Bently Nevada 330851-02-000-080-50-00-05 Proximity Probe – 3300 XL Series

Bently Nevada 330851-02-000-080-50-00-05 — 8 mm Eddy-Current Proximity Probe for Rotating Machinery Protection

The Bently Nevada 330851-02-000-080-50-00-05 is an 8 mm eddy-current proximity probe belonging to the 3300 XL Proximity Transducer System. It is designed for continuous, non-contact measurement of radial shaft vibration, axial position, and differential expansion in turbomachinery and other critical rotating equipment. The probe operates on the principle of electromagnetic induction: a high-frequency oscillating current driven through the probe tip coil generates an alternating magnetic field; when a conductive target surface enters this field, eddy currents are induced, loading the coil and producing a voltage output that is linearly proportional to the gap between probe tip and target. This mechanism delivers sub-micron resolution without any mechanical contact, eliminating wear-related drift over the service life of the installation.

Within a 3300 XL transducer chain, the 330851-02-000-080-50-00-05 probe connects to a matched 330180-series Proximitor sensor via a 330130-series extension cable. The Proximitor provides the oscillator drive, demodulates the gap-proportional signal, and outputs a DC voltage (nominally −18 VDC at mid-range) to the monitor rack. The 2 m integral cable on this probe variant is suited to installations where the Proximitor can be mounted close to the bearing housing, minimizing cable-induced signal attenuation. The 80 mm probe body length accommodates standard API 670 bracket geometries, and the 50 Ω coaxial connector ensures impedance-matched transmission to the extension cable.

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Technical Parameters

Hardware Logical Analysis

The 330851-02-000-080-50-00-05 embodies several hardware design decisions that distinguish it from generic eddy-current sensors in the industrial market.

Coil Geometry and Gap Linearity. The 8 mm tip diameter is not arbitrary. Bently Nevada’s coil winding geometry is optimized to produce a linear voltage-gap relationship across a 2 mm window (0.25 mm to 2.25 mm). Smaller-diameter probes exhibit a narrower linear range and higher sensitivity to target surface finish variation; larger probes sacrifice spatial resolution. The 8 mm format represents the engineering balance point for turbomachinery shaft diameters in the 50 mm–300 mm range, where API 670 mandates radial vibration measurement.

EMC Design and Shielded Coaxial Architecture. The integral cable uses a double-shielded coaxial construction: an inner braid shield referenced to the Proximitor oscillator ground, and an outer foil shield connected to the installation structure ground. This two-layer shielding arrangement attenuates common-mode electromagnetic interference (EMI) from adjacent variable-frequency drives, high-current bus bars, and RF sources typically present in turbine halls. The 50 Ω characteristic impedance is maintained throughout the probe-cable-Proximitor chain to prevent reflective signal distortion at the 1 MHz carrier frequency.

Thermal Stability and Calibration Traceability. The probe coil is wound on a ceramic bobbin with a low coefficient of thermal expansion (CTE), minimizing coil geometry change across the −35 °C to +177 °C operating range. Bently Nevada calibrates each probe-Proximitor pair as a matched system; the calibration data is encoded in the Proximitor’s internal resistor network, ensuring that the 7.87 V/mm scale factor is maintained without field adjustment. This factory-matched calibration approach eliminates the field calibration errors that are common with third-party replacement probes.

316 SS Housing and IP67 Sealing. The probe body is machined from 316 stainless steel, which provides adequate corrosion resistance in steam-saturated and hydrocarbon-laden atmospheres. The cable entry is sealed with a compression gland rated to IP67, preventing moisture ingress during water-wash operations or in high-humidity bearing housings. The probe tip face is flush-ground to within ±0.05 mm of the nominal geometry, ensuring that the installed gap measurement corresponds to the factory calibration curve without correction factors.

Impedance Matching and Signal Integrity. The 50 Ω coaxial connector at the probe tail mates directly with the 330130-series extension cable, which is also 50 Ω characteristic impedance. This matched-impedance chain prevents standing waves on the 1 MHz carrier signal, which would otherwise introduce periodic amplitude modulation indistinguishable from low-frequency shaft vibration. The result is a clean DC output from the Proximitor with a noise floor below 25 mV peak-to-peak, sufficient to resolve shaft vibration amplitudes as small as 3 µm.

System Integration Benefits

• Direct 3500 Series Monitor Compatibility: The probe-Proximitor output is a standard −2 VDC to −18 VDC DC signal, accepted natively by all Bently Nevada 3500 series monitor cards (3500/40M, 3500/42M, 3500/44M) without signal conditioning adapters, reducing BOM complexity and potential failure points.
• API 670 Compliance Out of the Box: The 330851-02-000-080-50-00-05 meets API 670 5th Edition requirements for proximity transducer systems, including scale factor tolerance, temperature range, and target material specification. This eliminates the engineering review burden for installations in API-governed facilities such as refineries and LNG terminals.
• Deterministic Real-Time Response: The eddy-current measurement principle has no moving parts and no mechanical resonance. The Proximitor demodulates the gap signal with a bandwidth of DC to 10 kHz, providing deterministic response to shaft dynamic events without the phase lag associated with accelerometer-based systems. This is critical for overspeed and high-vibration trip logic where response latency directly affects machinery protection effectiveness.
• Diagnostic Transparency via Gap DC Output: The DC component of the Proximitor output represents the average shaft centerline position (gap). Trending this DC value over time reveals bearing wear (increasing gap), thermal growth (decreasing gap), and shaft bow — failure modes that are invisible to AC-coupled vibration systems. The 330851 probe’s ±1% scale factor tolerance ensures that gap trend data is quantitatively reliable across the full temperature range.
• Plug-and-Play Replacement: The 330851-02-000-080-50-00-05 is a direct form-fit-function replacement for earlier 3300 XL 8 mm probes with 2 m cables. No bracket modification, cable rerouting, or Proximitor recalibration is required, reducing planned maintenance outage duration.
• Multi-Parameter Measurement from a Single Probe: A single 330851 probe installation simultaneously provides radial vibration (AC component), shaft average centerline position (DC component), and — when used in a differential expansion configuration — axial position data. This multi-parameter output from one transducer reduces the number of penetrations through bearing housing walls, simplifying mechanical design and reducing potential leak paths.
• Long-Term Spare Parts Availability: The 3300 XL series has been in continuous production since the 1990s and remains Bently Nevada’s primary proximity transducer platform. Spare parts, calibration services, and technical documentation are available through the global Baker Hughes service network, ensuring a long installed-base support horizon for asset owners with 20+ year plant lifecycles.
• Reduced Commissioning Risk: Factory-matched probe-Proximitor calibration means that the installed system’s scale factor is verified before delivery. Field commissioning is limited to gap setting and cable continuity checks, reducing the probability of commissioning errors that could result in incorrect vibration alarm setpoints.

Quality Assurance & Global Logistics

Every Bently Nevada 330851-02-000-080-50-00-05 unit supplied by siemensplc.com is sourced through verified distribution channels with full supply chain traceability. Units are inspected upon receipt against Bently Nevada’s published dimensional and electrical specifications: probe tip geometry, cable jacket integrity, connector pin condition, and coaxial impedance are verified before the unit enters our warehouse stock. A Certificate of Conformance (CoC) is issued with each shipment, and original manufacturer documentation is included where available.

Our logistics operations are based in Xiamen, China, a major port city with direct air freight connections to Singapore, Dubai, Frankfurt, Los Angeles, and Tokyo. Standard in-stock orders are dispatched within 1–2 business days via DHL Express, FedEx International Priority, or UPS Worldwide Expedited, with typical transit times of 3–5 business days to most destinations. For time-critical plant shutdowns, same-day dispatch is available for orders confirmed before 14:00 CST. DDP (Delivered Duty Paid) shipping is offered to the EU, UK, Australia, and Singapore, eliminating customs clearance burden for the buyer. All export documentation — commercial invoice, packing list, HS code 9031.80 declaration, and Certificate of Origin — is prepared by our in-house trade compliance team.

A 12-month warranty covers all units against manufacturing defects and out-of-specification performance. Defective units are replaced or credited within 5 business days of confirmed fault diagnosis. Our technical team, with direct experience in Bently Nevada 3300 XL and 3500 series systems, provides pre-sale application engineering and post-sale commissioning support at no additional charge.

Contact Information

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