In the design of pressure vessels, stress analysis is a key link to ensure its safe and reliable operation.

1. Load analysis

First, it is necessary to clarify the various loads that pressure vessels may bear. Internal pressure is the most common form of load, including constant pressure and alternating pressure. In addition, there are external loads such as vessel deadweight, wind load, seismic load, etc. Accurate analysis of the size, direction and point of action of these loads is the basis of stress analysis. For example, in seismically active areas, seismic loads may produce huge instantaneous impact forces on the container, which requires special consideration.

2. Geometric shape and structural discontinuities

The geometric shape of the container has a significant impact on the stress distribution. The stress distribution of regular shapes such as spheres and cylinders is relatively uniform, but at structural discontinuities, such as the connection between the nozzle, flange, head and cylinder of the container, stress concentration will occur. The stress concentration coefficient of these parts needs to be accurately calculated to ensure that there will be no excessive stress under the design pressure.

3. Material properties

Different materials have different mechanical properties, including elastic modulus, yield strength, Poisson's ratio, etc. In stress analysis, stress should be accurately calculated according to the characteristics of the selected material. For example, the strength of materials may decrease in high temperature environments. It is necessary to consider the effect of temperature on stress and conduct corresponding high temperature stress analysis.

4. Stress classification

The calculated stresses should be classified into primary stress, secondary stress and peak stress. Primary stress is the stress necessary to balance the external load, which is directly related to the strength and safety of the container; secondary stress is the stress generated by the coordination of structural deformation; peak stress is the additional stress generated at the local structural discontinuity. Different types of stress have different allowable limits, and accurate classification helps to reasonably evaluate the safety of the container.