RT - the most commonly used method. It deals with the so called “volume method” (it shows defects in the whole volume of material.) Checks detect defects of all their characters (pores, metal and non-metallic inclusions, cracks, cold welded joints.) The method is based on registering weaker ionizing radiation going through material. RT check is time consuming (processing RT photographs) space demanding (it is necessary to protect the vicinity from used ionizing radiation.) The imperfection of the method is that the defect, whose dimension in the direction of the passing radiation is minimal (e.g. crack, cold welded joints, oriented flatways), does not have to be detected – reduction of radiation is so small that it is not registered. The advantage is the permanent and unchangeable record of the checked area accepted by all third party organizations.

UT – volume method partly replacing or complementing RT check. The principle of the check is based on emitting a beam of UT waves into the material and scanning their reflection (respectively passage.) The beam of UT waves reflects off the boundary of individual materials (in pores, cold welded joints, cracks the boundary metal – air, in inclusions the boundary metal – material of inclusions.) The recorded reflections are made visible on the screen of the device. The disadvantage is high demands on practise and experience of its operator with the evaluation of displayed reflections. There is no record when the standard check is done. Technically advanced testing devices are able to provide us with records using 3D pictures, but this record is usually not accepted by third party organizations.

MT – surface method (it reveals defects communicating with the surface or situated in its close proximity.) Just the surface of the component is checked. In the tested item we energize magnetic field whose lines of force appear on the surface in the area of the defect. The protruding lines of force are made visible by the colourful or fluorescent magnetic powder in liquid suspension.

PT – surface method indicating only defects communicating with the surface. Colourful or fluorescent highly capillary liquid is applied on the tested surface and it penetrates the surface which is not compact for the appointed time. After the time passes the liquid is removed from the surface and a subtle layer of absorbent undercoat is applied. The penetration liquid is sucked by this undercoat from the surface which is not compact.

VT – surface check which is based on monitoring the surface and searching for defects which are visible on the surface. What belongs to them is for example lack of fusion, cracks and cold welded joints which appear on the surface, undercuts, the shape which does not correspond to its welded vertical distance, roughness or the condition of the component’s surface.

All the above mentioned checks are carried out by our own certified staff at least at level L II in compliance with the standard ČSN EN ISO 9712 and L II in compliance with SNT-TC-1A with substantiated and time-tested knowledge and long-time experience in the branch.

defectoscopy laboratory

© 2014 NDT Surman

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