Where does the maximum stress occur in a standard elliptical pressure vessel head subjected to internal pressure?
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As the title suggests, I need to solve this problem. Is the answer correct? If not, what should I choose?
The answer is D. Option A does not take into account the edge stress effect after connection to the cylinder ； Option B is incorrect because for a standard elliptical head, the ratio a/b is greater than 1.414; therefore, the junction between the head and the cylinder must withstand hoop stress. The error in option C is similar to that in option B: the standard elliptical head passes through the vertex, and the hoop stress gradually decreases, transitioning to compressive stress at the tangent point.
This post was last edited by QUYANHUA on 2021-4-13 at 15:56. In the case of a standard head (with a length-to-diameter ratio of 2:1), the maximum circumferential tensile stress occurs in the middle of the elliptical head, while the maximum circumferential compressive stress occurs at the edges of the head – specifically at the point where the diameter is largest, or at the junction where the straight edges meet the elliptical shape, also known as the folded edge. 2) The maximum radial stress is at the center of the elliptical head. The correct answer to this question is ‘A’. The knowledge background is the specialized course on process equipment — “Process Equipment Design” or “Chemical Pressure Vessels and Equipment”. Those who have graduated in process equipment engineering should all know the correct answer.
The maximum stress in D is on the inner surface of the transition zone (fold edge). Maximum stress = bending longitudinal tensile stress + longitudinal film tensile stress
This post was last edited by QUYANHUA on 2021-4-14 at 10:23. This problem should specify that the stress property is one-dimensional film stress. Because, 1. considering the local nature and self-limiting character of the discontinuous edge stresses at the junction between the elliptical head and the cylindrical shell, the value of this bending stress is not taken into account in practical engineering practices (B-150 & ASME VIII). The wall thickness of the cylinder and head is determined solely by film stress. 2. Both GB-150 and ASME VIII are based on the moment-free theory. If these two points are set aside, this problem will deviate from actual engineering practice.
This post was last edited by zjq1962 on 2021-4-14 08:39. To take into account the effect of edge stress, D should be chosen