Research On Mechanics Properties And The Wear Failure Of The Screw-Bushing Pairs Of Oil Extraction Progressing Cavity Pump

Because of less investment, simple equipment construction, easy operation, energy conservation and good adaptability, the progressing cavity pump (PCP)oil extraction has been paid much more attentions to in oil fields at home and abroad. Especially, more oil fields have been in the triple oil extraction stage. As an important artificial lifting method in oil field, its application is increasing. But now, the condition that the check period of the PCP oil extraction is short seriously has restricted the development of the PCP oil extraction technology. Abrasion failure which is between screw and the bushing of the PCP is one of the main reasons in the PCP failure.This paper which takes screw-bushing pairs of the oil extraction PCP as study objects, has comprehensively analyzed the motion traits of the screw in the bushing by theoretical analysis and artificial simulation. It has derived the mathematical expression which is the relative sliding velocity between the gear bulge contact spot and the gear concave contact spot of screw and bushing in curtate hypocycloid PCP, and has corrected the existing formula. The paper has contrasted the sliding velocity curves calculated by the formula to the curves calculated in motion emulation models, and has indicated that the mathematical expression of the rotor contact spot sliding velocity is correct. The method has been applied to the common hypocycloid PCP used extensively in oil fields. Comparing with other methods at present, its analysis procedure has been simplified. This method has also been applied to studying the curtate epicycloid PCP.The PCP modeling system which is appropriate for all kinds of the PCP is developed. If the basic construction parameters are input, the three-dimensional solid model of the PCP will be produced in SolidWorks. The paper has analyzed the PCP pressure formation and transmission, and has obtained the expression of the pressure distribution law.According to the working condition and relative test data of the progressing cavity pump, its three-dimensional solid finite element analysis models is established. The constitutive relation of stator rubber is Mooney model. The nonlinear contact finite element simulated computation has obtained the contact stress between screw and bushing, the shear stress and the equivalent stress of stator rubber, and its distribution law. Comparing the value of the average contact stress by simulated computation with by experiment, the error is 7%, indicating that the PCP finite element model is correct.The mechanical capacity of stator rubber is tested. According to relative standard, the stator rubber can meet static strength, and having the bigger margin; But, the abrasive resistance and swelling of stator rubber has just reached the minimum standard. It should be improved. Furthermore, the writer thinks that the dynamic property should be detected in the future.The friction coefficient and the wearing capacity of the screw-bushing have been measured by the simulation tests which weared between the metal and the stator rubber in the oil-water and in the oil-water-sand. The law that the friction coefficient and the wearing capacity varies as the normal load and the slide velocity has been obtained. According to the working condition of the oil exaction PCP and the research results of the kinetic, mechanics and wearing law of the screw-bushing, the wearing feature of stator rubber is analyzed, and the writer believes that the wearing styles of the PCP stator rubber are frictional wear, grain wear, fatigue wear and adhere wear. All kinds of wearing mechanism have been cleared, in addition, some means and ways to avoid abrasions are proposed.