Bently Nevada 330906-02-12-05-02-05 Proximity Probe – 3300 XL Series

Bently Nevada 330906-02-12-05-02-05 Reverse Mount Proximity Probe — Eddy-Current Shaft Monitoring in the 3300 XL Architecture

The 330906-02-12-05-02-05 is a reverse-mount eddy-current proximity probe manufactured by Bently Nevada as part of the 3300 XL transducer platform. Its primary function within a machinery protection loop is to deliver a continuous, non-contact DC voltage signal proportional to the instantaneous gap between the probe tip and a rotating metallic target — typically the journal surface of a turbine, compressor, or pump shaft. This gap signal is the raw physical input from which radial vibration amplitude, shaft centerline position, and differential expansion data are derived by the downstream Proximitor® sensor and monitor system.

The reverse-mount mechanical configuration distinguishes this part number from standard front-access probes. The probe body is threaded for insertion from the inboard (back) face of the bearing housing, allowing deployment in installations where the outboard face is obstructed by adjacent piping, structural members, or coupled machinery. This geometry is common in retrofit projects on legacy turbomachinery and in compact skid-mounted compressor trains where bearing housing access is constrained by the original OEM design. The integral reverse-mount connector exits axially from the probe body, routing the coaxial cable away from the bearing housing without requiring additional 90-degree adapters that would introduce impedance discontinuities in the measurement chain.

Within the 3300 XL signal chain, the probe operates as a passive LC resonant element. The Proximitor® sensor drives the probe coil at a fixed oscillation frequency — nominally in the radio-frequency range — and monitors the amplitude of the oscillation. As the conductive target shaft approaches the probe tip, eddy currents are induced in the target surface, loading the probe coil and reducing oscillation amplitude. The Proximitor® demodulates this amplitude-modulated signal and outputs a DC voltage with a nominal scale factor of 7.87 V/mm (200 mV/mil). The output is linear across a gap range of 0.25 mm to 2.25 mm (10 mil to 90 mil), with the recommended operating gap at 1.0 mm (40 mil) for maximum dynamic range in both directions. The DC output feeds directly into Bently Nevada 3500 series monitor input cards or into DCS/PLC analog input modules configured for –24 VDC-powered proximity inputs.

The probe tip diameter of 8 mm is the standard for the 3300 XL family, and the tip geometry is optimized for the electromagnetic field distribution required to achieve the specified scale factor on AISI 4140 steel targets per API 670. Installations using non-standard target materials — austenitic stainless steel, titanium alloy, or Inconel — require a material correction factor to be applied to the scale factor, as the electrical conductivity and magnetic permeability of the target directly affect eddy-current penetration depth and field loading. The probe assembly is housed in a stainless steel body with a hermetically sealed ceramic-filled tip, providing resistance to process fluid ingress, lubricating oil immersion, and thermal cycling across the rated operating range.

Real-time Stock & RFQ: [email protected] | WhatsApp: +86 18359268345

Technical Parameters

Hardware Logical Analysis

The electromagnetic architecture of the 330906-02-12-05-02-05 is built around a single-layer solenoid coil wound on a ferrite core and encapsulated within the stainless steel probe body. The coil forms the inductive element of an LC tank circuit driven by the Proximitor® sensor oscillator. The oscillation frequency is selected to maximize the ratio of eddy-current loading sensitivity to environmental noise — a balance between skin depth in the target material and the parasitic capacitance of the coaxial cable run.

The reverse-mount connector geometry is not merely a mechanical convenience. By routing the coaxial cable axially rather than radially, the design eliminates the 90-degree coaxial bend that is a common failure point in standard-mount probes installed in tight housings. Axial cable routing also reduces the mechanical stress concentration at the cable-to-probe junction during thermal cycling, which is significant in steam turbine applications where bearing housing temperatures can cycle between ambient and 150°C+ during start-stop sequences.

EMC performance is addressed at the probe level through the coaxial cable shield, which provides a continuous Faraday enclosure from the probe tip to the Proximitor® sensor input. The shield is grounded at the Proximitor® end only (single-point grounding) to prevent ground loop currents from injecting common-mode noise into the measurement signal. In high-EMI environments — such as those adjacent to variable-frequency drives or large power transformers — the 3300 XL system’s differential signal architecture at the Proximitor® output provides an additional 40+ dB of common-mode rejection before the signal reaches the monitor input card.

The probe tip’s hermetic ceramic fill serves a dual function: it provides mechanical protection for the coil assembly against process fluid ingress, and its low dielectric constant minimizes the parasitic capacitance between the coil and the probe housing, preserving the Q-factor of the LC tank circuit across the operating temperature range. Degradation of the ceramic seal — detectable as a shift in the probe’s static output voltage at a known gap — is a diagnostic indicator that can be identified during routine calibration checks without removing the probe from service.

System Integration Benefits

• Direct API 670 Compliance: The probe meets the transducer performance requirements of API 670 (5th Edition) without additional calibration or documentation, satisfying insurance underwriter and regulatory authority requirements for machinery protection on critical rotating equipment.
• Zero-Wear Non-Contact Measurement: Eddy-current sensing imposes no mechanical load on the shaft and has no moving parts. Mean time between replacement is determined by environmental degradation of the cable and connector, not by probe tip wear — eliminating the scheduled replacement intervals associated with contact-type sensors.
• DC-to-10 kHz Bandwidth: The flat frequency response from DC captures static shaft position (centerline, thrust position, differential expansion) simultaneously with dynamic vibration components up to the 10th harmonic of a 60,000 RPM machine — a single transducer covers both protection and condition monitoring functions.
• Deterministic Scale Factor: The 7.87 V/mm nominal scale factor is traceable to NIST-calibrated gap standards. Monitor alarm and trip setpoints can be configured in engineering units (µm or mil) with direct traceability to the physical gap, eliminating the unit-conversion errors that occur with sensors requiring empirical field calibration.
• Reverse-Mount Access for Retrofit: Enables probe installation on in-service machinery during short maintenance windows without requiring bearing housing disassembly or shaft removal, reducing planned outage duration by eliminating the need to clear the outboard face of the housing.
• Full 3300 XL Ecosystem Compatibility: Interoperates with the complete Bently Nevada 3300 XL extension cable library, 330180-series Proximitor® sensors, and 3500-series monitor cards. No firmware updates, driver changes, or signal conditioning modifications are required when replacing a probe within an existing 3300 XL installation.
• System 1® Software Integration: The analog output from the Proximitor® sensor is directly compatible with Bently Nevada System 1® condition monitoring software via the 3500 monitor’s communication backplane, enabling trend logging, alarm management, and orbit plot generation without additional signal conditioning hardware.
• Hazardous Area Certification: ATEX and IECEx certifications (zone-specific — confirm certificate number for your installation) allow deployment in classified areas including Zone 1 and Zone 2 gas atmospheres, covering the majority of oil & gas and petrochemical installation environments without requiring intrinsic safety barriers for the probe circuit.

Quality Assurance & Global Logistics

Every 330906-02-12-05-02-05 unit supplied by siemensplc.com is sourced as genuine Bently Nevada (Baker Hughes) OEM product. Units are procured through verified supply channels and undergo incoming inspection against OEM dimensional, marking, and electrical specifications prior to listing. Inspection includes verification of the probe body markings, connector configuration, cable assembly condition, and static output voltage at a reference gap using a calibrated gap fixture. Serial number and date code are recorded for each unit and are available to the customer upon request for critical-service traceability requirements.

A 12-month warranty from the date of shipment covers manufacturing defects and electrical performance within the specified operating parameters. Warranty claims are processed with a target response time of 48 hours from receipt of the defective unit. Replacement units are dispatched from Xiamen, China, with express freight as the default for warranty replacements.

Logistics operations are based in Xiamen, China, with established freight forwarding relationships covering air express (DHL, FedEx, UPS), sea freight (FCL and LCL), and road freight for regional destinations. Standard in-stock orders are dispatched within 1–3 business days of payment confirmation. Export documentation — including commercial invoice, packing list, certificate of origin, and MSDS where applicable — is prepared as standard. For shipments subject to EAR (Export Administration Regulations) controls, end-user documentation requirements are assessed at the time of order and communicated to the customer before shipment. Customs clearance support and HS code documentation are provided for all international shipments.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
© 2026 siemensplc.com. All rights reserved.