitivity matching with supporting proximitor module.
4. Electrical & Mechanical Technical Parameters
Nominal probe tip sensing diameter is 8 mm, standard linear measuring range covers 0 to 2.0 mm (80 mils) gap between probe front end and target surface, standard calibrated sensitivity is 19.7 mV/mm (0.5 mV/mil) under specified test condition of 24 VDC power supply and room temperature environment. Effective working frequency response ranges from DC up to 10 kHz to satisfy measurement demand of low-frequency static axial displacement and high-frequency dynamic shaft vibration signals. Probe body adopts standard thread mounting design for convenient screw-in installation on bearing pedestal and equipment casing; integral cable fixed length maintains 0.5 m without on-site adjustable cutting. Inner cable insulation material owns low capacitance and low dielectric loss property to minimize signal attenuation during short-distance signal transfer from probe to extension cable joint, all electrical indexes pass factory strict high-pot insulation test and impedance consistency inspection before outgoing.
5. Environmental Application Specifications
Continuous allowable operating ambient temperature scope ranges from -40℃ to +260℃ to adapt high-temperature working environment nearby turbine bearing housings and hot equipment compartments. Long-term spare storage temperature is controlled between -55℃ and +177℃ under dry non-condensation storage condition, applicable relative working humidity covers 5%RH~95%RH without dew accumulation on probe housing and cable outer jacket. The finished probe can withstand continuous industrial vibration of 10 Hz to 2 kHz generated by adjacent rotating machinery operation; long-term soaking in strong acid, alkali liquid and persistent high-temperature corrosive steam is forbidden to prevent shell corrosion and inner insulation aging failure. For installation position above 1000 meters altitude, shorten regular inspection cycle appropriately to track working status periodically.
6. Field Installation & Daily Maintenance Guidance
During on-site mounting, keep probe tip perpendicular to measured shaft metal target surface and reserve initial installation gap within the middle section of probe linear measuring range according to system commissioning parameter requirement. Separate probe cable routing away from high-power AC cable, inverter output wiring and high-voltage control line to reduce electromagnetic coupling interference; avoid sharp small-radius bending, excessive pulling and heavy squeezing on integral cable to prevent internal core breakage and impedance deviation. Within periodic maintenance work, visually inspect probe shell for corrosion crack and cable outer sheath for oil soaking abrasion, meanwhile check connector fastening tightness to eliminate loose contact-caused intermittent signal fluctuation. Once probe performance failure occurs, only replacement with identical full part number 21508-02-12-05-02 spare probe is allowed to keep whole transducer loop original calibration intact and measurement accuracy consistent.
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