Problems with Class D welds
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Is 100% UT testing required for Class D ring welds that are larger than 200 mm? Especially in the case of manholes?
It doesn’t seem that such a standard requirement exists; if magnetic particle testing is required, it is usually specified explicitly in the technical specifications of the drawings
What the original poster is referring to is probably the fillet welds at the junction of the shell and other components. For such fillet welds, codes and standards require a fully penetrated weld structure in some cases; there is no requirement for non-destructive testing. Generally, 100% surface inspection is carried out for media that are highly toxic or pose a serious risk.
GB150 10.8.4.2 Ultrasonic testing: a) If the vessel and pressure-bearing components meet the requirements of GB150 10.8.2.1, grade I is considered acceptable. b) If the vessel complies with the provisions of GB150 10.8.2.2, a grade of not lower than II is considered acceptable.
Whether to conduct testing depends on two factors: 1. Drawing requirements; 2. GB150, page 128, clause 10.8.2
UT testing is usually difficult to perform; MT or PT testing is more common, and it meets the requirements of JB/T4730 with a grade of I.
For Class C and Class D weld joints on containers that comply with item c)\d) of 10.8.2.1 in GB150, magnetic particle or penetrant testing shall be carried out in accordance with the methods specified in the drawings. There was no requirement for an ultrasound examination. The tolerance specifications also do not require ultrasonic testing; however, some designs specify higher requirements, indicating in the drawings that UT testing is necessary. UT can only be applied to fillet welds with a throat angle greater than 200, and it is difficult to perform this on small throats; in fact, it’s not possible at all for such cases
GB150 10.8.4.2 Ultrasonic testing: a) If the vessel and pressure-bearing components meet the requirements of GB150 10.8.2.1, a grade of I indicates compliance. Ultrasonic testing is often not convenient to use; instead, MT or PT testing is typically employed. Compliance with JB/T4730 also results in a grade of I as satisfactory
I took a closer look at 150; thank you all for your help to me
1. The butt welding joint formed by the connection of a butt-welded flange and a pipe fitting is a Class B welding joint； 2. Joints connecting to the shell, such as nozzles, manholes, flanges, and reinforcement rings, are classified as Class D welding joints ； 3. For equipment that requires 100% non-destructive testing or has special requirements specified in the drawings, Class D weld joints must undergo 100% PT or MT testing, with the acceptance level being Grade I ； 4. Since the main pressure-bearing components are restricted to pipes with a \"nominal diameter greater than 250 mm\", the non-destructive testing of such pipes is conducted in accordance with these guidelines.