Bently Nevada 330902-00-95-05-02-05 Proximity Probe – 3300 XL Series

330902-00-95-05-02-05 — 8mm Eddy-Current Proximity Probe in the 3300 XL Measurement Loop

The Bently Nevada 330902-00-95-05-02-05 is an 8 mm diameter eddy-current proximity probe belonging to the 3300 XL Series — a platform engineered specifically for continuous, non-contact displacement measurement in rotating machinery protection systems. Within a complete 3300 XL measurement loop, this probe functions as the primary sensing element: it generates a high-frequency electromagnetic field (nominally 1 MHz oscillation driven by the paired proximitor), induces eddy currents in the conductive target shaft, and converts the resulting impedance variation into a linear DC voltage proportional to the air gap between probe tip and shaft surface. The output sensitivity of 7.87 V/mm (200 mV/mil) provides the resolution necessary to detect shaft radial vibration amplitudes as small as a few micrometers — a requirement mandated by API 670 for machinery protection in critical rotating equipment.

In turbomachinery control architecture, this probe occupies the first node in a three-component signal chain: probe → extension cable → proximitor/driver. The 330902-00-95-05-02-05 is factory-matched to the 3300 XL 8mm driver family (e.g., 330180-X1-05), ensuring the system gap voltage, scale factor, and temperature compensation coefficients are pre-calibrated as an integrated assembly. Substituting non-matched components invalidates the calibration and introduces measurement error that cannot be corrected by software offset alone.

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Technical Parameters

Hardware Logical Analysis

The 330902-00-95-05-02-05 probe tip is constructed with a ceramic-filled epoxy encapsulant surrounding the sensing coil winding. This material selection is deliberate: ceramic filler raises the thermal conductivity of the encapsulant while maintaining a low dielectric constant, which preserves the coil’s resonant frequency stability across the full –35°C to +177°C operating envelope. Thermal drift in the oscillation frequency directly translates to a scale factor error in the output voltage; the ceramic-filled construction limits this drift to less than ±0.5% of full scale over the rated temperature range — a figure that satisfies API 670 Annex D calibration tolerance requirements without field recalibration.

The coaxial cable assembly uses a double-shielded construction: an inner braid shield referenced to the driver’s guard terminal, and an outer shield connected to instrument ground. This guard-driven shield topology actively cancels capacitive coupling between the signal conductor and external interference sources. In variable-frequency drive (VFD) environments — where common-mode noise on motor frames can reach several hundred millivolts — the guard shield reduces induced noise on the proximity output to below 25 mV peak-to-peak, well within the 50 mV noise floor specified by API 670 for vibration channels.

The probe body threads are machined to a tolerance of ±0.013 mm on the major diameter, ensuring repeatable installation depth when used with standard probe holders. Repeatable installation depth is critical because the gap voltage at the nominal operating gap (typically 1.0 – 1.5 mm for 8mm probes) must fall within the linear range of the calibration curve. A mounting depth error of 0.1 mm shifts the operating point by approximately 0.79 V on the output — sufficient to trigger a false alert on a 3500 Series monitor configured with tight alarm setpoints.

EMC design at the driver interface relies on a balanced transmission line between probe and proximitor. The driver’s internal oscillator maintains a constant current drive to the probe coil regardless of cable impedance variation caused by temperature or mechanical flexing. This constant-current architecture decouples the measurement sensitivity from cable resistance changes — a significant advantage in installations where the extension cable runs through conduit exposed to ambient temperature swings exceeding 60°C.

System Integration Benefits

• Pre-calibrated Loop Assembly: The 330902-00-95-05-02-05 is factory-calibrated as a matched set with its designated extension cable and 3300 XL driver. The calibration data sheet shipped with the assembly documents the actual scale factor, gap voltage at 1.0 mm, and temperature coefficient — eliminating the need for field calibration and reducing commissioning time by several hours per measurement point.
• Direct 3500 Series Rack Compatibility: The probe’s output signal (–2 VDC to –18 VDC, 200 mV/mil sensitivity) is natively accepted by Bently Nevada 3500/40M and 3500/42M proximity input cards without signal conditioning. The monitor’s internal gap alarm, direct vibration, and 1X/2X vector processing functions operate directly on the raw proximity signal.
• API 670 Compliance for Critical Machinery: The probe meets all dimensional, sensitivity, and temperature requirements of API 670 Fifth Edition, making it directly specifiable in machinery protection system documentation for petrochemical, LNG, and power generation facilities without additional qualification testing.
• Deterministic Frequency Response to 10 kHz: The –3 dB bandwidth of DC to 10,000 Hz supports vibration measurement at shaft speeds up to 600,000 RPM for fundamental frequency content, and captures sub-synchronous instability phenomena (oil whirl at 0.43–0.48× running speed) with full amplitude accuracy at typical turbomachinery operating speeds of 3,000 – 15,000 RPM.
• Non-Contact Measurement Eliminates Wear: Unlike accelerometers or contact-type displacement transducers, the eddy-current operating principle involves no mechanical contact with the rotating shaft. There is no wear mechanism, no periodic replacement interval, and no risk of probe-induced shaft damage during a rub event — the probe simply measures through the air gap.
• High-Temperature Probe Tip for Steam Turbine Bearing Pedestals: The 177°C probe tip rating covers the bearing pedestal temperatures encountered in steam turbines operating at inlet conditions up to 600°C, where bearing metal temperatures at the proximity probe mounting location typically reach 120–160°C under full load.
• Diagnostic Transparency via DC Gap Voltage: The DC component of the proximity output provides a continuous, real-time measurement of average shaft centerline position. Trending the gap voltage over time reveals bearing wear (increasing gap as the bearing shell wears), shaft bow (asymmetric gap variation at 1× running speed), and thermal growth (slow DC drift correlated with machine load changes) — all without additional instrumentation.
• Plug-and-Play Replacement in Existing 3300 XL Installations: The 330902-00-95-05-02-05 is a direct form-fit-function replacement for earlier 3300 XL 8mm probe assemblies. The thread form, cable connector, and electrical interface are backward-compatible, allowing replacement during a planned outage without rewiring the junction box or reconfiguring the monitor.

Quality Assurance & Global Logistics

Every Bently Nevada 330902-00-95-05-02-05 unit dispatched from our Xiamen, China facility is sourced through verified supply channels and subjected to incoming inspection before storage. Inspection protocol covers physical integrity of the probe tip encapsulant, continuity and insulation resistance of the coaxial cable assembly, connector pin condition, and verification of the factory calibration data sheet against the unit serial number. Units that do not pass inspection are quarantined and not offered for sale.

Packaging follows anti-static and mechanical shock protection standards: the probe coil assembly is wrapped in ESD-safe foam, the cable is coiled to a minimum bend radius of 50 mm to prevent coaxial dielectric deformation, and the complete assembly is boxed in double-wall corrugated carton with void fill. For international shipments, we use DHL Express, FedEx International Priority, and UPS Worldwide Express — all with door-to-door tracking. Transit time from Xiamen to major industrial hubs: Europe 3–5 business days, North America 4–6 business days, Southeast Asia 2–3 business days. Export documentation including commercial invoice, packing list, and certificate of origin is prepared same day for in-stock orders. HS Code 9031.80 applies for customs classification in most jurisdictions. All units carry a 12-month warranty against manufacturing defects from the date of shipment.

Contact Information

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