Research On High Temperature Resistant New Rubber Sealing Performance Of Roller Cone Bits

The roller cone bit and the cone-PDC compound drill bit commonly used in oil and gas mining have a cone on the top.Once the cone bearing fails,the bit drilling speed and life will be affected.In serious cases,the downhole accident of the cone will occur.Studies have shown that the performance and life of the cone bearing seals are the key factors affecting the life of the cone bearings,which is the key factor affecting the life of the cone bits.In this Thesis,the metal seals commonly used on the cone bearings have the problems of sensitive to the vibration of the cone,large space occupation,high manufacturing cost and high installation precision.Based on the hydrogenated nitrile rubber(HNBR)material with excellent comprehensive performance,a new type of high temperature resistant technology has been developed.The sealing performance of the new sealing ring was evaluated and studied by finite element simulation,indoor test and field application.The response surface method was used to optimize its structure.The main research contents of this thesis are as follows:(1)Comparative test of physical properties such as hardness and tensile strength of HNBR and nitrile rubber(NBR);Comparison of tensile strength and hardness under air aging test;A compression set test was performed under dry heat conditions.The test results show that HNBR has better mechanical properties and high temperature resistance than NBR.(2)Uniaxial,planar and biaxial stretching test were carried out on HNBR by cyclic loading at different strain levels,and the commonly used rubber constitutive model was used to fit the test data.The constitutive model and parameters that should be used for numerical simulation of the circle.(3)According to the physical properties of HNBR,different schemes are proposed according to the design concept of sealing contact surface area and contact pressure should not be too large,and the optimal scheme is selected.The finite element model of three-dimensional transient thermo-mechanical coupling analysis of sealing ring was established by using ABAQUS.The sealing performance of the sealing ring was evaluated by this model.In addition,the seal sealing performance was evaluated on a seal tester.(4)The performance of the new rubber seal was simulated,and the precompression rate range that should be used during installation was determined.The force and temperature changes of the seal under different environmental pressures,temperature,differential pressure,cone rotation speed and friction coefficient are obtained.In addition,the sealing ring was applied to the drilling site,and the appearance,size and hardness of the used sealing ring were tested.The results showed that the sealing ring did not fail and could still be used.(5)Firstly,the orthogonal test is used to find the structural parameters that have significant influence on the sealing performance and life of the sealing ring:the height,length and arc length radius of the sealing ring.Then the response surface method is used to establish the regression model between these structural parameters and the variables that can evaluate the sealing performance and life of the sealing ring.After verifying the accuracy of the model,the optimal value is obtained by solving the model.Finally,the stress and temperature distribution of the sealing ring before and after the comparison are compared.The results show that the Mises stress,contact pressure and temperature are reduced by the preferred sealing ring,indicating that the working life and sealing performance of the sealing ring are obtained.The improvement is preferred and the method is feasible.