Issues regarding non-destructive testing of the surface of end caps
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Requirement 6 of 4.5.3.2.4 Surface Non-Destructive Testing in TSGR0004 Fixed Volume Regulations stipulates that for vessels requiring local radiographic or ultrasonic testing, all joints at the convex head shall be assembled first before the head is formed； Since the splice joint has been tested at 100% RT, is it still necessary to conduct a surface inspection? How do your colleagues understand this clause?
I think it is necessary, because even if a part passes the RT test at level II by 100%, there may still be defects permitted under the criteria for level II RT testing, such as through-holes perpendicular to the weld seam (porosity) or near-surface defects. Therefore, add surface inspection as an additional control measure.
Surface crack defects may occur during the head forming process
This is a mandatory requirement that must be followed. It has nothing to do with radiographic testing or ultrasonic testing...
I agree with the view from the 4th floor; this is stipulated by the standards and must be followed.
No. 1. The reason is not that standards require it to be done, but rather that surface inspection cannot be covered by volume inspection. Each testing method has different focuses and advantages, as well as respective disadvantages; for example, RT is unable to detect the microcracks that are visible in the linear patterns detected by PT, while PT cannot identify internal defects that do not have surface openings. If RT covers PT and no microcracks are detected, crack propagation after service is likely to result in a major accident. 2. This is also a misconception regarding non-destructive testing; it cannot be simply assumed that volume-based testing methods, such as UT and RT, are more advanced than surface-based testing methods, such as PT and MT. Different testing methods are designed to detect different types of defects, and it is only by combining them that the quality can be ensured to the greatest extent possible. Typically, design and manufacturing inspections also require a combination of volume inspection and surface inspection.
Agree with what was said on the first floor; both the interior and the surface need to be inspected
Based on the material properties, if there is a risk of deformation cracks, then PT and MT should be performed
Yes, the items checked are different, but all are aimed at ensuring quality.