The Bently Nevada 330881-28-05-090-00-02 PROXPAC XL is an integrated proximity transducer assembly designed for the most demanding machinery protection environments. By combining the probe and the Proximitor sensor into a single, ruggedized housing, this module eliminates the need for external extension cables and separate sensor housings. It plays a critical role in Turbine Supervisory Instrumentation (TSI), providing non-contact displacement measurements that detect shaft vibration and position with sub-micron accuracy.
Specifically engineered for high-stress industrial applications like steam turbines and centrifugal compressors, the PROXPAC XL ensures that rotating assets operate within safe limits. Its robust mechanical design withstands heavy structural loads and environmental interference, making it the gold standard for reliable, real-time condition monitoring in oil, gas, and power generation sectors.
The Bently Nevada 330881 series utilizes a modular configuration system. Here is the engineering breakdown of the 330881-28-05-090-00-02 model:
This specifies a 3300 XL 8mm probe integrated within the housing. The "28" designation typically refers to a specific threaded case length and material selection optimized for standard industrial ports.
The 05 indicates a 50mm standoff distance. This physical spacer allows the probe tip to reach the target shaft while maintaining the main housing at a safe distance from the machine surface, preventing heat transfer and mechanical interference.
The 090 signifies a 9.0-meter equivalent electrical length. The system is factory-calibrated so that the combined electrical path behaves as a standard 9-meter 3300 XL system, ensuring compatibility with standard 3500 series monitoring racks.
The -00 confirms a no-fittings configuration for a streamlined profile, while the -02 specifies multiple agency approvals (including ATEX and CSA), certifying the unit for safe operation in Class I, Division 2 or Zone 2 hazardous areas.
| Parameter | Specifications |
| Transducer Type | Integrated Proximity Probe & Proximitor |
| Probe Diameter | 8.0 mm (0.315 in) |
| Linear Range | 2.0 mm (80 mils) |
| Scale Factor | 7.87 V/mm (200 mV/mil) |
| Input Voltage | -17.5 VDC to -26 VDC |
| Operating Temp | -35°C to +85°C (-31°F to +185°F) |
| Housing Material | Glass-reinforced Epoxy & Aluminum |
| Weight | 1.44 kg (approx. 3.17 lbs) |
Precision installation determines the longevity and accuracy of the 330881-28-05-090-00-02. Engineers should prioritize the following parameters:
The system requires a precise DC Gap voltage setting. Using a digital multimeter at the signal terminals, adjust the probe depth until the output reads -10.0 VDC. This voltage represents the "Zero" or center point of the 80-mil linear range for the 3300 XL 8mm system.
Ensure the mounting surface is flat and clean. This model features a horizontal mounting configuration. Tighten the mounting bolts to the specified torque to prevent mechanical resonance from affecting the vibration data. The housing itself can withstand up to 912N (205lbf) of load, but excessive vibration at the mounting base can introduce signal noise.
The integrated grounding liner is vital for signal integrity. Ensure the housing makes a solid electrical connection to the machine ground. For signal wiring, use twisted-shielded pair cables to prevent electromagnetic interference (EMI) from nearby high-voltage motor leads.
All-in-One Reliability: By integrating the Proximitor into the probe housing, the system removes the weakest link in proximity systems—the coaxial connector between the probe and extension cable.
Mechanical Robustness: The heavy-duty housing undergoes rigorous validation, ensuring it maintains structural integrity under the high-pressure and high-vibration conditions typical of offshore platforms.
TSI System Compatibility: This module interfaces directly with Bently Nevada 3500/05 Racks and 3500/40M Proximitor Monitors, providing a seamless upgrade path for aging infrastructure without requiring new software configurations.
Hazardous Area Certified: With ATEX/IECEx approvals, this unit operates safely in explosive atmospheres, meeting global safety standards for the petrochemical industry.
Q1: How do I troubleshoot a "Sensor OK" fault on the 330881 unit?
A1: Check the supply voltage first; it must be between -17.5 and -26 VDC. If the voltage is correct, measure the output signal. If the signal is stuck at 0V or exceeds -18V, the probe tip might be touching the shaft (short) or the internal sensor may be damaged (open).
Q2: Can I replace a standard 3300 XL 8mm probe with this PROXPAC XL?
A2: Yes, provided you have the physical clearance for the larger housing. The 330881 uses the same 3300 XL technology, so the electrical output and sensitivity (200 mV/mil) remain identical, making it a drop-in replacement for the signal chain.
Q3: What is the purpose of the 50mm standoff (Option -05)?
A3: The standoff acts as a thermal and mechanical buffer. It allows the sensor to monitor shafts in high-temperature environments while keeping the sensitive Proximitor electronics in the housing away from direct conductive heat.
Q4: Does this module require an Ethernet router for communication?
A4: No. Despite occasional mislabeling in logistics databases, the 330881 is an analog device. It outputs a voltage signal proportional to the distance between the probe tip and the shaft. Digital integration occurs at the 3500 Rack level, not at the sensor itself.
