Stress analysis of thin-walled containers
Thread Content
Design an absorption tower to calculate the circumferential stress on the tower wall (design pressure / (2 * wall thickness / tower diameter)) and the axial stress (design pressure / (4 * wall thickness / tower diameter)). For a tower with a length of 6000 mm, a wall thickness of 12 mm, and a design pressure of 0.05 MPa, the circumferential stress is 12.5 MPa and the axial stress is 6.25 MPa – these values are 100 times the design pressure. What properties do the circumferential and axial stresses reflect, and what is the purpose of calculating them? The design pressure is nothing but the maximum pressure capacity of the reaction vessel
It seems that your understanding of the various pressures in pressure vessels isn’t very thorough yet; the maximum allowable operating pressure represents the maximum pressure that a reaction vessel can withstand. Design pressure, calculated pressure, and operating pressure are all reference parameters that serve to ensure its safety.
Thank you. Yes, may I ask what properties of the container do various stresses reflect?
First, understand the relationships between various types of stress: there is work-related stress, followed by design-related stress, then calculation-related stress, and finally the maximum allowable working stress is determined. It cannot be said that these pressures reflect the properties of the container; rather, it can only be said that these pressures correspond to the process of the container’s creation. Work pressure, determine the usage status of the container ； The design pressure must ensure that products meeting the requirements are created to accommodate normal conditions of use, including aspects such as materials, structure, and functionality ； Calculate pressure: Determine the container wall thickness required to meet the operating pressure based on parameters such as material, structure, and operating temperature ； The maximum allowable operating pressure is determined by rounding the wall thickness of the actual container to the value obtained from the calculated pressure; this corresponds to the thickness specified for that series of steel materials. Taking into account the effects of corrosion, the operating pressure that the container can withstand is calculated inversely from this effective thickness, and this value represents the maximum allowable operating pressure. This value also depends on whether safety accessories are installed.
The concept of design pressure is the maximum pressure that the top of the container is designed to withstand. This pressure comes from the internal medium. Circumferential stress and axial stress are the amounts, per unit area of the container, of the loads acting on it (including but not limited to the internal pressure of the medium). These two stresses are not used for comparison with the design pressure; rather, they are compared with the allowable stress of the material multiplied by the weld joint factor. If the former is less than the latter, it indicates that the container is safe; otherwise, it is necessary to increase the wall thickness or use a material with higher strength.
Ring stress and axial stress are not the same concept as design pressure. Design pressure is the pressure acting inside the cylinder, while stress relates to the material itself. The criteria for checking ring stress and axial stress are the allowable stress of the material, not the design pressure. Design pressure is the cause, while ring stress is the effect; it is precisely because of the design pressure that the material experiences ring stress and axial stress. Therefore, these ring and axial stresses should be compared with the allowable stress of the material
Stability also needs to be calculated; under wind loads and seismic effects, horizontal forces and bending moments are present, so it is not possible to consider only the self-pressure