Abstract
In practice virtually all corrosion control is risk based. Typically in the first instance an attempt is made to identify the main mechanisms of corrosion attack, and thereafter a reasoned intervention program is considered. This may include a material change, inhibitor selection, or a design change to the component or indeed the physical conditions expected. The critical step is invariably the corrosion analysis, which often progresses to the modeling approach, which unfortunately is often at odds with actual field experiences. It is believed that a significant improvement to existing predictive methods is thus possible using more practical risk based methods. Most corrosion analyses and solutions are highly judgmental and often rely on imperfect sources of data, and so performance predictability over the life cycle tends to be inadequate, and results not well reproduced. The practical risk based analyses offer an alternative highly knowledge and experience based approach, which can be tailored via re-iteration to give improving accuracy and repeatability. The methodology uses numerically assigned logic, prioritization, and probability criteria expressed in the form of precise risk judgment sheets.
The paper gives a view of the relationships between Corrosion, Risk and Reliability, and is targeted to focus on how the 3 R’s may be customized and quantified for an integrated corrosion project. Guiding rules are presented and applied to areas of particular interest, namely non-steady design excursions, and differentiation between similar localized corrosion mechanisms, where most problems are noted. As a corollary, an important interpretation of practical loss prevention, and risk theory pertinent to corrosion is also included along with case histories from the oil and gas industry. The specialized input of risk analysts and in-service inspection practitioners is highlighted, and it is shown that such a risk based approach offers sound, cost effective answers and fosters the development of creative track initiatives. The role of such corrosion risk decision making within risk based safety and red flag verification regimes is also presented, and the methodology is argued to be a very powerful tool in life cycle corrosion management.
