Types of welded joints between spherical head and cylinder
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This post was last edited by hgm at 2020-5-3 14:45 GB150 regulations: The circumferential joint connecting the spherical head and the shell is a type A welded joint. Now I have a question.: 1. Does spherical head refer to exactly hemispherical head? Or does it include a spherical crown head? 2. If a piece of equipment uses a spherical head in the form of Appendix D.2.2 d) in GB150.3, and the cylinder has a chamfered edge, so that the butted spherical head is not exactly a hemispherical head, but also lacks the length of the chamfered edge, is this welded joint considered Category A or Category B?
This welded joint is considered Category A...
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1. Does not include the spherical head. 2. In order to ensure the strength of the cylinder, the thinned part of the cylinder is used as a part of the spherical head. 3. Any spliced joint on the convex head is a Class A joint. The annular seam between the spherical head and the cylinder is a Class A joint because hemispheres generally have no straight edges, so this annular seam is also a joint in any direction on the spherical head and bears the maximum principal stress on the spherical shell.
Hello, thank you for your answer. I still have two questions. 1. How is the spherical cap head defined in the standard? Does it count as long as the size is less than a hemisphere? 2. In the attached picture, the hemisphere is not a complete hemisphere. The hemisphere is a complete hemisphere when the trimmed edges are included. The hemisphere is a complete hemisphere when it reaches the tangent line of the cylinder. If it is not a complete hemisphere, does this weld belong to Class A or B welds?
This post was last edited by zjq1962 on 2020-5-4 11:04 1. From my understanding, the spherical cap-shaped head is indeed a part of the spherical shell and is used as the middle head or end head. Because it is an angular joint with the connected cylinder, there will be large local stress at the connection, and the local area needs to be strengthened. The stress situation far away from the edge is the same as that of the spherical shell. The spherical cap head is part of a spherical shell of equal diameter, but its depth dimension is relatively small (GB/T25198). 2. The cylinder is thinned. As a part of the spherical shell, the ring seam is equivalent to the patchwork seam on the spherical head, which is of course a Class A joint.
1. The standard classification of whether a weld is Class A or Class B depends on the primary stress the weld is subjected to. The primary stress of a Class A weld is twice that of a Class B weld, so it needs more attention.； 2. According to the description of the spherical crown head in GB/T25198-2010, it has no straight edge section, so the welding type between it and the cylinder is not butt joint, so it should be classified as a Class C weld. ； 3. As described in the head standard, the spherical head has no straight edge section and the weld is subject to greater secondary stress. Therefore, according to Article 5.5 of GB150.3-2011, it should have a reinforced section. 4. If the designer designs a transition section and a straight edge, the head should be similar to a dish-shaped head, and the weld between it and the cylinder is classified as Category B.