Non-destructive testing of butt joints with DN＜250mm?
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This post was last edited by ztr1118 on 2012-3-20 06:53 ——Understanding and implementation of the provisions in standard GB151.4-2011 ——Non-destructive testing for butt joints with DN＜250mm? GB151.4-2011, Clause 10.3.3: The inspection requirements for pipe fittings with a nominal diameter DN < 250 mm, as well as for joints formed by the connection of pipe fittings and high-neck flanges, shall be in accordance with the provisions specified in the design documents. Article 10.4: Surface inspection Welded joints that meet one of the following conditions require surface magnetic particle or penetrant inspection in accordance with the methods specified in the drawings: a) …… …… h) Joints where tubes are butted together or tubes are butted to high-neck flanges, and whose nominal diameter DN is < 250 mm, on containers for which full radiographic or ultrasonic inspection is required ； …… Based on the above provisions, can it be understood that: if the design documents do not specify anything and the situation does not fall under item h) of clause 10.4, then pipe fittings with a nominal diameter of DN < 250 mm, as well as joints formed by the connection of pipe fittings and high-neck flanges, do not require non-destructive testing (including radiographic, ultrasonic, and surface testing). Addition: Except as provided in clauses a), c), and d) of Article 10.4 of GB151.4-2011, and as otherwise specified in the Code for Fixed Pressure Vessels (2009).
Firstly, because fittings and flanges with a DN < 250 do not constitute primary pressure-bearing elements. Secondly, performing RT testing on such small tubes is relatively complicated; yet they are still considered pressure-bearing elements, so the quality of their butt welds must also be ensured. In environments where the working conditions are not severe, a simple surface inspection may suffice, but in cases involving hazardous substances, high pressures, or other harsh operating conditions, it is necessary to carry out RT testing either by inspecting small sections one by one or through double-wall transmission testing
As can be seen from the provisions of GB150 and the Code for Fixed Pressure Vessels, requirements have been established for important equipment, as well as for equipment made of relatively special materials or under special conditions； Therefore, except as specified and required by the drawings, no non-destructive testing is necessary, and the quality is the responsibility of the manufacturer.
Guuu~~(╯﹏╰)b..... What was said upstairs is correct. Our company tends to be conservative when it comes to weld inspection; what needs to be done must be done, but what isn’t necessary can also be skipped
We are in the container manufacturing industry, and we place great emphasis on an understanding of standards. The requirements specified by the standards must be met. When customers (including inspectors employed by them) have misunderstandings regarding the standards, we need to persuade them based on those standards. In product manufacturing and acceptance, when customers submit requests that exceed the standards, we can meet those requests if it is possible to do so through effort without incurring significant additional manufacturing costs. When it is not possible to meet the customer’s requirements, it is necessary to communicate with the customer, explain the reasons, and argue based on logic. Excess product quality means increased costs and reduced profits. Everyone understands this principle.
There are quite a number of cases related to 10.4 in GB150.4, and these need to be addressed one by one during design. The low-temperature scenario mentioned under a might be easily overlooked; after all, it applies not only to the weld itself. There is also controversy on the forum regarding 10.4 i) – the surface inspection of end caps that are first assembled and then formed through radiographic/ultrasonic testing. Our company still conducts surface inspection on end caps that have passed 100% RT testing; I’m not sure whether this is mandatory, but it is likely based on the provisions of 10.4i).
This post was last edited by ztr1118 on 2012-3-21 at 10:31. According to GB150.4-2011, for the joint connections on the convex end caps of vessels that require full radiographic or ultrasonic testing and are formed after panel assembly, there is no requirement for weld surface inspection (MT/PT). The requirements of this provision are exactly the same as those of the solid content regulations.
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That’s how I understand it too. I’m not sure if it’s correct
I also have doubts about this point. Currently, whether it’s partial or 100% testing of the heads, we still carry out surface inspection. According to some people, this practice is based on a rule from the Quality Inspection Administration stating that “non-destructive testing cannot be omitted just to reduce the welding joint factor.” I don’t find this argument convincing, as neither the pressure vessel regulations nor GB150 require surface inspection when 100% testing of the heads is carried out; therefore, it’s not valid to conclude that a factor of 0.85 requires surface inspection, and thus a factor of 1.0 also requires it. Haha, that’s confusing. Let me summarize my point: Heads that are subject to 100% testing do not require surface inspection (unless there are specific provisions in GB150)
The provisions of GB150.4-2011 are clearly stated. There are two constraints: 1. For Class A and Class B welds of the container, only partial non-destructive testing is required (note that this refers to the \"container\", not the \"head\"). According to the standards, 100% non-destructive testing is required for end caps, but the acceptance level depends on the grade of the welds in the main body of the container ； 2. The end cap is first assembled from panels and then shaped. Therefore, there are no regulations specifying whether surface non-destructive testing is required for all weld joints on the convex heads of containers that are formed by panel assembly followed by molding, and for which full radiographic or ultrasonic testing is required.