L-Scan (Linear Scan)
An L-scan is a phased-array ultrasonic image produced by electronically stepping a fixed-angle beam along the array aperture, generating a side-by-side series of A-scans at constant angle and varying position.
Definition
The Linear scan (L-scan) keeps the beam angle constant and steps the active aperture along the array, producing a series of A-scans at successive positions without physically moving the probe. The result is equivalent to a mechanized raster scan but acquired instantaneously.
Technical Context
L-scans are widely used for corrosion mapping with a 0° beam and for weld inspection with a 45°, 60°, or 70° angle.
What it represents
A linear scan display in phased array work, where the focal law steps the active aperture along the probe at a fixed angle, producing a cross-sectional view along the probe length rather than a fan of angles from one point.
How it is derived
Suited to thickness profiling and to examinations where a single angle is appropriate across a width — corrosion mapping and some weld configurations. Distinct from the sectorial S-scan, which sweeps angle from a fixed aperture.
Where it is defined
ASME Section V Article 4 phased array appendices; ISO 13588 display and recording requirements.
How it is misread
Reporting an L-scan as though it swept angles. Coverage in a linear scan is at one angle only; flaws requiring a different angle are simply outside what that scan interrogated.
Where L-Scan fits in an inspection programme
A term is only useful when it connects to a decision. L-Scan appears in written procedures, in technique sheets, and in the records an owner or accreditation body reviews afterwards — which means the way it is defined in your documentation has to match the way it is applied on site. Where the two drift apart, audits find it. Atlantis writes and reviews procedures against the governing codes, trains inspection personnel to apply them, and builds the record-keeping that makes the evidence retrievable years later. Procedure development and code consulting · NDT training and certification · Ask us about your programme.
Related terms
- S-Scan (Sectorial Scan) — An S-scan is a phased-array ultrasonic image showing a fan of beams swept through a range of angles from a single probe position, displaying defect indications across the angular range in a single view.
- Phased Array Ultrasonic Testing (PAUT) — PAUT is an advanced ultrasonic technique using a multi-element transducer (16–256 elements) with electronic beam steering and focusing, producing sectorial, linear, and compound scans for superior weld inspection and defect characterization.
More data terms
A-Scan · B-Scan · C-Scan · D-Scan · Distance-Amplitude Correction · Distance-Gain-Size · Time-Corrected Gain · Gating · Decibel · Indication
Where this comes up in practice
Terms like this one appear in three places that matter commercially: the written practice that governs how your personnel are qualified, the procedures and technique sheets that define how an examination is actually performed, and the evidence an auditor or client asks for when they want to know why an inspection was accepted. Getting the terminology right is the easy part; being able to produce the qualification record, the calibration traceability and the procedure revision that applied on the day of the inspection is the part that decides audits.
Atlantis NDT provides NDT training and certification against ASNT SNT-TC-1A and ISO 9712, ASNT Level III consulting for written practices and procedure approval, inspection management software that holds qualification, calibration and procedure-revision evidence in recoverable form, and an asset integrity platform that binds inspection results to the asset they describe. Browse the full NDT glossary or ask a Level III directly.