Dynamic Research On Derrick And Base Of ZJ70D Drilling Rig

ZJ70D drilling rig is a kind of large scale engineering equipments for petroleum exploration and development,the derrick and rig structure are the main bearing part and component of rig,and its essence is a space frame.The dynamic properties of the derrick of deep well rig have significant effects on the operating efficiency and security of drilling.This paper analyzed the structural characteristic of the derrick,and then,established its finite element model.First of all,this paper carried out static strength analysis based on API standard,under the ultimate load,the peak stress of the structure is within the safe range,the static strength meet the design requirement.Then,the modal characteristics of the whole structure of drilling rig under different constraint stiffness are analyzed.The results showed that the constraint stiffness has little effect on the first three order frequencies;compared with the full rigid constraint,the relative change is less than 10%.The fourth to seventh order frequency changes are most significant and relative rate of change in more than 30%.From the modal shapes we can see that the derrick is prone to vibrate in lateral direction and in the height direction,but the torsional vibration is not obvious.When the stiffness of the base is enough,the simplified model of the derrick and the foundation can be established,in a reasonable range of errors will greatly reduce the computational cost and modeling difficulty,the constraint stiffness of the foundation has a great influence on the modal characteristics,the numerical calculation should be combined with the actual situation of drilling site.Both the transverse and the lateral sinusoidal excitations are subjected to the most severe vibration near the resonance frequency of the base part and the resonance response of the structure is verified by the harmonic response analysis,In the z direction,the peak frequency is 5.525 Hz,and the peak frequency of x direction is 8.075 Hz,which corresponds to the first mode frequency of the base.In the case of the transient impact of the top of the derrick,the vibration deformation is similar to that of the derrick under the static load.The free vibration of the derrick is mainly in the front and back direction after instantaneous impact,and the first order mode dominates in the free vibration.In the end,this paper analyzes similarity criteria between original structural and the model,according to the dimensional analysis method and equation analysis.It deduced similarity ratio of similarity criteria,and the design of the model based on it.with a1/10-scale dynamic model derrick of the deep-well rig as studying object.The model is concerned with the finite element analysis and modal testing.it carried out mode analysis of the model derrick based on numerical method and impact testing using hammer excitation was used to measure the vibration properties of the model derrick.Compared with the same results obtained from FE and hammer testing,it showed that the relative error of the first five nature frequencies were less than 10% and dot the model shapes were gotten approximately.In this case,the analysis showed that the low order modes can effectively reflectively reflect nature frequencies and model shapes of the system,and the designing model derrick is feasible.The results of experiments and numerical simulation show that the third order natural frequency is near the working frequency of the rotary table,the 4,5 order mode frequency is close to the output shaft of the gearbox,and the low order resonance of the derrick is easily excited.