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Methods of non-destructive testing（5）

Release time:

Mar 24,2025

Methods of non-destructive testing（5）

 

This article focuses on PT，Other non-destructive testing methods will be introduced in subsequent articles.

Penetration testing (PT): a “catcher” of surface opening defects

        Penetrant inspection is to use the principle of capillary action of liquid, the penetrant containing color dyes or fluorescent agents coated on the valve surface. If there are open defects on the valve surface (e.g. cracks, porosity, porosity, etc.), the penetrant will penetrate into the defects by capillary action.

 

     The excess penetrant is then removed from the valve surface and a visualizer is applied . The developer will adsorb the penetrant from the defects, and under a suitable light source (e.g., natural or ultraviolet light), the defects will show a different color or fluorescence from the surrounding background, making the defects clearly visible . This is like applying a layer of “developer” to surface opening defects so that they have no place to hide.

 

        Penetration testing is suitable for detecting surface opening defects of various non-porous materials (such as metal, ceramics, glass, etc.). In the inspection of valves, whether metal or ceramic valves, as long as there are surface opening defects, penetration testing can be effectively detected.

 

        It has the advantages of simple operation, low equipment cost, and is applicable to valves of various shapes and sizes . Moreover, the detection results are intuitive and easy to determine the location and shape of the defects. However, penetration testing can only detect surface open defects, but not internal defects or surface closed defects.

 

        In addition, the valve surface needs to be strictly cleaned and pre-treated before inspection to ensure that the penetrant can fully penetrate into the defects . At the same time, the penetrant and developer used in the inspection process may have a certain degree of harm to the environment and human body, need to pay attention to protection and proper disposal.

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