1. Beam divergence
2. Surface roughness
3. Frequency of the ultrasonic waves
4. All of the above

(Explanation: Ultrasonic flaw detection in UT depends on several factors, with frequency selection being the most prominent. However, other factors also play a crucial role in achieving accurate results. 

• Beam Divergence: As sound waves travel through materials, their beam widens, making it harder to detect small flaws or locate them accurately.
• Surface Roughness: The quality of the material’s surface affects ultrasonic testing’s effectiveness. Rough surfaces scatter ultrasound beams, reducing signal strength and penetration, while smooth surfaces can cause reflections from internal flaws to be missed. 
• Frequency Selection: The frequency of ultrasonic waves used for testing affects the ability to detect specific types of flaws. Higher frequencies offer better detail but less penetration, while lower frequencies penetrate deeper but provide less detail. 

Other factors, such as pulse length, transducer design, and receiver circuitry, can also impact the accuracy of ultrasonic flaw detection. To ensure reliable and effective ultrasonic inspections, it’s essential to understand and optimize these factors based on the specific application.)

Q2. In Ultrasonic Testing (UT), what is the purpose of a reference block, and how does it contribute to the calibration process?

1. To measure the surface roughness of the test material
2. To provide a standard for adjusting the instrument’s sensitivity
3. To act as a reflector for ultrasonic waves
4. To assess the ambient temperature during testing

(Explanation: In Ultrasonic Testing (UT), a reference block is used to provide a standard for adjusting the instrument’s sensitivity during the calibration process. The purpose of the reference block is to ensure that the instrument is accurately detecting flaws in the test material. The block acts as a reflector for ultrasonic waves, allowing the operator to adjust the instrument’s sensitivity until it detects the reflected waves at the same amplitude as the reference block. www.weldingandndt.com

This ensures that the instrument is calibrated to the correct sensitivity level for the specific material being tested. Surface roughness and ambient temperature are not factors that a reference block is used to assess during the calibration process. However, Option 3 i.e. To act as a reflector for ultrasonic waves is partially correct, but the primary purpose of a reference block is calibration rather than acting as a reflector.)

Q3. What is the purpose of the Time-of-Flight Diffraction (TOFD) technique and how does it differ from conventional pulse-echo ultrasonic testing?

1. TOFD is used for measuring material thickness, while conventional pulse-echo is for detecting surface flaws.
2. TOFD provides real-time imaging of internal structures, whereas conventional pulse-echo measures material density. www.weldingandndt.com
3. TOFD is effective for sizing and positioning flaws in welds, while conventional pulse-echo primarily identifies material boundaries.
4. TOFD is suitable for inspecting metallic materials, while conventional pulse-echo is more applicable to non-metallic substances.

(Explanation: The Time-of-Flight Diffraction (TOFD) technique is distinct from conventional pulse-echo ultrasonic testing in that it focuses on detecting and sizing internal flaws rather than identifying material boundaries or surface defects. Unlike pulse-echo, which measures the amplitude of reflected waves, TOFD determines the time of flight of diffracted waves emitted from the edges of flaws, enabling precise measurements of flaw sizes and positions within welds. Additionally, TOFD can be used during production without interrupting operations, providing digital records for future reference, and delivering quick inspection results.)

Q4. In Ultrasonic Testing (UT), what is the purpose of a wedge in the inspection setup, and how does it contribute to the testing process?

1. The wedge is used to measure the velocity of ultrasonic waves in the test material, ensuring accurate calibration.
2. The wedge acts as a reflector, enhancing the detection of surface-breaking flaws.
3. The wedge helps to direct and focus ultrasonic waves into the test material at a desired angle for better penetration and defect detection.
4. The wedge is employed for temperature compensation, ensuring consistent testing results under varying environmental conditions.

(Explanation: In Ultrasonic Testing (UT) Level II, the purpose of a wedge in the inspection setup is to direct and focus ultrasonic waves into the test material at a desired angle for better penetration and defect detection. The wedge is used to position the transducer at an angle to the surface of the specimen so that the shear-wave-refraction angle is optimized. This contributes to the testing process by ensuring that the ultrasonic waves are directed effectively into the material, allowing for improved defect detection and accurate inspection results.)

Q5. In Ultrasonic Testing (UT), describe the purpose of a couplant in the inspection process, and how does it contribute to the effectiveness of ultrasonic wave transmission? 

1. The couplant is used to clean the surface of the test material, ensuring better contact with the ultrasonic probe.
2. The couplant serves as a corrosion inhibitor, preventing degradation of the test material during inspection.
3. The couplant acts as a sound reflector, enhancing the sensitivity of the ultrasonic waves to internal flaws.
4. The couplant facilitates the transmission of ultrasonic waves by eliminating air gaps between the probe and the test material.

(Explanation: The purpose of a couplant in the inspection process is to facilitate the transmission of ultrasonic waves by eliminating air gaps between the probe and the test material. The couplant serves as a medium to ensure efficient transfer of sound energy from the transducer to the test specimen, enhancing the sensitivity of the ultrasonic waves to internal flaws. It does not clean the surface of the test material or act as a corrosion inhibitor, nor does it serve as a sound reflector.)

Q6. Explain the significance of the Near-Field and Far-Field regions during an inspection, and how do these regions impact flaw detection in UT? 

1. The Near-Field region is where surface flaws are primarily detected, while the Far-Field region is critical for assessing internal defects.
2. The Near-Field region is characterized by reduced resolution, making it suitable for shallow flaw detection, whereas the Far-Field region provides better depth penetration.
3. The Near-Field region is where calibration is performed, ensuring accurate instrument settings, while the Far-Field region is where actual flaw detection takes place.
4. The Near-Field and Far-Field regions are interchangeable terms describing the same phase of ultrasonic testing with no distinct impact on flaw detection.

(Explanation: The Near-Field and Far-Field regions are significant during an inspection. Near-Field (also known as the near zone or Fresnel zone) and Far-Field (also known as the far zone or Fraunhofer zone) regions are crucial aspects of ultrasonic testing. The Near-Field region is characterized by extensive fluctuations in sound intensity near the source (reduced resolution and a higher concentration of energy), making it challenging to evaluate flaws accurately . On the other hand, the Far-Field region is where the ultrasonic beam is more uniform, provides better depth penetration and is essential for detecting flaws at greater depths within the material. Hence, optimal detection results are obtained when flaws occur in this area . www.weldingandndt.com

The transition between the Near-Field and Far-Field regions occurs at a distance, which is determined by the transducer diameter, frequency, and sound longitudinal velocity in the medium through which waves are transmitted. The Far-Field region is where most ultrasonic inspection procedures are designed to occur, and the intensity of the sound beam in this region falls off exponentially as the distance from the face of the transducer increases. The Near-Field and Far-Field regions are not interchangeable terms and have a distinct impact on flaw detection.)

Q7. What is the significance of the dead zone, and how does it impact flaw detection in UT?

1. The dead zone is where no ultrasonic waves can penetrate, making it ideal for calibrating instruments.
2. The dead zone is an area near the surface where flaws cannot be detected, affecting the reliability of inspections.
3. The dead zone indicates a region where material thickness is too low for accurate measurements. 
4. The dead zone is a term used to describe the time delay in ultrasonic testing, ensuring precise depth calculations.

(Explanation: Dead zone refers to the region close to the transducer where echoes from the initial pulse are still being received. During this time, the system is unable to detect flaws accurately. The dead zone can impact the reliability of flaw detection, especially for cracks which are on the surface of the material being tested.)

Q8. In Ultrasonic Testing (UT), why is the selection of an appropriate probe or search unit crucial, and how does it impact the inspection process?

1. The probe determines the color contrast in the ultrasonic display, enhancing flaw visibility.
2. The probe influences the calibration process, ensuring accurate measurement of material thickness.
3. The probe or search unit affects the frequency and beam characteristics, influencing flaw detection capabilities. 
4. The probe is responsible for cleaning the test material surface, improving contact for better wave transmission. 

(Explanation: The selection of an appropriate probe or search unit is crucial because it determines the frequency and beam characteristics of the ultrasonic waves. These factors directly impact the system’s ability to detect and characterize flaws within the inspected material. Different probes are chosen based on the specific inspection requirements, material properties, and the depth of flaws that need to be detected.)

Q9. Why angle probes are used, and how do they contribute to the inspection of materials in Ultrasonic Testing (UT)?

1. Angle probes are designed for surface cleaning, improving contact between the ultrasonic waves and the test material.
2. Angle probes facilitate temperature compensation during inspections, ensuring consistent results under varying environmental conditions. www.weldingandndt.com
3. Angle probes are used to adjust the frequency of ultrasonic waves, enhancing the accuracy of calibration.
4. Angle probes enable the inspection of materials at oblique angles, improving the detection of defects beneath the surface. www.weldingandndt.com

(Explanation: Angle probes are designed to allow the inspection of materials at oblique angles, enhancing the detection of defects located beneath the surface. These probes are particularly useful for inspecting welds and other components where the geometry may require testing at angles other than perpendicular to the surface.)

Q10. In Ultrasonic Testing (UT) of welds, what is the primary purpose of employing a phased array probe?

1. To measure the surface roughness of the weld material.
2. To enhance the sensitivity of the ultrasonic waves to internal defects.
3. To facilitate temperature compensation during the inspection.
4. To allow for the inspection of welds at multiple angles without moving the probe.

(Explanation: A phased array probe allows for the inspection of welds at multiple angles without physically moving the probe. This capability improves the flexibility and efficiency of the inspection process, especially in complex weld geometries.)

Q11. What is the name of the curve that shows the relationship between amplitude and distance traveled to reflectors of the same area in ultrasonic testing?

1. BAC curve
2. DAC curve
3. DGS curve
4. TTT curve

(Explanation: The Distance Amplitude Correction (DAC) curve is a graph that shows the relationship between the amplitude of an ultrasonic signal and the distance traveled by the signal to a reflector of a specific size and shape. The DAC curve is used to adjust the instrument’s sensitivity to ensure that signals from reflectors of different sizes and depths are detected and displayed accurately.)

Q12. A weld inspection is conducted using an angle beam probe with a frequency of 5 MHz. If the velocity of the ultrasonic wave in the material is 3000 m/s, What will be the the wavelength of the ultrasonic wave?

1. 0.0006 meters
2. 0.0007 meters
3. 0.0008 meters
4. 0.2 milimters

(Explanation: The wavelength can be calculated using the formula λ = v/f, where λ is the wavelength, v is the velocity of the wave, and f is the frequency of the wave. Substituting the given values, we get λ = 3000/5 x 10^6 = 0.0006 meters or 0.6 millimeters. Therefore, the wavelength of the ultrasonic wave is 0.0006 meters.)

Q13. During ultrasonic weld inspection, a technician uses a straight beam probe with a frequency of 10 MHz. If the ultrasonic waves travel through the weld material at a velocity of 2500 m/s, what will be the wavelength of the ultrasonic wave?

1. 0.21 mm
2. 0.15 mm
3. 0.06 mm
4. 0.00025 m

(Explanation: The wavelength can be calculated using the formula: wavelength (λ) = velocity (v)/ frequency (f). Putting the values, we get: wavelength (λ) = (2500 m/s) / 10 MHz = 0.25 mm = 0.00025 m. Therefore, the wavelength of the ultrasonic wave is 0.00025 meters.)

Q14. In Ultrasonic Testing (UT), what term describes the phenomenon where ultrasonic waves deviate from a straight path when encountering an interface between two different materials?

1. Beam divergence
2. Acoustic impedance
3. Refraction
4. Attenuation

(Explanation: When ultrasonic waves pass through an interface between two different materials, they change direction, and this phenomenon is known as refraction. The angle of refraction depends on the angle of incidence and the difference in acoustic impedance between the two materials. Refraction is an essential concept in ultrasonic testing, as it allows the operator to direct the ultrasonic beam to specific areas of the material being inspected and detect flaws that may be hidden from a straight beam inspection.)

Q15. Why is the concept of “beam divergence” important, and how does it affect the inspection process in UT?

1. Beam divergence ensures proper calibration of the ultrasonic instrument.
2. Beam divergence influences the color contrast of the ultrasonic display.
3. Beam divergence determines the spread of ultrasonic waves, impacting coverage and flaw detection.
4. Beam divergence compensates for temperature variations during inspections.

(Explanation: The concept of “beam divergence” is important because it determines the spread of ultrasonic waves, which can impact coverage and flaw detection. Beam divergence refers to the spreading out of the ultrasonic beam as it travels through a material. This can cause the beam to become wider and less focused, which can reduce the sensitivity of the inspection and make it more difficult to detect flaws. The angle of the beam and the frequency of the ultrasonic waves can also affect beam divergence. Therefore, it is important for technicians to consider beam divergence when selecting the appropriate probe and settings for an ultrasonic weld inspection to ensure accurate and reliable results.)

Q16. Which ultrasonic test frequency would probably provide the best penetration in a 300 mm thick specimen of coarse-grained steel?

1. 2.25 MHz
2. 10 MHz
3. 5 MHz
4. 1 MHz

(Explanation: In ultrasonic testing, higher frequencies generally provide better resolution but less penetration, while lower frequencies offer deeper penetration but lower resolution. Since, we have 300 mm thick specimen of coarse-grained steel, which requires good penetration, a lower frequency would be more suitable. A 1 MHz frequency would have a longer wavelength compared to higher frequencies, allowing it to penetrate deeper into the material.)

Q17. What leads to the attenuation of ultrasonic wave energy as it traverses through a material during testing?

1. Composition and contrast
2. Reflection and refraction
3. Dispersion and diffraction
4. Absorption and scattering

(Explanation: Attenuation in ultrasonic waves refers to the loss of energy as it travels through a material. This loss occurs mainly because of absorption and scattering. Absorption refers to the conversion of sound energy into heat as the wave travels through the material, while scattering involves the redirection of sound waves in different directions due to irregularities or inhomogeneities in the material.)

Q18. Angle beam testing of plate will often miss: 

1. Incomplete penetration at the root.
2. Inclusions that are randomly oriented.
3. Laminations that are parallel to the front surface.
4. A series of small discontinuities.

(Explanation: When laminations run parallel to the front surface of a plate, the sound waves can travel along them smoothly without encountering obstacles that would create reflections. This makes it possible for these defects to go undetected during angle beam testing. The way the defect aligns with the sound beam’s direction is a key factor in determining whether it can be detected effectively using this testing method.)

Q19. What characteristic of particular materials enables them to convert electric energy into mechanical energy and conversely, mechanical energy into electric energy?

1. Piezoelectric effect
2. Gamma-Beta effect
3. Acoustic Impedance
4. Attenuation effect

(Explanation: Certain materials have the unique ability to convert electrical energy into mechanical energy and vice versa, which is referred to as the piezoelectric effect. This phenomenon allows piezoelectric materials to transform mechanical stress into electricity or vice versa. That is why these materials are used in the probes or search units of a Ultrasonic Testing equipment.)

Q20. In ultrasonic testing using an angle probe for weld scanning, if the angle of the probe is 45 degrees and the sound velocity in the material is 3000 m/s, what is the depth of a flaw detected at a time interval of 10 microseconds?

1. 1.5 mm
2. 21.2 mm
3. 4.5 mm
4. 6 mm

(Explanation: The depth (d) of a flaw detected using ultrasonic testing can be calculated using the formula;

d = (V x t)/(2 x cos)

•  Sound velocity in the material
•  Time interval
•  Angle of the probe

Given values are;

• Sound velocity = 3000 m/s
• Time interval =  (which is 10×10^−6 seconds)
• Angle of the probe 

Putting the values d =(3000×10×10^−6)/(2 x cos 

Now, expressing  in millimeters (1 m = 1000 mm)

Q22. Which parameter is calculated by multiplying the density () of a material by its longitudinal wave velocity (V_L) in ultrasonic testing?

1. Ultrasonic Impedance ()
2. Acoustic Conductivity )
3. Acoustic Impedance ()
4. Density Velocity Product ()

(Explanation: In ultrasonic testing, the parameter that is calculated by multiplying the density (ρ) of a material by its longitudinal wave velocity (V_L) is called Acoustic Impedance (AI). Acoustic impedance plays a crucial role by determining how much sound energy bounces back when it encounters different materials. This bouncing back of energy affects how well we can find defects and understand the properties of the material being tested. When there is a big difference in acoustic impedance between materials, more energy reflects back, which can make the testing process less effective in detecting flaws accurately.)

Q23. Consider a steel specimen with a density of 7,850 kg/m³ and a longitudinal wave velocity of 5,900 m/s. Calculate the acoustic impedance of the steel specimen and explain its significance in the context of ultrasonic testing.

1. 46,415,000 kg/(m²s)
2. 35,000,000 kg/(m²s)
3. 52,150,000 kg/(m²s)
4. 40,000,000 kg/(m²s)

(Explanation: Acoustic Impedance (Z) = Density (ρ) X Longitudinal Sound Velocity (V_L)

Given:

• Density of steel specimen (ρ) = 7,850 kg/m³
• Longitudinal wave velocity of steel specimen (V_L) = 5,900 m/s

Substitute the values into the formula:
Z = 7,850 kg/m³ X 5,900 m/s
Z = 46,415,000 kg/(m²s)

Q24. Which type of ultrasonic scan is primarily used to determine the thickness of an object in ultrasonic testing?

1. A-scan
2. B-scan
3. C-scan
4. D-scan

(Explanation: The A-scan is primarily used to measure the thickness of an object in ultrasonic testing by analyzing the time it takes for an ultrasonic wave to travel from the transducer to the object and back.)

Q25. In ultrasonic testing, what is the formula to calculate the wavelength of an ultrasonic wave, and how is it related to the velocity of sound and frequency?

1. Wavelength (λ) = Velocity of wave (v) * Frequency (f)
2. Wavelength (λ) = Velocity of wave (f) / Frequency (f)
3. Wavelength (λ) = Frequency (f) / Velocity of sound (v)
4. Wavelength (λ) = Velocity of sound (v) + Frequency (f)

(Explanation: The wavelength of an ultrasonic wave is calculated by dividing the velocity of sound waves in the material by the frequency of the ultrasonic wave.)

Q26. A plate is 25.4 mm thick. Using the pulse-echo method with a straight beam, the measured elapsed time is 8 microseconds. Which material is it most likely to be?

1. Carbon steel
2. Lead
3. Titanium
4. Aluminum

(Explanation:  To find out the material, we need to calculate the speed of sound in the material using the thickness of the plate and the elapsed time for the pulse-echo method.

1. Given Data:
   • Plate thickness (𝑑) = 25.4 mm = 0.0254 mm
   • Elapsed time (𝑡) = 8 microseconds (µs) = 8×10⁻⁶ s
2. Pulse-Echo Method Explanation:
   • The sound wave travels to the back of the plate and returns, so it covers twice the thickness of the plate.
   • Therefore, the total distance covered by the sound wave is 2𝑑2d.
3. Formula for Speed of Sound: 𝑣=2𝑑/t​
4. Calculate Speed of Sound:

𝑣=(2×0.0254 m)/(8×10⁻⁶ s)

​= 6350 m/s

Now the typical Speeds of Sound in in different materials are:

• Carbon steel: ~ 5900 m/s
• Lead: ~ 2160 m/s
• Titanium: ~ 6100 m/s
• Aluminum: ~ 6320 m/s

Comparing the calculated speed of sound (i.e. 6350 m/s) with the different materials, the calculated value is closest to the speed of sound in aluminum (i,e 6320 m/s).

Conclusion: Hence, the most likely material of the plate is: Aluminum 

Q27. What is the typical frequency range used in commercial ultrasonic testing?

1. 5 MHz and 10 MHz
2. 1 MHz and 10 MHz
3. 10 MHz and 50 MHz
4. 2 MHz and 20 MHz

(Explanation: The choice of frequency in ultrasonic testing is crucial as it affects the penetration depth and resolution of the inspection. Lower frequencies, such as 1 MHz, are capable of penetrating deeper into materials but provide lower resolution images. Higher frequencies, up to 10 MHz, offer higher resolution but have shallower penetration depths. 

Thus, the 1 MHz to 10 MHz range offers a balanced trade-off between penetration and resolution, making it suitable for a wide variety of applications in industrial settings, such as inspecting welds, detecting flaws in metals, and assessing the integrity of structures.)

Q28. Which of the following materials are commonly used in ultrasonic transducers due to their ability to convert electrical energy into mechanical vibrations? 

1. Y cut crystals
2. Piezoelectric elements
3. Magnetostrictive elements
4. All of the above

(Explanation: Certain materials, known as piezoelectric elements, have the special ability to change electrical energy into mechanical vibrations and vice versa. This phenomenon is called the piezoelectric effect. When electricity is applied to these materials, they vibrate and produce sound waves. Similarly, when these materials are exposed to sound waves, they generate an electrical signal. 

Hence, piezoelectric materials are ideal for ultrasonic transducers because they can both create and detect sound waves. When an electric field is applied to piezoelectric materials, they change shape slightly, producing mechanical vibrations (sound waves). When they experience mechanical stress (like sound waves hitting them), they generate an electrical signal. This dual capability is essential for the effective operation of ultrasonic testing, allowing us to inspect materials like metals and ceramics for cracks or defects to ensure they are safe and reliable.

Examples of piezoelectric materials are Lithium sulfate, barium titanate, and lead metaniobate. 

A brief explanation of the other options given in this question and how they differ from piezoelectric elements is provided below:

Y-cut crystals: These refer to a specific orientation of a quartz crystal used in electronic devices. They are not the same as the piezoelectric materials mentioned in the question, as Y-cut crystals are primarily used for their frequency stability in oscillators and filters, rather than for generating mechanical vibrations. 

Magnetostrictive elements: These materials change their shape or size when exposed to a magnetic field. Unlike piezoelectric elements, which respond to mechanical stress or pressure, magnetostrictive elements rely on magnetic fields to induce vibrations.)

Q29. In which of the following forms can sound propagate through various materials?

1. Longitudinal Waves
2. Shear Waves
3. Surface Waves
4. All of the Above

(Explanation: Sound can propagate as all of the above: longitudinal waves, shear waves, and surface waves. Let’s understand more about these waves;

• Longitudinal Waves: These waves occur when particles in the medium move in the same direction as the wave itself. This is the primary way sound travels through gases and liquids, creating areas of compression and rarefaction. 
• Shear Waves: Also known as transverse waves, these involve particle movement that is perpendicular to the direction of wave travel. Shear waves can only propagate through solids due to their structural rigidity.
• Surface Waves: These are waves that travel along the surface of a medium. They are a combination of longitudinal and shear waves. Imagine ripples on a pond. 

So, depending on the medium through which sound is traveling (solid, liquid, or gas), it can propagate through all of these wave types.)

Q30. During ultrasonic inspection (UT) on a 20 mm thick weld, an indication having length 2 mm observed, which is characterised as lack of fusion between the base metal and weld metal. As per the acceptance criteria in ASME Section VIII Division 1, this defect is:

1. Not Acceptable
2. Acceptable
3. Acceptance depends upon the depth of flaw
4. None of above

(Explanation: According to ASME Section VIII Division 1, any indication characterized as a lack of fusion is unacceptable regardless of its size. Since the 2 mm long indication in the 20 mm thick weld has been characterized as lack of fusion, it would be unacceptable per ASME Section VIII Division 1 criteria, regardless of its size or depth.

To learn more about the acceptance criteria, Please read: https://www.weldingandndt.com/acceptance-criteria-for-weld-defects/)

Figure 1

Q31. Figure 1 (shown above) illustrates an ultrasonic test on a job. What does indication ‘A’ represent?

1. The initial pulse or front-surface indication
2. The discontinuity indication
3. The back-surface reflection
4. Baseline

(Explanation: Point ‘A’ represents the initial pulse, the emitted ultrasonic wave from the transducer, marking the sound wave’s entry into the material and appearing near time zero on the A-scan. This initial pulse creates a near-surface “dead zone” because the transducer’s subsequent “ring down” prevents the clear reception of early echoes from shallow depths, which are masked by the pulse’s tail. Consequently, the area directly beneath the transducer cannot be reliably scanned for defects during and immediately after the initial pulse, a limitation of single-element pulse-echo UT.)

Q32. In Figure 1, indication B represents:

1. The initial pulse or front-surface indication
2. The discontinuity indication
3. The back-surface reflection
4. Baseline

(Explanation: Point ‘B’ represents a defect echo, a signal that arises when the emitted ultrasonic wave encounters a discontinuity (the defect) within the test material and reflects back towards the transducer.)

Q33. In Figure 1, indication C represents:

1. The initial pulse or front-surface indication
2. The discontinuity indication
3. The back-surface reflection
4. Baseline

(Explanation: Point ‘C’ represents the back surface reflection, also known as the back wall echo, a signal generated when the ultrasonic wave travels through the entire material thickness, reflects off the back surface, and returns to the transducer. Appearing latest on the A-scan, its position indicates the material’s total thickness based on the sound’s round-trip travel time.)

Q34. What is the skip distance on a 10 mm plate with a 70 degree angle probe?

1. 20 mm
2. 100 mm
3. 10 mm
4. 55 mm

(Explanation: To calculate the skip distance (S) for a 10 mm plate with a 70-degree angle probe, we use the formula: Skip Distance (S) 

Where:

•  is the thickness of the plate (10 mm)
•  is the refracted angle of the probe (70 degrees)

Substituting the values: 

Skip distance represents the surface distance from the probe’s index point to where the sound beam reflects off the back wall and returns to the surface. To learn more about skip distance and beam path, please read: https://www.weldingandndt.com/angle-probe-calculation-for-ut/).

For question answer video lectures on UT, please watch:

• Hindi: https://youtu.be/Mb0ekRAkS_g
• English: https://youtu.be/GcVqVlHXqZI

• Ferromagnetic metals: Ferromagnetic metals are those, which are strongly attracted to a magnet and can be easily magnetized. Examples ferromagnetic metals are iron, nickel, and cobalt.
• Paramagnetic metals: Paramagnetic metals are those which are very weakly attracted by magnetic forces of attraction and cannot be magnetized such as austenitic stainless steel.
• Diamagnetic metals: Diamagnetic metals are those which are slightly repelled by a magnet and cannot be magnetized. Examples of diamagnetic metals are bismuth, gold, and antimony.

Only ferromagnetic metals can be effectively inspected by Magnetic Particle Testing

Principle of Magnetic Particle Test

This method uses the phenomenon of a magnet by virtue of which path of magnetic lines of force gets disrupted when a surface breaking is occurred in the path. Any magnet has two poles i.e. north pole at one end and south pole at the other. Magnetic lines of force (also known as magnetic flux) travel from north pole to the south pole, as shown in the below figure (Figure – 1).

(Figure — 1)

If there is any distinct change in the continuity (such as surface discontinuity) of magnet, then the magnetic lines of force will get distorted, this phenomenon is known as flux leakage. During flux leakage, additional North and South poles will be created near discontinuity (Figure — 2), and the magnetic lines of force will redistribute themselves in the material by bending around the discontinuity.

(Figure — 2)

How Magnetic Particle Test works:

When fine Iron particle (ferromagnetic particle) is spread over a magnet, it gets accumulated at the poles. But in case of any discontinuity, flux leakage would occur and the Iron powder will accumulate at the discontinuity, due to the creation of additional North and South poles at the discontinuity, as shown in Fig – 3.

(Figure — 3)

The accumulation of iron particle at the discontinuity would produce a visible indication of that discontinuity.

Detection Media:

Particles used for Magnetic particle testing is similar to ferromagnetic particle and is called as detection media. These particles may be applied in dry form or may be mixed with liquid and spread over the area where Magnetic particle test has to be performed. Liquid like kerosene or a similar petroleum distillate may be used. Water can also be used by using suitable additives such as wetting agents and antifoam liquids. To provide better contrast with the test objects and enhanced sensitivity, these particles are coated, there are two types of coating;

1. Color contrast coating

2. Fluorescent coating

Color contrast coating: Color contrast coatings are available in several colors such as red, blue, black and Gray etc. Color of particle are selected so as to provide a good contrast with test object.

Fluorescent coating: Fluorescent particles can be seen under a ‘Black light illumination’. These particles emit light when seen by a black light in a dark background. These particles provide excellent contrast in dark background.

How to temporarily magnetize the test object:

To carry out Magnetic Particle Testing we need to temporarily magnetize the test object. Magnetization should be temporary in nature. To magnetize the test piece, common instruments which are used are;

• Electromagnetic yoke
• Permanent Magnet
• Prod
• Coil

Electromagnetic Yokes (Figure – 4)are also called as AC yokes, it’s very portable and commonly used in Industries. Yokes are connected with AC power source (Battery pack version is also available). Many yokes come with adjusting legs, to facilitate wide range of area profiles. These yokes produce longitudinal magnetization. Hence, for complete inspection, re-positioning of yokes in at least two 90⁰ opposing direction is required.

(Figure — 4)

Permanent magnets (Horse shoe types) are also used to temporarily magnetize the work piece. But due to their strong fields, particles gets attracted to the legs more readily instead of the test surface. Hence, many a time it becomes difficult to inspect the test object. Prod and coil method is also used for temporarily magnetizing the test object. Prods require good contact with test object otherwise it can damage the test object, due to electrical arcing. Coil method produce longitudinal magnetization.

Flux Direction Indicators:

Before inspection, the yoke shall be properly checked by the flux direction indicators. The most common flux direction indicator used in the industries is ‘A Pie Gauge’. Other flux direction indicators are Burmah Castrol strips and Quantitative quality indicator (QQI).

A pie gauge is an octagonal flat plate which consists of eight low-carbon steel segments. The octagonal flat plate is copper coated from the back side to hide the joint lines. When particles are suspended, from back side, on the pie gauge (under the influence of magnetic lines of force), particles get accumulated at these joint lines revealing the eight segments.

How to perform the Magnetic Particle Test

To carry out Magnetic Particle Testing, we need to follow the following activities

1. Temporarily magnetize the test object
2. Suspend (spread) the magnetic particles (either dry or wet) on the test object
3. Inspection of test object either by black light (in case of wet fluorescent particle) in a dark area or inspection in sufficient light (in case of dry particle).

Various techniques are available to carry out the first two steps (mentioned above), these are;

• Dry Continuous
• Dry Residual
• Wet continuous
• Wet Residual

The term ‘Continuous’ is used when the particles are applied while the current is still flowing. And ‘Residual’ is used when particles are applied after the current has ceased. Out of these four techniques Dry continuous and Wet continuous techniques are widely used in Industries. A brief description of these two techniques are given below;

Dry Continuous: In dry continuous technique, dry magnetic particles are used. These particles are applied while the magnetizing force is on. Yokes or prods can be used to generate the magnetizing force. This technique is useful for detecting subsurface discontinuities, due to the higher permeability compared to the wet particles.

Wet Continuous: Particles are mixed with liquid and suspended on the test area, magnetization of test area and suspension of wet particles shall be done simultaneously. Liquids such as kerosene or petroleum distillates can be used for this purpose, water can also be used as a liquid carrier for particles. Kerosene and petroleum distillates are costly, highly inflammable and possesses safety related issues. However, water is inexpensive, available in abundance and possesses no safety related issues, but it can initiate corrosion in the test object.

Sound beam is emitted through a probe. The probe is made up of a piezoelectric material. Piezoelectric material has the ability of converting mechanical energy into electrical energy. It is reversible, hence an electrical energy can be converted into mechanical energy or sound energy. The probe receives electric signal from the Ultrasonic machine and converts it to sound beam, these sound beam travels into the test object and gets reflected at interfaces or discontinuity, the piezoelectric material (in probe) converts the reflected sound beam into electrical signal that can be displayed as visual signals on cathode ray tube (CRT) or liquid crystal display (LCD) screen of the machine. Three types of probes are generally used in industries;

• Normal Probe (Figure – 1)
• TR probe
• Angle Probe (Figure – 2)

In TR probe, two separate crystals are used to transmit and receive the sound energy in the same housing, whereas in Normal and Angle probes same crystal transmits as well as receives the sound beam. The normal probe emits sound energy at right angle to the transducer whereas, the angle probe can emit sound energy at an angle. Three types of angle probes are very popular among the industries, these are

• 45⁰ angle probe
• 60⁰ angle probe
• 70⁰ angle probe

Probe is also called as a “search unit” or “scanning device”. The probe is connected with the machine with the help of a connector (connecting wire). The machine has a screen (CRT or LCD) and adjustment/setting keys.

Normal Probe Scanning:

Waves emitted by a normal probe gets reflected at the interfaces or discontinuity (i.e at the change of medium), this is illustrated in figure – 3 and figure – 4. In figure 3, waves gets reflected at the back surface and the resulting echo is known as a Backwall echo. Whereas, in Figure 4 some of the transmitted waves gets reflected at the flaw, hence two echoes are visible in the machine, one is for the flaw and the other one indicates the backwall.

Angle Probe Scanning: 

Figure 5 shows an angle probe, Some part of the transmitted waves gets reflected at the flaw and the resulting echo is visible in the machine. To learn more about angle probe scanning please click here.

Modes of propagation of sound energy:

Sound waves are propagated, in a material, by the displacement of successive atoms in that material. These sound waves can be propagated in the material in many ways (modes). Three basic modes of propagation of sound energy in metals are being used in Ultrasonic test, these modes are:

1. Longitudinal waves
2. Transverse waves
3. Surface waves

Longitudinal waves: Longitudinal waves (Figure – 6) are also called as straight or compressional waves. These waveforms are the simplest of all other waveforms. These waveforms exist when the motion of the particle is parallel to the direction of sound beam propagation. These waves have a relatively high velocity and a relatively short wavelength. These waveforms are very useful for detection of inclusions and lamellar-type discontinuities in base metal. Normal probe emits longitudinal waves.

Transverse waves: Transverse waves (Figure – 7) are also known as shear waves. These waveforms exist when the motion of particle is perpendicular to the direction of propagation of the sound beam. The velocity of shear waves is approximately half to that of longitudinal waves. The lower velocities provide greater sensitivity to small indications. These waves are more easily dispersed and cannot be propagated in a liquid medium (water). These waves are very useful for the detection of weld discontinuities.

Shear waves are generated by transmitting longitudinal waves into the work piece at a predefined angle. The sensitivity of transverse waves is approximately double than that of longitudinal waves. Angle probe emits longitudinal waves.

Surface waves: Surface waves is the third mode of propagation of sound energy in metal. It is also known as Rayleigh waves. These waves are propagated along the surface of the metal. Since these waves have very little movement below the surface of a metal hence, these waves have a very limited application for the examination of welded joints.

Wave frequency: The sound wave frequency generally used for weld inspection is between 1 MHz to 6 MHz Higher frequency produce sharp and small sound beam which is very useful for thin-walled weldments. A 2.25 MHz frequency is often used in industries.

Couplant: For transmission of ultrasonic waves into the test object, a liquid couplant is generally used. Most commonly used couplants are water, light oil, glycerine, and cellulose gum powder mixed with water. Work piece must be smooth and flat to allow proper coupling of the transducer with the test specimen.

To read more please click here

There are three methods for selecting a probe angle, these are:

1. Based on groove angle:

            Probe Angle (Ø) = 90 – α/2

Where, α – Groove angle and Ø- Probe Angle

2. As per AWS:

• 0 – 30 mm Thickness – 70⁰ Probe
• 30 – 40 mm Thickness – 60⁰ Probe
• > 40 mm Thickness – 45⁰ Probe

2. As per approved procedure:

   Third way of selection of Probe angle is as per the procedure approved by any competent person/client.

SKIP DISTANCE AND BEAM PATH (SOUND PATH) CALCULATION:

1. Skip distance calculation:

(Abbreviations: HSD – Half Skip Distance, FSD – Full Skip Distance)

Tan Ø = Perpendicular (BG)/ Base (AG) = AC (or HSD)/THK

Hence, Tan Ø = HSD/T

Or, HSD = T X Tan Ø

Similarly, FSD = 2T X Tan Ø

And, 1-1/2 Skip Distance = 3T X Tan Ø

2. Beam Path calculation:

(Abbreviations: HBP – Half Beam Path, FBP – Full Beam Path)

Cos Ø = Base (AG) / Hypotenuse (AB) = THK/HBP

Or, HBP = T / Cos Ø

Similarly, FBP = 2T / Cos Ø

And, 1-1/2 Beam Path = 3T / Cos Ø

NOTE: 1. Scanning area should be 1-1/2 Skip Distance i.e. 3T X Tan Ø

              2. Probe Travel Speed shall not be more than 150 mm/S

Read more: How to write a Welding Procedure Specification (WPS)

Read more: Welding Positions

Read more: Preheating – How, When and Why

Read more: Welder Qualification test

Read more: Thickness range as per ASME Section IX

• Code compliance
• Workmanship control
• Documentation Control

The requirements of visual examination are:

1. Illumination should be at least 350 Lux (minimum) but it is recommended to carry out visual inspection at an illumination of more than 500 Lux.
2. The inspectors eye should be within the radii of 600 mm of the surface of item being inspected and the viewing angle must not be less than 30 degrees.

(Also read Thickness range for welder qualification test)

Other aids which may be required during visual examination are:

• Welding gauges (Figure 2a and 2b)
• Weld gap gauges
• Linear misalignment gauges (Hi-Low)
• Magnifying glass (X2 to X5)
• Mirrored boroscope or fibre optic viewing system (when access is restricted)

Visual inspection can be done at three stages;

• Before welding,
• During welding and
• After welding

Before Welding: The inspector shall be familiarized with the applicable codes and standards/drawings/welding procedures (WPS and PQR). Welder qualification shall be carried out before production welding. The inspector shall confirm the material and review the MTC. Welding consumables shall also be inspected before welding. Joint preparation and alignment shall also to be checked prior to welding. After confirmation of all the parameters (as mentioned above), the welding inspector can permit the welder to start the production welding. If preheat is applicable, then the preheat temperature shall be confirmed before starting the weld.

(Figure 3 shows improper groove face and root gap, a welding inspector must see the groove preparation and root gap before welding)

During Welding: The inspector shall check the welding process and welding parameters with respect to the welding procedure specification (WPS) at any time during welding. Root run and root run dressing, interpass temperature shall be witnessed by the inspector. The welding consumables shall also be checked during welding.

(Also read How to write a welding procedure specification – WPS)

After welding: After complete welding, identification number is punched near joint. Complete visual inspection is done and any surface breaking or defect shall be repaired as per approved procedure. Following defects (or discontinuity) can be revealed by visual inspection:

• Crack
• Underfill
• Undercut
• Surface porosity
• Overlap
• Lack of side wall fusion
• Arc strike
• Spatters
• Excessive Penetration
• Unacceptable weld profiles

[To know more about welding Defects, Please Click here]

(Figure 4: Welding inspector checking the weld reinforcement size by a Bridge Cam welding Gauge)

A dimensional survey shall be done to ensure the dimension of the part after welding. After satisfactory completion of welding proper documentation is prepared.

If a Post weld treatment is specified in WPS, Then the operation should be monitored and documented. Following parameters to be considered when Post weld heat treatment is required,

1. Area to be heated
2. Heating and cooling rates
3. Holding temperature and duration
4. Temperature distribution

In addition to visual inspection, a number of other NDT (Non Destructive Test) methods are available to check the quality of weldment, some of the most common NDT methods are;

1. Radiography testing (RT)
2. Ultrasonic testing (UT)
3. Magnetic particle testing (MT)
4. Liquid penetrant testing (PT)
5. Electromagnetic testing (ET)
6. Acoustic emission testing (AET)

Each NDT methods has its own significance and importance for example Liquid penetrant testing is very efficient and economical for checking surface defects, whereas, with the help of Ultrasonic test and Radiography test, entire depth of the weld can be inspected.

Selection of NDT methods depend on the requirements. Person engaged or assigned to carry out these tests must possess the necessary qualification. A written test procedure, format for reporting and the applicable code must also be decided before conducting the examination.

Also read P-number, F-number and A-number in welding (ASME Section IX)

Note: I had written this article for India welds newsletter- Vol 1:4 Oct-Dec 2018. Click here to read that newsletter.

Radiography films are primarily made up of two things;
1. Base
2. Emulsion

Base: Base is a transparent, flexible blue tinted object, usually made from a clear and flexible plastic such as cellulose acetate. It provides physical support to emulsion and does not participate in the image-forming process. It is not sensitive to radiation, nor can it record an image.

Emulsion: Emulsion consists of gelatin which consists of radiation sensitive silver halide crystals such as silver bromide & Chloride. Emulsion is coated on both sides of the base in layers about 0.0005 inches thick. Due to the emulsion coating on both sides of the base, the amount of radiation-sensitive silver halide gets doubled & hence it increases the film speed.

Development of radiography films:

Once a film has been exposed to sufficient amount of radiation, it captures the latent image. Now we need to chemically develop the film to convert the captured latent image to a visible image for the purpose of interpretation. To convert an exposed film (latent image) to an useful radiograph (visible image), following steps are followed;

1. Development
2. Stop bath
3. Fixing
4. Washing
5. Drying

Development: It is the initial step converting the latent image to a useful and readable image. Film is exposed to the developer solution. Developer makes the latent image visible. Main function of developer is to reducing (or eliminate) the exposed silver bromide crystals to black metallic silver. Developing the film is multi-step process. The developer solution contains chemicals comprised of alkali and metol or hydroquinone mixed with water. Alkali present in the development solution, penetrates the protective coating and allows the metol to reduce the exposed silver bromide to black metallic oxide.

Stop Bath: It is the second step in the processing of films. Function of stop bath is to quickly neutralize any excessive development of silver crystals. Since over development of the silver crystals may result in a radiographic image that is virtually impossible to interpret. This bath is comprised of a glacial acetic acid and water.

Fixing: Fixing (or fixer) is the third step followed in the development of a film. Fixer permanently fixes the image on the film. It is due to this process that the the radiographic image is preserved over a periods of time.
Fixing (or fixer) is also a multi-step process. The fixer removes any unexposed silver crystals and then hardens the remaining crystals in the emulsion.

Washing: Once the film has been properly developed, it is then rinsed in water to remove all the unwanted chemicals

Drying: Film is then left for drying. After drying, the film is ready for interpretation.

Interpretation is usually done with the help of a viewer. A viewer is a small box having sufficient light, upon which the film is kept and analyzed.

Short wavelength electromagnetic radiations such as X-rays or Gamma (γ) rays are used for Radiography testing. Both X-rays and Gamma rays have very high intensity and hence they are able to penetrate the material of any thickness. This high penetrating power is used during radiography testing.

The part to be inspected (Test material) is placed between the radiation source and a sensitive film. If the material is sound or flawless, entire rays (either X-rays or Gamma rays) pass through the material very evenly. But if the material contains any flaw (or flaws), then some of the rays which will pass through the flaws will get absorbed to some extent due to the change in the density. Please note that those rays which will not encounter any flaw will remain intact and will pass through the material evenly. These rays are finally made to fall on a light-sensitive film placed on the backside of the material being inspected.

The material (being inspected) and the sensitive film are kept under exposure to radiation (either X-rays or Gamma rays) for a certain period of time then the film is developed. Once the film is developed, it is called a radiograph.

The density of the film or the amount of darkness on the film will vary depending upon the amount of radiation reaching the film. The darker area on a radiograph indicates more exposure (higher radiation intensity) as compared to the lighter areas which receive less exposure. This variation in the image darkness reveals the presence of flaws or discontinuity inside the film. This variation in the darkness may also be used to determine the thickness or composition of the test material.

Please note that most of the defects possess lesser density than the sound parent metal, hence they transmit radiation (either X-rays or Gamma rays) much better than the sound metal does. Hence the film appears to be darker at the area exposed by the defects.

As explained earlier that both X-rays and Gamma rays are electromagnetic radiation having short wavelengths but very high intensity, now we will learn the steps to be followed for performing the Radiography Test.

Radiography by using X-rays:

X-rays are produced by an X-ray tube, which is an evacuated tube (usually made of glass) and it contains an electrically heated filament and a tungsten anode. The electrically heated filament releases electrons which are made to hit on the tungsten anode. Due to the collision of high-velocity electrons with the tungsten anode, X-rays are emitted.

These X-rays are allowed to pass through the test material. A cassette containing film is placed behind the test material (part to be inspected). A penetrameter (or Image Quality Indicator IQI) is placed on the side of the source adjacent to the weld.

After the prescribed time of exposure, the source is turned off and the film is sent for development in the darkroom (A darkroom is a place where the film is developed. Click here to learn how the film is developed in the darkroom). After development, the film is inspected with the help of a viewer.

Radiography by using Gamma-rays:

Gamma rays are produced by radioactive isotopes. The nucleus of a radioactive isotope remains unstable. Commonly used isotopes for industrial radiography are:

1. Cobalt 60 (Co 60):  Half-life of 5.3 years
2. Iridium 192 (Ir192): Half-life of 72 days
3. Caesium-137 (Cs137) : Half-life of 30 years

A lead or tungsten alloy container of sufficient thickness is used containing the gamma-ray source (300 mg). Such containers are used to provide the necessary protection. These Gamma rays are allowed to pass through the test material. A cassette containing film is placed behind the test material (part to be inspected). A penetrameter (or Image Quality Indicator IQI) is placed on the side of the source adjacent to the weld. The rest of the procedures is the same as the X-ray technique.

Radiography Test Video (Part 1);

Radiography Test Video (Part 2);

Radiography Test Video (Part 3);

Radiography Test Video (Part 4);

• Liquid Penetrant Inspection (LPI)
• Liquid Penetrant testing or Liquid Penetrant test (LPT)
• Penetrant Test or Penetrant Testing (PT)

The liquid penetrant test is one of the most widely used Non-Destructive Test (NDT) methods. It can be used to inspect almost all non-porous materials such as metals, plastics, ceramics, etc. We can only detect any surface discontinuity (or irregularity) such as surface cracks, porosity, pinholes, etc. by this test method.

Principle: DPT is based on the principles of CAPILLARY ACTION. By virtue of which, liquid tends to flow or seep into any narrow opening, even against external forces like gravity. This phenomenon occurs due to molecular attraction.

STEPS TO BE FOLLOWED FOR DYE PENETRANT TEST:

Procedure for Dye Penetrant Test can vary depending upon the factors such as the penetrant system being used and the condition and environment under which the inspection is performed. However, the general steps which are to be followed are as below;

1. Surface Preparation: The surface must be thoroughly cleaned, to make it free from dirt, oil, paint, grease, water, or other contaminants. For cleaning one can use dry cloths, solvents, cleaner, rust remover, etc. depending on the condition of the surface to be inspected.

2. Penetrant Application: After a thorough cleaning, Penetrant is applied. Penetrant is a red-colored Liquid. It can be applied on the surface by spraying (most common) or by brushing or by immersing the entire surface in a penetrant bath. The temperature of the surface shall be between 5^OC to 52^OC.

3. Dwell period: Leave the penetrant, as it is, on the surface for a minimum period of time (Known as Dwell Time or Dwell Period). During the dwell period, the penetrant seeps into the flaws (if present on the surface being inspected), due to Capillary action. The dwell period varies from 5 minutes to 60 minutes or even more than that depending upon the material and its service condition. The penetrant manufacturer also mentions the dwell period on the product itself. However, there is no harm in going beyond the minimum dwell period, provided that the temperature shall be ambient because at elevated temperature chances of penetrant getting evaporated will be always there. Hence at elevated temperature, one should strictly restrict to the recommended dwell time.

4. Removal of excess penetrant: After leaving the surface for the recommended dwell period, the penetrant shall be cleaned, for cleaning the excess penetrant cloth and penetrant removal shall be used. While cleaning the excess penetrant, two things shall be taken care of;

• Cleaning should be unidirectional i.e. cleaning shall be done in one direction only. To and fro cleaning shall be avoided.
• Penetrant remover/cleaner shall not be applied directly on the surface rather apply the penetrant remover/cleaner on the cloth and that cloth should be used for cleaning.

(Method of cleaning may vary, depending on the type of penetrant used)

5. Application of Developer: After a thorough cleaning, a thin layer of developer is applied. Two things shall be taken care of while spraying the developer;

• Shake the bottle rigorously
• Maintain a distance of 10 to 12 inches from the surface, while spraying the developer
• After spraying the developer wait for 10 minutes to 60 minutes (development time)

The developer sucks the trapped penetrant on the surface, from the flaws (if present). That is the penetrant bleeds out on the surface and it appears in sharp red color. The developer is a white color liquid and hence the penetrant appears in a sharp red color, hence we can easily identify the flaws.

6. Inspection: After the application of the developer wait for 10 to 60 minutes and then perform the inspection. Appropriate lighting is necessary to detect the indications from any flaws which may be present. The minimum light required is 1000 Lux or 100 foot-candles.

Advantages of Dye Penetrant Test:

• One of the major advantages of the Dye penetrant test (DPT) is its portability. The Penetrant testing kit (Penetrant/cleaner/developer) is very lightweight and small in size, hence can be easily transported at any place.
• Dye Penetrant test is quite inexpensive as compared to other non-destructive methods viz. MT, UT, RT, and ET, etc.
• DPT is very sensitive and small discontinuities can also be detected easily.
• Almost all non-porous materials such as metals, plastics, ceramics, etc. can be inspected by DPT.
• This test consumes very little time; hence material could be inspected rapidly.
• Complex geometric shapes can also be inspected with ease.

Disadvantages of Dye Penetrant Test:

• One of the major disadvantages of the Dye penetrant test (DPT) is that only surface flaws or discontinuities can be inspected.
• Requires pre-cleaning of the surface to be inspected.
• Only Non-porous materials can be inspected.
• Requires post cleaning
• Requires proper handling and disposal of chemicals.

Also, read Ultrasonic test (UT) basics

Also, read Radiography testing (RT)

Also, read Angle probe calculation for Ultrasonic test (UT)

Also, read: Thickness range for the welder qualification test

Watch this demo video (in Hindi/Urdu) to understand the steps involved in performing the Dye penetrant test.

Watch this demo video (in English) to understand the steps involved in performing the Dye penetrant test.

The following photographs are for your better understanding;