Bently Nevada 330904-00-24-10-02-00 Proximity Probe – 3300 NSv Series

Bently Nevada 330904-00-24-10-02-00: 8mm Eddy Current Proximity Probe in Rotating Machinery Protection Architecture

In a machinery protection system, the proximity probe occupies the most upstream position in the signal chain — it is the transducer that converts mechanical displacement into a proportional DC voltage, and every downstream decision made by the monitor, the DCS, or the safety instrumented system depends on the fidelity of that conversion. The Bently Nevada 330904-00-24-10-02-00 is an 8mm eddy current proximity probe from the 3300 NSv (Non-contacting Vibration) Series, a transducer family that has been the de facto standard for API 670-compliant shaft vibration and axial position measurement in critical rotating machinery for over two decades.

The part number encodes the full configuration: 330904 designates the 8mm probe body within the 3300 NSv family; 00-24 specifies a 24-inch (610 mm) armored extension cable; 10 indicates the 2-meter (200 cm) interconnect cable; 02-00 defines the connector and termination style. This level of part-number granularity is not administrative — each segment directly maps to a physical parameter that affects gap voltage, scale factor linearity, and system calibration. Substituting any segment without re-verifying the full transducer system against the Proximitor® sensor will introduce a scale factor error that the monitor cannot self-correct.

The probe operates on the eddy current principle: a high-frequency oscillator (typically 1.0 MHz carrier) drives a coil wound within the probe tip. When a conductive target — the shaft — enters the electromagnetic field, eddy currents are induced on the shaft surface, loading the oscillator circuit and reducing its amplitude. The Proximitor® sensor demodulates this amplitude change into a DC output voltage with a nominal scale factor of 7.87 V/mm (200 mV/mil). The output is linear across a measurement range of 0.25 mm to 2.25 mm gap, giving a usable span of 2.0 mm — sufficient to capture both static position (gap) and dynamic vibration (AC component) simultaneously on a single channel.

The frequency response of DC to 10,000 Hz is a defining characteristic. The lower bound — DC — means the probe measures static shaft position continuously, enabling axial thrust monitoring and slow-roll runout capture at shaft speeds as low as 1 RPM. The upper bound of 10 kHz means the probe faithfully resolves vibration components up to the 10th harmonic of a 60,000 RPM machine, or the 20th harmonic of a 30,000 RPM machine — well beyond the spectral content of any rotating machinery failure mode catalogued in ISO 13373 or API 670 Annex D. This bandwidth is not a marketing figure; it is a consequence of the probe’s coil geometry, the Proximitor® oscillator design, and the matched cable impedance of the 330904 system.

The 24-inch armored extension cable uses a stainless steel braid over a coaxial core, maintaining a controlled characteristic impedance from probe tip to Proximitor® input. Any impedance discontinuity in this cable — caused by a kink, a crush point, or moisture ingress at a connector — will shift the oscillator operating point and introduce a DC offset error that appears as a false gap change. The armor is not merely mechanical protection; it is an integral part of the transmission line. The 2-meter interconnect cable then carries the demodulated signal from the Proximitor® to the monitor input, where it is processed against configurable alert and danger setpoints.

Operating temperature range for the probe body is -35°C to +177°C, which covers the bearing housing environments of gas turbines, steam turbines, and high-temperature process compressors without requiring active cooling of the probe mounting. The Proximitor® sensor, mounted remotely from the heat source, operates within its own rated range. This thermal architecture — probe body rated for high temperature, electronics mounted remotely — is a deliberate design choice that eliminates the reliability penalty of exposing active semiconductor components to turbine-bay temperatures.

The 330904-00-24-10-02-00 is fully compatible with the Bently Nevada 3300 XL 8mm Proximitor® Sensor and the 3500 Series monitor platform (with appropriate adapter). It is a direct plug-and-play replacement for any existing 330904-00-24-10-02-00 installation — provided the replacement probe is the identical part number, no monitor recalibration is required, because the scale factor and gap voltage characteristics are held to OEM tolerances.

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Technical Parameters

Hardware Logical Analysis

The eddy current transducer system is a closed-loop impedance measurement circuit. The Proximitor® oscillator maintains a fixed drive voltage across the probe coil; as the target gap decreases, the reflected impedance increases, the oscillator amplitude drops, and the demodulator output voltage becomes more negative. This inverse-linear relationship between gap and output voltage is the physical basis of the 7.87 V/mm scale factor. The linearity of this relationship depends on three factors: coil geometry (fixed by the probe body), target material conductivity (fixed by the shaft specification), and cable impedance (fixed by the matched extension cable). The 330904 system is factory-calibrated as a matched set — probe, extension cable, and Proximitor® — against a 4140 steel target at 25°C. Any deviation from this calibration baseline (different target material, unmatched cable, temperature extremes) must be accounted for in the system error budget per API 670 Section 5.3.

EMC performance of the 330904 is governed by the coaxial cable architecture. The stainless steel armor provides a continuous Faraday shield from probe tip to Proximitor® input, attenuating radiated interference from variable-frequency drives, high-current bus bars, and RF sources common in turbine control rooms. The shield is grounded at the Proximitor® end only — a single-point ground that prevents shield current loops from injecting common-mode noise into the signal. This grounding topology is specified in Bently Nevada installation drawings and must be preserved during field installation; double-grounding the shield will introduce a 50/60 Hz ground loop that appears as a synchronous vibration component at 1× running speed, indistinguishable from genuine shaft vibration without phase reference data.

The probe tip geometry — 8mm diameter, M10 × 1.0 thread — is optimized for the target area ratio required to maintain linearity across the 2.0 mm measurement span. A smaller probe tip would reduce the linear range; a larger tip would increase sensitivity to shaft surface finish variations. The 8mm format represents the engineering balance point for general-purpose rotating machinery monitoring, where shaft diameters typically range from 50 mm to 500 mm and surface finish is held to Ra 0.4–0.8 µm per API 670 Annex B.

System Integration Benefits

• Direct 3300 XL and 3500 Series compatibility: The 330904-00-24-10-02-00 interfaces natively with Bently Nevada monitor platforms without signal conditioning adapters, preserving the calibrated scale factor end-to-end from transducer to monitor display.
• Simultaneous static and dynamic measurement: A single probe channel delivers both DC gap (axial position, eccentricity) and AC vibration (unbalance, misalignment, rub) — eliminating the need for separate position and vibration transducers on the same measurement plane.
• Zero mechanical wear: Non-contacting measurement principle means probe service life is determined by environmental exposure, not mechanical fatigue. Correctly installed probes in clean environments routinely exceed 10-year service intervals.
• Deterministic frequency response: The flat DC-to-10 kHz response eliminates phase shift errors in the vibration signal below 10 kHz, ensuring that vector subtraction (slow-roll compensation) and 1×/2× amplitude extraction in the monitor are computed from phase-accurate data.
• API 670 compliance: The 3300 NSv system meets the transducer performance requirements of API 670 5th Edition, enabling direct use in machinery protection systems for API-specified equipment without additional qualification testing.
• Plug-and-play replacement: Identical part number replacement maintains system calibration without monitor reconfiguration, reducing mean time to repair (MTTR) during unplanned outages where every hour of downtime carries measurable production cost.
• High-temperature probe body rating: The 177°C probe body rating allows direct mounting in bearing housing environments without thermal standoffs or active cooling, simplifying installation and eliminating a potential failure point.
• Armored cable mechanical protection: Stainless steel armor resists crush, abrasion, and rodent damage in cable trays and conduit runs, reducing nuisance faults from cable damage — a leading cause of false trips in machinery protection systems.
• Traceable OEM documentation: Each unit ships with a certificate of conformance referencing the Bently Nevada part number, supporting audit trails required by ISO 55001 asset management and functional safety (IEC 61511) documentation packages.
• Broad target material compatibility: While calibrated against 4140 steel, the 330904 system provides published correction factors for stainless steel, Inconel, and titanium shafts, enabling use across a wider range of rotating machinery without custom calibration.

Quality Assurance & Global Logistics

Every Bently Nevada 330904-00-24-10-02-00 unit supplied by siemensplc.com undergoes a structured pre-shipment verification protocol. Physical inspection covers probe tip condition, cable armor continuity, connector pin integrity, and thread gauge compliance against M10 × 1.0 specification. Part number verification cross-references the dataplate, label, and packaging against the ordered configuration — a step that eliminates the most common sourcing error in the proximity probe market, where similar-looking part numbers with different cable lengths are frequently confused.

Where test equipment is available, gap voltage and scale factor are verified against the 7.87 V/mm nominal at the standard 1.0 mm gap point. Units are packed in anti-static, shock-absorbing foam with a moisture barrier outer wrap — a packaging specification derived from the sensitivity of the coaxial cable assembly to connector corrosion during sea freight transit. A packing list and certificate of conformance are included with every shipment.

Logistics operations are based in Xiamen, China, a major southeastern port city with direct access to DHL Express, FedEx International Priority, and consolidated air freight services to all major industrial markets. Standard express delivery to Southeast Asia, the Middle East, and Europe runs 3–5 business days from order confirmation. North American destinations are typically 5–7 business days via express air. For time-critical plant shutdowns, same-day dispatch on confirmed orders received before 14:00 CST is available on in-stock items. Full export documentation — commercial invoice, packing list, certificate of origin, and HS code declaration — is prepared for every international shipment to minimize customs clearance delays.

Contact Information

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Location: Xiamen, China
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