Капиллярный контроль
Капиллярный контроль

Penetrant test is one of the main methods of non-destructive testing and is designed to detect surface and through defects in the controlled objects as well as determine their location, extent (for extended defects such as fissures, cracks) and their orientation on the surface. The penetrant test as a part of non-destructive testing (GOST 18442-80) is based on the penetration of indicator fluids inside the defect that wet the material of the object: the surface of the control and the subsequent registration of indicator traces (which is also called color defectoscopy).

In accordance with the technical requirements in most cases it is necessary to detect such small defects that it is practically impossible to notice them by means of visual inspection control with the naked eye. At the same time the application of optical instruments, for example a magnifier or a microscope, does not allow detecting surface defects due to insufficient contrast of the defect image against the background of the metal and the small field of view at large magnifications.

Dye penetrant test allows controlling objects of any size and shape made of various materials such as ferrous and non-ferrous metals, alloys, plastics, glass, ceramics, etc. Penetrant test has a wide demand for flaw detection of welded joints.

During inspection the colored penetrant is applied on the monitored surface and due to its special qualities, penetrates into the smallest defects that come to the surface of the investigated object. The developer applied to the surface of the test object dissolves the dye inside the defect and, due to diffusion, "draws" the penetrant remaining in the defect to the surface of the test object right after some time after careful removal the colored penetrant from surface. Existing defects are seen quite contrastingly. Indicator traces in the form of lines show cracks or scratches and individual points indicate the pores.

Penetrant test consists of 5 phases:

  1. Preliminary cleaning of the surface

    For the dye to penetrate into the defects on surface, the surface shall firstly be cleaned with water or an organic cleaner. All contaminants (oils, rust, etc.) any coatings (painting, metallization) shall be removed from the controlled area. After that, the surface shall be dried, so that there is no water or cleaner left inside the defect.

  2. Application of dye penetrant

    The penetrant (usually red) is applied on the surface by spraying, brushing or immersing the object of inspection in a bath, for good impregnation and full coverage with a penetrant at a temperature of 5 ... 50 ° C, for a time-period of 5 ... 30 min.

  3. Removal of penetrant surplus

    Surplus of the penetrant shall be removed by wiping with a napkin, rinsing with water or with the same cleaner as in the pre-treatment stage. In this case penetrant shall be removed only from the controlled surface, but not from the cavity of the defect. Then the surface is dried with a lint-free napkin or with air jet.

  4. Application of developer

    After drying a thin even layer of the developer (usually with) shall be applied immediately on the controlled surface.

  5. Control

    The detection of existing defects begins immediately after the end of the development process. During inspection, indicator traces shall be identified and recorded. The color intensity indicates the depth and width of the defect opening. The paler is the color, the smaller is the defect. Deep cracks have intensive colors. After the test the developer shall be removed with water or a cleaner.

Flaw-detective materials for dye penetrant test shall be selected depending on the requirements and condition imposed on the controlled object as well as conditions of the test. They are equipped in target sets which include fully or partially interconnected compatible flaw-detective materials.

Compatibility of flaw detection materials in sets or combinations is mandatory. The composition of the kit should not degrade the functional quality of the material at the monitored object. According to GOST 18442-80, the sensitivity class of the control is determined depending on the size of the detected defects. As a defect size parameter, is taken the transverse size of the defect on the surface of the inspection object, so-called defect opening width. The minimum value of detected defects is called the lower threshold of sensitivity and is limited to the fact that a very small amount of penetrant remained in the cavity of a small defect is insufficient to obtain a contrast indication at a given thickness of the developing agent layer. There is also an upper threshold of sensitivity, which is determined by the fact that from wide, but shallow defects, the penetrant is washed away by eliminating of excess penetrant on the surface.

The detection of indicator traces corresponding to the above main characteristics serves as the basis for an analysis of the defect admissibility in terms of its size, character and position.

GOST 18442-80 stipulates 5 types of sensitivity (according to minimum value) depending on defects size

Sensitivity grade

Defect opening width, mcm

  1. Less then 1
  2. from 1 to 10
  3. from 10 to 100
  4. from 100 to 500
  5. technological – no norms

Along with other physical methods (visual inspection control, X-ray inspection, ultrasonic testing, and magnetic particle test) the penetrant test is a reliable and highly effective means for detecting possible surface defects. It requires the availability of specially trained specialists, special equipment and auxiliary control means, besides, this test has special requirements for the preparation of the surface prior to control. The drawbacks of penetrant test include its high labor intensity in the absence of mechanization, the long duration of the test process (from 0.5 to 1.5 hours) as well as the complexity of mechanization and automation of the control process; decrease in reliability of results at negative temperatures; subjectivity of control in other words dependence of results reliability on the competence of the operator; limited storage period of flaw detection materials, the dependence of materials properties on storage conditions.

Some manufacturers ignore the performance of nondestructive testing of products or fulfill it only at the last construction stage right before commissioning because of finance economy or incompetence. This may lead to additional loss of time and unforeseen expenses when control is technically impossible. This attitude to quality control often leads to emergency situations in the process of operation and can lead even to technogenic disasters.

  • Statement of conformity to technical documentation requirements at the facility;
  • Certificate of NDT laboratory Attestation;
  • Certificate of NDT inspector Attestation;
  • Certificate of Equipment Verification.

Our laboratory provides the complete guarantee on all results of penetrant test.

All measuring equipment of our laboratory is itemized in state register. We offer our service throughout the territory of the Russian Federation. Attendance of NDT inspectors is possible right after confirmation of application and agreement on all nuances of magnetic particles test. The staff of our laboratory have II accreditation to provide penetrant test.

We provide an individual approach to every Client and agree with the cost of performed works. We also have a special bonus discount system for our standing customers. By ordering such a service as magnetic particles test of welded joints in our company, you can be sure that the work will be performed on time in a qualitative manner!

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