Load-Carrying Capacity Analysis on Derrick of Offshore Module Drilling Rig

Feng Guan1, Chuanxi Zhou1, Shizhong Wei1, 2, Wenxiu Wu1, Xianzhong Yi1
1 School of Mechanical Engineering, Yangtze University, Jingzhou 434023, China;
2 School of Materials Science and Engineering, Henan University of Science and Technology, Luoyang 471023, China

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© Guan et al.;

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the School of Mechanical Engineering, Yangtze University, Jingzhou 434023, China.


Offshore module drilling rig has become an important equipment of offshore oil and gas development, especially, the significantly future application in the field of deep water. Due to the long time working and complex working conditions of in-service derrick of offshore module drilling rig, analysis of its load-carrying capacity assessment is of great significance. Field test shows that in common the derrick of offshore module drilling has an intrinsic defect of stress concentration in addition to external damages including initial bending and load eccentricity. In this paper, the finite element method is combined with field test method, two assessment methods are put forward, respectively. Stress concentration detection on derrick main rod is carried out by using metal magnetic memory detector, and the detection results show that larger degree of stress concentration phenomenon exists on eleven rods of derrick, and stress concentration degree of individual rod is serious. Loading stress test and finite element analysis are carried out on the derrick of offshore module drilling rig. According to comprehensive comparison, it is concluded that hoisting capacity for the derrick cannot reach 4500 kN. Two kinds of structure reinforcement scheme are proposed, and comparison results show that the reinforcement scheme with four legs can improve the actual load-carrying capacity of the derrick. Reinforced derrick can achieve the new design value of derrick carrying capacity. In this study, the evaluation method is correct, which can analyze the derrick carrying capacity of offshore module drilling rig more objective and accurate, and we also provide a new train of thought and reference for the steel structure carrying capacity assessment.

Keywords: Assessment method, derrick, finite element analysis.