Bently Nevada 330704-000-030-50-02-00 Proximity Probe – 3300 XL Series

Bently Nevada 330704-000-030-50-02-00 — 11 mm Eddy-Current Proximity Probe in the 3300 XL Series: Shaft Displacement Measurement for Critical Rotating Machinery

The Bently Nevada 330704-000-030-50-02-00 is an 11 mm diameter eddy-current proximity probe belonging to the 3300 XL Series — a platform that has defined the benchmark for non-contact shaft displacement sensing in turbomachinery protection systems for decades. This specific configuration ships with a 3.0 m (approximately 10 ft) integral armored cable terminated in a 2-pin MIL-C-5015 style connector, and is calibrated for AISI 4140 steel targets at a nominal gap of 1.27 mm (50 mil), producing a DC output of approximately –10 VDC at the midpoint of its linear range when powered from a –24 VDC supply.

In a machinery protection architecture, the proximity probe is the first transducer in the measurement chain. Its output — a DC-biased, AC-modulated voltage proportional to the instantaneous gap between probe tip and rotating shaft — feeds directly into a Proximitor® driver (e.g., Bently Nevada 330180-X1-05), which conditions the signal before it enters a 3500 Series monitor card. The 330704-000-030-50-02-00 is fully pin-compatible with the legacy 3300 Series, enabling drop-in replacement without rewiring or recalibration of the downstream electronics.

Typical deployment environments include steam and gas turbines in combined-cycle power plants, centrifugal compressor trains in LNG and refinery service, boiler feed pumps, large fans, and marine propulsion shafting — anywhere API 670 (5th Edition) mandates continuous radial vibration and axial position surveillance. The probe’s –35 °C to +177 °C operating range covers hot-section turbine bearing housings without signal drift, and its shielded coaxial cable construction provides measurable rejection of conducted and radiated EMI in variable-frequency drive (VFD) dense environments.

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Technical Parameters

Hardware Logical Analysis

The operating principle of the 330704-000-030-50-02-00 is based on the Lenz’s Law induction effect: a high-frequency oscillator (typically 1.0 MHz carrier) drives a coil wound at the probe tip, generating an alternating electromagnetic field. When a conductive target enters this field, eddy currents are induced on the target surface, loading the coil and reducing its effective inductance and Q-factor. The Proximitor driver circuit detects this impedance change and converts it to a proportional DC voltage output — a fundamentally non-contact, wear-free measurement mechanism with no moving parts in the sensing element.

EMC Design: The 3300 XL probe cable uses a triaxial shielding arrangement — inner conductor, inner shield (driven at the same potential as the center conductor to eliminate cable capacitance effects), and outer shield connected to chassis ground. This driven-shield (guard) topology suppresses cable-induced capacitance errors at long cable runs and provides >40 dB common-mode rejection against conducted interference from adjacent power cables and VFD switching transients. In practice, this means the probe maintains measurement accuracy within ±1% of full scale even when routed alongside 480 VAC motor leads in cable trays.

Thermal Stability: The probe coil is wound with a temperature-compensated formulation, and the ferrite core material is selected for minimal permeability drift across the –35 °C to +177 °C range. Sensitivity variation across this temperature span is specified at less than ±0.5% per 10 °C, which is critical in steam turbine bearing housings where ambient temperatures can swing 80–100 °C between cold startup and full-load operation.

Pressure Containment: The 316 stainless steel probe body is rated to 500 psi (34.5 bar), enabling direct installation through pressurized bearing housings without an external pressure barrier. The thread form and sealing face geometry conform to Bently Nevada’s standard probe holder interface, ensuring metal-to-metal sealing integrity at operating pressure.

Backward Compatibility Logic: The 330704-000-030-50-02-00 maintains full electrical and mechanical compatibility with the legacy 3300 Series probe holders and Proximitor drivers. The connector pinout, cable impedance (nominally 50 Ω coaxial), and sensitivity specification are identical to the predecessor 3300 8mm and 11mm families, allowing direct substitution in existing installations without modifying the monitor’s scale factor or alarm setpoints.

System Integration Benefits

• API 670 Compliance Out of the Box: The probe meets all transducer requirements of API 670 (5th Edition) for radial vibration and axial position measurement, satisfying EPC contractor and end-user specifications without additional qualification testing.
• Zero-Deadband DC Response: The 0 Hz lower frequency limit means the probe captures true static position (shaft centerline) as well as dynamic vibration simultaneously — a single transducer delivers both the DC gap (position) and AC component (vibration amplitude) to the monitor card.
• 10 kHz Bandwidth for High-Speed Machinery: At 10 kHz (–3 dB), the probe resolves vibration harmonics up to the 10th order on a 60,000 RPM machine, covering gear mesh frequencies and blade-pass events in high-speed compressor and turbine applications.
• Direct 3500 Rack Compatibility: No signal conditioning adapter is required. The probe connects via standard extension cable to a 3300 XL Proximitor driver, which interfaces directly with Bently Nevada 3500/42M or 3500/40M monitor cards — preserving the existing rack architecture and alarm logic.
• Deterministic Measurement Latency: The analog output path from probe tip to monitor card input introduces less than 100 µs of signal latency, ensuring that the protection system’s trip response time is dominated by the monitor’s processing cycle (typically 20 ms) rather than transducer delay.
• Diagnostic Transparency via Gap Voltage: The DC gap voltage provides a continuous, real-time indicator of probe installation integrity. A gap voltage outside the –2 VDC to –18 VDC window (for a –24 VDC supply) immediately flags probe-to-target distance errors, cable faults, or Proximitor driver failures — enabling predictive maintenance before a false trip occurs.
• Non-Contact Sensing Eliminates Mechanical Wear: With no physical contact between probe and shaft, the sensing element is immune to the fretting, galling, and fatigue failure modes that affect contact-type transducers. Field MTBF data exceeds 200,000 hours in continuous service.
• Hazardous Area Variants Available: ATEX and IECEx zone-rated versions of the 3300 XL probe family are available for installation in classified areas (Zone 1/Zone 2, Group IIC), enabling the same measurement architecture in offshore platforms, gas processing plants, and chemical facilities without separate intrinsic safety barriers for the probe itself.

Quality Assurance & Global Logistics

Every Bently Nevada 330704-000-030-50-02-00 unit supplied through siemensplc.com is sourced as genuine OEM hardware through verified industrial distribution channels. Incoming inspection at our Xiamen facility covers dimensional verification of the probe tip and thread geometry, sensitivity measurement at the nominal 1.27 mm gap using a calibrated AISI 4140 target plate, cable continuity and insulation resistance testing, and connector pin integrity check. Units that do not meet factory specification are quarantined and returned — we do not rework or relabel substandard stock.

Full traceability documentation — including factory calibration data sheet, country of origin certificate, and packing list — ships with every order. For projects requiring NIST-traceable third-party calibration certificates, this service can be arranged prior to dispatch at an additional charge.

Logistics from Xiamen, China to major industrial hubs worldwide typically transit in 3–7 business days via DHL Express or FedEx International Priority. For urgent plant shutdown requirements, same-day dispatch is available on in-stock units when orders are confirmed before 14:00 CST. Export documentation, HS code classification (HS 9031.80), and EAR99 compliance handling are managed in-house, eliminating customs clearance delays for international buyers.

All units carry a 12-month warranty from the date of shipment, covering manufacturing defects and factory calibration accuracy. Warranty claims are processed within 5 business days of receipt of the returned unit at our Xiamen facility.

Contact Information

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