Bently Nevada 21000-34-05-15-056-04-02 Proximity Probe – 3300 XL Series

Bently Nevada 21000-34-05-15-056-04-02 — 5 mm Eddy-Current Proximity Probe, 15 ft Cable Assembly for 3300 XL Machinery Protection Systems

The 21000-34-05-15-056-04-02 is a factory-configured, matched-set eddy-current proximity probe manufactured by Bently Nevada (Baker Hughes) for deployment within the 3300 XL Proximity Probe System platform. Each field in the part number is a deterministic parameter string: probe tip diameter (5 mm), total cable length (15 ft / 4.57 m), sensitivity coefficient (200 mV/mil nominal), and connector configuration — all encoded at the factory and calibrated as an inseparable measurement chain. This unit is designed for continuous, non-contact shaft radial vibration and axial position measurement on rotating machinery classified under API 670 as critical or essential service.

In a machinery protection architecture, the proximity probe occupies the first stage of the signal chain. It generates a high-frequency electromagnetic field (typically 1.0 MHz oscillation frequency) through its tip coil. When a conductive target — typically AISI 4140 or 4340 steel shaft — enters the field, eddy currents are induced on the target surface. These eddy currents load the probe’s LC oscillator circuit, causing a measurable impedance shift. The Proximitor® driver (oscillator-demodulator) converts this impedance variation into a DC voltage output proportional to the probe-to-target gap, at a sensitivity of 200 mV/mil (7.87 V/mm). The resulting analog signal feeds directly into 3300 XL monitor rack I/O modules for alarm, trip, and data trending functions.

The 5 mm tip diameter of this probe is selected for applications where shaft journal geometry, bearing housing bore constraints, or installation envelope limits preclude the use of larger 8 mm probes. The 15 ft (4.57 m) cable length accommodates installations where the Proximitor® driver must be mounted at a distance from the bearing housing — a common requirement in high-temperature turbine pedestals or compressor skids where electronics must be isolated from radiant heat sources. The total cable length (probe body + extension cable) must match the driver’s calibration curve; this unit ships as a pre-matched assembly requiring no field trimming or recalibration.

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Technical Parameters

Hardware Logical Analysis

The eddy-current measurement principle employed in the 21000-34-05-15-056-04-02 is fundamentally immune to the contamination vectors that degrade optical and capacitive sensing technologies. Oil mist, condensate, metallic particulate, and process gas ingress — all endemic to rotating machinery environments — do not attenuate the electromagnetic field generated by the probe tip coil. This physical characteristic makes the 3300 XL probe the preferred sensing element in API 670-governed machinery protection systems where measurement continuity under adverse process conditions is a non-negotiable design requirement.

EMC Design Architecture: The probe cable is a precision coaxial assembly with controlled characteristic impedance matched to the Proximitor® driver input. The shield is continuous from probe body to connector, providing a Faraday enclosure that attenuates capacitively-coupled interference from adjacent high-voltage cabling, VFD switching transients, and RF sources common in industrial switchgear environments. The probe body’s 316 SS housing acts as a secondary electromagnetic shield for the tip coil assembly, reducing susceptibility to external field perturbation without introducing ferromagnetic distortion into the measurement field.

Thermal Stability: The probe tip coil is wound on a ceramic bobbin with a controlled thermal expansion coefficient. This construction minimizes sensitivity drift across the –35°C to +177°C operating range — a critical parameter in steam turbine pedestals where bearing housing temperatures can vary by 80–120°C between cold-start and full-load conditions. Factory calibration data accounts for the nominal thermal coefficient of sensitivity, and the matched-set calibration curve stored in the associated Proximitor® driver compensates for residual thermal drift at the system level.

Mechanical Robustness: The 5 mm probe tip is threaded into the 316 SS body with a locking mechanism that maintains tip-to-body concentricity within ±0.05 mm — a tolerance that directly affects the probe’s effective linear range and null-point repeatability. The integral cable strain relief is designed to withstand continuous vibration at the probe mounting point without inducing cable-generated noise into the measurement signal, a failure mode that manifests as elevated broadband noise floor in the vibration spectrum.

System Integration Benefits

• Zero-Wear Continuous Operation: Non-contact sensing eliminates mechanical degradation at the measurement interface; the probe’s mean time between failure (MTBF) in clean industrial environments exceeds 100,000 hours of continuous operation.
• Deterministic Signal Latency: The analog output signal from the Proximitor® driver reaches the 3300 XL monitor rack with sub-millisecond latency, preserving the phase integrity of vibration waveforms required for accurate orbit plot construction and 1X/2X vector analysis.
• Direct Rack Compatibility: Plug-and-play integration with 3300 XL/16 and 3300 XL/01 monitor modules eliminates signal conditioning adapters that introduce impedance mismatch and additional noise sources into the measurement chain.
• API 670 Alarm and Trip Compliance: The probe’s sensitivity and linear range are matched to the 3300 XL monitor’s configurable alarm and danger setpoints, enabling direct implementation of API 670 Table 1 vibration limits without scaling corrections.
• Broadband Frequency Coverage: DC to 10 kHz bandwidth captures the full spectrum of rotating machinery fault signatures — sub-synchronous instability (oil whirl/whip), 1X unbalance, 2X misalignment, and high-frequency gear mesh and blade-pass frequencies — within a single measurement channel.
• DCS/SCADA Integration Transparency: The –24 VDC analog output is directly compatible with standard 4–20 mA transmitter input cards via signal conditioning modules, enabling integration into ABB, Honeywell, Emerson DeltaV, and Yokogawa DCS platforms without proprietary gateways.
• Diagnostic Transparency via Gap Voltage: The DC gap voltage output provides a continuous, real-time indication of probe-to-shaft clearance. Trending this value over time reveals bearing wear, shaft thermal growth, and rotor position shifts that precede mechanical failure — enabling condition-based maintenance scheduling rather than time-based overhaul intervals.
• Matched-Set Calibration Traceability: Each probe-cable-driver assembly is calibrated as a unit at the factory, with calibration data traceable to NIST standards. This eliminates field calibration errors introduced when mixing unmatched probe and driver components — a common source of measurement uncertainty in field-assembled systems.

Quality Assurance & Global Logistics

Every unit of the 21000-34-05-15-056-04-02 offered through siemensplc.com is sourced from verified supply channels with documented chain of custody. Pre-shipment inspection covers visual integrity of the probe body and tip, coaxial connector condition, cable jacket continuity, and dimensional verification of the probe thread and tip concentricity. Serialization and factory date-code verification are performed on every unit prior to listing. Original factory packaging is preserved where available; all shipments are protected with anti-static shielding and moisture-barrier packaging to maintain the probe’s calibration integrity during transit.

A Certificate of Conformance (CoC) is available upon request for all units. For projects requiring full material traceability documentation, contact our technical team at the time of inquiry.

Logistics Base: Xiamen, China. We ship globally via DHL Express, FedEx International Priority, and UPS Worldwide Expedited. Standard export documentation — commercial invoice, packing list, and HS code classification — is prepared for every international shipment. For time-critical plant maintenance scenarios, same-day dispatch is available for in-stock units when orders are confirmed before 14:00 CST. Typical transit times: Southeast Asia 2–3 days; Europe 3–5 days; North America 4–6 days; Middle East and Africa 5–7 days. All shipments are fully insured and tracked from dispatch to delivery confirmation.

Contact Information

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