What is one of the limitations of liquid penetrant examination?

One of the key limitations of liquid penetrant examination is that it requires a clean surface for effective results. The penetrant must be able to infiltrate the surface opening to detect flaws, such as cracks or porosity. Any contaminants like dirt, oil, or grease can prevent the penetrant from fully penetrating into these surface flaws, resulting in missed defects. Therefore, proper surface preparation is crucial; if the surface is not adequately cleaned, the examination could yield false negatives, making it a significant limitation of this method.

The other options do not accurately represent the limitations of liquid penetrant examination. For example, while it is true that penetrant testing is faster than some other testing methods, it does not necessarily contribute to the examination's effectiveness. Additionally, the technique is specifically designed for surface flaws rather than subsurface defects, and while it can be performed in wet environments, this can also create challenges in terms of cleanliness and visibility.