Preparing for an NDT Level II interview? Wondering whether you’ve got the chops for a job in nondestructive testing? You’ve come to the right place. Here, we’ll explain what NDT Level II certification is and share some practice interview questions with sample answers to help you make a great first impression on prospective employers.
Nondestructive testing (NDT) personnel fall into one of three levels of certification, aptly titled Level I, II and III. Each advance in certification level comes with added job responsibilities and increased influence on how the testing at hand is carried out and interpreted.
Technicians at Level II, the middle level, are qualified to set up and calibrate equipment, interpret and evaluate results under the applicable codes, organize and report test results, and train the level of technicians beneath them. They must be familiar with the nuances of different testing techniques and understand the limitations of the test method they’re practicing.
NDT Level II personnel are needed in a wide range of industries, including aerospace, manufacturing, oil and gas, critical infrastructure, and more. Obtaining your Level II certification will help you not only qualify for these jobs, but expand your earning potential and open up the path to pursuing Level III certification and other advanced, specialized credentials.
Use these example NDT Level II questions and answers to prepare for your upcoming job interview.
It’s almost always advisable to use a developer when conducting liquid penetration testing (PT) as it multiplies the testing output and can have a dramatic impact on an inspection’s probability of detection. The type of developer you choose will depend on the level of sensitivity you need, the size of the area to be tested and the accessibility of the testing area, among other factors.
Sample answer: For the most sensitive PT results, I would choose a non-aqueous wet developer. While aqueous wet developers are also sensitive, defects can be concealed if the surface coating becomes too thick. Also, aqueous wet developers can lead to leaching and blurring of indications when combined with certain penetrants.
Permeability is a measurement of how easily a magnetic flux is established in a material. It’s a key factor in interpreting magnetic particle testing (MT) results.
Sample answer: Permeability is a fixed value that varies depending upon the type of material. It’s a ratio of the flux density created within the material to the magnetizing field, represented by the equation m = B/H. Permeability is important to understand because it affects residual magnetic fields, which are used in the interpretation of MT results.
Secondary radiation, also called scatter radiation, comes into play in radiographic testing (RT). It’s undesirable because it reduces the level of contrast and definition in the resulting images. Secondary radiation is reflected from nearby objects like walls or the floor, while backscatter comes from objects behind the film. Undercut happens when hollow areas in the tested object cause abrupt darkening of the radiograph. We want to control these because they can lead to blurring at the point of transition between solid and hollow areas.
Sample answer: To control backscatter, I would back the cassette with a sheet of lead. The sheet should be at least a hundredth of an inch thick. To control undercut, I would use a sheet of lead cut to fit or a liquid absorber to mask the hollow areas from excessive radiation.
Acoustic impedance refers to the product of wave velocity and density, represented by the equation Z = pV. Changes in impedance affect the amount of acoustic energy reflected and transmitted, which is an important factor in ultrasonic testing (UT).
Sample answer: Acoustic impedance helps us assess the absorption of sound in a material and determine the acoustic transmission and reflection where two dissimilar materials meet. This is important if we want to understand why certain things are happening as we perform an ultrasonic inspection. Acoustic impedance is also an important principle in transducer application and design.
The core goal of nondestructive testing is to determine whether a material is suitable for the intended use.
When a discontinuity is detected, it’s evaluated for possible rejection. The criteria for acceptance/rejection vary by test method and material, and NDT Level II personnel rely heavily on these official criteria. To set them, we have standards from various professional organizations.
Sample answer: To determine acceptance or rejection, I look to the standards outlined by groups like the American Society for Testing and Materials (ASTM International), American Society of Mechanical Engineers (ASME) and Aerospace Industries Association (AIA).
For example, if conducting an ultrasonic examination of a concrete structure, I would rely on ASTM E3100-17, the Standard Guide for Acoustic Emission Examination of Concrete Structures.
Several factors go into proper cleaning in the context of nondestructive testing. You can’t just use one type of cleaner across the board; you must assess the cleaner chemistry, the equipment that will be involved, the type and frequency of rinses and other specifications. Proper cleaning has a big bearing on the effectiveness of the test method and the accuracy of the result.
Sample answer: Proper cleaning is required to remove any surface residue or contaminants, which can interfere with test results and hide discontinuities. This has a larger implication than just the part being inspected; if the testing results are compromised, it could put the entire structure or piece of machinery the part will be used in danger of failure.
Visual testing has many advantages, including being cost effective, easy to train for, requiring little to no equipment and being able to be done almost anywhere. It can identify a number of flaws, including cracks, discoloration, corrosion and misalignment, as well as signs of deeper discontinuities for further testing. However, it’s not without its limitations, and part of a Level II technician’s job is to be aware of these.
Sample answer: The main disadvantage of visual testing is that it’s limited to detecting surface indications. It can generally only detect large flaws, and there’s always the danger of misinterpreting those flaws. However, visual inspection is great in that it can be used to identify where further testing is needed using other, more sensitive test methods.
According to ASTM E-1212, all test equipment must be calibrated and controlled to ensure the accuracy of test measurements. Once again, these calibrations depend on the testing method used and rely on the standards set by some of the organizations we discussed earlier. And yet, many companies fail to have regular calibration and maintenance programs in place. As an NDT Level II, calibration is part of your core job duties. Here, show employers how you’ll help make sure it’s a priority.
Sample answer: Calibration is essential to maintain traceability and test accuracy in the field. This includes equipment, tools, gauges, and all components used in testing. I ensure our equipment meets the standards for manufacturer calibration, which ensures the equipment is functioning as designed, and user calibration, which validates that the correct level of precision and accuracy are achieved.
Level II technicians are responsible for training and supervising the level of personnel beneath them. Outline your understanding of how this relationship should function and tie in any relevant prior experience.
Sample answer: In my current job, I provide guidance and on-the-job training to all of our Level I technicians. I give them specific written instructions that describe how the testing should be done and supervise them closely while they execute it.
For example, if a Level I technician was conducting a test with a handheld eddy current device, I would be nearby to ensure the device was functioning properly and that the correct frequency was achieved.
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