Configured for high-frequency vibration monitoring in turbomachinery protection systems, the Bently Nevada 330851-05-000-040-50-01-05 (3300 XL Proximity Probe) provides direct physical signal acquisition via eddy-current induction to measure shaft displacement and position.

Catalog Suffix Identification

• 330851: 3300 XL 25 mm Proximity Probe, standard configuration.

• 05: 1-12 UNF-2A thread probe case.

• 000: Minimum unthreaded length, 0 mm.

• 040: Case length, 40 mm.

• 50: Total probe length, 5.0 meters.

• 01: With SST (Stainless Steel) armor.

• 05: Multiple agency approvals.

Physical and Electrical Parameters

Eddy-Current Sensing Characteristics

The 3300 XL 25 mm transducer system relies on the conversion of high-frequency radio waves into a magnetic field, which induces eddy currents on the target surface. Proper scaling requires adherence to the nominal sensitivity of 7.87 mV/µm (200 mV/mil). Calibration must be performed against the specified target material (typically AISI 4140 steel) to ensure linear output. The system requires a nominal -10 VDC gap voltage bias for linear operation within the designated 0 mm to 12.7 mm (500 mil) linear range. Cross-talk suppression is maintained through integrated radio-frequency shielding to prevent interference in high-density probe installations.

Delivery Components

1. 1 x 3300 XL 25 mm Proximity Probe (with integral cable and armor)

2. 1 x Certificate of Conformance / Regulatory documentation

Mounting and Signal Integration

• Mechanical Positioning: Ensure the probe tip is installed perpendicular to the target surface. Utilize the 1-12 thread for depth adjustment; tighten locking nuts to ensure structural stability against vibration.

• Shielding Requirements: The SST armor must be protected from sharp bends. Ensure the minimum bend radius is maintained to prevent inner cable dielectric deformation.

• Grounding: The probe case must be electrically isolated from the machinery housing if required by the specific installation drawing to prevent ground loops.

• Signal Continuity: Verify termination at the Proximitor sensor interface to ensure the -10 VDC supply is stable before final gap setting.

Technical FAQs

• What is the maximum linear range for this 25 mm probe?

  The linear measurement range is typically 12.7 mm (500 mils), provided the gap is set to the correct center-line voltage.

• Is the SST armor field-replaceable?

  No, the armor is factory-integrated with the probe assembly. Any attempt to remove or modify the armor will compromise the probe's integrity.

• Does the probe require a specific target material?

  Standard calibration is based on AISI 4140 steel. Different target materials will necessitate a correction factor for the output scale.

• What is the effect of oil film on the probe performance?

  The eddy-current principle is largely unaffected by oil, water, or steam, making it suitable for internal turbine bearing monitoring.

• How should the gap be verified?

  Use a calibrated feeler gauge or a micrometer to verify the physical gap against the Proximitor output voltage.

• Can this probe be used without the 3300 XL Proximitor?

  No, the probe is a passive component and requires the matched 3300 XL Proximitor sensor for signal conditioning and linearization.

• What is the significance of the 5.0 meter cable length?

  The total length (probe + extension) is tuned to the specific inductance/capacitance of the system; shortening the cable will invalidate the calibration.

• Is the probe sensitive to temperature fluctuations?

  Yes, thermal expansion can alter the gap. Ensure the mount material matches the target expansion coefficient for high-accuracy stability.