Bently Nevada 21000-16-10-15-075-03-02 Proximity Probe Housing – 21000 Series

Bently Nevada 21000-16-10-15-075-03-02: 16 mm Eddy-Current Proximity Probe Housing Assembly for Continuous Shaft Monitoring

The Bently Nevada 21000-16-10-15-075-03-02 is a 16 mm diameter eddy-current proximity probe housing assembly engineered for permanent installation in rotating machinery protection and condition monitoring systems. Within a closed-loop vibration control architecture, this assembly occupies the sensing node of the measurement chain — converting mechanical displacement of a conductive target into a calibrated DC voltage signal that feeds directly into Bently Nevada 3500 Series monitor racks or equivalent signal conditioning hardware. The probe operates on the eddy-current induction principle: a high-frequency oscillator (typically 1.0 MHz) drives a coil embedded in the probe tip, generating an electromagnetic field that induces eddy currents in the proximate metallic target. As the air gap changes, the reflected impedance modulates the oscillator amplitude, which the driver/oscillator converts to a linear voltage output of −18 VDC nominal at the calibrated center gap.

The part number encodes the full mechanical and electrical configuration. Breaking down 21000-16-10-15-075-03-02: the 21000 prefix identifies the product family; 16 specifies the 16 mm probe body diameter; 10 denotes the probe cable length of 1.0 m; 15 indicates the extension cable length of 1.5 m; 075 references the 7.87 V/mm (200 mV/mil) sensitivity scale factor; 03 identifies the connector type; and 02 designates the temperature rating class. This deterministic naming convention eliminates ambiguity during procurement and ensures exact mechanical and electrical interchangeability with the installed base.

In turbomachinery protection applications — steam turbines, gas compressors, centrifugal pumps, and gearboxes — the 21000-16-10-15-075-03-02 provides the primary displacement signal for radial shaft vibration and axial position measurement. The 16 mm body diameter is selected where installation bores are sized for larger probe housings, offering a wider linear measurement range (typically 0.25 mm to 2.25 mm gap) compared to 8 mm variants, which is critical in applications with high shaft runout or where the target surface finish is not ideal. The assembly is fully compliant with API 670 (Machinery Protection Systems), the governing standard for vibration, position, and speed monitoring in the oil and gas, petrochemical, and power generation industries.

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Technical Parameters

Hardware Logical Analysis

Eddy-Current Transduction Architecture: The 21000-16-10-15-075-03-02 employs a passive LC resonant circuit at the probe tip. The coil geometry is precision-wound to achieve a tightly controlled inductance value, which, in combination with the driver/oscillator’s tuned capacitance network, establishes the 1.0 MHz carrier frequency. The reflected impedance from the target surface modulates the Q-factor of this resonant circuit. The driver/oscillator demodulates the amplitude envelope and outputs a linear DC voltage proportional to gap distance. The 16 mm coil diameter provides a larger sensing field diameter compared to 8 mm probes, resulting in a proportionally wider linear range and reduced sensitivity to minor surface irregularities or shaft eccentricity artifacts.

EMC and Shielding Design: The coaxial cable construction — with a braided shield referenced to the driver/oscillator ground — provides effective rejection of common-mode electromagnetic interference. In industrial environments where variable-frequency drives, high-current bus bars, and RF sources are co-located, the coaxial architecture maintains signal integrity across the full 2.5 m cable run. The probe housing is machined from stainless steel, which provides both mechanical protection and an additional Faraday shield layer around the coil assembly. The connector interface (Type 03) uses a precision-machined coaxial coupling that maintains characteristic impedance continuity, preventing reflections that would introduce measurement error at high shaft vibration frequencies.

Thermal Stability and Gap Voltage Linearity: 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 thermally induced mechanical stress on the coil winding, which would otherwise shift the inductance value and introduce a temperature-dependent offset in the gap voltage output. The result is a stable scale factor of 7.87 V/mm across the full −35°C to +177°C operating range, eliminating the need for temperature compensation in the signal conditioning chain. Factory calibration is performed against a certified reference target at multiple gap points, and the calibration curve is traceable to NIST standards.

Mechanical Housing and Installation Integrity: The 16 mm housing thread and locknut design allows precise gap adjustment during commissioning. The housing material and thread form are specified to resist galling and corrosion in steam-saturated or hydrocarbon-laden atmospheres. The integral cable strain relief prevents flexural fatigue at the cable exit point — a common failure mode in probes subjected to vibration from the machinery structure itself. The extension cable connector is a positive-locking coaxial type that resists vibration-induced loosening, maintaining contact resistance below the threshold that would introduce noise into the measurement chain.

System Integration Benefits

• Direct API 670 Compliance: The 21000-16-10-15-075-03-02 meets all transducer requirements of API 670 Fifth Edition, enabling direct use in machinery protection systems without additional qualification testing or derating.
• Deterministic Signal Latency: The eddy-current measurement chain introduces no mechanical hysteresis or pneumatic delay. The DC-to-10,000 Hz frequency response ensures that shaft vibration events at frequencies up to the 10th harmonic of a 1,000 RPM machine are captured without phase distortion, supporting accurate orbit plot generation in the 3500 monitor rack.
• Plug-and-Play Compatibility with 3500 Racks: The probe, when paired with a compatible Bently Nevada driver/oscillator, presents the standard −18 VDC output that the 3500/40M and 3500/42M monitor modules are calibrated to accept. No field recalibration of the monitor rack is required on replacement of a like-for-like 21000-16-10-15-075-03-02 unit.
• Wide Linear Range for High-Runout Shafts: The 0.25 mm to 2.25 mm linear range accommodates shafts with significant mechanical runout or where initial gap setting precision is limited by installation access. This reduces the risk of probe saturation during transient events such as startup or coast-down.
• Diagnostic Transparency via Gap Voltage Monitoring: The −18 VDC output at center gap provides a continuous, measurable indicator of probe-to-shaft gap. Operators can monitor the DC component of the probe output to detect slow-moving axial position drift, bearing wear, or probe fouling — without interrupting production.
• DCS and PLC Integration via Monitor Rack Outputs: The 3500 rack’s 4–20 mA and relay outputs interface directly with Siemens S7-300/400/1500 analog input modules, Allen-Bradley ControlLogix, and Emerson DeltaV, enabling vibration and position data to be integrated into plant-wide SCADA and historian systems without additional signal conditioning hardware.
• Reduced Commissioning Time: Factory-calibrated scale factor and documented gap voltage curve eliminate the need for field calibration against a reference target. Commissioning is reduced to gap setting and verification of the output voltage at the known installation gap — a procedure that can be completed in under 30 minutes per probe point.
• Long-Term Spare Parts Availability: The 21000 Series has been in continuous production for decades. The standardized part number structure ensures that replacement units sourced from authorized distributors are dimensionally and electrically identical to the installed base, eliminating compatibility risk during maintenance outages.
• Hazardous Area Suitability: When installed with appropriate certified barriers or isolators, the 21000-16-10-15-075-03-02 can be deployed in Zone 1/Zone 2 (ATEX) and Division 1/Division 2 (NEC) classified areas, covering the majority of oil and gas and petrochemical installation environments.

Quality Assurance & Global Logistics

Every Bently Nevada 21000-16-10-15-075-03-02 unit supplied by siemensplc.com is sourced through verified supply channels and subjected to incoming inspection prior to dispatch. Inspection protocol includes visual examination of the housing, cable jacket, and connector for transit damage; dimensional verification of the probe body diameter and thread form; and electrical verification of the open-circuit inductance and DC resistance of the probe coil against the OEM specification envelope. Units that do not pass inspection are quarantined and not dispatched.

Original manufacturer packaging, documentation, and where available, factory calibration certificates are preserved and shipped with the unit. Traceability records — including lot number, date code, and inspection results — are retained for a minimum of five years and are available to customers on request.

Logistics operations are based in Xiamen, China, a major international port city with direct air freight connections to Singapore, Dubai, Frankfurt, Los Angeles, and Tokyo. Standard dispatch lead time for in-stock units is 1–3 business days from order confirmation. International shipments are handled via DHL Express, FedEx International Priority, or UPS Worldwide Express, with typical transit times of 3–5 business days to Europe, North America, and Southeast Asia. Export documentation — including commercial invoice, packing list, and certificate of origin — is prepared in compliance with destination country import requirements. Customers in regions with specific import licensing requirements for industrial automation components are advised to contact us prior to ordering to confirm documentation requirements.

A 12-month warranty from the date of shipment covers manufacturing defects and verifiable OEM non-conformances. Warranty claims are processed with a target response time of 48 hours from receipt of the defective unit and supporting documentation.

Contact Information

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