Visual inspection is one of the non-destructive examination (NDE) disciplines and for some applications may be the only form.

For more demanding service conditions, visual inspection is usually followed by one or more of the other non-destructive testing (NDT) techniques – surface crack detection and volumetric inspection of butt welds.

Conditions for visual inspection


ISO 17637 states that the minimum illumination shall be 350 lux but recommends a minimum of 500 lux (normal shop or office lighting).


Access to the surface for direct inspection should enable the eye to be:

  • Within 600mm of the surface being inspected.
  • In a position to give a viewing angle of not less than 30°. 600mm (max.)