CWI NDE Methods and Symbols 2 — Questions and Answers
Question 1: Which NDE symbol on a weld drawing indicates that liquid penetrant testing should be performed?
- PT (Correct answer)
- MT
- UT
- RT
Correct answer: PT
PT is the AWS standard abbreviation for liquid penetrant testing used in NDE symbols on weld drawings.
Question 2: In ultrasonic testing, what does the term 'dead zone' refer to?
- The region near the transducer face where defects cannot be detected (Correct answer)
- An area with no acoustic coupling
- A zone where the beam diverges completely
- The area beyond the far field
Correct answer: The region near the transducer face where defects cannot be detected
The dead zone is the area directly beneath the transducer where ringing from the initial pulse masks any near-surface reflections.
Question 3: Which type of radiographic film has the finest grain size and highest resolution but requires longer exposure times?
- Class I (fine grain) (Correct answer)
- Class II (medium grain)
- Class III (coarse grain)
- Class IV (ultra-fast)
Correct answer: Class I (fine grain)
Class I fine-grain films produce the highest resolution images but require longer exposures because they are less sensitive to radiation.
Question 4: When performing magnetic particle testing, what is the purpose of the 'residual method'?
- Testing is done after the magnetizing force is removed, relying on retained magnetism (Correct answer)
- Testing is done while the magnetizing current is still flowing
- Testing is performed using permanent magnets only
- Testing that uses residual flux from previous welding
Correct answer: Testing is done after the magnetizing force is removed, relying on retained magnetism
The residual method applies particles after removing the magnetizing force, and works only on materials with sufficient residual magnetism (high retentivity).
Question 5: In liquid penetrant testing, what is the correct sequence of steps?
- Precleaning → Penetrant application → Dwell time → Excess removal → Developer → Inspection (Correct answer)
- Penetrant application → Precleaning → Developer → Inspection → Removal
- Precleaning → Developer → Penetrant application → Inspection
- Penetrant application → Developer → Dwell time → Inspection
Correct answer: Precleaning → Penetrant application → Dwell time → Excess removal → Developer → Inspection
The correct LP sequence is precleaning, penetrant application, dwell time, removal of excess penetrant, developer application, then inspection.
Question 6: On a weld NDE symbol, where is the arrow-side designation placed relative to the reference line?
- Below the reference line (Correct answer)
- Above the reference line
- To the left of the tail
- Inside the weld symbol triangle
Correct answer: Below the reference line
Per AWS A2.4, NDE requirements placed below the reference line apply to the arrow side of the joint.
Question 7: What is the primary advantage of phased array ultrasonic testing (PAUT) over conventional UT?
- The beam angle and focus can be electronically steered without moving the probe (Correct answer)
- It uses X-rays instead of sound waves for better resolution
- It eliminates the need for couplant
- It can detect defects in non-metallic materials only
Correct answer: The beam angle and focus can be electronically steered without moving the probe
PAUT uses multiple elements fired in sequence with controlled time delays, allowing electronic beam steering and focusing without mechanical probe movement.
CWI NDE Methods and Symbols 2
Which NDE symbol on a weld drawing indicates that liquid penetrant testing should be performed?