Product Overview

The Epro PR6424/016-021 16 mm Eddy Current Sensor is a non-contact displacement measurement probe designed for monitoring the operating condition of critical rotating machinery. It belongs to the PR6424 series developed for industrial machinery protection and condition-monitoring applications.

Manufactured under the EPRO product line associated with Emerson, the PR6424 sensor uses eddy current technology to measure the distance between the probe tip and a conductive target, typically a rotating steel shaft. This measurement principle allows the sensor to detect shaft displacement without physical contact, making it suitable for continuous monitoring in demanding industrial environments.

The PR6424/016-021 has a nominal sensor head diameter of 16 mm and is intended for applications involving shaft vibration, radial and axial displacement, shaft position, eccentricity, and speed-related measurements. It is commonly associated with machinery such as steam turbines, gas turbines, compressors, pumps, and industrial fans.

In a typical monitoring installation, the sensor works with a compatible signal converter and machinery protection or monitoring system. The sensor detects changes in the gap between its tip and the rotating shaft. The converter processes the sensor signal and produces an output that can be evaluated by monitoring equipment.

This arrangement helps maintenance teams identify abnormal shaft movement, mechanical imbalance, alignment problems, and other changes in rotating equipment behavior.

With a supplied weight of approximately 0.2 kg, the PR6424/016-021 is a compact sensing component for industrial machinery monitoring systems. Before purchasing a replacement, users should verify the complete model number, cable arrangement, connector type, probe length, and compatibility with the existing signal converter.

Technical Specifications

Note: The specifications above describe the PR6424 16 mm sensor family. Exact cable length, connector arrangement, mounting details, and temperature limits should be checked against the complete PR6424/016-021 ordering specification.

Function and Working Principle

The PR6424/016-021 operates using the eddy current measurement principle. It detects changes in the distance between the sensor tip and a conductive metallic target without requiring direct physical contact.

This technology is widely used in rotating machinery because it allows continuous measurement of shaft movement while the equipment is operating.

1. Non-Contact Displacement Measurement

The sensor generates an electromagnetic field at its measuring tip. When a conductive metal target approaches the probe, eddy currents are induced in the target surface.

These currents influence the electrical characteristics of the sensor. Changes in the distance between the probe and the target therefore produce corresponding changes in the sensor signal.

The resulting measurement can be used to determine shaft displacement and position.

Because the probe does not physically touch the rotating shaft, it avoids the mechanical wear associated with contact-based measurement methods.

2. Shaft Vibration Monitoring

One important application of the PR6424 series is shaft vibration measurement.

As a rotating shaft moves away from and toward the sensor, the gap changes continuously. The sensor detects these variations and provides a signal representing the shaft’s dynamic movement.

Monitoring systems can use this information to evaluate vibration amplitude and identify abnormal operating conditions.

Potential causes of abnormal vibration include:

• Rotor imbalance.
• Shaft misalignment.
• Mechanical looseness.
• Bearing-related problems.
• Rotor deformation.
• Changes in operating load.

The sensor provides measurement information; diagnosis requires interpretation of the signal together with machine operating conditions and other monitoring data.

3. Shaft Position and Axial Displacement

The PR6424 series can also be used for static shaft-position measurement.

In suitable installations, the sensor measures changes in the gap between the probe and the shaft or target surface. This information can help monitoring systems evaluate shaft position and axial movement.

For large rotating machines, position monitoring is particularly important because excessive shaft movement may indicate mechanical problems or changes in operating conditions.

4. Eccentricity Measurement

Shaft eccentricity describes the deviation of a rotating shaft from its intended geometric center.

The PR6424 sensor can detect changes in the distance between the probe and the shaft surface during rotation. These measurements can help engineers assess shaft eccentricity and related mechanical conditions.

Accurate results depend on the shaft surface, probe installation, target material, and correct signal conditioning.

5. Signal Conversion

The sensor is normally used as part of a complete measurement system rather than as an independent display device.

A compatible EPRO signal converter processes the probe signal and converts it into an output suitable for monitoring equipment.

Depending on the converter and monitoring configuration, the resulting signal can be used for vibration analysis, shaft-position monitoring, alarms, and machinery protection functions.

Role in Industrial Machinery Protection Systems

The PR6424/016-021 can form part of a continuous machinery condition-monitoring system. It provides measurement information that helps operators and maintenance engineers evaluate the mechanical condition of rotating equipment.

Turbine Monitoring

Steam and gas turbines operate at high rotational speeds and require continuous monitoring of critical mechanical parameters.

Eddy current sensors can measure shaft vibration and displacement, helping monitoring systems identify changes in rotor behavior.

When installed at appropriate measurement locations, the PR6424 series can contribute to turbine machinery protection and maintenance programs.

Compressor Condition Monitoring

Industrial compressors are widely used in petrochemical plants, oil and gas facilities, refineries, and manufacturing operations.

Changes in shaft vibration may indicate imbalance, alignment problems, bearing deterioration, or other mechanical conditions.

The PR6424 sensor can provide non-contact displacement measurements for compatible compressor monitoring arrangements.

Pump Monitoring

Large industrial pumps often operate continuously and may be exposed to changing process loads.

Shaft vibration and position measurements can help maintenance teams identify abnormal mechanical behavior before it develops into a more serious equipment problem.

The PR6424 series can be incorporated into suitable pump monitoring systems where its measurement range and installation configuration meet the application requirements.

Integration with Machinery Monitoring Equipment

The sensor works with compatible signal converters and machinery monitoring equipment.

A typical monitoring arrangement includes:

1. PR6424 eddy current sensor.
2. Compatible sensor signal converter.
3. Machinery monitoring or protection module.
4. PLC, DCS, or plant monitoring system.
5. Operator interface or maintenance workstation.

The exact arrangement depends on the installed monitoring platform and the required measurement functions.

Industrial Applications

The Epro PR6424/016-021 is designed for non-contact measurement in critical rotating machinery.

1. Steam Turbines

Steam turbines are used in power generation, industrial steam systems, and large process facilities.

Continuous shaft monitoring helps operators evaluate rotor movement during startup, normal operation, and shutdown.

The PR6424 sensor can be used in suitable turbine monitoring systems to measure shaft vibration and displacement.

2. Gas Turbines

Gas turbines operate under high temperatures and demanding mechanical conditions.

Shaft vibration and displacement measurements are important for evaluating rotor behavior and identifying abnormal operating trends.

The PR6424 series can support non-contact monitoring when the sensor installation and temperature conditions comply with the applicable specifications.

3. Hydro Turbines

Hydroelectric generating units contain large rotating assemblies that require long-term condition monitoring.

Eddy current sensors can measure shaft movement and provide information for evaluating rotor stability and mechanical performance.

4. Industrial Compressors

Centrifugal and other large industrial compressors are widely used in chemical processing, gas transportation, and refinery operations.

The PR6424 sensor can be used to monitor shaft vibration and position in compatible compressor protection systems.

5. Industrial Pumps

Large pumps in water treatment, power generation, and process industries often require continuous monitoring.

Non-contact shaft measurement can help maintenance teams evaluate mechanical movement and detect changes in operating conditions.

6. Industrial Fans

Large ventilation and process fans may experience imbalance, shaft movement, or mechanical wear.

A suitable eddy current monitoring arrangement can provide useful shaft-displacement information for maintenance and condition assessment.

Installation and System Integration

Correct installation is essential for obtaining reliable measurements from the PR6424/016-021.

The sensor’s performance depends on mounting position, target material, initial air gap, cable routing, and compatibility with the signal converter.

1. Verify Sensor Model and Configuration

Before installation, confirm the complete PR6424/016-021 model number.

Check the probe diameter, mounting thread, cable length, connector type, and any cable protection or extension arrangement.

The suffix of an EPRO sensor model can identify configuration differences. A replacement should therefore be matched by its complete model designation rather than by sensor diameter alone.

2. Select the Correct Mounting Position

The sensor must be positioned so that its measuring tip faces the intended metallic target.

For shaft vibration measurement, the probe is commonly installed near the shaft surface at a location selected by the machinery monitoring design.

Ensure that the installation provides sufficient clearance and that nearby metallic objects do not interfere with the measuring field.

3. Set the Initial Air Gap

The initial air gap is an important installation parameter.

The PR6424 family has a nominal center air gap of approximately 2.7 mm under its specified measurement conditions.

The final setting must follow the applicable sensor and converter instructions. Incorrect gap adjustment can reduce the usable measurement range or affect measurement accuracy.

4. Connect the Compatible Signal Converter

The sensor must be paired with a compatible signal converter.

Confirm that the converter supports the relevant PR6424 sensor configuration, cable arrangement, and electrical characteristics.

Using an incompatible converter may produce incorrect measurements or prevent the system from operating properly.

5. Route and Protect the Cable

The sensor cable should be routed away from high-voltage power conductors and sources of strong electromagnetic interference where practical.

Observe the specified minimum bending radius and avoid excessive pulling, twisting, or mechanical stress.

Cable protection should be selected according to the installation environment, particularly in machinery areas exposed to heat, vibration, oil, or mechanical impact.

6. Verify the Measurement Signal

After installation, check the initial gap, signal output, and measurement stability.

Confirm that the monitoring system displays reasonable values and that the signal responds correctly to changes in shaft position.

Document the installation position and baseline measurements for future condition-monitoring comparisons.

Compatible System Components

The PR6424/016-021 is normally used with additional components to create a complete machinery monitoring system.

The components listed above are examples of equipment used in a complete monitoring arrangement. They are not necessarily included with the sensor.

Alternative Models and Replacement Considerations

The PR6424 belongs to the EPRO family of 16 mm eddy current sensors. Other sensor variants may have similar measuring principles but different cable lengths, connector arrangements, mounting details, or ordering configurations.

Before selecting a replacement, compare:

• Complete sensor model number.
• Sensor head diameter.
• Probe length and mounting thread.
• Cable length and protection type.
• Connector configuration.
• Measurement range and sensitivity.
• Operating temperature.
• Compatible signal converter.
• Monitoring system input requirements.
• Installation and calibration requirements.

A sensor with the same 16 mm diameter is not necessarily a direct replacement. The entire measurement chain should be checked before installation.

Key Advantages

Non-Contact Measurement

The eddy current principle allows shaft displacement to be measured without physical contact, reducing mechanical wear at the sensing point.

Continuous Shaft Monitoring

The sensor can provide measurement signals for continuous monitoring of rotating machinery.

Suitable for Critical Machinery

The PR6424 family is designed for applications involving turbines, compressors, pumps, and other important rotating equipment.

High Measurement Sensitivity

The family specification includes a sensitivity of 4 V/mm, supporting the measurement of small changes in the sensor-to-target gap.

Vibration and Position Measurement

The sensor can be used for both dynamic shaft vibration and static shaft-position measurement in compatible monitoring systems.

Industrial Construction

The stainless-steel sleeve and PTFE cable construction are intended for industrial sensor applications within the specified environmental limits.

Integration with Machinery Monitoring Systems

When paired with a suitable converter, the sensor can provide measurement information to machinery protection and condition-monitoring equipment.

Technical FAQs

1. What is the Epro PR6424/016-021?

The Epro PR6424/016-021 is a 16 mm eddy current sensor designed for non-contact measurement of shaft vibration, displacement, position, and eccentricity in rotating machinery.

2. What is the sensor head diameter?

The nominal sensor head diameter is 16 mm.

3. How does the PR6424 sensor work?

It generates an electromagnetic field at the probe tip. When a conductive metal target approaches the sensor, eddy currents are induced in the target. Changes in the distance between the probe and target affect the sensor signal, allowing displacement to be measured.

4. What is the measurement range?

The PR6424 family specification includes a static measurement range of approximately ±2.0 mm and a dynamic measurement range of 0–1,000 μm.

5. What is the sensitivity of the sensor?

The published family sensitivity is 4 V/mm, equivalent to approximately 101.6 mV/mil.

6. Does the PR6424/016-021 measure shaft vibration?

Yes. It can be used in suitable monitoring arrangements to measure dynamic changes in the distance between the sensor and a rotating shaft.

7. Which machines commonly use this sensor?

Typical applications include steam turbines, gas turbines, hydro turbines, industrial compressors, pumps, and large fans.

8. Does the sensor work independently?

No. It is normally used with a compatible signal converter and a machinery monitoring or protection system.

9. Can another PR6424 model replace the PR6424/016-021?

Not automatically. Different variants may have different cable lengths, connectors, probe dimensions, and installation arrangements. Confirm the complete model number and converter compatibility before replacement.

10. What is the weight of the PR6424/016-021?

The supplied product weight is approximately 0.2 kg. Actual shipping weight may vary depending on packaging and included accessories.

Procurement and Maintenance Recommendations

When purchasing the Epro PR6424/016-021, confirm the complete model designation and compare it with the sensor currently installed in the machinery monitoring system.

Pay particular attention to the probe diameter, mounting thread, cable length, connector, and compatible signal converter. These details are essential for ensuring that the replacement sensor can be installed and calibrated correctly.

For used or surplus sensors, inspect the probe tip, stainless-steel sleeve, cable insulation, connector, and identification label. Request clear product photographs and available test information before purchasing.

During maintenance, avoid mechanical damage to the probe tip and cable. Check the cable routing, mounting stability, connector condition, and initial measurement gap. Any replacement sensor should be calibrated and verified according to the monitoring system manufacturer’s procedures.

For critical machinery, maintain records of sensor installation locations, baseline measurements, calibration information, and replacement history. These records help maintenance teams compare operating trends and investigate changes in machinery condition.

Conclusion

The Epro PR6424/016-021 16 mm Eddy Current Sensor is an industrial non-contact measurement probe designed for monitoring shaft displacement, vibration, position, and eccentricity in critical rotating machinery.

With a 16 mm sensor head and a supplied weight of approximately 0.2 kg, it is suitable for integration into compatible EPRO machinery monitoring arrangements used in turbines, compressors, pumps, and fans.

For replacement and maintenance applications, verifying the complete model number, cable configuration, connector, mounting dimensions, and signal converter compatibility is essential for reliable system operation.