Research On Fitness-for-Service For Local Thinned Pressure Pipelines

Pressure pipelines are special equipment with high potential risk that widely used in process industry. The defects in pressure pipelines always lead to disastrous consequences and great economic loss. Local thinning is a kind of common volume defect that happens on pressure pipelines. The occurrence of local thinnings will greatly reduce load-carrying ability, residual strength and safety reliability, increase the initiation possibility of cracks, local bulge, leakage and explosion, also increase corrosion inspection and pipelines maintenance cost. At Present,kinds of FFS method with different application requirement are existing for the assessment of LTA pipelines in the world which greatly increase the difficulty of method-selection for engineering staff.In this thesis, comparison and analysis of convertism will be carried out among the four most widely-used FFS standards for LTA defects:ASME B31G,DNV RP-F101, API579and Shell-92.Factors that have influence on the complicated loads and stress distribution in real piping systems and the residual life will be researched,either.What is more,a reasonable FFS method selection criterion and general assessment procedure will be given finally to help engineers tochoose the method in thier practical assessment work, so taht they can increase their assessment efficiency and offer decisive suggestions for the check work, maintenance, alteration of corroded pressure pipelines.