Fatigue life estimate for coiled tubing

On the basis of analyzing the bending tensile stress,radial stress,circumferential stress and equivalent stress of coiled tubing(CT),the predicting model for fatigue life of coiled tubing was established;Then based on the predicted calculation,through analyzing the influence of many factors,such as internal liquid stress of CT,outer diameter,wall thickness,diameter of rolled canister and tensile strength on the fatigue life of CT,this paper put forward the practical methods improving the service life of CT.