Bently Nevada 330881-28-10-060-06-02 Proximity Transducer – PROXPAC XL

330881-28-10-060-06-02: Factory-Matched Eddy-Current Transducer Assembly for Turbomachinery Protection

The Bently Nevada 330881-28-10-060-06-02 is a complete, factory-calibrated PROXPAC XL proximity transducer assembly designed for continuous shaft displacement measurement in critical rotating machinery. The assembly integrates a 28 mm diameter eddy-current probe, a 6.0 m factory-matched extension cable, and an integrated proximitor driver into a single traceable unit. This configuration eliminates inter-component calibration variance — a common source of measurement drift in field-assembled systems — and delivers a verified output sensitivity of 7.87 V/mm (200 mV/mil) from the moment of installation.

Within a 3300 XL machinery protection architecture, this transducer assembly occupies the front-end signal acquisition layer. The probe tip generates a high-frequency oscillating electromagnetic field (typically 1.0–1.5 MHz carrier) directed at the shaft surface. As the conductive shaft moves relative to the probe face, eddy currents induced in the target material alter the probe coil impedance. This impedance modulation is transmitted via the matched coaxial extension cable to the integrated proximitor, which demodulates the carrier and outputs a DC-coupled voltage signal with a nominal –24 VDC bias. The resulting analog signal is linearly proportional to the air gap across a calibrated range of 0.25 mm to 2.25 mm (10 mil to 90 mil), and is fed directly into 3300 XL monitor input cards for alarm, trip, and trend processing.

The –28– probe tip diameter is selected for installations requiring a wider electromagnetic field footprint, improving signal-to-noise ratio on shafts with surface finish irregularities or minor runout. The –060– cable designation specifies a 6.0 m extension, the most common field length for installations where the proximitor must be located outside the bearing housing thermal envelope. The –06– proximitor code identifies the standard 3300 XL driver module, and the –02 output suffix denotes the standard voltage output configuration compatible with all 3300 XL monitor input channels.

This assembly is specified under API Standard 670 (Machinery Protection Systems) for radial shaft vibration, axial position, and differential expansion measurement on steam turbines, gas turbines, centrifugal compressors, and large motor-generator sets. Its frequency response of DC to 10,000 Hz (–3 dB) captures the full spectrum of sub-synchronous, synchronous, and super-synchronous vibration components relevant to rotating machinery diagnostics.

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Technical Parameters

Hardware Logical Analysis

The 330881-28-10-060-06-02 assembly is built around a single-coil eddy-current probe topology. The probe coil, embedded in the 28 mm stainless steel tip housing, forms part of a Colpitts-type LC oscillator circuit within the proximitor. The oscillator operates at a carrier frequency in the 1.0–1.5 MHz band — a range selected to balance penetration depth into the target material against sensitivity to surface conductivity variations. At this frequency, the electromagnetic skin depth in AISI 4140 steel is approximately 0.08–0.12 mm, ensuring that the eddy-current field interacts only with the shaft surface layer and is not influenced by sub-surface material heterogeneity.

The 6.0 m extension cable is a controlled-impedance coaxial assembly, factory-matched to the specific probe coil inductance. Cable impedance mismatch — even at the level of a few picofarads of parasitic capacitance — shifts the oscillator resonant frequency and introduces a proportional DC offset error at the proximitor output. By factory-matching cable and probe, Bently Nevada eliminates this error source and guarantees the published 7.87 V/mm scale factor without field trimming.

The integrated proximitor performs amplitude demodulation of the carrier signal using a precision envelope detector, followed by low-pass filtering to extract the DC-coupled displacement signal. The –24 VDC bias point is set at mid-gap (approximately 1.25 mm), providing symmetric headroom for both positive and negative shaft displacement excursions. The output stage is a low-impedance voltage driver capable of driving the 3300 XL monitor input impedance (typically 10 kΩ) with less than 0.1% loading error.

EMC performance is achieved through a combination of the coaxial cable shield (grounded at the proximitor end only, per Bently Nevada single-point grounding practice), the stainless steel probe housing acting as a Faraday shield for the coil, and the proximitor enclosure’s continuous metal shell. This topology suppresses common-mode interference from variable-frequency drives, high-voltage bus bars, and RF sources common in turbomachinery environments, maintaining measurement integrity in environments with conducted EMI levels up to 10 V/m (per IEC 61000-4-3 Class A).

System Integration Benefits

• Zero-calibration installation: Factory-matched assembly ships with a calibration certificate traceable to NIST standards. No field oscillator adjustment or sensitivity verification is required before commissioning, reducing installation time by 60–90 minutes per measurement point.
• Direct 3300 XL monitor compatibility: Output signal (–24 VDC bias, 7.87 V/mm) is natively accepted by all 3300 XL monitor input cards (3300/16, 3300/20, 3300/25, 3300/55) without signal conditioning adapters or scaling adjustments.
• API 670 compliance: Assembly meets API Standard 670 requirements for radial vibration, axial position, and differential expansion transducer systems, supporting SIL-rated machinery protection loops without additional documentation burden.
• Full-spectrum vibration capture: DC to 10 kHz bandwidth resolves sub-synchronous instabilities (oil whirl, surge), 1× and 2× synchronous components, and blade-pass frequencies on multi-stage compressors — all within a single transducer channel.
• High-temperature probe rating: +177°C probe tip rating accommodates direct installation in steam turbine bearing housings where ambient temperatures routinely exceed +120°C, eliminating the need for thermal standoffs or remote probe mounting brackets.
• Deterministic signal latency: The analog output path (probe → cable → proximitor → monitor) introduces less than 50 µs of signal latency, preserving phase accuracy for orbit plot analysis and cross-channel timing measurements critical to machinery diagnostics.
• Diagnostic transparency: The –24 VDC bias output provides a continuous, self-indicating health signal. A bias voltage outside the –18 VDC to –26 VDC window indicates probe gap error, cable open/short, or proximitor power fault — enabling rapid fault isolation without specialized test equipment.
• Reduced spare parts complexity: A single PROXPAC XL assembly replaces three separately managed spare parts (probe, cable, proximitor). This consolidation reduces warehouse SKU count, eliminates the risk of mismatched component assembly in the field, and simplifies maintenance planning for multi-unit installations.

Quality Assurance & Global Logistics

Every 330881-28-10-060-06-02 unit supplied through siemensplc.com is sourced from verified distribution channels with full supply chain traceability. Incoming inspection protocols include visual examination per IDEA-STD-1010, connector integrity verification, and output bias voltage functional check. Certificate of Conformance (CoC) documentation is available upon request for installations requiring formal quality records.

Shipments originate from our Xiamen, China operations center, strategically positioned for efficient access to major international air freight hubs including Xiamen Gaoqi International Airport (XMN). Standard export documentation — commercial invoice, packing list, and EAR99 classification confirmation — is prepared for every shipment. Typical dispatch lead time is 2–5 business days from order confirmation. Express air freight to North America, Europe, Southeast Asia, and the Middle East is available with transit times of 3–7 business days door-to-door. All units are packed in anti-static, shock-absorbing packaging to protect the precision probe tip and connector interfaces during transit. A 12-month warranty against manufacturing defects applies from the date of shipment.

Contact Information

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