PAUT on wind turbine blades: what the C-scan actually shows
A visual inspection tells you what the blade looks like. Ultrasonic testing tells you what is happening under the surface, where the expensive damage starts.
What PAUT does differently
Conventional ultrasonic testing (UT) uses a single beam. Phased array testing (PAUT) uses a probe with many elements, fired in sequence, so one pass covers a band of material. Combined with position encoding, the data becomes a map of the inspected area and not a list of single readings.
What a C-scan shows
Think of it as a plan view of the laminate. Each point is coloured by signal amplitude or by depth, so sound material appears as an even field and an anomaly stands out as a change in colour or depth, with its position and size visible.
On composite blades, typical targets are:
- Delamination between laminate layers
- Disbonds and voids in bonding lines
- Condition around shear webs and spar caps
- Damage under the surface after a lightning strike
Where the limits are
Composite material scatters and attenuates sound much more than steel. Thick laminates, carbon areas, core materials and rough surfaces all reduce what the method can see. Good results need a reference block that matches the laminate, stable coupling and a clean surface. On an installed blade, access decides whether all of that is possible, which is why rope access matters here.
What a useful report contains
The report should state the method, equipment and calibration, the location and severity of each finding, photos, and a recommendation. Acceptance is judged against client or OEM criteria by EN ISO 9712 qualified personnel.
Our inspectors are rope access technicians, so UT and PAUT come to the blade, tower or tank without scaffolding.
