Bently Nevada 21000-00-00-00-250-03-02 Armored Eddy Current Probe Assembly Product Specification

The 21000-00-00-00-250-03-02 is a factory pre-calibrated heavy-duty armored eddy current proximity probe within Bently Nevada 21000 series integrated armored probe product lineup. Developed for deep embedded installation inside heavy-duty bearing pedestals under severe operating environments featuring high temperature, heavy oil mist and complicated mechanical assembly stress, this unit integrates standard 3300XL proximity sensing core encapsulated inside a full metal protective armored sleeve. When matched with original designated proximitor transducer and certified supporting extension cable, it forms a complete non-contact displacement measurement system fully compliant with API 670 international machinery protection specification. Widely deployed on large steam turbines, heavy industrial gas turbines, oversized centrifugal compressors and high-power turbo-generator sets in power generation, petrochemical and metallurgical industries, the probe continuously monitors shaft radial vibration, axial thrust displacement and keyphasor rotational speed. It outputs over-limit alarm and emergency unit trip interlock signals to avoid destructive equipment damage caused by abnormal operating parameters. Each finished probe assembly goes through full-range linear calibration, high-low temperature cyclic aging test and full hermetic sealing inspection before factory shipment to sustain stable measuring accuracy throughout long-term harsh on-site operation.

The seven-position part number follows Bently’s unified coding rule for armored proximity probe configuration definition. The leading code 21000 represents heavy-duty full-armored probe series with integrated anti-impact and oil-proof metal protective casing; the second code 00 indicates standard 8 mm diameter 3300XL internal sensing core together with matched aluminum alloy armored housing structure; the third code 00 means no factory pre-molded integral cable attached to probe body, requiring separate connection with user-configured original matched extension cable on site; the fourth code 00 stands for fully recessed sensing tip design with zero tip length protruding out of armored sleeve front face for complete anti-collision and abrasion prevention during installation and running; the fifth code 250 defines total armored sleeve length of 25 inches, specially customized for ultra-deep bore embedded mounting on extra thick heavy-duty bearing housings; the sixth code 03 specifies 3/4-14 NPT tapered pipe thread as standard mounting thread for bearing pedestal threaded holes; the last suffix code 02 refers to standard rear-end general industrial sealing structure and miniature coaxial connector without special explosion-proof certification, delivered under original factory calibration configuration. Random replacement with unmatched specification probes will invalidate factory preset matching calibration and lead to measurement deviation or undesired protection channel tripping.

The armored outer sleeve and front protective structure are precision manufactured from high-strength corrosion-resistant stainless steel, delivering excellent endurance against lubricant erosion, high-temperature oil vapor and accidental mechanical impact inside closed bearing chambers. The internal induction coil of sensing core is fully potted with high-temperature resistant epoxy resin to eliminate internal air gaps, effectively preventing coil displacement and inter-turn short-circuit faults triggered by long-period equipment vibration and fluctuating ambient temperature. Since no integral cable is pre-attached at factory, field wiring must adopt genuine original matched extension cable complying with 75-ohm controlled impedance standard; random cutting, splicing or replacement with non-original cable is strictly prohibited to avoid permanent failure of factory calibrated electrical parameters. Fully recessed probe tip plus ultra-long armored sleeve design is exclusively optimized for ultra-deep embedded installation of extra thick-wall heavy-duty bearing seats, isolating assembly extrusion stress and protecting sensing core from scratch damage. Built-in open-circuit and short-circuit self-diagnosis function rapidly reflects abnormal wiring status through obvious output voltage offset to simplify daily field troubleshooting work. Reliable linear measuring performance of the whole monitoring system can only be maintained by original matching of this probe, designated extension cable and compatible proximitor transducer.

The matched proximitor requires regulated negative DC power supply ranging from -17.5 VDC to -26 VDC, with -24 VDC set as nominal standard operating voltage for regular industrial field application. Factory fixed calibrated sensitivity is 7.87 V/mm (200 mV/mil) referenced to standard AISI4140 carbon steel target material, and full-range linearity error is controlled within ±5% per API 670 requirements. Valid linear measuring range covers 0 mm to 2.54 mm to satisfy regular radial vibration and long-stroke axial clearance measurement for large-diameter industrial rotating shafts. Effective frequency response spans DC up to 10 kHz to synchronously collect low-frequency static thermal expansion drift and high-frequency dynamic shaft vibration signals. The recommended pre-installation gap is positioned near the midpoint of linear range to keep stable DC bias working point for long-term uninterrupted equipment continuous operation.

The probe sensing section supports continuous operating temperature ranging from -35°C to +120°C to fit high-temperature installation surroundings adjacent to heated bearing housings and turbine casings. Storage temperature for spare probe assemblies is maintained between -55°C and +85°C under dry non-condensing storage conditions; applicable working relative humidity ranges from 5%RH to 95%RH without dew accumulation on probe outer casing and connecting cable jacket. The probe can withstand regular industrial mechanical vibration of 10 Hz ~ 2 kHz generated by nearby continuously running rotating equipment. Long-term continuous soaking or exposure in corrosive liquid, acid mist and persistent high-temperature steam is forbidden to prevent outer casing corrosion and premature aging of internal insulating materials. For installation locations above 1000 meters altitude, regular inspection interval shall be appropriately shortened.

Cut off total power supply of the entire monitoring loop before field installation, screw the threaded probe body into pre-machined ultra-deep threaded hole of bearing pedestal or custom mounting fixture via standard 3/4-14 NPT thread, adjust pre-set installation clearance to rated design value and fasten lock nut tightly to eliminate loosening risk induced by long-running operational vibration. During subsequent cable connection and routing, separate signal wiring away from high-current AC power cables and inverter output lines to minimize cross electromagnetic coupling interference. Avoid sharp small-radius bending, excessive stretching and heavy mechanical squeezing on matched extension cable to prevent inner conductor fracture and abnormal impedance shift. Within fixed maintenance cycles, periodically check probe housing for corrosion and mechanical damage, inspect connecting cable outer sheath for oil corrosion, abrasion and cracking, and verify locking tightness of rear-end coaxial connector. When replacement is required after probe failure, only spare unit with identical part number 21000-00-00-00-250-03-02 is permitted for direct swap. All replacement probes complete full electrical performance testing and alternating temperature aging screening before factory outbound delivery to guarantee full interchangeability inside original vibration monitoring loops.