Liquid Penetrant Testing

Liquid penetrant testing (PT) is a non-destructive testing method applied to welded joints to detect open defects such as cracks and pores on the surface. This method can be used especially in non-metallic materials or non-magnetic metals and is effective in determining defects limited to the surface.

Steps of Liquid Penetrant Testing:

Surface Preparation: The surface to be tested is cleaned. Oil, dirt, paint or other contaminants are cleaned to better detect defects.

Penetrant Application: A special penetrant liquid (usually a red-colored dye or fluorescent liquid) is applied to the surface. The liquid penetrates into open defects such as cracks or pores on the surface.

Dwelling Time: A certain period of time is waited for the penetrant liquid to completely penetrate into the defects.

Surface Cleaning: Excess penetrant on the surface is cleaned, but the liquid remaining in the defect is preserved.

Developer Application: Developer spray or powder is applied. This substance attracts the penetrant remaining in the defect to the surface, so the defect becomes clearly visible.

Inspection: Defects are examined visually or under UV light; If fluorescent penetrant is used, UV light makes the defects more visible.

Advantages:

Can be used on a variety of metal and non-metal surfaces.

Effective in detecting even very small defects on the surface.

Relatively easy and economical to apply.

Limitations:

Can only detect obvious defects on the surface, not effective on internal defects.

Cleanliness and smoothness of the surface are very important; otherwise, incorrect results may be obtained.

Liquid penetrant testing can be time-consuming and requires special care in surface preparation and cleaning.