Doubts regarding certain provisions of GB/T150-2024

1. I think ‘first paneling, then shaping’ refers specifically to the head section. 2. The recommendation seems not to imply any obligation. 3. I don’t understand why it is said that X-ray inspection cannot be used for small-diameter high-pressure equipment Plates with a thickness of 200 mm can be detected at the standard X-ray inspection AB sensitivity

Regarding your questions about certain provisions of GB/T150-2024, I have tried to provide answers: 1. **Explanation of clause 10.3.2 a) in GB/T150.4-2024:** – “Assembling the plates first and then shaping them” usually refers to the process of joining the plates together before shaping them into cylinders or other components. In the manufacturing of cylinders and flangeless cone sections, if the sheet metal is first assembled into a complete plate and then shaped into a cylinder or cone section through rolling or other methods, this situation should be considered as \"assemble first, then shape.\" - The rounding process is usually a post-forming operation aimed at ensuring that the roundness of the cylinder or cone section meets the required standards. This process does not fall under the category of \"paneling first, then shaping,\" and therefore is not covered by the provisions of this clause. 2. **Explanation of clause 10.3.3 a) in GB/T150.4-2024:** – Ultrasonic testing can employ the non-recordable pulse-reflective ultrasonic (UT) method, but phased-array ultrasonic testing is recommended due to its higher flexibility and precision. Regarding whether a phased array must be used, the provisions recommend its use but do not impose a requirement. - The determination of the qualified level should be based on relevant standards and specifications; typically, this information is detailed in specific implementation standards or industry standards. 3. **Explanation of clause 10.5.3 in GB/T150.4-2024:** – For high-pressure equipment with small diameters and thick wall thicknesses, if X-ray inspection is not possible and the equipment is not suitable for ultrasonic testing methods, other approved inspection methods such as gamma-ray testing can be considered. Furthermore, if there are technical limitations in practical operations, it is necessary to communicate with the relevant quality supervision departments or industry experts to seek solutions or alternative methods for such situations. - This clause is indeed more applicable to larger devices that can undergo X-ray inspection or recordable ultrasound inspection. For other cases, the testing method should be appropriately adjusted based on the specific conditions of the equipment and the available testing techniques. I hope these explanations will help you understand and apply the relevant provisions of GB/T150-2024 better. If you have any other questions or need further clarification, feel free to ask. .

Personal understanding: 1. Assemble first, then shape: The cylinder body and the conical shell can be assembled first before being shaped. For example, if the diameter of the cylinder body is large and there aren’t long enough steel plates available, the longitudinal seams can be welded together first, after which the piece can be rolled into a cylindrical shape; the same principle applies to the conical shell； 2. Phased array ultrasonic testing is only recommended, not mandatory. The use of non-recordable ultrasonic testing methods is not recommended. According to the requirements of 10.1.3, if non-recordable ultrasonic testing is employed, other ultrasonic testing methods must be used as a supplement. To avoid trouble, it is recommended to use other ultrasound detection methods except those that cannot be recorded. 3. Given the disadvantages of gamma-ray detection, it is recommended that people avoid using this method. For example, for containers without manholes, X-rays can be used for double penetration testing; there is no need to rely on gamma rays just for simplicity’s sake.

Laminating is carried out first followed by shaping; the shaping process generally results in high deformation rates, and external forces cause the existing minor defects such as pores or inclusions in the joints to expand and crack. Therefore, all areas that undergo further large-deformation processing after panel assembly should be rechecked 100%.

Phased arrays are likely to become the preferred method in the future, and as the cost of such equipment decreases, their use will continue to increase as part of new standard revisions.

Assembly before shaping refers to the process of transforming a flat sheet into a component with the desired shape, involving the rolling of cylindrical shells and the forming of end caps; if a conical shape is achieved through assembled plates, it also falls under the category of assembly before shaping. Straightening is merely one of the steps in the shaping process

Regarding the issue of cylinders and conical sections that are first assembled from panels before being shaped, literally it is as you said, but in practice: cylinders that need to be joined due to insufficient length are mostly used in applications where the diameter is large and the pressure is low, with a relatively thin wall thickness. Moreover, the coiling process has little impact on this butt weld (the longitudinal weld of the cylinder). In most cases, such equipment requires only partial radiographic inspection – is it really necessary to carry out 100% inspection? In that case, devices with large diameters will basically face this problem (the expanded length of large-diameter devices is large, making it easy for the length of the plate assembly to be insufficient)