330878-50-00 | Bently Nevada 3300 XL 50 mm Proximitor Sensor

Product Overview

The Bently Nevada 330878-50-00 is a 3300 XL 50 mm Proximitor Sensor designed for critical machinery protection systems. As part of the industry-standard 3300 XL series, it delivers high-accuracy vibration and position measurements for large steam turbine generators, compressors, and other rotating equipment. The 50 mm probe diameter provides the longest linear range in Bently Nevada's eddy current transducer line, making it ideal for measuring differential expansion (DE) and rotor expansion (RX) where significant axial growth differential exists between the turbine rotor and machine stator.

Key Specifications

• Product Type: 3300 XL 50 mm Proximitor Sensor
• System Length: 5.0 meters (16.4 feet)
• Mounting Option: Panel mount
• Measurement Range: 0 to 50 mm (0 to 2.0 inches)
• Linear Range: 27.9 mm (1,100 mils) — longest in the 3300 XL eddy current transducer family
• Output Resistance: 50 Ω
• Capacitance: 69.9 pF/m (21.3 pF/ft) typical
• Power Supply: -24 Vdc regulated
• Operating Temperature: -35°C to +177°C (-31°F to +351°F)
• Accuracy: ±1% of full-scale range
• Frequency Response: DC to 10 kHz (-3 dB)
• Environmental Rating: IP67
• Material: Stainless steel probe, A380 aluminum housing
• Weight: Approx. 0.246 kg
• Country of Origin: USA
• Agency Approval: 00 = None

Features & Benefits

• Longest linear range available — 27.9 mm (1,100 mils) enables measurement of extreme differential expansion in large steam turbines without probe replacement
• Complete system interchangeability — probe, extension cable, and proximitor sensor can be mixed and matched within the 3300 XL 50 mm family without recalibration
• Backwards compatible — accepts non-3300 XL series transducer system components for phased upgrade paths
• Large 50 mm coil diameter — provides superior signal stability and reduced sensitivity to target surface irregularities compared to smaller probe diameters
• Panel mount configuration — secure, traditional mounting for control cabinet installations with standard hardware

Typical Applications

• Large steam turbine generator differential expansion (DE) monitoring
• Rotor expansion (RX) measurement in fossil and nuclear power plants
• Gas turbine axial position monitoring with long-throw requirements
• Hydroelectric generator thrust bearing position measurement
• Large compressor and pump axial displacement monitoring
• Any application requiring measurement ranges exceeding 25 mm (1,000 mils)

Installation Guide

1. Verify system compatibility — confirm your monitoring system supports 3300 XL 50 mm transducer systems (e.g., 3500/42M, 3500/45).
2. Mount the proximitor sensor — use the panel mount holes to secure the sensor in a vibration-free location within 5.0 meters cable reach of the probe.
3. Connect extension cable — join the probe to the proximitor using the 3300 XL 50 mm extension cable; ensure connectors are fully seated and locked.
4. Apply -24 Vdc power — connect regulated -24 Vdc supply; verify output bias voltage of approximately -8.5 Vdc with probe at mid-gap.
5. Set probe gap — with the machine at rest, gap the probe to the target collar to achieve the recommended linear range midpoint (typically 13–14 mm from target).
6. Verify linear range — use a micrometer or calibration fixture to confirm the system responds linearly across the full 27.9 mm range.
7. Route cables away from EMI sources — maintain 300 mm (12 in) separation from high-voltage cables, VFDs, and welding equipment.

FAQ

Q: What is the difference between 330878-50-00 and 330878-90-00?
A: The 330878-50-00 has a 5.0 meter (16.4 ft) system length with panel mount, while the 330878-90-00 has a 9.0 meter (29.5 ft) system length with panel mount. Both are 50 mm proximitor sensors with identical electrical performance. Choose based on your probe-to-cabinet cable run distance.

Q: Can I use this proximitor with an 8 mm or 11 mm probe?
A: No. The 330878 series is specifically designed for 50 mm probes. The coil geometry, impedance matching, and scale factor are unique to the 50 mm system. Using an 8 mm or 11 mm probe will result in incorrect output scaling and potential damage.

Q: What target material is required for factory calibration accuracy?
A: Factory calibration is performed on AISI 4140 steel targets 102 mm (4.0 in) diameter or larger. Using other target materials (e.g., stainless steel, Inconel) will shift the scale factor and may require in-situ system calibration.

Q: Is this sensor suitable for hazardous area installation?
A: The -00 suffix indicates no agency approvals. For hazardous area applications (Class I, Div 1 or ATEX Zone 0/1), select a variant with -05 or -CN suffix or install with approved intrinsic safety barriers.

Q: What is the maximum cable length between probe and proximitor?
A: The total system length is 5.0 meters including probe, extension cable, and proximitor lead. Do not exceed this length; signal degradation and increased noise will occur beyond the rated system length.

Selection Tips

• Choose the 330878-50-00 when your probe-to-panel distance is ≤5.0 meters and you require standard panel mounting.
• If your installation requires 9.0 meters of total cable run, upgrade to the 330878-90-00 to avoid signal degradation from excessive extension cable splicing.
• For DIN rail mounting in high-density cabinets, look for the -51 suffix variants (not available in 50 mm; panel mount is standard).
• Always verify your target material and minimum target diameter before ordering — 50 mm probes require larger targets than 8 mm systems.
• Confirm your monitoring system supports the 3300 XL 50 mm scale factor (typically 0.787 V/mm or 20 mV/mil) before procurement.