Bently Nevada 31000-16-05-00-068-03-02 Proximity Probe Housing – 3300 Series

Bently Nevada 31000-16-05-00-068-03-02 — Proximity Probe Housing Assembly for Continuous Shaft Monitoring in Rotating Machinery

The Bently Nevada 31000-16-05-00-068-03-02 is a 5.0 m (16 ft) proximity probe housing assembly engineered for the 3300 and 3100 Series eddy-current transducer systems. Its primary function within a machinery protection loop is to convert mechanical shaft displacement into a proportional DC voltage signal, delivering sub-micron resolution position data to the connected Proximitor® sensor and, ultimately, to the 3500 Series rack-mounted monitor. In turbomachinery protection architectures governed by API 670, this assembly occupies the first stage of the signal chain: any degradation in probe geometry, cable impedance, or connector integrity propagates directly into measurement uncertainty at the monitor level. The 31000-16-05-00-068-03-02 addresses this criticality through a stainless-steel housing rated for continuous operation across a wide thermal envelope, a factory-terminated coaxial cable with controlled characteristic impedance, and a standardized M8 thread form that ensures repeatable installation depth and gap voltage reproducibility across maintenance cycles.

In radial vibration measurement, the probe tip is positioned at a nominal gap of approximately 1.0 mm to the shaft surface, producing a –10 VDC bias output. Shaft orbital motion modulates this voltage at frequencies corresponding to running speed harmonics, sub-synchronous instabilities, and structural resonances. The 5.0 m cable length encoded in the part number is matched to the system’s total cable length budget — probe cable plus extension cable must sum to the value specified in the Proximitor® sensor’s calibration curve to maintain the ±0.5% full-scale linearity specification. Substituting an unmatched cable length invalidates the calibration and introduces a static offset error that cannot be corrected by monitor scaling alone.

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Technical Parameters

Hardware Logical Analysis

Eddy-Current Transduction Principle and Coil Architecture: The probe tip houses a planar coil driven by a high-frequency oscillator (typically 1.0 MHz) within the Proximitor® sensor. The coil generates an alternating magnetic field that induces eddy currents in the conductive target surface. These eddy currents create a counter-magnetic field that loads the oscillator circuit, reducing its amplitude in proportion to the probe-to-target gap. The 31000-16-05-00-068-03-02 housing is machined to maintain coil-to-tip-face concentricity within ±0.05 mm, a tolerance that directly governs the angular sensitivity error — any eccentricity introduces a cosine-law deviation from the nominal sensitivity curve.

EMC Design and Shielding Architecture: The coaxial cable assembly uses a double-braid shield with 95% optical coverage, terminated at both ends to the connector shell ground. This architecture provides greater than 60 dB of common-mode rejection across the 10 Hz – 100 kHz band, suppressing variable-frequency drive (VFD) switching noise and ground-loop interference that are endemic in motor-driven compressor trains. The probe housing itself is constructed from non-magnetic 316 stainless steel, which eliminates permeability-induced sensitivity drift that would occur with carbon steel housings in high-temperature service.

Thermal Stability and Gap Voltage Drift: The probe tip assembly uses a ceramic-filled epoxy potting compound with a coefficient of thermal expansion (CTE) matched to the stainless-steel housing. This minimizes differential thermal expansion between the coil former and the housing bore, limiting thermally induced sensitivity drift to less than ±0.5% over the full –35°C to +177°C operating range. In steam turbine applications where probe tip temperatures can approach 150°C during transient load changes, this thermal stability is essential for maintaining alarm setpoint accuracy without requiring temperature-compensated calibration offsets in the monitor.

Connector Integrity and Signal Integrity: The gold-plated MIL-spec connector contacts maintain contact resistance below 5 mΩ over 500 mating cycles, preventing the intermittent high-resistance connections that manifest as spurious high-vibration trips in machinery protection systems. The connector shell provides 360° EMI shielding continuity, eliminating the shield discontinuity that occurs with standard BNC connectors used in lower-grade proximity systems.

System Integration Benefits

• Direct API 670 Compliance: The assembly meets API 670 4th Edition requirements for proximity transducer systems used in machinery protection, eliminating the need for additional compliance engineering when specifying the system for new installations or insurance audits.
• Deterministic Signal Latency: The matched 50 Ω cable impedance eliminates reflections that would introduce group delay variation across the measurement bandwidth, ensuring that the monitor’s time-domain waveform capture (used for orbit plot generation) accurately represents shaft motion without phase distortion between X and Y probe channels.
• Plug-and-Play Replacement: The M8 thread form and standardized connector interface allow direct replacement of existing 3300/3100 series probes without re-cabling or re-commissioning the Proximitor® sensor, reducing planned maintenance downtime from hours to minutes.
• Diagnostic Transparency via Gap Voltage Monitoring: The –10 VDC nominal gap voltage is continuously monitored by the 3500 Series monitor’s OK relay circuit. Any probe failure mode — open circuit, short circuit, or excessive gap — drives the gap voltage outside the –2 VDC to –18 VDC OK window, triggering a NOT OK condition that is distinguishable from a genuine high-vibration alarm, preventing false shutdowns.
• Broadband Frequency Coverage: The DC to 10,000 Hz frequency response captures not only 1× and 2× running speed components but also blade-pass frequencies, gear mesh frequencies, and sub-synchronous instabilities (oil whirl, oil whip) that are diagnostic indicators of bearing and seal degradation in turbomachinery.
• Multi-Axis Scalability: The standardized housing geometry allows installation in both radial (X-Y pair, 90° apart) and axial (thrust position) configurations using the same part number, simplifying spare parts inventory management for facilities operating mixed turbine-compressor trains.
• Compatibility with 3500 Series Rack Integration: The probe’s output signal is directly compatible with the 3500/40M and 3500/42M proximity monitor modules, enabling seamless integration into existing 3500 Series racks without signal conditioning adapters or impedance matching networks.
• Reduced Calibration Overhead: Factory-matched cable length eliminates field calibration of the sensitivity curve. The system sensitivity of 7.87 V/mm is pre-validated at the factory against the specific Proximitor® sensor model, and the calibration certificate documents the as-shipped sensitivity within ±1% of nominal — a requirement for API 670 compliant installations.

Quality Assurance & Global Logistics

Every Bently Nevada 31000-16-05-00-068-03-02 unit supplied by siemensplc.com is sourced from verified OEM distribution channels with full part-number traceability. Prior to dispatch from our Xiamen, China facility, each assembly undergoes a four-stage inspection protocol: visual examination of housing, cable jacket, and connector contacts; part-number cross-reference against Bently Nevada’s official product matrix; coaxial cable continuity and shield integrity verification; and connector mating force and retention force measurement to confirm contact spring compliance.

Shipments originate from Xiamen, Fujian Province, China, with access to Xiamen Gaoqi International Airport (XMN) and Xiamen Port for both air and sea freight. Standard export documentation — commercial invoice, packing list, certificate of origin, and HS code classification — is prepared for every shipment. Typical air freight transit times are 3–5 business days to Europe and North America via DHL Express or FedEx International Priority. For bulk orders, sea freight consolidation via Xiamen Port provides cost-effective delivery to major global ports within 15–25 days. All units are shipped in anti-static packaging with foam-lined outer cartons rated for ISTA 2A drop and vibration testing, ensuring connector and cable integrity upon arrival.

A 12-month warranty against manufacturing defects is provided on all units. Warranty claims are processed within 5 business days of receipt of the returned unit, with replacement shipment from Xiamen stock upon confirmation of the defect.

Contact Information

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