Sub-Surface Flaw Detection
Sub-surface flaw detection uses ultrasound to examine the volume of a component rather than its surface. Sound is introduced into the material and any internal discontinuity — a lamination, an inclusion, a crack — reflects part of the beam back to the probe, where it is measured and located by depth.
Why sub-surface flaw detection matters
Surface methods such as magnetic particle and dye penetrant are highly sensitive but only to defects that break the surface. A component can pass those inspections while carrying a substantial internal flaw. In material that is loaded in service — a forging, a heavy section, a casting — internal flaws are exactly where failures initiate, so a volumetric method is required to establish that the material is sound throughout.
What it detects
Where it is applied
- ●Forgings, castings and heavy sections
- ●Plate before fabrication
- ●Components under high cyclic load
- ●Incoming material verification
DELIVERED USING ULTRASONIC TESTING (UT)
Applicable Standards
SANS 3577-2, ISO 17640, ASME Section V
Professional Equipment
GE USM Go+ Flaw Detectors, Olympus EPOCH 650, Phased Array Systems
Common questions
Why not just use magnetic particle or dye penetrant testing?
Those methods only find defects that break the surface. They are more sensitive than ultrasound for that specific case, but they cannot see into the material at all. Where the concern is internal soundness, a volumetric method is required.
Can it tell how deep a flaw is?
Yes. Depth is derived from the time the ultrasonic pulse takes to return, so an indication is reported with its position through the thickness, not merely as present or absent.
Does the component need special preparation?
The surface must be clean enough for sound to couple into the material, and a couplant is applied. Rough or heavily corroded surfaces may need local preparation to get a reliable result.
Where we deliver it
MPIA Services is based in Durban (also known as eMkhomazi), KwaZulu-Natal, and carries out sub-surface flaw detection on site across all nine South African provinces. Mobile field units travel to the asset, so the work happens in place — on live rail corridors, in yards and depots, and at industrial sites — rather than requiring components to be sent away. See where we work.
Need sub-surface flaw detection?
Tell us the asset, the standard you need to satisfy and where the work is. We will come back with scope, timing and a quotation.
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