Research On The Evaluation Method Of The Derrick Bearing Capacity And Structure Strength Of Workover Rig

The offshore drilling and workover rig is an important equipment to ensure the normal production of offshore oil,and the derrick is one of the important components of the lifting equipment of the workover rig.It is frequently used in the offshore platform operation,with many members and complex stress conditions.Various damage defects caused in the use have an impact on its load-bearing capacity,making its load-bearing capacity lower than the original design value,so the strength of the derrick in service is affected The research is of great significance to ensure the safety of derrick in service.It is of great practical significance to summarize the damage rule of derrick structure.Various factors affecting derrick structure are incorporated into the mathematical analysis model.With the help of the mathematical analysis model,the comprehensive evaluation and prediction effect of derrick structure damage can be realized,and the stability and service life of derrick structure can be improved.Through the analysis of derrick structure damage,it is concluded that derrick structure corrosion is the main damage problem faced by derrick in service.The limited area reduction caused by corrosion can be reflected by the thickness of derrick members.Compared with other forms of damage,the thickness change of members caused by corrosion of derrick section can be measured directly and the rule can be easily obtained.The commonly used methods of derrick strength evaluation are stress test method and finite element method,which is different from the actual working condition of derrick.In view of this,the actual geometric parameters of the derrick are obtained by ultrasonic thickness measurement to improve the accuracy of the finite element model.The strength of the derrick is evaluated by this model.After that,the derrick is tested and fitted with the test results.Compared with the finite element model analysis,combined with the finite element analysis and the field stress test data,the overall strength of the existing JJ180/33-k derrick is analyzed And assess.After the investigation of thickness measurement data of JJ180/33-k derrick with different service life in the same sea area,the corrosion law of derrick structure is obtained by regression analysis.The main work of this paper is as follows:(1)Taking the finite element method as the basic numerical simulation method of derrick structure evaluation,the theoretical model of JJ180/33-k derrick in service is established by using ANSYS large-scale finite element analysis software.Through geometric measurement,ultrasonic thickness measurement,magnetic particle inspection and other means to obtain the actual geometric parameters of the derrick,and based on this,modify the theoretical model of the derrick,analyze and determine the load on the derrick in operation,and then carry out static analysis on the derrick under 10 typical working conditions,and study the bearing capacity of the existing derrick in terms of strength.(2)Combined with the finite element simulation results of the derrick,the field stress test is carried out on the weak link of the derrick,and the bearing capacity of the derrick under the ultimate load is obtained by linear extrapolation of the test data.The accuracy of the finite element analysis is verified by comparing the stress test and the finite element simulation data.(3)The thickness measurement data of derrick with different service life in the same sea area are investigated,and the corrosion rule of well frame parts is summarized,which provides a certain basis for the finite element analysis of derrick by predicting the geometrical parameters of components in the evaluation period.(4)At the end of the paper,the work content and research results are summarized in general,hoping that the research can provide reliable technical guarantee for the subsequent derrick safety assessment,and provide valuable reference for the in-depth research and discussion of derrick structure strength detection,assessment,operation and maintenance and other related topics.