On the applicability of dye penetrant tests on vacuum components: Allowed or forbidden?

Abstract

The penetrant testing (PT) is a common non-destructive procedure for the testing of components and in particular of welds. With PT it is possible to detect surface imperfections (e.g. cracks) which have a special potential to lead to the failure of the component or of the weld. PT is substantially more sensitive than a purely visual examination.Because the complicated geometries of fusion experiments make the accessibility for repairs during the operation extremely difficult, very high efforts on testing with sensitive procedures, for instance with dye penetrant testing during assembly is required. In contrast to this desire for widespread penetrant testing, however, is the general fear that dye penetrant tested components or welds, which are used in the vacuum, are contaminated by the dye in such a way that they do not fulfill the cleanliness requirements for vacuum components. Therefore dye penetrant testing of such vacuum components is usually considered problematic.This study aims to clarify the applicability of dye penetrant tests on components exposed to high-vacuum. Recommendations are formulated concerning the PT procedure of vacuum components and the cleaning procedures for penetrant tested areas under vacuum necessary after a dye penetrant test.Keywords: dye penetrant testing, vacuum component, UHV, NDT BackgroundFusion experiments are complex equipments with often complicated geometry. It is desirable to operate the machines over long time periods without shut-down interruptions for repair or service. If there are interruptions of the regular experiment operation, the search for failures and the repair will be very difficult and extensive in time and costs. To avoid these kinds of breakdowns, a strong effort on quality control is necessary like e. g. non-destructive testing procedures during the manufacturing of components and its assembly. Beside the visual examination (VT), the method of penetrant testing (PT) is often most common non-destructive procedure for the testing of surfaces of components and in particular of welds.In contrast to this desire for widespread penetrant testing, however, there is the general fear that components or welds tested with the dye penetrant and which are used in the environment of cryo-vacuum and particularly in the ultra-high vacuum conditions are contaminated by the dye in such a way that they do not fulfill the cleanliness requirements for vacuum components. This fear is mainly based on the high penetrating property of the dye and its particular creeping characteristics, which just is the property required for the test procedure. After the penetration test, however, the penetrant dye may remain in cavities like porosities or in cracks and might cause virtual leaks during the evacuation and in the vacuum, due to extended outgassing. As the penetrant dye primarily consists of hydrocarbons, which are considered critical for outgassing in fusion devices, a penetrant test of such vacuum components is usually considered problematic.In this investigation we try to quantif...

Self-Loosening Failure Analysis Considering Vibration Frequency: Experimental Study for the Spare Tire Carrier

“…A visual investigation was conducted with a penetrant fluid to determine whether the components cracked or not after the test [34]. The penetrant fluids perform crack checking, a non-destructive test that several researchers have suggested and widely used [35,36]. These checks confirm the presence or absence of cracks and observe the deformation of the parts in contact as the vibration occurs [37,38].…”