The Bently Nevada 330881-28-15-122-03-02 PROXPAC XL is a robust, integrated proximity transducer assembly designed for critical machinery protection. This sophisticated system combines a 3300 XL 8mm probe, an extension cable, and a Proximitor sensor into a single, environmentally hardened housing. Engineered specifically for high-value rotating assets such as steam turbines, centrifugal compressors, and large pumps, the PROXPAC XL eliminates the need for external Proximitor housings and vulnerable exposed coaxial cable runs.
By utilizing non-contact eddy current technology, this transducer captures shaft radial vibration and axial position with microscopic precision. The integrated design streamlines installation on the machine deck while providing Type 4X and IP66 protection against moisture, oil, and corrosive atmospheres. This unit serves as a primary sensing element for Turbine Supervisory Instrumentation (TSI), delivering high-fidelity data that empowers maintenance teams to identify mechanical issues before they lead to catastrophic equipment failure.
The model 330881-28-15-122-03-02 employs a specific modular code to define its mechanical dimensions and electrical system length:
This specifies a probe with a 2.8-inch (approx. 71mm) case length. This dimension determines the penetration depth of the 8mm probe tip into the machine casing to reach the target shaft.
The -15 designation indicates a 1.5-inch standoff adapter. This component provides the necessary mechanical spacing and clearance between the integrated housing and the machine's external surface.
The -122 signifies a 9.0-meter (approx. 29.5 feet) total system length. The internal probe and cable are electrically matched to this 9.0m calibration to ensure the industry-standard 200 mV/mil scale factor remains accurate without field recalibration.
The -03 specifies the mounting thread and fitting type (one M20 fitting and two plugs). The -02 option confirms Multi-Agency Approvals (ATEX, IECEx, and CSA), authorizing use in Class I, Division 2 or Zone 2 hazardous industrial areas.
| Feature | Specification Details |
| Transducer Type | Integrated 3300 XL 8mm System |
| Linear Range | 2.0 mm (80 mils) |
| Nominal Sensitivity | 7.87 V/mm (200 mV/mil) |
| Enclosure Rating | Type 4X / IP66 (Weatherproof) |
| Mounting Thread | 3/4-14 NPT (Base) |
| Standard Target Material | AISI 4140 Steel |
| Operating Temperature | -35 °C to +85 °C (-31 °F to +185 °F) |
| System Length | 9.0 Meters (Matched Internal) |
Proper installation ensures the signal integrity required for mission-critical monitoring:
Users must set the static gap by measuring the DC voltage between the "OUT" and "COM" terminals inside the housing. Rotate the PROXPAC assembly within its mounting port until the voltage reads -10.0 VDC. This voltage indicates the probe is positioned at the center of its 80-mil linear range. Secure the locknuts once this value is stable.
When installing multiple transducers in close proximity, maintain a minimum of 40mm (1.6") separation for axial probes and 38mm (1.5") for radial probes. Proximity closer than these limits allows the magnetic fields of the sensors to overlap, creating "cross-talk" interference exceeding 50mV.
Optimal measurement requires a shaft diameter of at least 76.2mm (3.0"). While the system functions on shafts as small as 50mm (2.0"), smaller diameters may cause variations in the scale factor (sensitivity), requiring specialized calibration for radial vibration accuracy.
Integrated Hardening: Housing the Proximitor sensor directly at the probe exit eliminates the "weak link" of coaxial extension cables, protecting sensitive electronics from mechanical damage and EMI.
Corrosion Resistance: The stainless steel and aluminum construction, combined with Viton O-ring seals, withstands harsh hydrocarbon processing environments and coastal salt spray.
TSI Seamless Integration: The analog output integrates natively with the Bently Nevada 3500 series monitoring rack, allowing immediate access to Orbit plots and spectrum analysis.
API 670 Compliance: The system adheres to the rigorous requirements of the American Petroleum Institute for machinery protection, ensuring reliability and global industry acceptance.
Q1: How do I verify if the O-rings are seated correctly?
A1: Because probes are not pressure-tested before shipment, you must visually inspect the Viton O-ring at the probe tip and the Neoprene O-ring at the housing interface during installation. Proper seating prevents oil from leaking out of the bearing housing into the transducer enclosure.
Q2: Can I use this unit with a different length extension cable?
A2: No. This unit is an "all-in-one" 9.0m system. The internal wiring is factory-calibrated for 9.0 meters. Adding or removing cable length will alter the system's impedance and destroy the accuracy of the 200 mV/mil scale factor.
Q3: Does the 330881 support Ethernet communication?
A3: No. This is a common clerical error in logistics databases. The PROXPAC XL provides raw analog voltage signals. Digital networking (Ethernet/Modbus) is handled solely at the 3500 Rack or communications gateway level.
Q4: What is the benefit of the -03 M20 fitting option?
A4: The -03 option provides a metric M20 conduit fitting, which is standard for many European and Asian installations, ensuring the housing remains sealed against moisture while complying with local electrical conduit standards.
