Non-destructive testing for butt joints of fittings with a diameter less than 250 mm.
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According to Article 88 of the Code for Pressure Vessels: for vessels with a nominal diameter of less than 250 mm and a wall thickness of 28 mm or less, only surface non-destructive testing is required, and the acceptable quality level is Grade I as specified in JB4730. Can it be understood that all butt-welded flanges with a diameter of less than 250 mm are subject to surface non-destructive testing, with the acceptance standard being Grade I as specified in JB4730 (including: low-pressure equipment, and the welds at the joints of elbows and fittings)?
No, surface non-destructive testing is required only when the relevant conditions are met; see GB150 10.8.2.1 and 10.8.3
It should be understood that when non-destructive testing is required, only surface testing can be performed. It can be omitted when no testing requirements are present.
Thank you to all the teachers for their guidance. It seems I still need to study this standard more carefully by looking at it several times.