Bently Nevada 21505-00-40-10-02 Proximity Probe – 3300 Series

Bently Nevada 21505-00-40-10-02 — 8 mm Eddy Current Proximity Probe for Critical Rotating Machinery Protection

The Bently Nevada 21505-00-40-10-02 is an 8 mm non-contact eddy current proximity probe belonging to the 3300 Series transducer system — a measurement platform that has accumulated decades of field deployment across power generation, oil & gas, petrochemical, and heavy manufacturing installations worldwide. This probe functions as the primary sensing element in a three-component measurement chain: probe body, extension cable, and Proximitor® driver. Its role is to convert the physical gap between its tip and a rotating shaft surface into a proportional DC voltage signal, delivering continuous, real-time shaft radial position and dynamic vibration data to the connected monitor rack.

In a machinery protection architecture, the proximity probe occupies the most mechanically exposed position in the signal chain. It is threaded directly into the bearing housing or bracket, with its tip held at a calibrated gap — typically 1.0 mm (40 mil) — from the shaft surface. Any change in that gap, whether from shaft vibration, thermal growth, or rotor bow, produces a corresponding change in the output voltage. The 21505-00-40-10-02 delivers a nominal sensitivity of 200 mV/mil (7.87 V/mm) across a linear measurement range of 10 to 90 mil (0.25 to 2.29 mm), providing the resolution necessary to detect sub-micron shaft displacement events that precede bearing failure or rotor instability.

Real-time Stock & RFQ: [email protected] | WhatsApp: +86 18359268345

Technical Parameters

Hardware Logical Analysis

The operating principle of the 21505-00-40-10-02 is grounded in Faraday’s law of electromagnetic induction. The probe tip contains a wound coil energized by a high-frequency oscillator circuit housed in the companion Proximitor® driver — typically operating at 1.0 MHz carrier frequency for 3300 Series 8 mm probes. This oscillating magnetic field radiates from the probe tip and induces eddy currents in the conductive target surface. The magnitude of those eddy currents is an inverse function of the probe-to-target gap: as the gap decreases, eddy current density increases, loading the oscillator and reducing its amplitude. The Proximitor® demodulates this amplitude-modulated signal and outputs a DC voltage proportional to gap distance.

The 8 mm tip geometry of the 21505-00-40-10-02 is a deliberate engineering trade-off. Larger tip diameters produce a wider sensing field and greater linear range but require more installation clearance. The 8 mm format achieves a linear range of 80 mil (2.03 mm) — sufficient for the full dynamic excursion of most industrial rotating shafts — while fitting within the compact bearing housing geometries common in centrifugal compressors and steam turbine pedestals.

The probe body is machined from 316 stainless steel, providing resistance to the hydrocarbon-laden, high-humidity atmospheres found in refinery and offshore environments. The tip is hermetically sealed, preventing process fluid ingress that would alter the dielectric properties of the gap medium and introduce measurement error. The coaxial cable jacket is rated to 177°C continuous, matching the probe body’s thermal ceiling and ensuring the measurement chain does not become the thermal weak link in high-temperature installations such as gas turbine bearing pedestals.

EMC performance is inherent to the eddy current measurement architecture. Because the probe outputs a low-impedance DC voltage signal (after Proximitor® demodulation), it is substantially less susceptible to capacitively coupled noise than high-impedance piezoelectric sensors. The coaxial cable geometry provides a continuous shield from probe tip to monitor input, attenuating radiated interference from variable-frequency drives, switchgear, and high-current bus bars — all common noise sources in industrial plant environments.

System Integration Benefits

• Direct 3500 Series rack compatibility: The 21505-00-40-10-02 integrates without signal conditioning modification into Bently Nevada 3500/40M and 3500/42M monitor modules, preserving existing alarm setpoints and channel configurations during probe replacement.
• Deterministic signal latency: The eddy current measurement chain introduces no mechanical resonance or damping artifact. Signal propagation from shaft motion to monitor input is bounded by the Proximitor® carrier frequency and demodulation filter — typically <1 ms group delay — supporting the deterministic response requirements of API 670 machinery protection systems.
• Dual-measurement capability: A single probe installation can simultaneously provide radial vibration (AC component, 0–10 kHz bandwidth) and average shaft centerline position (DC component), eliminating the need for separate displacement transducers and reducing bracket complexity.
• Non-contact operation eliminates wear: With no physical contact between probe and shaft, the 21505-00-40-10-02 has no inherent mechanical wear mechanism. Mean time between replacement is governed by environmental degradation of the cable jacket and connector, not by sensing element fatigue.
• Calibration traceability: Each 3300 Series probe is factory-calibrated against AISI 4140 steel targets. The calibration data is encoded in the part number suffix, allowing maintenance engineers to verify system sensitivity without field recalibration equipment.
• Diagnostic transparency: The DC bias voltage output provides a continuous, passive health indicator. A bias voltage outside the nominal −10 VDC ± 2 VDC window at the calibrated gap indicates probe damage, cable fault, or Proximitor® failure — enabling fault isolation without removing the probe from service.
• Multi-plane vibration mapping: Two probes mounted at 90° in the X-Y plane around a shaft journal provide the orthogonal displacement data required to compute shaft orbital plots — the primary diagnostic tool for identifying rotor imbalance, misalignment, oil whirl, and rub conditions.
• Retrofit compatibility: The 3/8-24 UNF-2A thread and 8 mm tip geometry are dimensionally identical across the 3300 Series 8 mm probe family, allowing the 21505-00-40-10-02 to serve as a direct mechanical replacement in existing probe brackets without machining or adapter hardware.

Quality Assurance & Global Logistics

Every 21505-00-40-10-02 unit supplied by siemensplc.com is sourced through verified channels and subjected to a structured incoming inspection protocol before dispatch. Part number and date code are cross-referenced against OEM documentation. The probe tip, cable jacket, and coaxial connector are visually and dimensionally inspected. Units exhibiting tip damage, jacket abrasion, or connector deformation are quarantined and not shipped. Traceability records — including sourcing batch, inspection date, and inspector ID — are retained for a minimum of three years and are available to customers in regulated industries upon written request.

Packaging follows anti-static and moisture-barrier protocols. Each probe is individually wrapped in conductive foam, sealed in a moisture-barrier poly bag with desiccant, and placed in a rigid carton with foam cushioning. This packaging specification is designed to survive the mechanical shock and humidity excursions of air freight from Xiamen, China to destinations across Southeast Asia, the Middle East, Europe, and the Americas.

Logistics operations are based in Xiamen, China, with direct access to Xiamen Gaoqi International Airport and Xiamen Port — two of China’s primary export hubs for industrial goods. Standard dispatch lead time is 1–3 business days from order confirmation for in-stock units. International shipments are supported by DHL Express, FedEx International Priority, and UPS Worldwide Express, with typical transit times of 3–5 business days to major industrial centers. Full export documentation — commercial invoice, packing list, certificate of origin, and airway bill — is provided with every shipment. All units carry a 12-month warranty from the shipment date, covering manufacturing defects and premature failure under normal operating conditions.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
© 2026 siemensplc.com. All rights reserved.