Mixed Deck — All NDT Topics Flashcards

An eddy current scan of a heat exchanger tube shows a signal whose depth reading is 80% through-wall. Per most fitness-for-service criteria, this tube should be:

Answer: Plugged or repaired immediately

Most industry standards (ASME, TEMA) require plugging or repair of heat exchanger tubes when wall loss reaches or exceeds 40–80% depending on code; 80% typically requires immediate action.

Which type of radiation has the greatest penetrating power?

Answer: Gamma rays

Gamma rays are highly penetrating electromagnetic radiation requiring dense shielding materials like lead or concrete.

At what temperature range is standard liquid penetrant testing considered valid per ASTM E165?

Answer: 50°F to 125°F (10°C to 52°C)

ASTM E165 specifies the standard temperature range for PT as 50°F to 125°F (10°C to 52°C) without special qualification.

For aerospace NDT applications, which specification is most commonly referenced for personnel certification requirements?

Answer: NAS 410 (now ATA Spec 105)

NAS 410, now superseded and aligned with ATA Spec 105, governs qualification and certification of NDT personnel specifically in the aerospace industry.

In ASME B31.3 Process Piping, what is the required volumetric examination percentage for normal fluid service welds?

Answer: 10%

ASME B31.3 requires 5% random radiographic or ultrasonic examination of welds in normal fluid service as the base examination requirement.

When using the continuous method of magnetic particle testing, particles are applied:

Answer: While the magnetizing current is flowing

In the continuous method, magnetic particles are applied while the magnetizing current is actively flowing, taking advantage of the stronger applied field rather than only residual magnetism.

After magnetic particle testing, why is demagnetization often required?

Answer: To prevent residual magnetism from interfering with machining, gauging, or service performance

Residual magnetism can attract metal chips during machining, cause erroneous compass or instrument readings, and interfere with arc welding and electronic equipment in service.

What does the term 'false indication' mean in penetrant testing?

Answer: An indication produced by poor technique or contamination rather than a true discontinuity

A false indication results from improper cleaning, poor rinsing, or contamination and does not represent an actual discontinuity in the material.

In a specific substance, the sound speed is:

Answer: Is constant

The speed of sound in a specific homogeneous material is a fundamental and constant property of that material under given conditions, such as temperature. It does not change with distance from the transducer or other factors during an ultrasonic test. This consistent speed is crucial for accurate distance measurements and flaw location in ultrasonic testing.

A 'two-man rule' in radiographic testing requires that:

Answer: At least two qualified individuals must be present during source exposure operations

The two-man rule ensures that at least two qualified radiographers are present during any exposure, providing a safety check and emergency response capability.

Which of the following personnel monitoring devices is designed to provide an immediate, real-time reading of accumulated radiation dose and often includes an alarm feature?

Answer: Electronic Personal Dosimeter (EPD)

An Electronic Personal Dosimeter (EPD), also known as an alarming dosimeter, provides a direct, digital readout of the accumulated dose in real-time. It can be set to alarm at a preset dose or dose rate, providing immediate warning to the radiographer. Film badges, TLDs, and OSLs are passive dosimeters that record the cumulative dose over a period (e.g., a month or quarter) and must be processed by a lab to be read.

What is the acoustic impedance of a material defined as?

Answer: The product of material density and ultrasonic wave velocity

Acoustic impedance (Z) equals material density (ρ) multiplied by the ultrasonic wave velocity (v), expressed as Z = ρv.

What type of crack is typically found in aluminum castings and is commonly detected by PT?

Answer: Hot tears

Hot tears form in castings during solidification when thermal stresses exceed the strength of the partially solidified metal and are readily detected by PT.

What is the purpose of a non-aqueous wet developer in liquid penetrant testing?

Answer: To draw penetrant out of discontinuities and provide a contrasting background

Non-aqueous wet developer uses a carrier solvent that evaporates, leaving a white powder coating that draws penetrant out and creates contrast.

On an impedance plane display, where does a large subsurface void typically appear relative to a surface crack signal?

Answer: Further along the resistive axis with greater phase lag

Subsurface defects show greater phase lag than surface defects because the eddy currents travel deeper before interacting with the discontinuity.

Most materials can be tested with LPI as long as the part's surface is

Answer: Is not extremely rough or porous

Liquid Penetrant Inspection (LPI) relies on the penetrant entering surface-breaking discontinuities. If the part's surface is extremely rough or porous, the penetrant can become trapped in the surface texture itself, leading to false indications or making it difficult to properly wash off excess penetrant. This can obscure actual defects or make interpretation unreliable, hence the need for a relatively smooth, non-porous surface.

During a shear wave ultrasonic inspection of a weld, the technician observes a sharp, high-amplitude signal that moves across the A-scan display as the transducer is moved parallel to the weld. The signal's amplitude changes significantly with slight angulation of the transducer. This is most characteristic of:

Answer: A planar discontinuity, such as a crack or lack of fusion.

Planar discontinuities like cracks or lack of fusion act like mirrors to the ultrasonic beam. They produce sharp, high-amplitude signals but are very sensitive to the angle of incidence. The significant change in amplitude with slight transducer angulation (rocking) is a classic sign of a planar, crack-like flaw.

According to SNT-TC-1A, which level of VT certification has the primary responsibility for interpreting and evaluating test results?

Answer: Level II

SNT-TC-1A Level II personnel are qualified to set up, calibrate, conduct, and interpret/evaluate VT results.

What type of discontinuity is most likely indicated by a broad, fuzzy magnetic particle indication?

Answer: A subsurface discontinuity

Subsurface discontinuities produce broader, less sharply defined (fuzzy) indications because the leakage field spreads as it reaches the surface above the defect.

Which of the following best defines 'calibration' in NDT practice?

Answer: Adjusting equipment settings to a known reference standard to ensure accurate measurements

Calibration is the process of adjusting or verifying NDT instrument settings against a traceable reference standard to ensure measurement accuracy and consistency.