Structural integrity and life assessment of oil drilling rig pipes using analytical method

Structural integrity and life assessment of oil rig pipes using analytical method is presented and applied to an oil drilling rig pipe. The new concept based on risk evaluation according to probability and consequence of failure is used. Analytical expressions for surface cracks, provided by Raju and Newman, are used to calculate stress intensity factors for different crack geometries. Furthermore, the rig welded pipe failure probability is estimated by simple application of the Failure Assessment Diagram (FAD) and used together with potential consequences to evaluate the risk level by application of risk matrix. The same logic is employed in the case of cyclic loading, i.e. fatigue crack growth, by using Paris law to calculate crack length depending on the number of cycles. Simple numerical integration is applied to take into account the change of the geometry parameter Y due to increasing depth of a surface crack