Weld defect issues
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What should be done when the design drawings require 20% RT for Class A and B welds, but RT or PT is not possible for a jacketed vessel with δ=6?
For jacketed vessels, the jacket can be manufactured first, along with 20% RT or PT welding at the longitudinal and circumferential seams (of course, one end must be left free for the inner cylinder to be fitted). The inner wall of the last ring seam after fitting must not be PT ； Its RT may also not be clear; quality must be ensured through welding techniques.
Magnetic particle testing can be considered first, followed by hydraulic or airtightness testing.
From a welding perspective, it is necessary to ensure that TIG welding is used for the root pass, with a fully penetrative weld structure; for inspection, methods such as ultrasonic testing, coloring, or magnetic particle testing can be employed.
Use UT instead; for those cases where RT is not possible due to structural reasons, UT can be used as a substitute, and most customers will accept this
Only the last circumferential weld cannot be inspected, and it is not practical to use UT instead of RT for plates with δ=6. The argon arc backing welding process should be used to ensure full penetration.
What was said upstairs is correct; I’ve encountered similar problems as well:(