Session: CS-01-01 Structural Integrity of Pressure Components

Paper Number: 107243

107243 - Design of Ellipsoidal Heads and Torispherical Heads in Pressure Vessels and Review of Restrictions for Onset of Buckling in ASME Sec. VIII Div. 1– A Comparative Study of Various Codes of Construction 

Pressure Vessels are made with various types of end closures. Commonly used end closures are ellipsoidal dished ends, torispherical dished end and hemispherical dished ends. For design of these end closures the rules provided in ASME Sec. VIII Div. 1 and ASME Sec. VIII Div. 2 differ significantly, and a similar phenomenon could be observed when a review is done against popular international Codes for pressure vessel design like PD 5500, EN 13445. The difference in the design methodology is due to the design approach used in developing the equations in these Codes of Construction.

ASME Sec. VIII Div.1 in Para UG-32(c) and (d) for design of all torispherical heads and Ellipsoidal heads subject to internal pressure having ts/L ratio less than 0.002 directs the user to para 1-4 (f) of Mandatory Appendix 1. The requirements at para 1-4 (f) are added to prevent the possibility of buckling of the heads as the thickness is reduced as compared to spherical radius. Buckling as a mode of failure is only envisaged when ts/L ratio is less than 0.002 and no check on buckling is required when ts/L ratio is greater or equal to 0.002.

If we refer other Codes like ASME Sec. VIII Div.2, PD 5500 and EN 13445, one can observe that the design of dished head is based on plastic collapse and buckling failure approach and these codes make it mandatory to check both the failure modes in all the circumstances.

The work reported in this paper is an attempt to review the restrictions of ASME SEC.VIII DIV.1 indicating the onset of buckling failure for the ellipsoidal and torisphecial dished ends when ts/L ratio is less than 0.002 and the comparison is made against various other international codes. Also, FEA of the dished ends is carried out to determine the stresses induced, buckling and displacement of dished ends. Further comparison is made against various Codes classical formula requirements.

Presenting Author: Sujay S. Pathre LRQA Inspection Services India LLP

Presenting Author Biography: International professional engineer with 20 years of design experience in pressure equipment

Authors:

Sujay S. Pathre LRQA Inspection Services India LLP
Ameya Mathkar LRQA Inspection Services India LLP
Shyam Gopalakrishnan LRQA Inspection Services India LLP