Deformation control in pressure vessel manufacturing

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Welding deformation: Metal containers are prone to structural deformation when subjected to high-temperature welding, which can even affect their corrosion resistance and load-bearing capacity. Therefore, the welding process is directly related to the safety performance and quality of the container to a certain extent; moreover, it also affects the production efficiency of the product. When welding, it is necessary to pay attention to the sequence of welding steps, ensuring that the welding environment, welding methods, welding techniques, and technical parameters meet the design standards. To address the deformation of containers that occurs during welding, its control is primarily achieved through the following measures: First, when welding spherical pressure vessels, it is essential to pay attention to the order of assembly – the main structure must be assembled first before welding takes place. It is also important to ensure that the container is heated evenly during welding, as well as to use symmetric welding methods. Secondly, when carrying out multi-group welding, it is necessary to account for the corresponding shrinkage amount of the pressure vessel; however, different metal materials have different shrinkage rates. Therefore, during the actual welding process, it is essential to analyze and calculate the shrinkage rate of the material to be used. Finally, when welding, the welder should, based on their welding experience, start welding in the opposite direction from the areas most prone to deformation, thereby counteracting the welding-induced deformation artificially. Molding errors: It is essential to pay close attention to the issue of significant size errors in containers that occur during actual production, and to take measures to control these errors. This involves strictly controlling the manufacturing processes and standardizing operating procedures, regularly checking the dimensions of molds and templates, and promptly replacing those that are no longer usable. Proper control of the geometric errors of molds plays a very important role in ensuring the proper formation of containers. Furthermore, when designing molds, it is necessary to take into account the size variations caused by thermal expansion and contraction during actual production, as these can lead to substandard product quality. Internal stress deformation: During the manufacturing process, pressure vessels undergo multiple heat treatments. However, during assembly, internal stresses inevitably arise due to the lifting force of cranes and the weight of the vessel itself. The presence of internal stress can cause cracks or deformation in the container during use; therefore, appropriate control measures must be taken to eliminate this internal stress. Generally, the main method for eliminating stress in containers is heat treatment. However, during actual operation, it is necessary to pay attention to the procedures and standards, to ensure that the temperature remains within the designated range and that the container is heated evenly. Currently, the commonly used heat treatment method is nozzle-type treatment, but a fire barrier must be installed during actual operation to prevent uneven heating of the container, which could lead to secondary deformation of it. Furthermore, during heat treatment, since the properties of metal materials tend to change under high temperatures, certain reinforcement measures must be taken to ensure the stability of the container. Flame cutting deformation: If errors occur in the cutting dimensions due to calculation mistakes, the pressure vessel produced will not be qualified either. Therefore, the cutting dimensions must be verified in a timely manner. The specific control measures mainly include: first, section control, that is, using symmetric cutting or mechanical processing during flame cutting in order to control container deformation. Secondly, control the steel slab stock. If the steel slab is uneven, it should be corrected in time before cutting, or the machining allowance should be increased. Finally, control the head shape: during flame cutting to form the head, high temperatures can cause deformation in its surrounding areas, resulting in a reduction of the head’s diameter. When processing the entire head interface, it is necessary to take this shrinkage into account when designing the mold, in order to minimize losses.