ASNT VT Level III flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Visual testing definition

A nondestructive method in which light is used to examine a surface for discontinuities, relying on the observer's vision, illumination, and contrast.

Angular resolution of eye

The unaided human eye resolves about one arc minute of angular separation, which sets the practical limit of detail visible without magnification.

Contrast and detectability

Detection requires a luminance difference between indication and background; higher contrast and adequate illuminance increase the probability of detection.

Specular versus diffuse reflection

Specular surfaces reflect light directionally and can cause glare; diffuse surfaces scatter light and provide more uniform contrast for inspection.

Oblique lighting purpose

Directing light at a low angle to the surface enhances shadows from surface relief, improving visibility of shallow scratches and cracks.

Color vision requirement

VT personnel need normal color perception because color-blind observers may fail to distinguish color-contrast indications; testing is required by certification programs.

Illuminance unit lux

Lux is lumens per square meter; one footcandle equals about 10.76 lux, and surface illuminance governs visual detectability.

Cosine correction

Light meter photocells are cosine-corrected so their response matches the angle of light incidence on the surface being measured.

Magnifier power tradeoff

Higher magnifying power increases detail but reduces field of view and depth of field, so power is matched to the inspection task.

Borescope versus fiberscope

Rigid borescopes give better image quality but require straight access; flexible fiberscopes reach curved paths at some loss of resolution.

Videoscope resolution check

Camera-based systems must have resolution and field of view sufficient to detect the smallest required discontinuity; verify against a documented criterion.

Surface comparator use

Comparator specimens or surface finish standards let the inspector judge acceptability of surface condition against a documented reference.

Direct visual testing

The observer views the surface directly, typically within about 600 mm and at an angle of at least 30 degrees to the surface.

Remote visual testing

Inspection using borescopes, fiberscopes, or cameras when access or distance prevents direct viewing; lighting and resolution must be documented.

Translucent testing

Transmitted light through a translucent material reveals internal flaws such as cracks or inclusions in glass, plastics, and thin sections.

Surface preparation in VT

Cleaning and removing coatings or scale before inspection prevents masking of discontinuities and avoids false indications from surface debris.

VT procedure contents

A written procedure specifies illumination, viewing distance and angle, magnification, surface condition, equipment, and acceptance criteria.

Scanning overlap

Adjacent fields of view should overlap during scanning so no area is missed between successive passes of the inspection pattern.

Near vision acuity test

VT personnel demonstrate near vision acuity, often Jaeger 1 or equivalent, and color perception, with periodic re-examination per the program.

Crack appearance in VT

Cracks typically appear as sharp, dark linear indications; length and orientation are measured and compared with the acceptance limit.

Acceptance criteria source

Rejectable limits come from the governing code or standard, such as AWS D1.1 or ASME, not from the inspector's personal judgment.

Relevant indication

An indication caused by an actual discontinuity that must be evaluated against acceptance criteria; non-relevant indications arise from geometry or finish.

Corrosion evaluation

Corrosion and erosion are assessed by depth and extent, often using pit-depth gauges or comparators, then compared with allowable limits.

False indication confirmation

Changing illumination angle or cleaning the surface helps confirm whether an apparent indication is a true discontinuity or a lighting artifact.

Coating masking effect

Coatings and surface condition can hide discontinuities, so localized removal or preparation may be required before visual inspection.

SNT-TC-1A purpose

A recommended practice for employer-written qualification and certification programs; the employer is responsible for certifying NDT personnel.

CP-189 versus SNT-TC-1A

ANSI/ASNT CP-189 is a standard, more prescriptive than SNT-TC-1A, covering qualification and certification of NDT personnel.

Level III responsibilities

Level III duties include procedure development, technique selection, standards interpretation, and training and qualifying lower-level personnel.

Certification examination types

Certification requires passing general, specific, and practical examinations for the method, plus documented training hours and experience.

Governing document identification

The Level III must identify which code or standard applies to each job, since acceptance criteria and methods differ between documents.

Recertification requirement

Recertification typically requires periodic re-examination or documented continued satisfactory performance, as defined by the certifying program.

Ethics in NDT reporting

Level III personnel must avoid conflicts of interest and report results accurately and objectively, documenting findings without bias.