Questions about Clause 6.8 of GB151!
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This post was last edited by scaaa on 2009-11-11 09:42. According to Article 6.8 of GB151, if the lateral opening in the tube box exceeds 1/3 of the inner diameter of the cylinder, stress-relief heat treatment must be carried out! What is the basis for this? Is this executed in regular containers? It’s frustrating! ~
1# scaaa is used only in heat exchangers; for ordinary containers, the 150 specification applies
The main consideration is that welding deformation is significant after welding flanged connections with openings; therefore, for carbon steel and low-alloy steel pipe boxes as well, we follow the regulations by performing post-weld heat treatment followed by secondary precision machining of the flange sealing surface.
Secondary processing is carried out after heat treatment deformation.
The amount of welding is substantial, which results in significant welding deformation; the aim is to eliminate residual welding stresses, stabilize dimensions, and machine the sealing surface after welding.
It should be possible; it can’t be limited to heat exchangers alone!
This is based on experience: the straight sections of the tube sheet in a tube box are generally not long, and the openings are usually located near the tube sheet or flanges. When the openings in the tube box are large, significant welding stresses are generated. After a certain period of time (due to what is known as aging effects), deformation occurs at the sealing surfaces as a result of coordinated deformation, leading to leaks at those surfaces. This is similar to what happens when the sealing surfaces are processed after heat treatment.
Generally, secondary machining of the tube sheet flange surfaces is carried out after heat treatment, with the aim of eliminating welding stresses and reducing welding deformation.
It is applied only to heat exchangers, where heat treatment is used to relieve welding stresses and prevent welding deformation