Finite Element Modeling of Variable Membrane Thickness for Field Fabricated Spherical (LNG) Pressure Vessels

Oludele Adeyefa, Oluleke Oluwole

Department of Mechanical Engineering, University of Ibadan, Ibadan, Nigeria.

DOI: 10.4236/eng.2013.55056                

Abstract

This study investigated thickness requirements for field fabricated (large) spherical liquefied natural gas (LNG) pressure vessels using the finite element method. In the FEM modeling, 3-dimenisonal analysis was used to determine thickness requirements at different sections of a 5-m radius spherical vessels based on the allowable stress of the material as given in ASME Section II Part D. Shallow triangular element based on shallow shell formation was employed using area coordinate system which had been proved better than the global coordinate system in an earlier work of the authors applied to shop built vessels. This element has five degrees of freedom at each corner node-five of which are the essential external degrees of freedom excluding nodal degree of freedom associated with in plane shell rotation. Set of equations resulting from Finite Element Analysis were solved with computer programme code written in FORTRAN 90 while the thickness requirements of each section of spherical pressure vessels subjected to different loading conditions were determined. The results showed membrane thickness decreasing from the base upwards for LNG vessels but constant thickness for compressed gas vessels. The obtained results were validated using values obtained from ASME Section VIII Part UG. The results showed no significant difference (P > 0.05) with values obtained through ASME Section VIII Part UG.

Keywords

LNG; FEM; Field Fabricated Pressure Vessels; Shell Thickness; Modeling

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	H. M. Koh, J. K. Kim and J. H. Park, “Fluid-Structure Interaction Analysis of 3-D Rectangular Tanks by a Variationally Coupled BEM-FEM and Comparison with Test Results,” Earthquake Engineering and Structural Dynamics, Vol. 27, No. 2, 1998, pp. 109-124. doi:10.1002/(SICI)1096-9845(199802)27:2<109::AID-EQE714>3.0.CO;2-M
[2]	Y.-S. Choun and C.-B. Yun, “Sloshing Analysis of Rectangular Tanks with a Submerged Structure by Using Small-Amplitude Water Wave Theory,” Earthquake Engineering and Structural Dynamics, Vol. 28, No. 7, 1999, pp. 763-783. doi:10.1002/(SICI)1096-9845(199907)28:7<763::AID-EQE841>3.0.CO;2-W
[3]	J. Dong, et al., “Numerical Calculation and Analysis of Single –Curvature Polyhedron Hydro-Bulging Process for Manufacturing Spherical Vessels,” Institute of Nuclear Energy Technology, Tsinghua University, Beijing, 2005.
[4]	O. A. Adeyefa and O. O. Oluwole, “Finite Element Modeling of Stress Distribution in Spherical Liquefied Natural Gas (LNG) Pressure Vessels,” Proceedings of the Nigerian Institute of Industrial Engineers, Nigerian Institute of Industrial Engineers, Abuja, 2011, pp. 65-78.
[5]	O. A. Adeyefa and O. O. Oluwole, “Finite Element Analysis of Von-Mises Stress Distribution in a Spherical Shell of Liquified Natural Gas (LNG) Pressure Vessels,” Engineering, Vol. 3, No. 10, 2011, pp. 1012-1017.
[6]	O. A. Adeyefa and O. O. Oluwole, “Finite Element Modeling of Shop Built Spherical (LNG) Pressure Vessels,” Engineering, Unpublished, 2013.
[7]	AIJ, “Design Recommendation for Storage Tanks,” 2011. www.aij.or.jp/jpn/databox/2011
[8]	Kolmetz, “Storage Tanks Selection and Sizing,” 2011. http://kolmetz.com/pdf/EDG/ENGINEERING_DESIGN_GUIDELINE__storage_tank_rev_2.pdf
[9]	Wilco, “Spherical Compressed Natural Gas Vessels,” 2012. www.wilcofab.com/wilcocompressedn.html
[10]	Y.-M. Yang, J.-H. Kim, H.-S. Seo, K. Lee and I.-S. Yoon, “Development of the World’s Largest Above-Ground Full Containment LNG Storage Tank,” 23rd World Gas Conference, Amsterdam, 5-9 June 2006, pp. 1-14.
[11]	EGPET, “LPG Spherical Storage Tank Design,” 2012. www.egpet.net/vb/threads/25114Sphericalstoragetank
[12]	Wikipedia, “Storage Tank,” 2012. http://en.wikipedia.org/wiki/Storage_tank
[13]	Wikipedia, “Pressure Vessel,” 2012. http://en.wikipedia.org/wiki/Pressure_vessel
[14]	S. I. Mahadeva, “Analysis of a Pressure Vessel Junction by the Finite Element Method,” Ph.D. Dissertation, Texas Tech University, Lubbock, 1972.
[15]	O. C. Zienkiewicz and R. L. Taylor, “The Finite Element Method Set,” 5th Edition, Vol. 2: Solid Mechanics, Butterworth-Heinemann, Oxford, 2000.
[16]	E. Reissner, “On Some Problems in Shell Theory,” Proceedings of 1st Symposium on Naval Structural Mechanics, California, 11-14 August 1958.
[17]	H. L. Langhaar, “Energy Methods in Applied Mechanics,” Wiley & Sons, New York, 1962.