Pressure vessels are globally ubiquitous. They have not always been so.
For millennia, engineers harnessing natural forces for benefit of the human race could use only natural materials. They were mostly adequate for the task that they had set for themselves. Where they were not, performance was restricted accordingly.
With the advent of steam power, pressure vessels began to appear. As the search for efficiency got into its stride and the importance of higher pressures and temperatures began to be understood; the engineers found that traditional materials would not answer. Ever since, pressure vessels have presented an engineering problem of enormous importance. Why?
The energy in an engineering structure is usually in the form of strain energy of a relatively stiff, rigid material. On the other hand, the energy in any fluid is mostly in the form of temperature and pressure. If the fluid is in the form of gas, it is compressible. If it is in the form of a liquid it is shape-changing. In both of these last two cases the energy that is stored is usually much greater than in a rigid structure alone For either, when contained in a vessel, the fluid hydraulics and thermodynamics introduce many different forms of stress in the vessel. These are a most searching examination of the integrity of the pressure vessel. In the latter part of the Nineteenth Century that integrity was frequently found wanting
Pressure Vessels are found in every power station, chemical plant, ship and many road and rail vehicles in every continent. They bring in their train a commanding and mighty risk of wide ranging human death and injury coupled with crippling, economic damage. The fact that this risk reduced through the Twentieth Century and in the last few decades is seldom made manifest is entirely to the credit of the engineers and their development of the Code.
It is impossible to demonstrate the number of accidents that would have occurred if the Code had not existed. However, it is possible to show something of the accident rate over the time that the Code has been in existence. (Chart below, Ref 3)
Some of the Design Problems controlled by the Code.
In the safety of pressure vessels, in addition to a high quality design process, there are a number of other topics that need to be addressed. Such topics are material properties, fabrication methods, testing and vessel care: these are all included in The Code. However, in this post the design process is outlined.
It considers, for the design engineer, the different sort of stress and sets limits to control them. To protect against complete disruption, there are the primary stresses, where the design load moves inexorably towards the ultimate strength of the material.
All practical vessel designs combine different shapes that flex by different amounts under the any given internal pressure. These are the secondary stresses that make continuous what would otherwise be discontinuity.
In addition, she uses the Code to calibrate the spiky, peak stresses against fatigue. On top of all this, the vessel duty and therefore, its stresses are continually cycling and in flux over time Thus it is that the fluids searchingly probe the structural integrity of every vessel.
Code Extracts
The hard copy embodiment of the Code in its many Sections takes the form of many thousands of pages. Below are copies of a few pages. Regrettably, the reproduction quality is limited here by the graphics copying method available to this post. The quality of the documents as supplied by ASME is much higher. These extracts are published here with the consent of ASME.
Pressure Vessels
Below to give an impression of pressure vessels and pipework, each potentially containing and controlling large amounts of energy, is a small, fairly arbitrary collection of unrelated images showing various pressure vessels. It is in no way a complete survey of the myriad types of vessels covered by the Code.
Stress Analysis Graphics
These figures show the stresses [shown as different colours] as calculated by modern finite element methods [FEM] of stress analysis for pressurised components. It demonstrates two aspects of the engineering vessel designer. Firstly, it shows the complexity of the stress field with which she has to grapple to ensure its safety under the various loads experienced in service. The ASME Code has to generate limits to apply in such a complex situation. Secondly, it shows the subtlety of the output of FEM.
ASME Organisation
The two specific nominees, the current ASME president and CEO are nominated as the leading representatives of all those over the century who have been responsible for bringing the Code into being and maintaining its global importance and reach.
ASME sells the Code now but it is unlikely that finance was significant in the early days when firm foundations were being laid on the basis of safeguarding the community and its commerce. Even so, commerce is one of the essential drivers of engineering economics, along with capital, men and materiel. Also the effort that was required over the period of a century to keep the Code viable as a vital PV design tool seems more than most Institutions can manage and is very estimable.
The ‘Sultana’ accident
The Sultana was beating upstream, on the Mississippi river, on April 27, 1865 (Ref 5).
Hurrying on at full steam ahead against an abnormally strong current, the big, new steamboat Sultana was ‘jammed from stem to stern’ with 2200 souls, mostly Union soldiers returning home from Confederate prisons. One of her four boilers, with a botched repair, exploded and took two others with it. Within 15mins Sultana was burned out and more than 1700 were dead.[Ref 1]
Other accidents like Brockton Reference 2 Spence and Tooth
References
Ref 1 – “The Code” ASME brochure – http://files.asme.org/Catalog/Codes/PrintBook/34011.pdf
Ref 2 Pressure Vessels Design. Concepts & Principles. J Spence & A S Tooth. Published Chapman & Hall London, 1994
Ref 3 ASME Presentation – “About ASME” – Mike Dodge
Ref 4 – World Trade Organization, Decision of the Committee on Principles for the Development of International Standards, Guides and Recommendations with Relation to Articles 2, 5 and Annex 3 of the Agreement G/TBT/1/Rev.10, June 2011 http://docsonline.wto.org/imrd/directdoc.asp?DDFDocuments/t/G/TBT/1R10.doc
Ref 5 – D Sniderman https://www.asme.org/engineering-topics/articles/boilers/the-greatest-maritime-disaster-in-u-s-history
Ref 6– The National Board Bulletin, 100th Anniversary of the ASME Boiler & Pressure Vessel Code, Winter 2014, pp. 20-29 (http://www.nationalboard.org/SiteDocuments/Bulletins/WI2014.pdf
Ref 7 – ASME Foundation – https://community.asme.org/asme_foundation/default.aspx
Ref 8 – http://www.fendti.com/index.php?_m=mod_product&_a=view&p_id=347
Acknowledgements
In the earliest stages of drawing up this nomination, Professor John Spence, Mr Paul Lam of Lloyd’s Register EMEA and Melanie Collins of Lloyd’s Register Foundation, Ms Debbie Sniderman of VI Ventures LLC, Victoria Druce of the Royal Society, Mairi-Claire McGeady of the University of Strathclyde and were of great help to me personally.
My thanks must also go to those eminent engineers Professor David Nash, Mr Stuart Cameron, Mr Kenneth Balkey and to Professor Lin Shuqing for agreeing to support my personal ASME Nomination project and to provide references.