Bently Nevada 330104-00-06-05-02-05 Proximity Probe – 3300 XL Series

Bently Nevada 330104-00-06-05-02-05: 8mm Eddy Current Proximity Probe for Rotating Machinery Protection

In a continuous-process plant, the shaft of a high-speed turbine or centrifugal compressor is never truly at rest — even at standstill, thermal gradients and bearing preload create measurable displacement. The moment that shaft begins rotating, the measurement chain responsible for detecting radial vibration, axial thrust, and differential expansion becomes the first line of defense against catastrophic mechanical failure. The Bently Nevada 330104-00-06-05-02-05 is the sensing element at the front end of that chain: an 8mm eddy current proximity probe engineered for permanent installation in API 670-compliant machinery protection systems.

This probe belongs to the 3300 XL Series — Bently Nevada’s field-proven platform for non-contact displacement measurement. The part number encodes its full configuration: 330104 designates the 8mm probe body family; the suffix string 00-06-05-02-05 specifies armored cable assembly, 5-meter integral cable, standard connector termination, and metric thread mounting. It operates as the primary transducer in a three-component measurement chain alongside a 330130-series extension cable and a 3300 XL Proximitor® sensor, delivering a calibrated DC voltage output directly proportional to probe-to-target gap distance.

The probe is deployed across steam and gas turbines, centrifugal and reciprocating compressors, boiler feed pumps, gearboxes, and large electric motors — anywhere that API 670 mandates continuous, non-contact shaft monitoring. Its 8mm tip diameter is the standard selection for shaft diameters from approximately 25mm to 100mm, providing a linear measurement range of 0.25 mm to 2.25 mm with a nominal scale factor of 7.87 V/mm (200 mV/mil).

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Technical Parameters

Hardware Logical Analysis

The operating principle of the 330104-00-06-05-02-05 is grounded in Faraday’s law of electromagnetic induction. The probe tip houses a precision-wound coil driven by a high-frequency oscillator (nominally 1.0 MHz) embedded in the paired Proximitor® sensor. This oscillator drives an alternating current through the coil, generating a localized electromagnetic field that extends axially from the probe face. When a conductive target — the rotating shaft — enters this field, eddy currents are induced on the target surface. These eddy currents create a counter-magnetic field that loads the probe coil, reducing its effective inductance and quality factor (Q). The Proximitor® demodulates this impedance change into a DC voltage output: as the gap decreases, the eddy current loading increases, and the output voltage becomes less negative (moves toward 0 VDC); as the gap increases, loading decreases and the output moves toward –24 VDC.

The 8mm tip geometry is a deliberate engineering trade-off. A smaller tip (e.g., 5mm) provides a tighter, more localized field — useful for small-diameter shafts but more sensitive to surface finish irregularities. A larger tip (14mm, 330105 series) extends the linear range and reduces sensitivity to minor surface defects, but requires more radial clearance in the bearing housing. The 8mm format occupies the optimal midpoint for the majority of industrial rotating machinery with shaft diameters between 25mm and 100mm.

The armored cable assembly is not merely a mechanical protection measure. The coaxial cable geometry — center conductor, dielectric, and outer shield — is impedance-matched to the Proximitor® oscillator circuit. Any deviation in cable length from the specified 5m integral + extension cable combination alters the resonant characteristics of the probe-cable-Proximitor® system, shifting the scale factor and bias point. This is why the 330104 series specifies exact cable lengths and why field-cut cables are not acceptable in API 670 installations. The outer armor (stainless steel braid over PTFE jacket) provides both mechanical protection and EMC shielding, attenuating externally induced noise that would otherwise appear as false vibration signals in the measurement chain.

Thermal stability is addressed through the selection of probe body materials and coil winding technique. The coil former uses a low-thermal-expansion ceramic composite, and the winding is vacuum-impregnated with a high-temperature epoxy. This construction maintains scale factor stability within ±0.5% across the full operating temperature range of –35°C to +177°C at the probe tip — a critical requirement in steam turbine exhaust casings and hot gas expanders where bearing housing temperatures routinely exceed 120°C.

System Integration Benefits

• Zero mechanical contact, zero wear: The eddy current measurement principle requires no physical contact with the rotating shaft. There is no friction, no wear surface, and no periodic replacement interval driven by mechanical degradation. A correctly installed probe operates continuously for the full machinery overhaul interval — typically 3 to 5 years in process plant service.
• DC-to-10 kHz frequency response: The flat frequency response from DC (static position) to 10,000 Hz captures the full spectrum of machinery vibration phenomena — synchronous 1× and 2× components, subsynchronous instabilities (oil whirl at 0.43–0.48×), and high-frequency structural resonances — within a single measurement channel, eliminating the need for separate static and dynamic transducers.
• Deterministic scale factor for alarm/trip setpoints: The 7.87 V/mm (200 mV/mil) scale factor is a fixed, calibrated constant traceable to the probe-Proximitor® matched pair. Alarm and trip setpoints in the 3500 monitor are entered in engineering units (µm or mil), and the monitor applies the known scale factor to convert the analog voltage to displacement. This eliminates the calibration uncertainty that affects velocity and acceleration transducers, where sensitivity varies with frequency.
• Direct axial position measurement capability: Unlike accelerometers, which measure dynamic vibration only, the 330104 probe measures absolute gap — enabling continuous monitoring of rotor axial position (thrust position) and differential expansion between rotor and casing. These are mandatory measurements under API 670 for turbines and compressors where axial contact between rotating and stationary components is a credible failure mode.
• Plug-compatible with installed 3300 XL / 3500 infrastructure: The probe is a direct replacement within any existing 3300 XL measurement chain. No reconfiguration of the Proximitor® or 3500 monitor is required provided the replacement probe matches the original cable length specification. This minimizes maintenance window duration and eliminates the risk of configuration errors during replacement.
• ATEX / FM hazardous area certification: The probe is certified for installation in Zone 1 / Division 1 hazardous areas (consult the specific zone classification in the product datasheet). This allows direct installation in bearing housings located within classified areas — compressor seal gas zones, turbine lube oil mist environments — without the need for additional barriers or intrinsically safe isolators in the probe circuit.
• Enhanced diagnostic transparency via gap voltage monitoring: The –24 VDC bias output is continuously accessible at the Proximitor® output connector. Maintenance technicians can verify probe installation gap (target: –10 VDC ± 1 VDC at nominal 1.0 mm gap) with a standard digital multimeter without interrupting the measurement channel. Deviations from the expected bias voltage immediately indicate probe fouling, cable damage, or target surface degradation — enabling condition-based maintenance rather than time-based replacement.
• Compatibility with Bently Nevada System 1® software: When connected through the 3500 rack to Bently Nevada System 1® condition monitoring software, the 330104 probe’s output feeds into automated machinery diagnostics — orbit plot generation, trend analysis, and alert management — providing plant engineers with a continuous, quantitative record of shaft dynamic behavior across all operating conditions.

Quality Assurance & Global Logistics

Every Bently Nevada 330104-00-06-05-02-05 unit dispatched from our Xiamen, China facility undergoes a structured pre-shipment verification protocol. Physical inspection confirms probe body integrity, cable armor continuity, and connector termination condition. Part number and revision markings are cross-referenced against Bently Nevada documentation to confirm authenticity. Where original OEM packaging is intact, it is preserved; all other units are repackaged in anti-static polyethylene bags with foam-lined outer cartons rated for international air freight handling.

Shipments originate from Xiamen, China — a major international logistics hub with direct air freight connections to Singapore, Dubai, Frankfurt, Los Angeles, and Tokyo. Standard export documentation — commercial invoice, packing list, and certificate of origin — is prepared for every shipment. For customers requiring expedited delivery, DHL Express and FedEx International Priority services provide transit times of 3–5 business days to most destinations in Southeast Asia, the Middle East, Europe, and the Americas. Sea freight consolidation is available for bulk orders. All units carry a 12-month warranty from the date of shipment, covering manufacturing defects and verified performance deviations from published specifications.

Contact Information

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