The function of the cylinder is to provide the pressure-receiving space required by the process, which is one of the most important pressure elements of the pressure vessel, and its internal diameter and volume often need to be determined by process calculations. Cylindrical cylinders (ie cylinders) and spherical cylinders are the most commonly used cylinder structures in engineering.
When the diameter of the cylinder is small (generally less than 500mm), the cylinder can be made of seamless steel pipe. At this time, there is no longitudinal weld on the cylinder; when the diameter is large, the steel plate can be rolled into a cylinder on a coiling machine or used in a hydraulic press. Two semi-cylinders are pressed into the upper and the two are welded together with a weld to form an entire cylinder. Since the direction of the weld is parallel to the longitudinal direction (ie, axial direction) of the cylinder, it is referred to as a longitudinal weld, or as a longitudinal weld. If the diameter of the vessel is not very large, there is usually only one longitudinal weld; as the diameter of the vessel increases, there may be two or more longitudinal welds due to the limitation of the web size. In addition, shorter length containers can be attached directly to the ends of a cylinder to form a closed pressure space and a pressure vessel housing is also formed. However, when the container is long, due to the limitation of the size of the steel sheet, it is necessary to use a steel plate to be welded into several sections of the cylinder (a section of the cylinder is called a tube section), and then two or more tube sections. The group is welded into the cylinder of the required length. The joint weld between the barrel section and the barrel section and between the barrel body and the end seal head is called a circumferential weld seam and is referred to as a girth weld seam because its direction is perpendicular to the axial direction of the cylinder body.