Bently Nevada 330194-18-25-50-00 Proximity Probe – 3300 XL ETR

Bently Nevada 330194-18-25-50-00: 8mm Extended Temperature Range Eddy Current Proximity Probe for Critical Rotating Machinery Protection

The Bently Nevada 330194-18-25-50-00 is an 8mm eddy current proximity probe rated for Extended Temperature Range (ETR) operation, engineered as a primary sensing element within the 3300 XL Proximity Transducer System. It delivers continuous, non-contact displacement and vibration measurement in rotating machinery where ambient temperatures at the probe tip exceed the threshold of standard-grade assemblies. The part number encodes its physical configuration: 18-inch integral cable, 25-foot extension cable interface, and temperature code 50 (ETR), distinguishing it from the standard 05-coded variant limited to approximately 120 °C.

In a machinery protection architecture compliant with API 670, this probe functions as the first element in a three-component transducer chain — probe, extension cable (330130 series), and driver/oscillator (330180 series) — feeding a 3300/16 or 3500/42 Proximitor Monitor. The eddy current principle requires no physical contact with the rotating shaft, eliminating wear and enabling indefinite service life under normal operating conditions. Output is a DC voltage proportional to the gap between probe tip and target surface, with a nominal sensitivity of 200 mV/mil (7.87 V/mm) into AISI 4140 steel targets.

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Technical Parameters

Hardware Logical Analysis

The 330194-18-25-50-00 operates on the Lenz’s Law eddy current principle: a high-frequency oscillator within the 330180 driver energizes the probe coil, generating an alternating electromagnetic field at the tip. When a conductive target enters this field, eddy currents are induced on the target surface, loading the coil and reducing oscillation amplitude. The driver converts this impedance change into a proportional DC voltage output — a fundamentally passive measurement at the probe tip with no moving parts and no mechanical wear mechanism.

ETR Cable Architecture: The integral 18-inch cable uses a high-temperature fluoropolymer (PTFE/FEP) dielectric and stainless-steel armor braid, maintaining stable coaxial impedance across the full −50 °C to +177 °C range. Standard-grade probes use PVC-jacketed cable rated to approximately 120 °C; substituting a standard probe in a high-temperature bearing housing introduces dielectric softening, capacitance drift, and sensitivity error — a failure mode that is non-obvious until calibration verification reveals output offset.

EMC Design: The coaxial cable geometry provides inherent common-mode rejection of radiated interference. The 330180 driver incorporates differential input buffering and a regulated oscillator that maintains constant drive frequency regardless of supply voltage variation within the ±2 V tolerance band. This ensures that electromagnetic noise from adjacent VFDs, switchgear, or high-current bus bars does not modulate the carrier frequency and introduce false vibration signals into the monitoring system.

Target Material Sensitivity: Output sensitivity is factory-calibrated against AISI 4140 steel. Shafts manufactured from austenitic stainless steel (e.g., 316L), titanium alloys, or Inconel exhibit different electrical conductivity and magnetic permeability, shifting the sensitivity coefficient by 5–25%. The 3300 XL system accommodates this through driver gain adjustment, but the probe itself must be re-characterized against the actual target material if non-standard alloys are used — a requirement that is documented in Bently Nevada Application Note 44 and must be reflected in the system calibration record.

Mechanical Mounting Stability: The M10 × 1.0 thread and locknut assembly provides a rigid, vibration-resistant mount. Probe tip-to-target gap is set at installation to the nominal 50 mil (1.27 mm) quiescent point, placing the operating range symmetrically within the linear zone. Thermal expansion of the probe body (316 SS, CTE ≈ 16 µm/m·°C) is negligible relative to the 80 mil linear range across the ETR temperature span, requiring no thermal compensation in the gap calculation for standard steel structures.

System Integration Benefits

• Direct API 670 compliance: The 330194-18-25-50-00 is a listed component in Bently Nevada’s API 670-compliant machinery protection system documentation, eliminating the engineering burden of qualifying a non-OEM sensor for safety-critical applications.
• Zero-wear measurement principle: Non-contact eddy current sensing produces no mechanical loading on the shaft and no probe degradation from contact, supporting continuous operation across multi-year maintenance intervals without sensor replacement.
• Deterministic output latency: The 330180 driver outputs a DC voltage with a response bandwidth of DC to 10 kHz, sufficient to resolve sub-synchronous instabilities, oil whirl, and rub events without phase lag introduced by the transducer chain.
• Dual-parameter measurement: A single probe installation simultaneously provides radial vibration (AC component) and relative shaft position (DC component), reducing the number of penetrations required in the bearing housing and simplifying the instrumentation BOM.
• Diagnostic transparency via gap voltage: The quiescent DC output voltage is directly readable on the 3500/42 monitor as a gap channel, enabling maintenance personnel to detect probe fouling, target runout, or mounting looseness without removing the probe from service.
• Seamless 3500 system integration: When paired with the 3500/42 Proximitor Monitor, the probe feeds both the vibration and position channels with a single cable run, and the monitor’s internal OK relay provides continuous transducer health supervision — flagging open-circuit or short-circuit faults within one monitor scan cycle.
• High-temperature environment suitability: The ETR rating permits installation in gas turbine bearing housings, hot-section compressor casings, and steam turbine pedestals where standard probes would exhibit insulation breakdown within months of service.
• Interchangeability within the 3300 XL family: The 330194 series maintains dimensional and electrical compatibility across all 8mm ETR variants, allowing field replacement without recalibration of the driver or monitor — provided the replacement probe is from the same series and temperature code.

Quality Assurance & Global Logistics

Every Bently Nevada 330194-18-25-50-00 unit supplied through siemensplc.com is sourced from verified supply channels with full traceability to OEM manufacturing records. Pre-shipment inspection covers output sensitivity verification at nominal gap, insulation resistance measurement (≥100 MΩ at 500 VDC), connector continuity, and visual inspection of cable armor integrity. Units failing any parameter are quarantined and not shipped.

Shipments originate from our warehouse in Xiamen, China, with access to DHL Express, FedEx International Priority, and UPS Worldwide Expedited services. Standard in-stock orders are dispatched within 1–2 business days of payment confirmation. Export documentation — including commercial invoice, packing list, and certificate of origin — is prepared in compliance with HS Code 9031.80 for precision measurement instruments. ATEX/IECEx certification documentation is available upon request for installations in classified hazardous areas.

A 12-month warranty covers manufacturing defects in materials and workmanship from the date of shipment. Warranty claims are processed with replacement unit dispatch upon receipt of the defective item and inspection confirmation. Calibration certificates and OEM conformance documentation are available for quality-system requirements under ISO 9001 or equivalent frameworks.

Contact Information

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