Structural Analysis And Design Of Work-over Derrick

Work-over rig is the essential equipment for workover operation, and the keypart of work-over rig is derrick, which is used to replace oil pipelines and suckerrod. The derrick’s operating situation is a little complex, which is not only used toinstall lifting machines, such as crown block, Travelling block, and hooks, but alsoto bear the loads causing by the operations of workover and sucker rod.This article analyzes work-over rig’s structural features, simplifies derrick’scomplicated structure, and builds up the model through ensuring all loads andrestricting the original working conditions, according to the normal structuralJJ135/33derrick of80t&100t work-over rigs（commonly applied in oilfield）.Thesoftware, ANSYS, is applied to analyze three different JJ135/33oil derrickoperating status: maximum hook load condition, expected condition and unexpectedcondition, in order to get the displacement and stress state of certain loads.Through loading maximum hook loads to analyze the structure strength ofJJ135/33derrick, we can confirm the stress-concentrated position and advance thestructure of derrick. The structural optimization is done from the following aspects:the taper angle of upper part, inclined support place-form and the profile andmaterial of the derrick. Less material will be required and its weight can be reducedby partial optimization to the structure of derrick, which gets the biggest economicbenefit and is able to improve the reliability in the meantime.As typical truss structure, the buckling stability analysis and modal analysis ofthe derrick are carried out. The overall stability and the leg stability are checked inmaximum hook load condition through buckling analysis. The first eight step freevibration frequency and vibration modes are analyzed in ANSYS through modalanalysis.By using finite element intensity analysis method, calculating progress can besimplified, so that design efficiency can be improved and time can be saved. Thecomputation results can be used to choose proper production structure, improve thereliability, as well as cut down the cost.