This article presents an operating process of running and pulling oil tube with dumbbell coupling by single elevator.

The analysis of fracture causation of 139.7 mm center-latch elevators for handling 18-degree external upset drill pipe;

Based on morphology analysis and dimension measure and material tests for failure tubing and worn elevator,it is concluded that tubing material is in accordance with API SPEC 5CT,and the cause of tubing fracture and bending is due to one side of tubing co.

If the main load parts of elevators are forged, it must be detected by ultrasonic method.

After an analysis of the 3D stress field on a Model CD350 drill pipe elevator, the stress intensity factors(SIFs) of the surface corner crack with different depths and shapes on the critical section are worked out by the finite element displacement method, and the pattern of variation of SIFs along the front of the crack is presented.

In this paper the three dimensional stress field of the CD350 casing elevator was analysed and stressintensity factors Of the crack with different depth and shape on the critical section was solved by FEM displacementmethods.