B-Scan (Brightness-Scan) — Definition & NDT Use
A two-dimensional cross-sectional display of ultrasonic data showing depth (vertical axis) and distance along the scanning path (horizontal axis), with signal amplitude represented by brightness. B-scans provide visual representation of internal material structure and defect locations within a vertical plane. This presentation mode is more intuitive than A-scans and helps visualize the exact position and extent of discontinuities within the material thickness.
From the inspector's bench, B-Scan is run as a defined sequence: equipment verification on a known reference, scan setup against the procedure, scanning the part, and writing the indications into the report. Procedure writing, inspector qualification, and the reference block establish the chain that lets a remote engineer trust an indication called a kilometre away from the office.
B-Scan is selected when the failure mode the engineer cares about — surface crack, internal void, wall loss, lack of fusion — lines up with what the technique is physically capable of detecting.
- Etymology / Origin
- B for 'brightness' display; carried over from medical ultrasound notation where pixel brightness encodes echo amplitude.
- Formula
- Image is built by stacking A-scans along the scan axis x; pixel intensity I(x,t) = |A(x,t)|.
- Units
- Horizontal axis in scan distance (mm); vertical axis in time (µs) or depth (mm).
- Typical Range
- Encoder pitch 0.5–2 mm typical for manual scanners; resolution limited by transducer beam width and pulse length.
- Measured / Produced By
- Encoded pulse-echo UT scanner with a wheel encoder, or a phased-array probe scanned mechanically.
- Code References
- ASME Section V Article 4 Mandatory Appendix VIII (PAUT); ISO 16811 (sensitivity setting)
- Worked Example
- A 100 mm scan with 1 mm encoder pitch produces 100 A-scans; a 5 mm linear flaw aligned with the scan axis appears as a 5-pixel-wide bright stripe at its time-of-flight.
ASME Section V Article 4
Ultrasonic examination methods for welds and components.
ASTM E114 / E164 / E2375
ASTM straight-beam, contact, and wrought-product UT practices.
ISO 16810 / ISO 16811
General principles and sensitivity setting for industrial UT.
The most expensive mistake with B-Scan is treating it as a yes/no test rather than a characterisation — an indication called without a sizing strategy forces a repair where a fitness-for-service review might have left the part in service.
What does "B-Scan" mean in NDT?
A two-dimensional cross-sectional display of ultrasonic data showing depth (vertical axis) and distance along the scanning path (horizontal axis), with signal amplitude represented by brightness. B-scans provide visual representation of internal material structure and defect locations within a vertical plane
Which standards govern the use of B-Scan?
B-Scan is most often referenced under ASME Section V together with the relevant ASTM practice or the matching ISO standard for the method; the contract or purchase order will name the controlling document and edition for any specific job.
What other NDT concepts should I read alongside B-Scan?
The most directly related entries in this glossary are "a scan", "c scan", "cross section"; reading those together gives you the surrounding vocabulary used in inspection reports and procedures.