Bently Nevada 21000-16-05-30-026-04-02 Proximity Probe – 21000 Series

Bently Nevada 21000-16-05-30-026-04-02 — 16 mm Proximity Probe Housing Assembly in Industrial Shaft Monitoring Loops

The 21000-16-05-30-026-04-02 is a 16 mm diameter proximity probe housing assembly from Bently Nevada’s 21000 Series, a product line engineered specifically for continuous, non-contact measurement of radial shaft vibration and axial position in rotating machinery. Within a complete eddy-current measurement chain — probe, extension cable, and Proximitor sensor — this housing assembly defines the mechanical interface between the sensing tip and the machine casing, directly governing gap stability, thermal drift, and long-term signal integrity. Its dimensional encoding (16 mm probe body, 5 m extension, 0–30 mil linear range, 026-series connector, 04-series cable jacket, 02-series termination) is not arbitrary; each segment of the part number maps to a specific electromechanical parameter that must be matched to the target Proximitor driver and monitoring rack to maintain calibrated output.

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Technical Parameters

Hardware Logical Analysis

The 21000 Series probe operates on the eddy-current (electromagnetic induction) principle. The probe tip houses a flat coil wound on a ferrite core, driven by a high-frequency oscillator (typically 1.0 MHz carrier) embedded in the paired Proximitor sensor. When the conductive target shaft enters the probe’s electromagnetic field, eddy currents are induced on the shaft surface, loading the oscillator circuit and reducing its output amplitude. The Proximitor demodulates this amplitude-modulated signal into a DC voltage proportional to the probe-to-shaft gap — a linear relationship maintained across the 0–30 mil range with less than ±1% non-linearity error under standard conditions.

EMC and Shielding Architecture: The 16 mm housing diameter is not merely a mechanical choice — it determines the coil geometry and, consequently, the depth of the eddy-current field penetration into the shaft. A 16 mm probe produces a field depth of approximately 3–5 mm into the target, sufficient to detect surface and near-surface shaft deformation while remaining immune to sub-surface metallurgical variations. The coaxial cable construction (02-series termination) provides continuous 360° electrostatic shielding from probe tip to Proximitor input, suppressing capacitively coupled interference from adjacent high-voltage conductors common in turbine generator environments. The shield is grounded at the Proximitor end only, eliminating ground-loop currents that would appear as low-frequency noise on the output signal.

Thermal Stability: The PEEK (polyether ether ketone) tip insert provides a coefficient of thermal expansion (CTE) of approximately 50 µm/m·°C, significantly lower than standard nylon alternatives. This minimizes dimensional shift of the coil-to-target gap across the –35°C to +121°C operating envelope, which is critical in steam turbine bearing housings where metal temperatures can cycle ±60°C during startup and shutdown sequences. The 316 stainless steel body resists hydrogen sulfide stress corrosion cracking (NACE MR0175 considerations) relevant in sour gas compressor applications.

Cable Jacket (04-Series): The 04-series cable jacket designation specifies a fluoropolymer (ETFE or FEP) outer sheath rated to 105°C continuous, with a braid shield coverage of ≥95%. This jacket formulation resists hydrocarbon fluid ingress, turbine lube oil, and steam condensate — the three most common cable degradation agents in rotating machinery installations. The 5 m extension length positions the Proximitor sensor outside the high-temperature zone of the bearing housing while keeping total cable capacitance within the Proximitor’s specified load range (typically ≤1,000 pF for the 3300 XL driver).

System Integration Benefits

• Direct compatibility with Bently Nevada 3500 Series MPS: The 21000-16-05-30-026-04-02 is calibrated for use with the 3500/42M Proximitor I/O module. No field recalibration is required when replacing a like-for-like unit, reducing maintenance window duration by eliminating the gap-setting verification loop.
• Deterministic latency in protection loops: The DC-to-10 kHz flat frequency response ensures that shaft vibration events at 1× running speed (up to 600 Hz for 36,000 RPM machinery) and their harmonics are captured without phase lag introduced by the sensor itself. Protection system trip latency is governed solely by the monitoring rack’s processing cycle, not the probe.
• Dual-use measurement — vibration and position: A single probe installation simultaneously provides radial vibration amplitude (AC component) and average shaft centerline position (DC component). This eliminates the need for separate displacement transducers in many bearing monitoring configurations, reducing penetration count through the bearing housing.
• Diagnostic transparency via gap voltage monitoring: The –1 VDC to –17 VDC output range allows the 3500 rack to continuously monitor probe gap voltage as a diagnostic channel. Gradual drift in DC gap voltage indicates bearing wear, shaft bow, or probe mounting loosening — all detectable before a vibration alarm threshold is reached.
• Redundant probe pair support: The 3500/42M module supports dual-probe redundant configurations on a single channel pair. The 21000-16-05-30-026-04-02 can be deployed as either the primary or redundant sensor without hardware modification, with the rack performing automatic switchover on probe failure detection.
• Compatibility with ADRE data acquisition: The analog output is directly compatible with Bently Nevada ADRE 408 DSPi and ADRE SXP portable analyzers, enabling offline vibration spectrum analysis and ODS (Operating Deflection Shape) measurements without disconnecting the probe from the protection system.
• Reduced installation error risk: The 16 mm body diameter with standard thread pitch (M20×1.5 or 3/4-inch NPT depending on housing variant) matches the most common probe boss dimensions in OEM turbine and compressor designs. This dimensional standardization eliminates the need for adapter bushings that introduce additional mechanical compliance into the probe mounting stack.
• Long-term signal stability: Eddy-current probes exhibit no mechanical wear mechanism — there is no contact between the probe and the rotating shaft. Mean time between replacement (MTBR) in clean industrial environments exceeds 10 years, with the primary failure mode being cable jacket degradation rather than sensing element failure. This characteristic makes the 21000 Series suitable for continuous online monitoring without scheduled replacement intervals.

Quality Assurance & Global Logistics

Every 21000-16-05-30-026-04-02 unit supplied by siemensplc.com is sourced through verified distribution channels with full OEM traceability. Units are inspected against Bently Nevada factory acceptance criteria: housing dimensional check (±0.05 mm on probe body OD), connector pin integrity, cable continuity and insulation resistance (≥100 MΩ at 500 VDC), and label authenticity verification against current OEM part marking standards.

Shipments originate from our warehouse in Xiamen, China — a major international logistics hub with direct access to DHL Express, FedEx International Priority, and UPS Worldwide services. In-stock units are dispatched within 1–3 business days. Standard export documentation — commercial invoice, packing list, certificate of origin, and packing declaration — is provided with every shipment. For project-volume orders, sea freight consolidation and EXW/FOB/CIF Incoterms are available. All shipments comply with applicable export control regulations. Anti-static protective packaging is used for all probe assemblies to prevent electrostatic discharge damage to the coil winding during transit.

A 12-month warranty against manufacturing defects is included from the ship date. Warranty claims are handled directly with replacement unit dispatch or full credit, subject to inspection of the returned item.

Contact Information

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