Product Overview

The Bently Nevada 330708-00-20-50-02-00 is an 11 mm 3300 XL proximity probe designed to deliver high-resolution displacement and vibration measurement for industrial rotating machinery. Utilizing advanced eddy-current sensing technology, the 11 mm probe architecture offers a broader linear range compared to standard 8 mm probes, making it the preferred choice for machines with larger shaft orbits or lower-frequency displacement requirements.

As a core component of the Bently Nevada 3300 XL transducer system, this probe is engineered for extreme reliability in harsh environments. It features the patented TipLoc design, ensuring a permanent, high-strength bond between the sensor tip and the probe body. This construction effectively prevents the "tip separation" common in high-vibration applications. Compliant with API 670 standards, the 330708-00-20-50-02-00 is widely used in mission-critical TSI (Turbine Supervisory Instrumentation) environments, providing the stable, high-fidelity signals necessary for predictive maintenance and automated machine protection.

Technical Specifications

Model Configuration Explanation

The part number breakdown identifies the specific mechanical and electrical properties:

• 330708: Identifies the 11 mm 3300 XL proximity probe series.

• 00: Unthreaded length (0 mm, fully threaded).

• 20: Case length of 20 mm.

• 50: Total system length of 5.0 meters (Probe + Extension Cable).

• 02: Connector and mounting configuration.

• 00: Standard agency approval rating (non-hazardous).

Typical Applications

The 11 mm probe is specifically utilized where increased sensing range is needed:

• Steam and Gas Turbines: Monitoring large-diameter shafts where radial clearance is significant.

• Large Centrifugal Compressors: Capturing wider displacement orbits in high-thrust environments.

• Hydroelectric Turbines: Monitoring slower speed, high-mass shafts where 11 mm sensitivity is optimized.

• R&D Test Stands: Where the expanded linear range of the 11 mm probe allows for wider data capture of machine dynamics.

• Bearing Journal Monitoring: Providing robust data for machines prone to high-amplitude transient vibrations.

System Compatibility

The 330708-00-20-50-02-00 is fully integrated into the Bently Nevada monitoring ecosystem:

• Proximitor Sensors: Designed for compatibility with 3300 XL 11 mm Proximitor sensors (must match the 5.0m system length).

• Extension Cables: Must be used with 3300 XL 11 mm extension cables.

• Monitoring Racks: Fully compatible with 3500 and 3300 series vibration monitoring hardware.

• Mounting Hardware: Compatible with 3/4-16 UNF probe housings and conduit mounting kits.

Installation Guidelines

• Surface Preparation: Ensure the mounting port is free of debris. Use high-quality sealant for thread engagement in fluid-exposed areas.

• Gap Setting: Use a depth micrometer to ensure the probe tip is at the nominal gap recommended by the machine’s specific monitoring manual.

• Alignment: Mount the probe perpendicular to the shaft centerline to ensure the eddy-current field is focused and linear.

• Torque Management: Secure with jam nuts; do not over-tighten, as the 3/4-16 thread allows for significant leverage that could damage the housing.

• Shielding: Route cables through dedicated conduit to prevent electromagnetic interference.

• Connection: Secure ClickLoc connectors until they "click," confirming a positive, low-resistance electrical connection.

Product Advantages

• Extended Range: The 11 mm diameter provides a larger sensing footprint, offering a wider linear measurement range than 8 mm probes.

• TipLoc Technology: Enhanced durability against vibration-induced mechanical failure.

• Chemical Resistance: FEP-jacketed cables and stainless steel construction endure exposure to industrial oils and high-temperature environments.

• API 670 Compliant: Guarantees industrial-grade accuracy and machine protection compliance.

• Consistent Data: Reduced signal noise leads to clearer machinery diagnostics and fewer false alarms.

Ordering Information

The assembly includes the 11 mm probe, lock nuts, and washers. Please verify your Proximitor sensor calibration—this probe must be paired with an 11 mm-specific Proximitor calibrated for a 5.0-meter total system length to ensure accuracy.

Frequently Asked Questions

• Can I use an 11 mm probe with an 8 mm Proximitor?

  No. The Proximitor and probe must be matched by diameter (11 mm) and system length to maintain calibrated accuracy.

• What is the advantage of the 5.0m system length?

  The 5.0m length is the standard for most rack-mounted installations; it accounts for the total signal path, including probe and extension cable, ensuring correct impedance.

• Is the 11 mm probe more sensitive than the 8 mm?

  It offers a different linear range. It is generally chosen for its ability to monitor larger displacement amplitudes rather than just higher sensitivity.

• Can the cable be trimmed to fit?

  Absolutely not. Trimming the cable changes the electrical characteristics, leading to severe measurement errors and non-compliance with calibration standards.

• How do I confirm the gap is correct?

  Monitor the DC gap voltage at the rack's input card; it should be within the range specified for your machine (often -10 VDC).

• Does this probe require special conduit?

  While it uses standard Bently Nevada conduit hardware, ensure the conduit is properly grounded to protect against EMI.

• What does the "00" agency approval mean?

  It indicates the unit is for standard industrial use. If you require hazardous area (e.g., ATEX or CSA) certification, you must select the appropriate option code.

• How does vibration affect the probe life?

  The 3300 XL series is built to withstand high vibration; however, ensuring the probe housing is rigidly mounted is vital for longevity.