Product Overview

The Bently Nevada 330878-51-00 3300 XL 50 mm Proximitor Sensor is a signal-conditioning component designed for use in the 3300 XL 50 mm proximity transducer system. It works with a compatible 50 mm proximity probe and extension cable to provide non-contact measurement signals for monitoring the movement and position of rotating machinery shafts.

Manufactured for industrial machinery protection and condition monitoring applications, the 3300 XL 50 mm system is particularly relevant to large rotating equipment where substantial axial movement and differential expansion need to be measured. Typical applications include steam turbines, large compressors, and other critical machinery used in power generation and heavy industrial facilities.

The 330878-51-00 is a 5.0-meter system-length configuration with DIN-rail mounting. The complete measurement system consists of a compatible proximity probe, extension cable, and Proximitor Sensor. The combined probe and extension cable length must match the system length specified for the Proximitor Sensor.

The 50 mm system uses eddy-current measurement technology. As the metallic target moves relative to the probe tip, the electrical characteristics of the probe circuit change. The Proximitor Sensor processes these changes and produces an output signal that can be used by a compatible machinery monitoring system.

One important characteristic of the 3300 XL 50 mm product family is its extended linear measurement range. This makes it suitable for applications such as differential expansion and rotor expansion monitoring, where the relative axial movement of large turbine rotors must be measured.

The -51 configuration identifies the DIN-rail mounting option. This allows the Proximitor Sensor to be installed in an appropriate control or monitoring cabinet while the probe and extension cable are positioned near the machine.

Technical Specifications

Note: The 5.0-meter value is the total transducer-system length, not the length of the Proximitor Sensor housing. The 3 kg value is the supplied shipping weight and should not be interpreted as the sensor’s net weight.

Function and Working Principle

The 330878-51-00 operates as the signal-conditioning element of a 3300 XL 50 mm proximity transducer system. Its main purpose is to convert changes detected by the proximity probe into electrical signals that can be interpreted by machinery monitoring equipment.

1. Eddy-Current Measurement Technology

The 3300 XL 50 mm system uses an electromagnetic field generated by the proximity probe. When the probe is positioned near a conductive metallic target, eddy currents are induced in the target surface.

The strength and characteristics of these currents change as the distance between the probe and target changes. The resulting electrical variation is detected by the transducer system and converted into a measurement signal.

Because measurement takes place without physical contact, the system can monitor shaft movement without requiring a mechanical connection to the rotating component.

2. Signal Conditioning

The Proximitor Sensor receives the electrical response from the compatible probe and extension cable. It processes this response and produces an output suitable for connection to a compatible machinery monitoring channel.

The output can represent the relative position of the monitored shaft or target. Dynamic changes in the signal can also be used to evaluate shaft vibration when the system is configured for that purpose.

Correct matching of the probe, extension cable, and Proximitor Sensor is essential. Using components with incompatible electrical characteristics or total system lengths can affect measurement performance.

3. Shaft Position Measurement

The system can monitor the relative position of a shaft with respect to the probe mounting location. This information is useful for identifying changes in shaft position that may result from bearing movement, thermal expansion, mechanical displacement, or other operating conditions.

For large rotating machines, accurate shaft-position information can support equipment condition assessment and machinery protection strategies.

4. Differential Expansion Monitoring

Differential expansion refers to the difference in thermal expansion between a turbine rotor and its surrounding casing. During startup, shutdown, and changing operating conditions, the rotor and casing may expand at different rates.

The 3300 XL 50 mm system can be used in suitable differential expansion arrangements to measure relative axial movement. Depending on the measurement setup, two transducers can be installed to provide complementary or redundant measurements.

This type of monitoring is particularly important for large steam turbines, where excessive relative movement may affect internal clearances and mechanical operating conditions.

5. Output Signal Transmission

The Proximitor Sensor provides an output signal for a compatible monitoring system. The receiving equipment can process the signal to display measurements, evaluate alarm conditions, and support machinery protection functions.

The Proximitor Sensor itself is not a complete machinery protection system. It must be connected to compatible monitoring hardware configured for the intended measurement.

Role in Industrial Machinery Monitoring Systems

The Bently Nevada 330878-51-00 is generally installed as part of a larger machinery condition monitoring arrangement. It provides the measurement signal required by monitoring channels to evaluate shaft position and movement.

Turbine Monitoring

Steam and gas turbines operate under changing thermal and mechanical conditions. Shaft displacement and differential expansion measurements can help engineers evaluate rotor movement during startup, normal operation, and shutdown.

The 3300 XL 50 mm system is designed for applications requiring a relatively large linear measurement range.

Compressor Monitoring

Large industrial compressors contain high-speed rotating assemblies. Proximity measurement systems can provide information about shaft position and movement, supporting condition monitoring and maintenance decisions.

The appropriate probe location and measurement direction depend on the compressor design and monitoring requirements.

PLC and DCS Integration

A compatible monitoring system may communicate with plant-level PLC or DCS equipment. The Proximitor Sensor supplies the measurement signal, while the monitoring equipment performs channel processing, alarm evaluation, and signal distribution.

Engineers should verify the receiving module’s input requirements and signal compatibility before connecting the sensor system.

Machinery Protection Systems

The Proximitor Sensor can form part of a machinery protection architecture. When connected to a suitable monitoring platform, its measurement signal can support alarm and trip logic based on configured operating limits.

Protection decisions must be implemented through the appropriate monitoring and control equipment rather than relying on the sensor alone.

Industrial Applications

1. Steam Turbine Differential Expansion Monitoring

Large steam turbines experience thermal expansion during startup and changes in operating load. The rotor and casing may expand at different rates.

A 3300 XL 50 mm proximity system can be configured to measure relative axial movement, helping operators identify abnormal differential expansion conditions.

2. Rotor Expansion Measurement

Rotor expansion monitoring is important in large turbine-generator installations. The measurement system can monitor axial movement relative to a suitable reference target.

The extended linear range of the 50 mm system makes it useful for selected applications involving substantial rotor movement.

3. Gas Turbine Monitoring

Gas turbines operate under high temperatures and demanding mechanical conditions. Shaft position and movement measurements can contribute to a broader machinery monitoring strategy.

The sensor system must be selected and installed according to the turbine’s mechanical arrangement and monitoring-channel requirements.

4. Large Compressor Monitoring

Industrial compressors used in petrochemical plants, refineries, and gas-processing facilities may require continuous monitoring of shaft displacement and vibration.

A compatible proximity system can provide measurement signals for monitoring equipment, helping maintenance teams evaluate changes in machine behavior.

5. Power Generation Equipment

Power generation facilities use large rotating machines that require continuous condition monitoring. Proximity transducer systems can provide information about shaft movement and relative mechanical position.

The 330878-51-00 may be used in suitable 3300 XL 50 mm monitoring arrangements where the required system length and measurement range match the application.

Installation and System Integration

Correct installation is essential for obtaining reliable measurements from the 3300 XL 50 mm system.

1. Verify the Complete System Configuration

Before installation, confirm that the Proximitor Sensor, proximity probe, and extension cable are compatible.

The 330878-51-00 is configured for a 5.0-meter total system length. The probe length and extension cable length must add up to the required system length.

Do not select the probe and extension cable independently without checking the complete transducer configuration.

2. DIN-Rail Mounting

The -51 configuration is designed for DIN-rail mounting. Install the Proximitor Sensor securely in a suitable instrumentation cabinet or control enclosure.

Ensure that the mounting location provides adequate access for wiring, inspection, and maintenance. Avoid locations exposed to excessive vibration, moisture, or contamination unless the enclosure provides appropriate protection.

3. Probe Installation and Gap Adjustment

The proximity probe must be installed at the specified measurement location and positioned relative to the target surface.

The initial probe gap should be adjusted according to the manufacturer’s installation procedure. An incorrect gap can reduce the available measurement range or produce an unsuitable output signal.

The target material and surface condition should also be considered because they influence the electrical response of an eddy-current system.

4. Extension Cable Connection

Connect the compatible extension cable between the probe and Proximitor Sensor. Ensure that connectors are clean, secure, and correctly matched.

Avoid unnecessary cable routing near high-power conductors or sources of electromagnetic interference. Follow the manufacturer’s recommendations for cable routing, grounding, and connector handling.

5. Monitoring System Connection

Connect the Proximitor Sensor output to the appropriate monitoring channel. Verify the receiving channel’s input configuration, measurement scaling, and alarm settings.

The monitoring system must be configured for the correct transducer type and measurement purpose.

6. Commissioning and Verification

After installation, check the probe gap, cable connections, power supply, and output signal. Verify that the monitoring channel displays a plausible measurement under the actual installation conditions.

Record the initial readings and configuration parameters. These values can serve as a reference during future maintenance and troubleshooting.

Compatible System Components

The 330878-51-00 operates as part of the 3300 XL 50 mm proximity transducer system. The following components may be required depending on the measurement arrangement.

Not all components are included with the Proximitor Sensor. Confirm the supplied package contents before ordering.

Alternative Models and Replacement Considerations

The 3300 XL 50 mm product family includes different system-length and mounting configurations. Replacement selection must account for these differences.

A replacement should not be selected based only on the 3300 XL 50 mm family name. Confirm the complete part number, system length, mounting style, approval requirements, and probe compatibility.

Key Advantages

Extended Linear Measurement Range

The 3300 XL 50 mm system provides a maximum linear range of up to 27.9 mm under the specified measurement configuration. This makes it suitable for selected applications involving substantial shaft movement.

Non-Contact Measurement

Eddy-current technology measures the distance between the probe and a conductive target without requiring physical contact. This is useful for continuous monitoring of rotating machinery.

DIN-Rail Installation

The -51 configuration supports DIN-rail mounting, making it convenient to install within suitable instrumentation cabinets.

Integration with Machinery Monitoring Systems

The Proximitor Sensor supplies measurement signals to compatible monitoring equipment, supporting shaft-position and machinery-condition monitoring.

Suitable for Large Rotating Equipment

The 50 mm system is designed for applications such as turbine differential expansion and rotor expansion measurement.

Defined System-Length Configuration

The 5.0-meter configuration provides a specified total transducer-system length. Correct matching of the probe and extension cable helps maintain the intended electrical characteristics.

Technical FAQs

1. What is the Bently Nevada 330878-51-00?

It is a 3300 XL 50 mm Proximitor Sensor used in a non-contact proximity transducer system for monitoring shaft position and movement in rotating machinery.

2. What does the -51 suffix mean?

The -51 configuration identifies a 5.0-meter total system length and DIN-rail mounting. The final -00 indicates the no-agency-approval configuration.

3. Does the 5-meter length refer to the sensor cable?

No. It refers to the total transducer-system length. The compatible probe and extension cable lengths must add up to the system length specified for the Proximitor Sensor.

4. What is the maximum linear range of the 3300 XL 50 mm system?

The system has a maximum linear range of up to 27.9 mm in the specified configuration. Actual measurement performance depends on the complete system arrangement and installation.

5. What machinery can use this sensor?

Typical applications include large steam turbines, gas turbines, compressors, and other rotating equipment requiring shaft-position or differential-expansion monitoring.

6. Can it measure shaft vibration?

The proximity transducer system can provide signals used for dynamic shaft-vibration monitoring as well as relative shaft-position measurement. The receiving monitoring equipment must be configured for the intended measurement.

7. Can it connect directly to a PLC?

The Proximitor Sensor provides an analog measurement output, but the receiving PLC input must be electrically and functionally compatible. In many machinery protection applications, a dedicated monitoring system processes the signal before plant-level integration.

8. Is the 330878-51-00 a complete proximity measurement system?

The part number identifies the Proximitor Sensor configuration. A complete measurement installation also requires a compatible probe and extension cable, as well as suitable monitoring equipment.

9. What should be checked before replacement?

Verify the complete part number, total system length, DIN-rail mounting configuration, approval requirements, probe compatibility, extension cable length, and receiving monitoring-channel configuration.

10. What does the 3 kg weight represent?

The 3 kg value supplied for this listing is the shipping weight. It should not be treated as the net weight of the Proximitor Sensor itself.

Procurement and Maintenance Recommendations

When purchasing the Bently Nevada 330878-51-00, verify the complete part number and ensure that the product is the 5-meter DIN-rail configuration. Confirm whether the probe and extension cable are included or must be purchased separately.

For used or refurbished equipment, request clear photographs of the nameplate, enclosure, terminals, and connectors. Ask for available test records and confirm the unit’s condition before purchasing.

During installation, use compatible 3300 XL 50 mm probe and extension cable components. Incorrect system length or incompatible components can affect measurement performance.

For maintenance, inspect the wiring, connectors, mounting arrangement, and probe installation. Check for loose connections, cable damage, contamination, and changes in the measured signal. Keep a record of the initial gap setting and operating readings to support future troubleshooting.

For critical machinery, verify the complete measurement channel rather than testing the Proximitor Sensor in isolation. The probe, extension cable, Proximitor Sensor, monitoring input, and configured alarm logic all contribute to the final measurement result.

Conclusion

The Bently Nevada 330878-51-00 is a 3300 XL 50 mm Proximitor Sensor configured for a 5.0-meter total system length and DIN-rail mounting. It is designed to work with compatible proximity probes and extension cables to provide non-contact measurement signals for rotating machinery monitoring.

Its extended linear measurement capability makes the 3300 XL 50 mm system suitable for selected applications involving turbine differential expansion, rotor expansion, and shaft-position monitoring. Correct component matching, probe-gap adjustment, cable installation, and monitoring-channel configuration are essential for reliable operation.

For maintenance and replacement projects, confirming the complete model number and system-length configuration helps ensure compatibility with the existing machinery monitoring installation.