Engineers' Resources

Pressure Vessels and Heat Exchangers


Disclaimer


Pressure Vessel Design

As a qualified Mechanical Design Engineer, I take this opportunity to remind all potential users of the following code fragments that it is YOUR responsibility to ensure that all designs generated are verified manually, and that such designs comply with the current edition of the appropriate code. Time has elapsed since I practised, and there is a possibility that code included here may not comply with current editions.

I also remind you that in submitting designs for approval, that design checks made by clients may be performed by trainee engineers, not yet fully conversant with such codes, i.e. it is possible that YOU MAY BE PERSONALLY LIABLE FOR ERRORS.

For those unaware, there was a pressure vessel incident in the UK (1950's), at a plant of a well known chemical processing company. A vessel exploded, causing massive devastation of the surroundings.

Gases under pressure are far more dangerous than liquids since the energy stored is far greater. When a vessel containing a liquid fails under pressure, the bulk modulus properties of liquids usually tend to cause a rapid loss of pressure. Failure may often only be observed at localised crack sites, hence first time pressure vessel testing with water (or a subsitute where water would be injurous to the vessel). Gases however lose their pressure more slowly under such conditions, and it is most common that crack propagation will occur with accompanying plastic failure, leading to catastrophic failure, and possible loss of life unless the vessel is enclosed in an adequate blast proof test chamber or situated in a remote place.

I accept no liability for any use of the following code fragments. I emphasise that it is designer's responsibility. Programmers should also ensure that appropriate range checks are made within calling code. Programmers and system testers from outside a mechanical engineering discipline must be made aware of the consequences of mistakes.

Iain W. Bird BEng(Hons) Mechanical Engineering, University of the West of England


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