Keywords: submarines, pressure hulls, hydrostatic pressure, structural design.

This paper presents an investigation into various methods of calculating the theoretical collapse loads for a pressure vessel, under uniform external hydrostatic pressure; based on different design codes. The design codes used for the investigation were BS 5500, for vessels under external pressure and also, the design charts of Ross of the University of Portsmouth [1]. It is the opinion of the present authors that the current design methodology, namely BS 5500 was difficult to use and gave inaccurate collapse pressures for some large-scale pressure vessels. Moreover, BS 5500 appeared to be too pessimistic for one mode of failure and too optimistic for another mode of failure.

For the present study, two full-scale 'theoretical' pressure vessels were used and the fore mentioned methodologies applied in its design to see if there were any similarities that each method may have had.

From the results obtained, it became apparent that some methodologies were more accurate than others, depending on the mode of collapse. Moreover, it also became apparent that some of the methods themselves were outdated, user-unfriendly and in some cases, may have even been dangerous.

Modern man has lived on planet Earth for approximately 160,000 years, and in that time he/she has explored and harvested most of what the dry surface of the earth has to offer. Yet the earth is only partially covered in land, as some 71% of the earth's surface is covered by water with over half those waters being over 3000m in depth. Moreover, man has only explored about 1% of these waters. Despite only a limited amount of exploration having been conducted, we have already discovered pockets of methane and methane hydrate, once only though to exist on the moons of Saturn! [2]. These sources of fuel could sustain the Earth for centuries to come. What else will lie below the ocean depths? Minerals, oil, or possibly finds of a historic nature, such as fossils, ruins etc. which could further our understanding of the earth's history.

Structures designed to withstand the extreme water pressure experienced at the ocean depths are usually constructed in the form of thin-walled pressure vessels [3,4]. They typically consist of cylinders, cones and domes due to their practical use in pressure vessel design [4].

The study of the design and theoretical/practical collapse pressure of thin-walled pressure vessels and ring reinforced circular cylinder under external pressure is very important in order to help enhance the designs that can be used to build submarines and submersibles [4].

1

C.T.F. Ross, K.O. Okoto, A.P.F. Little, "Buckling by General Instability of Cylindrical Components of Deep Sea Submersibles", Applied Mechanics and Materials, 13-14, 289-296, 2008. doi:10.4028/0-87849-367-0.289

2

L. Lewis, "Hidden Source of Power Could Last 100 Years", The World Time Supplement, 33, April 14th, 2008.

3

W.A. Nash, "Hydrostatically Loaded Structures: The Structural Analysis and Design of Powered Submersibles", 1995.

4

C.T.F. Ross, "Pressure Vessels: External Pressure Technology", Horwood Publishing, Chichester, 2001.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £145 +P&P)