Why are steam drums or some pressure vessels cylindrical?

In terms of material usage, it is most economical; for the same amount of material, an object in circular shape will have the largest volume.

You’re right about one thing – it must be due to the design of the pressure vessel.

This question is quite interesting. Yeah, what is it asking here? I think, in addition to what was mentioned above, the manufacturing process could also be simpler – it’s possible to use a sheet metal bending machine for shaping, which results in fewer welds and thus less work required.

1. Low material consumption and simple manufacturing process； 2. Good pressure resistance ； 3. Small footprint, easy to install ； 4. Smooth and attractive appearance ； 5. Relatively low cost.

The main reason is even stress distribution; if it were made square, a very thick wall thickness would be required, along with reinforcing ribs.

Compared to squares, it has the largest volume for the same surface area, and compared to spheres, its manufacturing process is relatively simple.

It is best to design pressure vessels as cylindrical containers. Pressure vessels are classified by their geometric shape, including spherical vessels, cylindrical vessels, conical vessels, and composite vessels. (1) Due to the central symmetry of its geometric shape, a spherical vessel is subjected to uniform stress. Under the same wall thickness conditions, a spherical vessel has the highest load-bearing capacity; in other words, under the same internal pressure, it requires the thinnest wall thickness. Under the same volume conditions, a spherical vessel has the smallest surface area. Therefore, in terms of stress conditions and material savings, the spherical shape is the most ideal form for pressure vessels. For example, in a plant capable of producing 1,500 tons of synthetic ammonia per day, the original design called for two cylindrical liquid ammonia separators with a wall thickness of 254 mm. Later, spherical liquid ammonia separators were used instead; only one such separator was needed, and its wall thickness was reduced to 168 mm. The total height of the spherical separator was half that of the cylindrical ones, which is said to have resulted in savings of around 160,000 yuan in investment costs. Given the excellent advantages of spherical containers, why can’t they replace pressure vessels of other geometric shapes? This is because, first, spherical containers are difficult to manufacture, often requiring cold forming or hot forming methods. For small spherical vessels, they are first stamped into two hemispheres and then welded together to form a complete sphere. Due to the large depth of stamping for the hemispheres, significant deformation of the steel occurs; this requires large-scale stamping equipment, and it also leads to the formation of stamping cracks as well as excessive thinning in certain areas of the wall thickness. For large spherical vessels, it is usually necessary to first stamp them into several spherical segments, which are then assembled and welded together to form a complete sphere. The shaping and welding of spherical segments are both challenging, as excessive angular deformation and welding internal stresses can occur. This not only deteriorates the stress conditions but also increases the risk of welding cracks. For extremely large spherical vessels, due to transportation constraints, it is necessary to shape the spherical segments at the manufacturing plant first, and then transport them to the site where they will be assembled into a sphere. The welding conditions at the site are inferior to those in the manufacturing facility, making it even more difficult to ensure product quality. The results of a nationwide survey of spherical vessels (including both domestic and imported ones) conducted in previous years showed that the vast majority of such vessels had quality issues to varying degrees. Second, as a petrochemical equipment, it is difficult to arrange components inside a spherical vessel; if there are such components, this **increases the structural complexity and poses a range of difficulties in terms of design and manufacturing. Therefore, spherical vessels are mostly used as storage tanks for pressurized liquids or gases, as well as in applications where the internal structure is very simple. (2) Cylindrical pressure vessels are characterized by axial symmetry in their geometry. Although they are subject to stresses to a lesser extent than spherical vessels, the absence of sudden shape changes in their exterior results in a more uniform stress distribution, as well as higher load-bearing capacity. Compared to spherical containers, the main advantage of cylindrical containers is their ease of manufacture (which also makes it easier to ensure their quality), as well as the simplicity in arranging and removing internal components; for these reasons, they are used most widely. In petrochemical enterprises, the vast majority of equipment is designed in a cylindrical shape. (3) Simple conical containers are rare in engineering, as under pressure, the joints of such containers (i.e., the areas where the shape changes) experience significant additional bending stresses, resulting in an unsatisfactory stress condition. Conical shells are generally used in combination with cylindrical shells to form a complete container, where the conical shell serves as a reducer or amplifier to gradually change the flow rate of gaseous or liquid media, or to facilitate the discharge of solid or viscous materials. (4) Composite containers are formed by combining cylindrical or conical shells with various shaped end caps; therefore, they also belong to the category of cylindrical containers. The separators produced by our factory are often designed as composite containers. Its main body (i.e., the cylinder portion) is cylindrical in shape, with a hemispherical top at the upper end and a conical bottom designed to facilitate the removal of the internal components (Lash ring packing). A comprehensive comparison shows that cylindrical containers offer the best cost-performance ratio, which is why they are widely used in the design and manufacture of pressure vessels.

Under the same conditions, a circle may be able to withstand pressure while a square cannot

A circular cross-section is the best for withstanding forces, so the least amount of material is required. A spherical shape represents the most ideal structure, while a square shape is the worst structure: victory:

It’s analyzed from the perspective of the force direction, right? For the same type of container, there is a significant difference in thickness between those with flat end caps and those with circular cylinders

It is mainly due to pressure-bearing and economic considerations

1. Good load-bearing capacity. 2. Fewer welds, resulting in a simpler manufacturing process. 3. Less material is required for the same volume, leading to lower production costs. 4. Easy to support

For pressure vessels, safety is of course a key consideration. The stresses are the same in all directions, which reduces the likelihood of stress concentration. That’s why there are requirements regarding the roundness of pressure vessels

It is mainly determined by considering factors such as pressure resistance and manufacturing costs.

Circular shapes use the least amount of material; they are also the easiest to manufacture, with fewer welds and less need for inspection, which helps save costs. Additionally, the stress is distributed evenly, and the wall thickness can be minimized as calculated, thus further reducing the amount of material needed

For containers of the same volume, a circular shape requires the least amount of material. More importantly, a circular container distributes forces evenly; in fact, the ideal shape for a container is spherical.

Under the existing manufacturing processes, the shape with the highest strength and the fewest potential defects is the cylindrical shape