The Bently Nevada 330704-020-100-90-02-00 represents a pinnacle in non-contact displacement sensing technology. As a core component of the 3300 XL 11mm Proximity Transducer System, this probe tracks the vibration and position of critical rotating shafts with microscopic precision. Engineered for heavy-duty industrial machinery—such as steam turbines, high-pressure compressors, and large pumps—it provides the essential data required for Turbine Supervisory Instrumentation (TSI).
By utilizing advanced eddy current principles, the sensor detects shaft movement without physical contact, eliminating wear and ensuring long-term reliability. This specific 11mm variant offers an extended linear range compared to standard 8mm probes, making it the preferred choice for applications where larger thermal expansion or greater shaft axial movement is expected. It functions seamlessly within the Bently Nevada 3500 monitoring framework, upholding the highest standards of machinery protection.
The 330704 series follows a specific configuration logic that defines its physical and electrical characteristics. Each segment of the part number 330704-020-100-90-02-00 corresponds to a specific engineering requirement:
This represents an 2.0-inch unthreaded length. Engineers select this based on the mounting bracket thickness and the required penetration depth into the machine casing.
The probe features a 10.0-inch total case length. This length ensures the probe tip reaches the target material while providing sufficient housing for stable installation.
This indicates a 9.0-meter (approx. 29.5 feet) total system length. This value is critical; the probe must match the extension cable and Proximitor sensor's calibrated length to maintain signal accuracy.
The -02 designates the inclusion of a miniature coaxial connector with a connector protector, ensuring moisture-proof integrity. The -00 indicates standard agency approvals (such as ATEX/IECEx and CSA) for hazardous area operation.
| Feature | Specification Details |
| Probe Tip Diameter | 11 mm (0.43 in) |
| Linear Range | 4.0 mm (160 mils) |
| Standard Target Material | AISI 4140 Steel |
| Sensitivity (ISF) | 3.94 V/mm (100 mV/mil) ± 10% |
| Operating Temperature | -51 °C to +177 °C (-60 °F to +351 °F) |
| Pressure Rating | Sealing up to 70 psi (4.8 bar) |
| Ingress Protection | IP68 / NEMA 4X (When properly sealed) |
| Material Construction | Polyphenylene Sulfide (PPS) tip and Stainless Steel body |
Successful deployment of the 330704-020-100-90-02-00 requires strict adherence to mechanical and electrical tolerances:
Installers must set the initial gap using a digital multimeter. For the 3300 XL 11mm system, the typical "center-scale" voltage is -10.0 VDC, which corresponds to the midpoint of the linear range. Adjust the probe position until the Proximitor output reaches this value before tightening the locknuts.
The coaxial cable carries high-frequency signals. Maintain a minimum bend radius of 25.4 mm (1.0 inch). Avoid using zip-ties directly on the cable; instead, use cushioned clamps to prevent "cold flow" of the insulation, which can cause impedance shifts and signal noise.
Always use the connector protectors included with the -02 option. In environments with high oil mist or humidity, apply silicone grease to the connector threads to prevent corrosion and maintain a low-resistance ground path.
Extended Linear Displacement: The 11mm tip geometry allows for a wider measurement window, essential for monitoring axial thrust in large-scale turbines where 8mm probes lack sufficient range.
Immunity to Interference: Advanced EMI/RFI shielding protects the signal from the electrical noise generated by Variable Frequency Drives (VFDs) and large motor starters.
API 670 Compliance: This probe fully meets the American Petroleum Institute (API) 670 requirements for machinery protection systems, ensuring global interoperability and safety.
Interchangeability: The 3300 XL series components are designed to be chemically and physically robust, allowing for direct replacement of legacy 3300 series 11mm probes without system redesign.
Q1: How do I verify if the 330704 probe is functioning correctly after installation?
A1: You can verify the probe by measuring the DC gap voltage at the Proximitor. A healthy probe in the middle of its range will show approximately -10.0 VDC. If the voltage is near 0V or -24V, the system likely has a short or an open circuit in the cabling.
Q2: Can I use this 9.0-meter probe with a 5.0-meter Proximitor?
A2: No. The total electrical length of the probe and extension cable must match the calibration of the Proximitor (e.g., a 9.0m probe system requires a 9.0m Proximitor). Using mismatched lengths will result in significant linearity errors and incorrect vibration readings.
Q3: What is the benefit of the PPS (Polyphenylene Sulfide) tip?
A3: The PPS tip provides exceptional chemical resistance and thermal stability. It protects the internal sensing coil from caustic industrial fluids and maintains its structural integrity at temperatures up to 177°C.
Q4: Does this probe require a special router for communication?
A4: No. Contrary to some database errors, this is a passive analog sensor. It connects via coaxial cable to a Bently Nevada Proximitor, which then sends a 4-20mA or voltage signal to a 3500 Rack or a PLC/DCS. It does not connect directly to Ethernet routers.
