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The Eddy Current Testing of Heat Exchanger Tubes

In this blog post, you’ll read:A good understanding of how heat exchangers work during production can help highlight their importance in different industries. These devices help in transmitting heat between fluids.

Table of Contents


A good understanding of how heat exchangers work during production can help highlight their importance in different industries. These devices help in transmitting heat between fluids. Hence, examining them to make sure they are in top shape with an appropriate testing method like the Eddy Current Testing ensures that they are safe for use. Tube heat exchangers have several tubes joined together while protected by a shell all around. They are also more common in the industry than other types of heat exchangers. Since they have extensive use cases, including for power plants, automotive engines, and chemical plants, it is therefore important to ensure that they meet the highest standards of quality.


I. What is Eddy Current Testing?


While there are several non-destructive testing methods, Eddy Current testing is categorized among NDTs that can detect anomalies both on the surface and sub-surface of materials. Additionally, it is a reliable and accurate method that is widely used in various industries like manufacturing, energy, and automotive to ensure the integrity and safety of components and structures. A magnetic field is created by the induction of an alternating current (AC) on the test material’s surface, and this sums up its workings. If there is a surface crack or other flaw present, it will disrupt the magnetic field and produce a detectable signal. The eddy current testing process begins by cleaning the surface of the material to be tested and applying a probe, which consists of a coil of wire that is connected to a signal generator and an amplifier. The signal generator produces an AC current, which is passed through the coil and into the surface of the material. If the surface of the material is smooth and free of cracks, the magnetic field will flow smoothly around the probe. However, if there is a surface crack present, it will disrupt the flow of the magnetic field and cause it to produce eddy currents. To make the defect detectable, a signal is sent out by the interference of the new magnetic fields created by these Eddy currents.


II. The advantage of Eddy Current Testing for Heat Exchanger Tubes


One of the several non-destructive tests often classified among the easiest and most effective methods of detecting surface and subsurface flaws in heat exchanger tubes is the Eddy Current test. Frankly, its speed and efficiency are huge advantages which accounts for its preference to other testing methods when inspecting heat exchanger tubes. Here are some other common advantages of eddy current testing for heat exchanger tubes.

  • Non-destructive testing: The primary benefit of using an Eddy Current test is its non-destructive nature. This means that the heat exchanger tubes do not have to be taken out of service or dismantled in order to be tested. This is especially useful in critical systems where downtime is not an option. 
  • Fast and efficient: Eddy current testing is a fast and efficient way to inspect heat exchanger tubes. The testing process is quick and can be done on-site, which reduces the time and cost of transporting the tubes to a laboratory for testing.
  • Detects surface and subsurface flaws: Eddy current testing can detect both surface and subsurface flaws in the heat exchanger tubes. This is important as it allows technicians to identify problems that may not be visible to the naked eye, such as corrosion under the surface of the tube.
  • High sensitivity: Eddy current testing is highly sensitive and can detect even small defects in the heat exchanger tubes. This is important as small defects can lead to larger problems if left unaddressed.
  • Easy automation: The ease of automating the Eddy Current testing process gives technicians and professionals less stress, more speed, and higher efficiency when carrying out the test. Automated testing systems can cover large areas quickly and provide accurate and consistent results. 

Lastly, the speed and effectiveness of Eddy current testing as a non-destructive test suitable for detecting defects in heat exchanger tubes makes it a favorite among industry professionals. It is highly sensitive and can detect both surface and subsurface flaws, and can be automated for faster testing. It goes without saying the importance of Eddy Current testing in quality, safety, and reliability assurance for heat exchanger tubes. 


III. How to choose the proper Eddy Current Instrument?


Eddy Current Testing of Heat Exchanger Tubes
source: @zetec

Choosing the best suited eddy current testing equipment is more than sampling several suppliers and brands. It involves the careful consideration of specific parameters and these parameters can make or mar the testing process while evaluating the integrating of components like heat exchanger tubes.  Here are some critical steps you should consider when choosing the proper eddy current instrument. 

  • Math the eddy instrument with the type of testing: There are several types of eddy current instruments available, including portable hand-held units, benchtop units, and online systems. Portable hand-held units are useful for on-site testing, while benchtop units are more suitable for laboratory testing. Online systems are used for continuous monitoring of components during operation.
  • Consider the frequency range: Eddy current testing can be conducted at a variety of frequencies, ranging from low to high. The appropriate frequency range depends on the type of material being tested and the size of the flaw being detected. It is important to choose an instrument with a frequency range that is suitable for the application.
  • Determine the required sensitivity: The sensitivity of the eddy current instrument should be appropriate for the size and type of flaw being detected. Higher sensitivity is required for detecting smaller flaws, while lower sensitivity is sufficient for detecting larger flaws.
  • Consider the size and weight of the instrument: If the eddy current instrument will be used for on-site testing, it is important to choose a unit that is portable and easy to handle. The size and weight of the instrument should be suitable for the testing environment and the operator.
  • Evaluate the software and data acquisition capabilities: Eddy current instruments typically come with software that is used to analyze and interpret the data obtained during testing. It is important to choose an instrument with software that is user-friendly and has the necessary capabilities for the application.



Finally, Eddy Current Testing is critical for the accurate evaluation of heat exchanger tubes. More importantly, choosing the right Eddy current Testing equipment can save you a lot of headache which is why considering essential factors like the type of instrument needed, the frequency range, sensitivity, size and weight, and software and data acquisition capabilities is vital. By taking these factors into account, it is possible to select the best eddy current instrument for the job. Still, don’t forget to also consider your choice of supplier when in the market for an Eddy Current test equipment. Ensure you select one with a consistent track record of quality manufacturing and reliability like NDT-KITS with over three decades of supplying quality Eddy current test kits both locally and internationally with a commitment and great focus on quality and customer satisfaction.

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