Regarding the surface inspection of heads under the Fixed Capacity Regulations
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Due to my ongoing doubts regarding the surface inspection requirements for heads as specified in the Fixed Volume Regulations, I posted a question on the website of the General Administration of Quality Supervision, Inspection and Quarantine. Finally, I received a response; however, after reading it, I had another question: \"If for containers that require either radiographic or ultrasonic testing, it is necessary to conduct surface non-destructive testing on the joints formed after the panels are assembled to create the convex head, then why isn’t it required that surface non-destructive testing be carried out on all such joints right from the start?\" ” Query Number: 20101231-1736-13748] http://tzsbaqjcj.aqsiq.gov.cn/gzly/lyhf/index_2.htm Question: Dear leaders of the General Administration, hello. The first amendment to the new regulations adds the following in section 4.5.3.2.4 on surface non-destructive testing: “For welded joints that meet one of the following conditions, their surfaces shall be subjected to magnetic particle or penetrant testing using the methods specified in the drawings: (6) All weld joints on the convex heads of containers for which local radiographic or ultrasonic testing is required, after the panels have been assembled.” ”I would like to ask: 1. Does surface inspection involve checking the inner surface of the head, the outer surface, or both? 2. For containers that require full radiographic or ultrasonic testing, can the joint at the convex head formed by panel assembly be omitted, thereby avoiding surface non-destructive testing? 3. For containers that require partial radiographic or ultrasonic testing, the joints on the convex heads should be fabricated by panel assembly first; the level of radiographic testing should be increased to 100% testing. After meeting Grade II requirements, is it then possible to omit surface non-destructive testing? Looking forward to your reply. Thank you! Answer: 1. Both sides should be processed when conditions permit ； 2. No ； 3. Increasing the proportion of radiographic testing cannot replace surface non-destructive testing.
1. First, adding surface inspection to the head is intended to prevent defects on the weld surface or potential defects that might arise as a result of compression, leading to an enlargement of such surface defects. 2. “Why not simply require that all weld joints on the convex heads, which are first assembled into panels before being shaped, undergo surface non-destructive testing?” ” According to the reply, surface testing is also carried out even with 100% inspection; I’m wondering why it isn’t required that all joint connections on the convex heads, which are formed after panel assembly, undergo surface non-destructive testing. Is it because of certain special circumstances? Such as the dome-shaped head in floating-head heat exchangers? Or a pressure vessel at normal pressure? Another explanation is this: since 20% of cases require table exploration, then 100% certainly also need it – there’s no need to emphasize it! ! Hehe, those are just my personal opinions~
I went to check the reply from the General Administration. Haha. According to them, I personally think it would be sufficient to simply state that all joint connections on convex heads that are first assembled into panels before being shaped should undergo surface non-destructive testing – why go to the extra trouble?
I have learned about this, and I agree with what the original poster said: The equipment heads manufactured by my company are also formed through panel assembly, after which the welds are subject to 100% RT inspection as well as 100% surface inspection (Note: For head weld joints, a factor of 1 is used, or full flaw detection is required for such heads)
Who can explain why surface inspection is necessary in this case? To be honest, the new appearance regulations are a tragedy. Alloy steel welding joints also require surface inspection. What is alloy steel? Are 10 steel and 20 steel considered dissimilar steels? “(6) In vessels requiring local radiographic or ultrasonic testing, all butt joints on the formed convex head shall be welded after the plates are assembled. ” According to normal logical reasoning, how can this statement lead to the conclusion that “for welded joints on convex heads that are assembled prior to forming in vessels requiring full radiographic or ultrasonic testing, non-destructive surface testing must also be performed”? ”? If this requirement is reasonable, then why not change the clause to: “all joint connections on all convex heads that are first assembled as panels before being formed”? It can be interpreted, but not imagined arbitrarily! Using such word games to deceive us – is that considered skill or what?
If such specific technical requirements are not mentioned in the Code, it might be better to specify them in product standards such as GB150. Just one year after the new code was issued, an amendment was released, which shows a move toward alignment with international standards; don’t ASME standards also have supplements issued every year? If there are issues with the tolerance specifications, they can still be modified. The bigger problem is that the new version of GB150 keeps not being released. Perhaps the Pot Capacity Standards Committee is afraid of being criticized, which is why it dares not release a new version.
Poster: I couldn’t find the First Amendment to the New Capacity Regulations on the General Administration’s website
Can those who consider themselves standard be a little more serious?! Let’s see which **standard is better, and then copy the entire text!
Is it necessary to make such a request? Have there been similar accidents before? Otherwise, wouldn’t it be a waste of resources?
Reply to 6# yaoyongyoyo: Surface inspection is also required for welded joints of dissimilar steels. What are dissimilar steels? Are 10 steel and 20 steel considered dissimilar steels? Answer: The difference between different types of steel should be between carbon steel and low-alloy steel. Steels such as 20 steel, Q235B, and Q345R are dissimilar steels. 10 steel and 20 steel are the same type of steel.
In fact, surface inspection cannot be replaced by radiographic or ultrasonic testing. I think all welded joints that undergo RT or UT should be subjected to surface inspection. Isn’t this what’s meant by different non-destructive testing methods complementing each other? However, some of the requirements of the new regulations are indeed difficult to understand. Do learned people all like this, perhaps? It’s to show that one’s level is different from that of those who just look at the standards, right?