Product Overview

The EPRO PR6424/018-021 16 mm Eddy Current Sensor is a non-contact displacement measurement device designed for monitoring the condition and operating behavior of critical rotating machinery. It belongs to the PR6424 sensor family developed for industrial machinery protection and condition monitoring applications.

Manufactured under the EPRO product line associated with Emerson, the PR6424 series is commonly used in steam turbines, gas turbines, hydro turbines, compressors, pumps, and industrial fans. Its primary purpose is to measure shaft movement without requiring physical contact between the sensor tip and the rotating target.

In rotating equipment, changes in shaft position and vibration can provide important information about machine operating conditions. Excessive shaft movement, abnormal vibration, and changes in axial position may indicate mechanical problems such as bearing wear, rotor imbalance, misalignment, or other developing faults. The PR6424 sensor provides measurement signals that can be processed by compatible monitoring equipment.

The PR6424/018-021 features a nominal 16 mm sensor head diameter and uses eddy current measurement technology. It is designed to detect changes in the distance between the probe tip and a suitable conductive target. When connected to a compatible signal converter and monitoring system, the sensor can support measurements of shaft displacement, vibration, position, and eccentricity.

This sensor is particularly relevant to machinery protection systems where continuous monitoring is important for equipment reliability and maintenance planning. Its non-contact operating principle allows it to measure dynamic shaft movement without mechanically loading the rotating component.

Technical Specifications

Note: The technical values above are PR6424 family reference specifications. Confirm the complete suffix configuration, cable length, connector arrangement, thread option, and applicable temperature limits against the exact product documentation before installation.

Function and Working Principle

The PR6424/018-021 uses the eddy current principle to measure the distance between the sensor tip and a conductive target. It generates a high-frequency electromagnetic field and detects changes in the electrical characteristics of the sensing coil when a suitable metal surface approaches or moves away from the probe.

1. Non-Contact Displacement Measurement

The sensor is installed near a rotating shaft, with a small controlled gap between the probe tip and the target surface.

As the shaft moves, the distance between the target and sensor changes. The probe detects these changes and produces a corresponding electrical response.

This measurement method is suitable for applications where physical contact with the rotating shaft would be impractical or undesirable.

2. Eddy Current Detection

The sensing coil generates an alternating electromagnetic field. When a conductive target enters this field, eddy currents are induced in the target material.

These currents affect the impedance of the sensor coil. The resulting change is related to the distance between the sensor and the target.

A compatible signal converter processes this response and provides a usable measurement output for the machinery monitoring system.

3. Shaft Vibration Measurement

When installed near a rotating shaft, the sensor can detect repeated changes in shaft-to-probe distance.

These changes can be used to calculate shaft vibration. Monitoring systems can analyze the resulting signal to identify abnormal vibration patterns and changes in machine behavior.

The PR6424 family supports dynamic measurement ranges up to 1,000 μm, depending on the complete measurement-chain configuration and operating conditions.

4. Shaft Position Measurement

The sensor can also measure relatively slow or static changes in shaft position.

This is useful for monitoring bearing clearances, rotor movement, and other mechanical conditions where the position of the shaft is important.

The PR6424 family has a reference static measurement range of ±2.0 mm.

5. Signal Conversion and Monitoring

The sensor normally operates as part of a measurement chain rather than as a standalone monitoring instrument.

A compatible converter processes the probe response and provides an output suitable for a machinery protection or condition monitoring system. The monitoring equipment can then display measurements, generate alarms, and provide information to plant operators.

The exact converter and monitoring module must be selected according to the probe configuration and system requirements.

Role in Industrial Machinery Protection Systems

The PR6424/018-021 can serve as a measurement component in machinery protection and condition monitoring installations.

Turbine Monitoring

Steam, gas, and hydro turbines operate with rotating shafts that require continuous mechanical condition monitoring. Shaft vibration and displacement measurements can help operators identify changes in rotor behavior.

The sensor can provide non-contact shaft measurements for compatible turbine monitoring systems.

Bearing Condition Monitoring

Shaft displacement measurements can help engineers evaluate the movement of a rotor relative to its bearing supports.

Changes in shaft position or vibration may indicate bearing wear, abnormal clearance, or developing mechanical problems. The sensor provides measurement data, while the monitoring system performs the alarm and diagnostic functions.

Compressor Protection

Industrial compressors operate under varying load and process conditions. Shaft vibration and position monitoring can help maintenance teams identify abnormal rotor movement before it develops into more serious mechanical damage.

The PR6424 family is designed for use in critical rotating machinery applications, including compressors.

Integration with Monitoring Equipment

The sensor can be connected to a compatible EPRO or Emerson signal converter and machinery monitoring platform.

Depending on the complete system design, measurement data may be used for:

• Shaft vibration monitoring.
• Radial and axial displacement measurement.
• Rotor position monitoring.
• Eccentricity measurement.
• Machinery alarm and protection functions.
• Condition monitoring and maintenance analysis.

The sensor, converter, connecting cable, and monitoring module must be treated as one measurement chain. Compatibility should be verified before replacing any individual component.

Industrial Applications

1. Steam Turbines

Steam turbines operate at high rotational speeds and require reliable monitoring of rotor movement and vibration.

The PR6424 sensor can measure shaft displacement in suitable turbine monitoring installations. Its non-contact measurement principle makes it appropriate for monitoring rotating shafts without physical contact.

2. Gas Turbines

Gas turbines are important components in power generation and industrial energy systems. Continuous monitoring of shaft vibration and position helps maintenance teams assess mechanical operating conditions.

The sensor can provide measurement signals for compatible gas turbine protection systems.

3. Hydro Turbines

Hydroelectric turbines operate under changing water-flow and load conditions. Shaft movement and vibration monitoring can help identify mechanical changes affecting the turbine and its supporting structure.

The PR6424 series is designed for critical turbomachinery applications, including hydro turbines.

4. Industrial Compressors

Large compressors are commonly used in petrochemical plants, refineries, gas processing facilities, and other industrial installations.

Shaft vibration and displacement measurements can help identify abnormal rotor behavior, support maintenance planning, and improve equipment availability.

5. Industrial Pumps

Large process pumps may operate continuously in demanding industrial environments. Monitoring shaft movement can help engineers identify changes associated with bearing wear, rotor imbalance, or mechanical misalignment.

The sensor can be used in suitable pump monitoring arrangements when the probe and converter are correctly matched.

6. Industrial Fans

Large fans and ventilation systems may require continuous shaft vibration monitoring, particularly when they operate as part of essential plant utilities.

The PR6424 family can support non-contact shaft measurement in compatible fan monitoring applications.

Installation and System Integration

Correct installation is essential for measurement accuracy and reliable machinery monitoring.

1. Select the Correct Installation Position

Install the sensor at a location that provides a suitable measurement surface and stable mounting arrangement.

The probe should be positioned according to the machinery manufacturer’s monitoring design. Engineers must consider shaft geometry, target material, probe clearance, mounting rigidity, and accessibility for maintenance.

2. Maintain the Correct Air Gap

The distance between the sensor tip and the target surface is a critical installation parameter.

The PR6424 family specifies a nominal center air gap of approximately 2.7 mm. The actual setup must follow the applicable calibration and installation instructions for the complete measurement chain.

An incorrect air gap can affect measurement linearity, available measurement range, and signal accuracy.

3. Check the Target Material

The PR6424 family is designed for use with ferromagnetic steel targets, with 42CrMo4 referenced as a standard material.

Target material and surface characteristics can influence the measurement response. Verify the shaft material and calibration requirements before commissioning.

4. Verify Mechanical Mounting

The PR6424 family uses a threaded sensor mounting arrangement, commonly specified as M18 × 1.5.

Confirm the exact mounting thread and mechanical dimensions for the /018-021 variant before preparing the installation point. Secure the probe properly to prevent unwanted movement caused by machinery vibration.

5. Check Cable Routing

The sensor cable must be routed carefully to avoid mechanical damage, excessive bending, heat exposure beyond its rating, and electromagnetic interference.

Keep the cable away from high-power conductors where possible. Follow the manufacturer’s minimum bending radius and cable protection requirements.

The precise cable length and connector configuration should be checked against the complete /018-021 part number.

6. Connect to a Compatible Converter

The sensor must be paired with a compatible signal converter. The converter should match the sensor’s electrical characteristics and provide the required output for the monitoring system.

Do not assume that every PR6424 probe variant can be connected directly to any converter. Confirm the complete probe, extension cable, connector, and converter combination.

7. Commission the Measurement System

After installation, verify the sensor gap, mechanical stability, cable connections, and converter configuration.

Check the output signal under stationary conditions and compare it with the expected measurement response. Where possible, confirm the measurement against an independent reference during commissioning.

Record the installation dimensions, calibration information, and initial operating values for future maintenance.

Compatible System Components

The PR6424/018-021 is normally used as part of a complete machinery measurement and monitoring arrangement.

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

Alternative Models and Replacement Considerations

The PR6424/018-021 belongs to the EPRO PR6424 16 mm sensor family. Replacement selection should consider the entire measurement chain rather than probe diameter alone.

Before replacing the PR6424/018-021, verify:

• Complete model number and suffix.
• Sensor head diameter.
• Thread and mounting dimensions.
• Cable length and cable construction.
• Connector and adapter arrangement.
• Static and dynamic measurement ranges.
• Sensitivity and calibration requirements.
• Compatible signal converter.
• Monitoring-system input configuration.
• Operating temperature and installation environment.

A probe with the same 16 mm head diameter is not automatically interchangeable. Differences in cable configuration, connector arrangement, and electrical characteristics can affect the complete measurement system.

Key Advantages

Non-Contact Measurement

The eddy current principle allows the sensor to measure shaft movement without physical contact with the rotating target.

Shaft Vibration Monitoring

The sensor can detect dynamic shaft movement and provide measurement information for machinery condition monitoring.

Static Displacement Measurement

It supports measurement of shaft position and displacement within the specified static range.

High Measurement Sensitivity

The PR6424 family specifies a sensitivity of 4 V/mm, supporting accurate displacement measurement when used with the appropriate converter.

Industrial Machinery Applications

The series is designed for critical rotating machinery, including turbines, compressors, pumps, and fans.

Stainless Steel Sensor Sleeve

The stainless steel sleeve provides a durable mechanical construction suitable for industrial sensor installation.

PTFE Cable Construction

The family specification identifies PTFE cable material, which is used in demanding industrial measurement environments. Actual temperature limits depend on the complete cable and probe configuration.

Integration with Machinery Monitoring Systems

The sensor can provide measurement signals for compatible EPRO and Emerson monitoring equipment, supporting centralized machinery condition monitoring.

Technical FAQs

1. What is the EPRO PR6424/018-021?

The PR6424/018-021 is a 16 mm eddy current displacement sensor designed for non-contact measurement of shaft movement in rotating machinery.

2. What is the sensor head diameter?

The sensor head diameter is 16 mm.

3. What is the measurement principle?

It uses eddy current technology. An electromagnetic field interacts with a conductive target, and changes in the sensor coil response are used to determine the distance between the probe and the target.

4. What is the static measurement range?

The PR6424 family specifies a static measurement range of ±2.0 mm.

5. What is the dynamic measurement range?

The family specification lists a dynamic measurement range of 0–1,000 μm.

6. What is the sensitivity of the PR6424 sensor?

The typical specified sensitivity is 4 V/mm, with linearity of up to ±1.5% under the stated measurement conditions.

7. Which materials can be measured?

The PR6424 family is designed for ferromagnetic steel targets. The standard reference material is 42CrMo4 steel.

8. Does the sensor work without a signal converter?

The PR6424 is normally used with a compatible signal converter. The converter processes the probe response and provides a suitable signal for the machinery monitoring system.

9. Where is the PR6424/018-021 commonly used?

Typical applications include steam turbines, gas turbines, hydro turbines, compressors, pumps, fans, and other critical rotating machinery.

10. What should be checked before purchasing a replacement?

Confirm the complete model number, cable length, connector arrangement, mounting thread, sensor diameter, and compatibility with the existing signal converter and monitoring system.

Procurement and Maintenance Recommendations

When purchasing the EPRO PR6424/018-021, verify the complete part number rather than selecting a replacement based only on the PR6424 family name.

The suffix configuration may determine cable length, connector arrangement, mounting details, and other installation characteristics. These details are important when replacing a probe in an existing machinery protection system.

For spare-parts procurement, check the sensor’s physical condition, cable insulation, connector condition, threaded sleeve, and sensing tip. Confirm whether the item is supplied as a complete sensor assembly or whether additional cables and adapters are required.

During routine maintenance, inspect the sensor mounting arrangement and cable routing. Look for damaged insulation, loose connections, contamination, and signs of mechanical interference. Avoid changing the probe gap without following the manufacturer’s installation and calibration procedures.

It is also advisable to retain the original sensor configuration and commissioning records. These records help maintenance personnel identify the correct replacement and restore the intended measurement performance.

Conclusion

The EPRO PR6424/018-021 16 mm Eddy Current Sensor is designed for non-contact shaft displacement and vibration measurement in critical industrial rotating machinery. Its eddy current measurement principle allows it to monitor shaft movement without physical contact, making it suitable for compatible turbine, compressor, pump, and fan monitoring systems.

With a 16 mm sensor head, a typical sensitivity of 4 V/mm, and a PR6424 family static measurement range of ±2.0 mm, the sensor can provide important measurement information for machinery condition monitoring and protection.

For replacement and procurement projects, confirming the complete model suffix, cable configuration, connector arrangement, and compatible signal converter is essential to ensure reliable integration with the existing monitoring system.