Designing software algorithms for critical steps, which can not be implemented by software according to standards directly, is an important and difficult task because those steps need the intervention and experience of engineers.Software algorithms for two critical steps in SY/T 6477-2000/API 579,the metal loss dimension determination and the subsections generation,were proposed. The metal loss dimension determination can not be implemented directly because of its dependence on graph. To solve this problem, Critical Thickness Profiles (CTP) graph was constructed using linear interpolation, and then the software algorithm for dimension determination of metal loss was designed based on the CTP graph. The subsections generation can not be implemented directly because of its dependence on the experience of engineers. To handle this problem, the cyclical iteration which used the change rate of Remaining Strength Factor (RSF) as the termination condition, was designed. Utilizing the cyclical iteration, the software algorithm for subsections generation was designed.The validity of the algorithm was proved. The program flow charts of both software algorithms were given in order to provide direct instructions for software implementation.
