330878-90-00 | Bently Nevada 3300 XL 50 mm Proximitor Sensor

Product Overview

The Bently Nevada 330878-90-00 is a 3300 XL 50 mm Proximitor Sensor with a 9.0 meter (29.5 feet) system length and panel mount configuration. Designed for critical rotating machinery protection, it provides the longest linear range in Bently Nevada's eddy current transducer portfolio — 27.9 mm (1,100 mils) — making it the standard choice for measuring differential expansion (DE) and rotor expansion (RX) on large steam turbine generators where rotor-to-stator growth differentials are substantial.

Key Specifications

• Product Type: 3300 XL 50 mm Proximitor Sensor
• System Length: 9.0 meters (29.5 feet)
• Mounting Option: Panel mount
• Measurement Range: 0 to 50 mm (0 to 2.0 inches)
• Linear Range: 27.9 mm (1,100 mils)
• Output Resistance: 50 Ω
• Power Supply: -24 Vdc regulated
• Operating Temperature: -35°C to +177°C (-31°F to +351°F)
• Storage Temperature: -51°C to +100°C (-60°F to +212°F)
• Accuracy: ±1% of full-scale range
• Frequency Response: DC to 10 kHz (-3 dB)
• Environmental Rating: IP67
• Material: A380 aluminum housing, stainless steel probe
• Weight: Approx. 0.3 kg
• Country of Origin: USA
• Agency Approval: 00 = None

Features & Benefits

• Extended 9.0 meter system length — accommodates installations where the monitoring cabinet is remote from the machine train, eliminating the need for intermediate junction boxes or signal repeaters
• Longest linear range in the portfolio — 27.9 mm enables redundant DE measurements using complementary transducer arrangements on opposite sides of a collar
• Complete interchangeability — all 3300 XL 50 mm probes, extension cables, and proximitor sensors are interchangeable without field recalibration
• Backwards compatible architecture — allows phased upgrades from legacy 3300 RAM or 3000/7000 series systems
• Panel mount for secure cabinet installation — traditional mounting with standard hardware for long-term stability

Typical Applications

• Large steam turbine generator differential expansion monitoring with remote monitoring cabinets
• Combined cycle power plant HRSG and steam turbine DE/RX measurement
• Nuclear power plant main turbine axial growth monitoring
• Large industrial gas turbines with extended cable routing requirements
• Refinery cracking compressor axial position monitoring
• Any critical rotating machine where probe-to-cabinet distance exceeds 5 meters

Installation Guide

1. Verify monitoring system compatibility — ensure your rack (e.g., 3500/42M, 3500/45) supports 3300 XL 50 mm transducer systems and the associated scale factor.
2. Plan cable routing — with 9.0 meters total system length, route the extension cable through cable trays or conduits, maintaining 300 mm separation from high-voltage or VFD cables.
3. Mount proximitor in control cabinet — secure using panel mount holes; ensure the mounting surface is free from vibration and thermal cycling.
4. Connect probe and extension cable — join the 50 mm probe to the extension cable, then to the proximitor; verify all connectors are fully locked.
5. Apply -24 Vdc power — connect a regulated -24 Vdc supply; measure output bias voltage (~-8.5 Vdc) to confirm proper operation.
6. Gap probe to target — with machine at rest, set gap to the midpoint of the linear range (approximately 13–14 mm from the DE collar).
7. Perform system verification — use a calibration fixture or micrometer to sweep the probe through its linear range and verify ±1% accuracy.

FAQ

Q: What is the difference between 330878-90-00 and 330878-50-00?
A: The 330878-90-00 provides 9.0 meters of total system length versus 5.0 meters for the 330878-50-00. Both use panel mount and have identical electrical specifications. Choose 90 for remote monitoring cabinets; choose 50 for compact installations.

Q: Can I extend the cable beyond 9.0 meters?
A: No. Exceeding the rated system length degrades signal quality, introduces noise, and voids the accuracy specification. If longer runs are required, relocate the proximitor closer to the machine or use a signal conditioner with separate cable runs.

Q: What is the minimum target size for accurate measurement?
A: Bently Nevada specifies a minimum target of 102 mm (4.0 in) diameter of AISI 4140 steel for factory-calibrated accuracy. Smaller targets or different materials require in-situ calibration.

Q: Is this suitable for redundant DE measurement configurations?
A: Yes. The 27.9 mm linear range supports both same-side redundant and complementary opposite-side transducer arrangements. For complementary setups, two 50 mm systems can measure up to 56 mm total DE range.

Q: Does this proximitor require special mounting considerations for CE compliance?
A: No. The 3300 XL series has improved RFI/EMI immunity that achieves CE mark approvals without special mounting or shielding considerations beyond standard industrial practice.

Selection Tips

• Select 330878-90-00 when your probe-to-panel distance is between 5.1 and 9.0 meters. For shorter runs, the 330878-50-00 is more cost-effective.
• Verify that your DE collar or target is sufficiently large (≥102 mm diameter) and made of AISI 4140 steel for factory-calibrated accuracy.
• For hazardous area installations, you will need intrinsic safety barriers or a variant with hazardous area approvals (-05 suffix).
• Consider ordering a spare extension cable (330130-XX-XX-05 for 50 mm systems) to minimize downtime during cable damage events.
• Confirm your monitoring system configuration supports 50 mm transducer scale factors before procurement.