What is UCS-66 indicating? Impact exemption for components or welded joints?
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This post was last edited by Claymore2000 on 2024-7-4 16:27. Dear teachers, I have a few questions regarding ASME UCS-66: 1) The control thickness tg described therein refers to the control thickness of the component (the welded assembly of the head, shell, tube sheet, and tube inserts); it applies to the component itself, and its purpose is to discuss the impact exemption conditions for the component, rather than those for the welded joints? (2) If the objective of Question 1 is the component, and since the component is a welded part, should each welding joint on Component A be assigned a control thickness of tg1, tg2, …., and then the maximum value among these control thicknesses for all welding joints be taken as the control thickness for Component A? That is, tgA = max(tg1, tg2, tg3,…). Although the control thickness of the weld joints is used in the comparison, the purpose of this comparison is to determine the maximum value, thereby identifying the control thickness for that component; the ultimate goal remains to establish the control thickness of the component. 3) Regarding the “all weld joint control thicknesses” on component A, the term “all” includes not only the weld joints on the component itself but also those at the edges where the component is connected to other components; these are also taken into account in the comparison (Figures 1 and 2) For example, in Figure 3, the spherical head has its control thickness determined according to USC-66; this thickness is denoted as tg_head. The head is equipped with a type D fitting, tg1, and the wall thickness of this fitting is 5 mm, while the thickness of the head itself is 30 mm. Therefore, tg1 = min(5, 30) = 5. The seam between the individual pieces that make up the head has a thickness of tg2 = 30 mm. The head and the cylinder are joined by a joint where the thicknesses differ – the hemisphere-shaped head has a thickness of 30 mm, while the cylinder has a thickness of 50 mm. Hence, the thickness of the joint between the cylinder and the head is tg3 = max(30, 50) = 50. Finally, according to USC-66, the control thickness for the head itself is tg_head = max(tg1, tg2, tg3) = 50, rather than max(tg1, tg2) = 30? Although TG3 is no longer on the head itself, when discussing the TG of the head, the welds connecting it to the surrounding components also need to be taken into account for comparison – is that what it means?
UCS-66 is primarily used to specify the impact tolerance of components, not that of welded joints. The control thickness tg described is based on the overall structure of the component (such as heads, cylinders, etc.) and the thickness of the weld joints, and it is used to determine whether the component itself needs to undergo impact testing. For all the weld joints on a component, it is indeed necessary to define control thicknesses such as tg1, tg2, etc., separately, and then take the maximum value among these control thicknesses of the weld joints as the control thickness for that component. Furthermore, the weld joints where the edges of the components meet other components should also be included in the comparative discussion. For example, in the case of the spherical head you mentioned, the weld at the junction between the head and the cylinder is also taken into account when determining the control thickness of the head. So the final controlled thickness of the head is 50 mm, rather than just 30 mm for the head itself. This ensures that all factors that may affect the impact resistance of the component are taken into account. .
You’re welcome! I’m glad I could help you! If you have any other questions or need further clarification, please feel free to let me know. Wish you success in your work! .
UCS-66 is used to determine the base material; logically, your third question is incorrect, and of course the value of tg chosen is also wrong. It’s best to seek guidance from your supervisor – otherwise, with equipment like containers, such problems can be very troublesome for designers. Also, read more in the English version; some of the translations in Chinese are unreasonable.
This post was last edited by Claymore2000 on 2024-7-10 07:38. I didn’t use ASME guidelines for mine; I figured it out on my own. There’s also the third issue you mentioned: there’s a problem with the value of tg. What exactly is the problem? Could you explain it in more detail?
The book you’re reading mentions \"the controlled thickness of all welded joints on Component A\"; if you read it thoroughly, you’ll notice that a word is missing here – it should be \"the controlled thickness of all welded joints on Component A\".
We’re still exploring it now; the risks need to be carefully managed. As for TG being the most important difference between ASME and national standard containers, it certainly cannot be explained in just one or two sentences. Here’s the approach: first, evaluate each individual component, then assess the assemblies as a whole, and finally use the highest temperature as the minimum MDMT that the container can withstand. You can add me on WeChat at jch758332183; we can discuss this when we have time and learn from each other*.
1. UCS-66 is primarily concerned with the impact exemption provisions for components; as for the impact requirements related to welding processes, UCS-67 should be referred to. 2. When controlling the thickness, it is necessary to consider it in terms of thicknesses that are greater. It can be understood in this way: whether looking at the curve graph or calculating the amount of temperature reduction, the thicker the thickness, the higher the temperature on the curve graph and the smaller the amount of reduction. By thinking in this manner, a more conservative approach can be adopted.
As I understand it, if you are evaluating the curves of the head, you should consider the cylinder section with its butt welds; only if you take the material of the nozzles into account do you need to consider the fillet welds between those nozzles and the spherical head.