Proportion of weld inspection for the inner cylinder of jacketed vessels
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Paragraph b) of 10.3.2 Local radiographic or ultrasonic testing in GB150.4-2011: Welded joints that are covered by gussets, supports, shims, internal components, etc； According to the regulations, 100% inspection is required for this area. My question is: for the inner cylinder of a jacketed pressure vessel, if 20% RT inspection is required for the inner cylinder, then do the Class A and Class B welds on the inner cylinder that are covered by the jacket fall under the scope of these regulations regarding welded joints that require 100% inspection? There are currently two views. The first is 20%; the reason is that the inner cylinder has undergone all necessary inspections before the jacket is fitted on it, including pressure testing and leak testing, and all such procedures have been completed. It can therefore be regarded as a complete structural unit. This differs from the current arrangement, under which the welds are covered before the equipment is fully constructed, which makes it impossible to detect any leaks that may occur during pressure testing or leak testing ； II. 100%, Reason: Since it is covered, it should be 100%. May I ask, which view is the correct one? I hope everyone will discuss this; if there are any references, it would be good to provide them. Thank you
While prioritizing quality leads to a significant increase in costs, key equipment is necessary, whereas regular equipment is not that important. I think there should be some basis for this; what were the considerations of those who formulated it in the first place? It’s not just a quality issue, right? If it were about quality, then all those with jackets would be 100% perfect, wouldn’t that be better?
You also mentioned critical equipment and regular equipment; this reflects the level of risk acceptability. Which one is key? Which routine? By sorting this out, it will be clear whether it’s 100% FULL or 20% RANDOM.
For key equipment, 100% has been taken into account in the design of the inner cylinder; since 20% is specified for the inner cylinder, the requirements regarding the equipment generally shouldn’t be that important. Since the standard sets this requirement but doesn’t specify it clearly, different opinions arise, with everyone having their own reasoning, haha
It’s a personal opinion; considering both the medium inside the inner cylinder and the jacket, it’s up to the designer to decide!
For the Type A and Type B welds of the inner cylinder covered by the jacket, clause d) of Section 10.3.1 on all radiographic or ultrasonic testing in GB/T150.4-2011 shall be applied:
Typical reaction vessels are equipped with manholes that allow for internal inspection. Condition d) represents a situation where internal inspection is not possible; and even if internal inspection were feasible, would 100% coverage still be required?
If designed this way, it won’t pass the inspection by the special inspection agency.
Yes, different places have different understandings; some allow it while others don’t