Bently Nevada 330881-28-04-080-03-02 Proximity Transducer Assembly – PROXPAC XL

Bently Nevada 330881-28-04-080-03-02 PROXPAC XL 28mm Proximity Transducer Assembly — Eddy-Current Shaft Monitoring for Critical Rotating Machinery

The Bently Nevada 330881-28-04-080-03-02 is a factory-matched, three-component eddy-current proximity transducer assembly belonging to the PROXPAC XL product family. It integrates a 28 mm diameter probe, a 4-metre extension cable, and a 3300 XL-series oscillator/driver into a single pre-calibrated unit with a total system cable length of 8.0 metres. The assembly is engineered for continuous, non-contact measurement of radial shaft vibration, axial position (thrust), differential expansion, and eccentricity on turbines, compressors, pumps, and other API 670-governed rotating equipment.

Unlike field-assembled transducer systems where probe-to-driver matching must be verified on-site, the PROXPAC XL ships as a calibrated set. Sensitivity is guaranteed at 7.87 V/mm (200 mV/mil) across the full linear gap range, eliminating the calibration step during commissioning and reducing the risk of sensitivity drift caused by mismatched components. This characteristic is particularly significant in machinery protection applications where a 1% sensitivity error can translate directly into a missed alarm threshold.

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Technical Parameters

Hardware Logical Analysis

The 330881-28-04-080-03-02 operates on the principle of electromagnetic induction. The oscillator within the 3300 XL driver generates a high-frequency carrier signal — typically in the range of 1.0 MHz to 1.5 MHz — which is transmitted through the extension cable to the probe coil. When a conductive target (shaft) enters the probe’s electromagnetic field, eddy currents are induced on the target surface. These eddy currents load the probe coil, reducing its effective inductance and causing a measurable change in the oscillator’s output amplitude. The driver demodulates this amplitude-modulated signal and outputs a DC voltage proportional to the gap distance between the probe tip and the shaft surface.

EMC Design Architecture: The PROXPAC XL assembly addresses electromagnetic compatibility through several hardware-level decisions. The extension cable uses a coaxial construction with a continuous shield bonded at both the probe end and the driver end, providing a low-impedance return path for induced noise currents. The driver housing is constructed from die-cast aluminium with conductive gaskets at all seams, achieving a shielding effectiveness consistent with IEC 61000-4-3 Class III environments. Internal signal traces within the driver are routed to minimise loop area, reducing susceptibility to magnetic field coupling from adjacent motor drives or transformer installations — a common interference source in turbine hall environments.

Probe Coil and Gap Linearity: The 28 mm probe diameter of the 330881 series provides a larger sensing field compared to the 8 mm probes used in the 3300 XL standard series. This larger coil geometry extends the linear measurement range and reduces sensitivity to minor shaft surface irregularities such as machining marks or minor corrosion pitting. The probe body is constructed from a non-magnetic, corrosion-resistant alloy housing with a PEEK (polyether ether ketone) tip, which maintains dimensional stability across the full operating temperature range of −35 °C to +121 °C without introducing thermal expansion errors into the gap measurement.

Cable Impedance Matching: The 4-metre extension cable is impedance-matched to the probe coil and driver input. Substituting a non-matched cable — even one of identical physical length — will shift the oscillator’s operating point and alter the sensitivity coefficient, potentially by 3–8%. The PROXPAC XL’s factory-matched architecture eliminates this variable entirely, which is why the assembly is supplied and replaced as a complete unit rather than as individual components.

System Integration Benefits

• API 670 Compliance Out of the Box: The assembly meets the machinery protection standard for turbines, compressors, and pumps without requiring additional field verification of sensitivity or linearity, accelerating FAT and SAT timelines.
• Direct 3500 Series Monitor Compatibility: The 330881-28-04-080-03-02 interfaces directly with Bently Nevada 3500/40M, 3500/42M, 3500/45, and 3500/46M monitors. No signal conditioning adapter is required between the driver output and the monitor input card.
• Deterministic Alarm Response: Because sensitivity is factory-guaranteed at 7.87 V/mm, alarm and danger setpoints configured in the 3500 monitor translate directly to physical gap distances without a calibration correction factor. This eliminates a common source of setpoint error during commissioning.
• Reduced Commissioning Time: Pre-matched probe-cable-driver assemblies remove the need for on-site sensitivity verification using a calibration fixture. Field engineers can install, gap the probe, verify the static gap voltage, and confirm the system is operational — a process that typically takes under 30 minutes per measurement point.
• Diagnostic Transparency via Gap Voltage Monitoring: The −24 VDC output architecture allows continuous monitoring of the static gap voltage as a secondary diagnostic channel. A drift in static gap voltage over time indicates shaft centreline migration, bearing wear, or probe mounting bracket movement — all detectable before a vibration alarm threshold is reached.
• DCS and Safety System Integration: The driver output is compatible with 4–20 mA output modules and MODBUS/PROFIBUS gateways used in Emerson Ovation, Honeywell Experion, and ABB 800xA DCS platforms, enabling vibration data to be integrated into plant-wide condition monitoring dashboards without additional signal conversion hardware.
• ATEX Hazardous Area Deployment: ATEX-certified variants of the 330881 series are available for Zone 1 and Zone 2 classified areas, covering gas groups IIA and IIB. This allows deployment in petrochemical and LNG plant environments where the standard industrial version cannot be used.
• Long-term Spare Parts Availability: The 330881 part number family has been in continuous production for over two decades and remains an active catalog item under Baker Hughes. Stocking this assembly as a critical spare eliminates the lead-time risk associated with obsolete or discontinued transducer systems.

Quality Assurance & Global Logistics

Every unit of the Bently Nevada 330881-28-04-080-03-02 supplied through siemensplc.com is sourced from verified supply chains with full traceability documentation. Pre-shipment inspection covers visual examination of the probe tip and cable jacket for mechanical damage, dimensional verification of the probe tip diameter, and functional verification of the driver output voltage at a known reference gap. A Certificate of Conformance (CoC) is issued with every order, and test reports are available on request for critical applications.

Anti-counterfeit verification is available for all Bently Nevada part numbers. Given the prevalence of non-genuine proximity transducer assemblies in the secondary market — particularly for high-demand PROXPAC XL configurations — buyers are advised to request CoC documentation and verify the driver’s serial number against Bently Nevada’s factory records.

Logistics are managed from our warehouse in Xiamen, China, with same-day or next-business-day dispatch for in-stock units. Standard export channels include DHL Express (3–5 business days to most destinations), FedEx International Priority, and sea freight for bulk orders. Export compliance review under EAR/ECCN classification is completed prior to shipment for all international orders. Units are packed in anti-static foam-lined cartons with humidity indicator cards to protect the probe coil and driver electronics during transit.

Contact Information

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