Capillary inspection of welds

Capillary methods are based on the capillary penetration of indicator liquids into the cavities of surface and through discontinuities in the material of the test objects and registration of the resulting indicator traces visually or using a transducer.

The capillary testing method is designed to detect surface and through defects in test objects, determine their location, extent (for extended defects such as cracks) and orientation along the surface.

Capillary control allows you to control objects of any size and shape, made of ferrous and non-ferrous metals and alloys, plastics, glass, ceramics, and other solid non-ferromagnetic materials.

It is used to control objects made of ferromagnetic materials, if their magnetic properties, shape, type and location of defects do not allow achieving the sensitivity by the magnetic particle method and the magnetic particle method of control is not allowed to be used according to the operating conditions of the object.

A necessary condition for the detection of defects such as discontinuity of the material by capillary methods is the presence of cavities free from contaminants and other substances that have access to the surface of objects and a propagation depth that is much greater than the width of their opening.

Capillary methods are divided into basic, using capillary phenomena, and combined, based on a combination of two or more non-destructive testing methods that are different in physical essence, one of which is capillary.

The main capillary control methods are classified:

• depending on the type of penetrating substance on:
• penetrating solutions,
• filterable suspensions;
• depending on the method of obtaining primary information on:
• brightness (achromatic),
• color (chromatic),
• luminescent,
• luminescent color.