Fatigue Machine Design and Fatigue Life Test of Coiled Tubing

Factors affecting the low cycle fatigue life of coiled tubing were studied by fatigue test to CT80 steel grade domestic coiled tubing with independently design first home-made coiled tubing bending fatigue machine. The results show that the fatigue life of the coiled tubing could be improved by increasing wall thickness, decreasing outside diameter, enhancing yield strength, dropping inner stress, reducing surface damage and improving welding quality of the coiled tubing.