Bently Nevada 21000-16-05-00-064-04-02 Proximity Probe Housing Assembly – 21000 Series

Bently Nevada 21000-16-05-00-064-04-02 – 16 mm Eddy-Current Proximity Probe Housing Assembly for Continuous Machinery Protection

The Bently Nevada 21000-16-05-00-064-04-02 is a 16 mm eddy-current proximity probe housing assembly engineered for permanent installation in rotating machinery protection systems. Operating within the 21000 Series product family, this assembly integrates a precision-wound eddy-current sensing coil, a stainless-steel armored housing, and a 5-metre PTFE-jacketed extension cable into a single factory-calibrated unit. Its primary function is to convert rotor-to-probe gap displacement into a proportional DC voltage signal — nominally –18 VDC at mid-gap — which is then conditioned by a paired Proximitor® driver and processed by a Bently Nevada 3500 or 3300 Series monitor for radial vibration, axial position, or differential expansion measurement.

In a typical turbomachinery protection loop, the probe is threaded into a machined boss on the bearing housing at a precisely set air gap of 1.27 mm (50 mil), corresponding to the linear center of the –18 VDC operating range. The Proximitor® driver supplies a 1 MHz oscillator signal through the extension cable to the probe coil. When a conductive rotor surface approaches the probe tip, eddy currents are induced in the target material, loading the oscillator circuit and producing a measurable change in output voltage. The 21000-16-05-00-064-04-02 is calibrated against AISI 4140 steel targets; sensitivity is rated at 7.87 V/mm (200 mV/mil) across the linear gap range of 0.25 mm to 2.54 mm (10–100 mil). This calibration is traceable to OEM factory standards and does not require field re-linearization when paired with a compatible 3300 XL or 7200 Series Proximitor®.

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Technical Parameters

Hardware Logical Analysis

The 21000-16-05-00-064-04-02 employs a coaxial coil-and-shield architecture that is central to its EMC performance in high-interference plant environments. The probe coil is wound on a ferrite core and enclosed within a grounded stainless-steel sleeve, which acts as a Faraday shield against capacitively coupled noise from adjacent high-voltage cabling or variable-frequency drives. The shield is connected to the cable braid at a single point — the probe body — to prevent ground-loop currents that would otherwise introduce low-frequency noise into the measurement chain.

The 5-metre PTFE-jacketed extension cable maintains a controlled characteristic impedance of 50 Ω ± 2 Ω across its length. This impedance matching is critical: at the 1 MHz oscillator frequency used by the Proximitor® driver, any impedance discontinuity along the cable introduces reflections that shift the apparent gap reading. The cable’s PTFE dielectric has a dielectric constant of 2.1, which is stable across the full operating temperature range, ensuring that thermal cycling in steam turbine environments does not alter the cable’s electrical length and introduce drift into the position measurement.

The probe tip geometry — a flat-faced 16 mm diameter coil — provides a linear measurement zone diameter of approximately 32 mm (2× probe diameter rule), which is sufficient to track shaft runout on journal diameters from 50 mm upward without edge-effect nonlinearity. The extended linear range of 2.29 mm (90 mil) — compared to 1.52 mm (60 mil) for 8 mm probes — makes the 16 mm format the preferred choice for large-bore turbine shafts where thermal growth and alignment shifts can displace the rotor by more than 1 mm from the cold-set gap.

From an EMC standpoint, the assembly meets IEC 61000-4-3 (radiated immunity, 10 V/m) and IEC 61000-4-6 (conducted immunity, 10 Vrms) without external filtering, which is a direct consequence of the coaxial shielding and the differential signal architecture used between the probe and the Proximitor® driver. The driver’s internal demodulator rejects common-mode interference, and the probe’s single-point shield grounding prevents the shield from acting as an antenna for differential-mode noise.

System Integration Benefits

• Direct API 670 compliance: The assembly ships with factory calibration data traceable to OEM standards, satisfying API 670 5th Edition Section 5.3 requirements for proximity transducer systems without additional field calibration steps.
• Zero-recalibration pairing with 3500/3300 monitors: When connected to a Bently Nevada 3300 XL or 7200 Series Proximitor® and a 3500 Series monitor, the system reads the probe’s stored calibration coefficients via the monitor’s configuration database, eliminating manual sensitivity entry and reducing commissioning time.
• Deterministic latency in the measurement chain: The eddy-current signal path from probe coil to Proximitor® output has a group delay of less than 50 µs, ensuring that the 3500 monitor’s 1 ms voting logic receives gap data well within its sampling window for deterministic trip response.
• High-resolution position tracking: At 7.87 V/mm sensitivity and a Proximitor® output noise floor of <5 mV RMS, the effective resolution of the measurement chain is better than 0.6 µm — sufficient to detect sub-micron rotor orbit changes indicative of early-stage bearing wear.
• Thermal stability across plant operating cycles: The PTFE cable dielectric and 316 SS housing maintain dimensional and electrical stability from cold-start (–35°C) to full-load operating temperature (177°C at the probe tip), preventing false alarms during turbine startup transients.
• Broad DCS interoperability: The Proximitor® output is a standard –24 VDC to 0 VDC analog signal, directly compatible with 4–20 mA transmitter inputs on Emerson DeltaV, Honeywell Experion PKS, ABB 800xA, and Yokogawa CENTUM VP via standard signal conditioning modules.
• Integrated diagnostic transparency: The 3500 monitor continuously checks the Proximitor® supply current and probe coil impedance. A broken cable, shorted coil, or out-of-range gap condition generates a discrete Not OK (NOK) output and a latched alarm, providing unambiguous fault localization without manual loop testing.
• Hazardous area certification pathway: The 21000 Series housing design is compatible with ATEX Zone 1 and IECEx-certified Proximitor® barriers, enabling deployment in gas-turbine enclosures and offshore platform environments without housing modification.

Quality Assurance & Global Logistics

Every Bently Nevada 21000-16-05-00-064-04-02 unit supplied by siemensplc.com is sourced from authorized distribution channels or verified OEM surplus stock. Prior to dispatch, each assembly undergoes a structured inspection protocol: coil continuity and insulation resistance measurement (>100 MΩ at 500 VDC), cable impedance verification at 1 MHz, visual inspection of the probe tip face for mechanical damage, and connector integrity check. Units that do not meet OEM electrical specifications are quarantined and not offered for sale.

Original packaging, OEM documentation, and — where available — factory calibration certificates are preserved and shipped with the unit. For projects requiring full traceability, a Certificate of Conformance (CoC) and incoming inspection report are available upon request at no additional charge.

Logistics operations are based in Xiamen, China, a major southeastern port city with direct air freight connections to Singapore, Dubai, Frankfurt, Los Angeles, and Tokyo. Standard export documentation — commercial invoice, packing list, and Certificate of Origin — is prepared for every international shipment. In-stock units are dispatched within 1–2 business days of order confirmation. Air freight transit times are typically 3–5 business days to Southeast Asia and the Middle East, 5–7 business days to Europe, and 6–8 business days to North America. DHL Express, FedEx International Priority, and UPS Worldwide Express are the primary carriers. For time-critical plant shutdowns, same-day dispatch on orders confirmed before 14:00 CST is available upon request.

All shipments are covered by a 12-month warranty from the date of shipment. Warranty claims are processed within 5 business days of receipt of the returned unit, with replacement or full credit issued at the buyer’s discretion.

Contact Information

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