Bently Nevada 330705-02-18-10-02-CN Proximity Probe – 3300 XL Series

Bently Nevada 330705-02-18-10-02-CN — 8mm Reverse Mount Eddy Current Proximity Probe in Rotating Machinery Protection

The Bently Nevada 330705-02-18-10-02-CN is an 8 mm reverse-mount eddy current proximity probe belonging to the 3300 XL Proximity Transducer System. It performs continuous, non-contact measurement of shaft radial vibration and axial position in critical rotating machinery — turbines, centrifugal compressors, pumps, and gearboxes — where API 670 machinery protection compliance is mandatory. The reverse-mount mechanical configuration allows probe installation from the rear face of the bearing housing, resolving access constraints that are common in compact turbomachinery skids where front-face clearance is insufficient for a standard forward-mount probe body.

The operating principle is based on Faraday’s law of electromagnetic induction. A high-frequency oscillator (typically 1.0 MHz) drives an LC tank circuit whose inductive element is the probe tip coil. When a conductive target — nominally AISI 4140 steel — enters the probe’s electromagnetic field, eddy currents are induced on the target surface. These eddy currents load the tank circuit, reducing its Q factor and shifting the oscillator amplitude. The Proximitor sensor converts this amplitude change into a DC voltage output with a nominal scale factor of 7.87 V/mm (200 mV/mil), providing a linear, phase-lag-free signal from DC to 10,000 Hz. This flat frequency response is essential for capturing both low-frequency shaft bow (sub-synchronous) and high-frequency blade-pass or gear-mesh events within a single transducer channel.

The CN suffix designates a China-region configuration. Electrically and mechanically, the 330705-02-18-10-02-CN is identical to the -00 (standard) suffix variant. The regional designation affects documentation and regional compliance labeling only; no derating or functional difference applies. This probe ships with a 2-meter integral armored cable terminated for connection to a 3300 XL 8mm Proximitor sensor, which must be ordered separately and matched to the correct extension cable length to maintain system calibration.

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

Technical Parameters

Hardware Logical Analysis

The 330705-02-18-10-02-CN probe body is constructed with a threaded stainless steel housing that provides mechanical rigidity and corrosion resistance in oil-mist and high-humidity bearing environments. The probe tip coil is encapsulated in a thermosetting polymer compound rated to 177°C, isolating the winding from mechanical shock, lubricant ingress, and thermal cycling stress. This encapsulation also serves as the primary dielectric barrier, maintaining coil geometry stability — a critical factor because any dimensional change in the coil alters the LC resonant frequency and introduces scale factor drift.

The integral armored cable uses a coaxial construction with a low-loss dielectric. Cable capacitance per unit length is tightly controlled to ±2% tolerance, because the Proximitor’s oscillator circuit is tuned to a specific total cable capacitance (probe + extension cable combined). Exceeding the specified total cable length without recalibration shifts the operating point outside the linear range, producing a non-linear output that appears as a measurement offset rather than a fault — a failure mode that is difficult to detect without a gap voltage verification procedure.

The reverse-mount mechanical design positions the probe body behind the bearing housing mounting flange. The probe tip extends through a precision-bored hole in the housing to achieve the correct air gap to the shaft. This geometry eliminates the need for a probe holder bracket in front of the bearing, reducing the risk of bracket resonance at shaft rotational frequencies. In high-speed machinery (above 10,000 RPM), bracket resonance can introduce spurious vibration signals that mask genuine shaft motion — the reverse-mount configuration structurally eliminates this error source.

EMC performance is achieved through the coaxial cable shield, which is grounded at the Proximitor end only (single-point grounding). This topology prevents ground loop currents from flowing through the shield conductor, which would appear as a common-mode noise voltage superimposed on the measurement signal. In environments with high variable-frequency drive (VFD) switching noise or adjacent power cables, the single-point shield ground is the primary defense against 50/60 Hz and harmonic interference in the measurement chain.

System Integration Benefits

• DC-coupled output eliminates phase shift at low frequencies: The DC-to-10,000 Hz flat response means shaft bow, thermal growth, and slow-roll vibration below 1 Hz are captured without the phase distortion introduced by AC-coupled sensors, preserving vector accuracy in slow-roll compensation algorithms.
• Non-contact measurement eliminates bearing load from the transducer: Unlike contact-type displacement sensors, the eddy current probe imposes zero mechanical load on the shaft, ensuring that the measurement itself does not alter the dynamic behavior being measured — a fundamental requirement in API 670 machinery protection.
• Reverse-mount geometry enables installation in space-constrained bearing housings: Turbomachinery skids with close-coupled bearing arrangements often lack front-face clearance for standard probes. The reverse-mount configuration resolves this without requiring housing modification or custom brackets.
• Direct compatibility with Bently Nevada 3500 Series monitoring racks: The probe, when paired with the 3300 XL 8mm Proximitor, produces a signal fully compatible with 3500/40M, 3500/42M, and 3500/45 monitor cards, enabling plug-and-play integration without signal conditioning adapters.
• System 1 software integration for predictive diagnostics: The −18 VDC bias output is directly readable by Bently Nevada System 1 condition monitoring software, enabling trend logging, alarm setpoint management, and orbit plot generation without additional signal processing hardware.
• Deterministic frequency response supports high-speed machinery: The 10,000 Hz upper bandwidth accommodates blade-pass frequencies in compressors with up to 60 blades running at 10,000 RPM (10,000 Hz blade-pass), ensuring that aerodynamic excitation events are captured within the transducer bandwidth.
• Factory calibration traceability reduces commissioning time: Each probe is factory-calibrated against a certified AISI 4140 target. The calibration certificate provides the as-shipped scale factor, allowing commissioning engineers to verify system gain without performing a field calibration loop.
• API 670 compliance simplifies machinery protection system certification: Specifying an API 670-compliant transducer system reduces the scope of site-specific validation required during machinery protection system acceptance testing, shortening project commissioning schedules.
• 12-month warranty with documented traceability: All units supplied by siemensplc.com carry a 12-month warranty from shipment date, backed by original manufacturer documentation and lot traceability records — a requirement for regulated industries including power generation, oil & gas, and petrochemical.

Quality Assurance & Global Logistics

Every Bently Nevada 330705-02-18-10-02-CN unit dispatched from our Xiamen, China facility undergoes a structured incoming inspection protocol: visual examination of probe tip encapsulation integrity, connector condition verification, cable armor continuity check, and confirmation of original manufacturer packaging and documentation. Units are stored in a temperature- and humidity-controlled warehouse to prevent electrostatic discharge damage and moisture ingress into the cable assembly.

Shipment from Xiamen is executed via DHL Express, FedEx International Priority, or UF Express for domestic China delivery, with typical international transit times of 3–7 business days to major industrial hubs in Southeast Asia, the Middle East, Europe, and the Americas. Export documentation — including commercial invoice, packing list, and certificate of origin — is prepared in compliance with destination country import requirements. For orders requiring CITES, dual-use, or end-user certificate documentation, our logistics team coordinates the necessary paperwork prior to shipment to prevent customs clearance delays.

B2B customers with recurring procurement requirements can establish a blanket purchase order arrangement for priority stock allocation and fixed lead times. Contact our sales team to discuss volume pricing, consignment stock options, and dedicated account management.

Contact Information

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