Bently Nevada 21000-16-05-00-073-04-02 Proximity Probe – 21000 Series

Bently Nevada 21000-16-05-00-073-04-02: Eddy-Current Proximity Probe Housing Assembly for Critical Rotating Machinery Protection

The Bently Nevada 21000-16-05-00-073-04-02 is a 16 mm eddy-current proximity probe housing assembly engineered for continuous, non-contact displacement and vibration measurement on high-speed rotating machinery. Operating within the Bently Nevada 21000 Proximity Probe System, this assembly integrates a field-replaceable probe tip, a 5-metre armour-free extension cable, and a 073-series connector into a single traceable unit. Its primary function within a machinery protection loop is to convert shaft radial displacement into a proportional DC voltage signal — at a nominal sensitivity of −7.87 V/mm — which is then processed by a Bently Nevada 3500 or 3300 Series monitor to generate alarm and trip outputs in accordance with API 670.

Unlike general-purpose inductive sensors, the 21000 series probe is factory-calibrated as a matched system: probe, extension cable, and Proximitor® sensor are characterised together to achieve a linear output across the full −24 VDC supply range. This matched-system architecture eliminates field calibration drift caused by cable impedance mismatch — a failure mode that accounts for a significant proportion of false trips in eddy-current monitoring installations. The 16 mm probe diameter provides a target area sufficient for shaft diameters down to 50 mm, maintaining measurement linearity within ±0.5% of full-scale across the rated gap range of 0.25 mm to 2.54 mm.

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Technical Parameters

Hardware Logical Analysis

The 21000-16-05-00-073-04-02 operates on the principle of electromagnetic induction: a high-frequency oscillator within the Proximitor® sensor drives an alternating current through the probe coil, generating an electromagnetic field that penetrates the conductive target (shaft). Eddy currents induced in the shaft surface create a counter-magnetic field that loads the probe coil, reducing oscillator amplitude in proportion to the probe-to-shaft gap. The Proximitor® sensor demodulates this amplitude variation into a DC voltage output.

EMC Design: The coaxial cable geometry of the 5-metre extension provides inherent shielding against radiated electromagnetic interference. The shield is grounded at the Proximitor® sensor end only (single-point grounding), preventing ground-loop currents that would introduce 50/60 Hz noise into the displacement signal. In high-EMI environments — such as variable-frequency drive cabinets or large transformer bays — the 073-series connector’s impedance-matched termination maintains signal integrity without additional filtering hardware.

Thermal Stability: The 316 stainless steel housing and hermetic epoxy seal maintain probe coil geometry across the full −35 °C to +177 °C operating range. Thermal expansion of the probe body is characterised during factory calibration, and the sensitivity coefficient is adjusted accordingly, so the −7.87 V/mm output remains within specification across the entire temperature envelope. This is critical for steam turbine bearing housings where probe body temperatures can reach 150 °C during sustained operation.

Matched-System Calibration: Each 21000 probe, extension cable, and Proximitor® sensor is serialised and calibrated as a matched set. The calibration data is encoded in the Proximitor® sensor’s internal EEPROM (on 3500-series monitors), enabling the monitor to apply a unit-specific correction curve rather than a generic sensitivity value. Substituting an unmatched cable or probe degrades linearity by up to 3% and invalidates the API 670 calibration record — a compliance risk in regulated industries.

Mechanical Robustness: The M10 × 1 thread and locknut arrangement allows precise gap setting during installation, with a recommended torque of 2.3 N·m to prevent probe rotation under vibration. The hermetic seal rating ensures ingress protection equivalent to IP67, making the assembly suitable for oil-mist environments in gearbox and compressor bearing housings.

System Integration Benefits

• Direct API 670 Compliance: The assembly is designed and tested to meet API 670 (5th edition) machinery protection requirements, eliminating the need for third-party compliance verification when used with a certified 3500-series monitor.
• Deterministic Signal Latency: The eddy-current measurement chain introduces less than 1 ms of signal latency from shaft displacement to monitor input, supporting trip response times within the 3500 monitor’s 20 ms voting window.
• Plug-and-Play Monitor Integration: The 073-series connector mates directly with Bently Nevada 3500/40M and 3500/42M Proximitor® Monitor inputs without adapters, reducing installation wiring errors.
• Diagnostic Transparency: The 3500-series monitor continuously checks probe gap voltage against configured OK limits (typically −10 V to −18 V). A gap outside this window triggers a Not-OK (NOK) status, distinguishing a probe fault from a genuine shaft event — a capability absent in generic vibration sensors.
• Redundant Voting Architecture Support: The 16 mm probe diameter and standard M10 thread are compatible with dual-probe bracket configurations, enabling 1oo2 or 2oo3 voting logic for SIL-rated protection loops without custom machining.
• Wide Target Material Compatibility: The eddy-current principle operates on any conductive shaft material — carbon steel, 17-4 PH stainless, Inconel 718 — without sensitivity recalibration, provided the target material’s electrical conductivity is within the characterised range.
• Minimal Maintenance Interval: With no moving parts and a hermetically sealed housing, the probe assembly requires no scheduled maintenance beyond periodic gap verification (recommended annually or after any bearing replacement).
• Scalable to Multi-Channel Architectures: A single 3500/40M monitor accepts up to two probe inputs per channel card. The 21000-16-05-00-073-04-02 can be deployed in X-Y radial pairs on a single bearing, providing full orbital analysis data within one monitor slot.

Quality Assurance & Global Logistics

Every Bently Nevada 21000-16-05-00-073-04-02 unit supplied by siemensplc.com is sourced through verified channels with full traceability documentation. Prior to dispatch from our Xiamen, China warehouse, each assembly undergoes a three-stage inspection protocol: visual examination of the probe tip, cable jacket, and connector for mechanical damage; dimensional verification of the M10 thread and probe tip diameter; and functional verification of the coil impedance at 25 °C against the factory calibration record.

Calibration certificates, material test reports, and country-of-origin documentation are available upon request at no additional charge. All units are serialised, and serial numbers are cross-referenced against OEM databases where accessible to confirm authenticity. Anti-static packaging with foam-lined transit cases protects the probe coil geometry during international freight.

Logistics from Xiamen operate via DHL Express, FedEx International Priority, and UPS Worldwide Express. Standard in-stock orders are dispatched within 1–2 business days. Export documentation — including commercial invoice, packing list, and HS code 9031.80 classification — is prepared in-house to minimise customs clearance delays. Delivery to major industrial hubs in Europe, the Middle East, Southeast Asia, and North America typically completes within 3–7 business days from dispatch.

A 12-month warranty covers manufacturing defects from the date of shipment. Warranty claims are processed with a target response time of 48 hours, and replacement units are dispatched from Xiamen stock where available.

Contact Information

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