Session: DA-04-01 Inelastic, Nonlinear, and Limit Load Analysis

Paper Number: 154406

154406 - Improved Knockdown Factors for the Design of Hemispherical, Torispherical and Ellipsoidal Heads Under External Pressure 

Abstract: 

Pressure vessel heads, particularly hemispherical, torispherical, and ellipsoidal heads, are widely used in industries such as petroleum, chemical, and nuclear power. Heads with a high radius-to-thickness ratio are prone to buckle under external pressure. Due to the existence of shape imperfections, the buckling pressure of actual heads is significantly lower than that of perfect heads. The knockdown factors (KDFs) are used to correct buckling pressure. However, KDFs of these heads are still lack in investigation. In ASME BPVC VIII-2, the KDF for formed heads is set at a constant value of 0.124. NASA SP-8032 delivered KDFs by a function of geometry parameter and a KDF curve from test results. In this paper, we first established finite element models with initial shape imperfections, which were collected from various in-service heads using a 3D laser scanner. Next, the KDFs were determined by the radio of buckling pressure of imperfect heads with the maximum allowable shape imperfections permitted by ASME BPVC VIII-2 to buckling pressure of perfect heads. We then analyzed the effects of head geometrical parameters and material properties on KDFs and developed a method for calculating threshold KDFs. Finally, the developed threshold KDFs were validated with a large number of experimental data, and compared with guidelines currently used by ASME and NASA.

Presenting Author: Jiajun Sun Zhejiang University

Presenting Author Biography: I'm originally from Wenzhou, Zhejiang, China and now I’m a junior student at Zhejiang University. I major in process equipment and control engineering. My interest in engineering began as a child when I first saw eletrical machines. It's my honor to have the opportunity to study engineering at Zhejiang University and conduct scientific research practice including FEA of reinforced spherical tanks.

Authors:

Jiajun Sun Zhejiang University
Keming Li Zhejiang University
Tao Shen Zhejiang University