Reliability in design for gas and oil power plants

One of the problems that has to be dealt with when designing gas & oil power plants is assessing how thick the walls of the pipes which transport the working fluid should be. The fluid in question usually has considerable corrosive properties and so the thickness of the metal has to be sufficient to prevent the tube being prematurely perforated (which could have fatal consequences when the fluid being transported contains a high percentage of H2S). The thickness of the metal walls must be sufficient to guarantee that the pipes are still functional after 20 years of plant life; it is well known that every year a certain amount of the metal is corroded (corrosivity, in mm/year). Quantifying the corrosivity of a given working fluid is not, however, easy; experimental formulas are used for this purpose but these are not very accurate because they can only take some of the parameters determining corrosivity into consideration. For this reason DFSS techniques have been adopted for ascertaining the error inherent in the correlation most widely used for corrosion phenomena.