Bently Nevada 33105-02-12-05-02-00 Eddy Current Proximity Probe – 3300 XL Series

Bently Nevada 33105-02-12-05-02-00 — Reverse Mount Eddy Current Proximity Probe for Critical Rotating Machinery Protection

The Bently Nevada 33105-02-12-05-02-00 is a reverse-mount eddy current proximity probe belonging to the 3300 XL 8 mm Proximity Transducer System. It is engineered for continuous, non-contact measurement of radial shaft vibration and axial position displacement in critical rotating machinery where conventional front-access probe installation is mechanically impractical. The reverse-mount mechanical interface allows the probe body to be inserted from the non-drive end of a bearing housing, eliminating the need for additional machining or structural modification to the machine casing.

This probe operates as the sensing element within a three-component transducer chain: the probe tip generates a high-frequency electromagnetic field (nominally 1 MHz oscillation frequency), the extension cable transmits the RF signal with matched impedance to the driver/oscillator, and the driver conditions the output to a DC voltage proportional to the gap between probe face and conductive target shaft. The conditioned signal feeds directly into Bently Nevada 3500 Series rack-mounted monitor cards for alarm, trip, and continuous data acquisition. The 33105-02-12-05-02-00 is fully interchangeable within existing 3300 XL infrastructure without requiring recalibration of the monitoring rack.

Deployed across power generation, oil and gas, petrochemical, and heavy industrial sectors, the 3300 XL probe series has accumulated decades of field validation in API 670-compliant machinery protection systems. The 33105 reverse-mount variant is the preferred selection for steam turbine HP/LP stages, centrifugal compressor trains, boiler feed pumps, and hydro turbine vertical shaft machines where bearing housing geometry restricts standard probe access.

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Technical Parameters

Hardware Logical Analysis

The eddy current sensing principle in the 33105-02-12-05-02-00 relies on the interaction between the probe coil’s oscillating electromagnetic field and the conductive target surface. When the probe tip is energized at approximately 1 MHz by the matched driver oscillator, the field penetrates the target material and induces circulating eddy currents. The magnitude of these induced currents is an inverse function of the air gap distance: as the shaft approaches the probe face, eddy current density increases, loading the probe coil and reducing its effective inductance. The driver circuit detects this inductance shift and converts it to a proportional DC output voltage at the calibrated scale factor of 7.87 V/mm.

Reverse-Mount Mechanical Interface: The 33105 series uses a threaded body designed for insertion from the rear face of the bearing housing bracket. The probe tip protrudes through the housing bore to the correct installation gap (nominally 1.0 mm from shaft surface), while the cable exits rearward — away from the machine casing — reducing cable routing complexity and mechanical stress at the cable-probe junction. This geometry is particularly advantageous in turbine pedestals and compressor bearing housings where front-face access is blocked by coupling guards or structural members.

EMC Design: The integral stainless steel armored cable provides continuous electromagnetic shielding from probe tip to driver input, maintaining signal integrity in environments with high-frequency switching drives, large motor fields, and ground loop interference common in industrial plant rooms. The coaxial cable construction maintains a controlled characteristic impedance matched to the driver input, preventing signal reflection and scale factor drift across the cable run.

Thermal Stability: The probe coil assembly is wound on a thermally stable ceramic former and encapsulated in a high-temperature compound rated to +177°C. This construction maintains coil geometry and inductance characteristics across the full operating temperature range, limiting thermal scale factor drift to within the system specification. In steam turbine applications where bearing housing temperatures can exceed 120°C during steady-state operation, this thermal margin provides a reliable safety buffer without derating the measurement accuracy.

Target Material Sensitivity: The 7.87 V/mm scale factor is calibrated against AISI 4140 alloy steel, the standard shaft material specified in API 670. For shafts manufactured from stainless steel, titanium, or other non-ferrous alloys, the effective scale factor will differ due to variations in electrical conductivity and magnetic permeability. Bently Nevada provides target material correction factors; these must be applied during system commissioning to maintain measurement accuracy within ±1% of full-scale range.

System Integration Benefits

• Direct 3500 Series Compatibility: The 33105-02-12-05-02-00 integrates without signal conditioning adapters into Bently Nevada 3500/40M, 3500/42M, and 3500/45 monitor cards. The –24 VDC supply and DC voltage output protocol are native to the 3500 rack backplane, eliminating interface engineering effort during system expansion or probe replacement.
• Dual-Parameter Measurement from Single Installation: A single probe installation simultaneously delivers the dynamic AC vibration component (shaft orbit, 1X/2X amplitude) and the static DC position component (average shaft centerline position). This eliminates the need for separate displacement transducers for position monitoring, reducing hardware count and bearing housing penetration requirements.
• DC to 10 kHz Bandwidth: The flat frequency response from DC to 10,000 Hz captures sub-synchronous instabilities (oil whirl, oil whip), synchronous 1X imbalance, and high-frequency structural resonances within a single measurement channel. This bandwidth exceeds the API 670 minimum requirement of DC to 1,000 Hz, providing diagnostic margin for early-stage fault detection.
• Non-Contact Operation Eliminates Wear: The absence of physical contact between probe and rotating shaft means zero mechanical wear on the sensing element. Mean time between replacement is governed by environmental degradation (temperature cycling, chemical exposure) rather than mechanical fatigue, supporting multi-year continuous operation intervals between planned maintenance outages.
• Deterministic Signal Latency: The eddy current transducer chain introduces no digital processing latency. The analog DC output responds to gap changes within the driver’s bandwidth (DC to 10 kHz), ensuring that the 3500 monitor receives real-time displacement data with no buffering delay. This is critical for machinery protection applications where trip response time is specified in milliseconds.
• Plug-and-Play Replacement: The 33105-02-12-05-02-00 is a direct mechanical and electrical replacement for worn or damaged probes within the 3300 XL system. No driver recalibration or monitor card reconfiguration is required, provided the replacement probe is from the same 3300 XL family with matching scale factor. This minimizes planned outage duration during probe replacement activities.
• ATEX/IECEx Zone Compatibility: When paired with a certified 3300 XL driver carrying the appropriate ATEX/IECEx certification, the probe assembly is suitable for installation in Zone 1 and Zone 2 hazardous area classifications. This makes the system applicable to offshore platform compressor trains, refinery process gas machinery, and LNG facility rotating equipment without requiring additional intrinsic safety barriers.
• Diagnostic Transparency via Bently Nevada System 1: The analog output of the 33105-02-12-05-02-00 is fully compatible with Bently Nevada System 1 condition monitoring software. When connected through the 3500 rack’s communication gateway, the probe data stream supports shaft centerline plots, orbit diagrams, trend analysis, and alarm event logging — providing maintenance engineers with full diagnostic transparency without additional hardware investment.

Quality Assurance & Global Logistics

Every Bently Nevada 33105-02-12-05-02-00 unit supplied by siemensplc.com is sourced through verified industrial automation supply channels with full part number traceability to the Bently Nevada (Baker Hughes) product catalog. Prior to dispatch, each probe undergoes a pre-shipment inspection covering physical housing integrity, armored cable continuity, coaxial connector condition, and part number label verification against the order specification. Certificate of conformance documentation is available upon request for critical plant applications requiring material traceability records.

Our logistics operations are based in Xiamen, China — a major international freight hub with direct air cargo connections to Europe, North America, Southeast Asia, the Middle East, and Oceania. Standard international shipments are dispatched within 1–3 business days of order confirmation. Express freight options (DHL Express, FedEx International Priority, TNT) are available for urgent plant shutdown scenarios requiring next-flight-out delivery. All shipments include full tracking from dispatch to delivery, with export documentation (commercial invoice, packing list, certificate of origin) prepared to the destination country’s import requirements.

For volume procurement, long-term supply agreements, and consignment stock arrangements, our engineering sales team provides dedicated account management with lead time commitment and price validity periods. All units carry a 12-month warranty from the date of dispatch, covering manufacturing defects and component failure under normal operating conditions.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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