Research On Swelling Behavior And Wear Resistance Performance Of NBR In The Crude Oil Medium

The screw pump is composed by metal rotor and rubber stator mainly. In the work process, they make a dynamic seal chamber that transfer the oil to ground. Due to the complicated production conditions, which is often accompanied by high temperature, pressure, sand, gas, H2 S, CO₂ and other corrosive gas, it makes a degradation on rubber wear resistance performance, and then affect the efficiency and service life of the screw pump work. According to different production conditions to choose the corresponding formula of NBR is the foundation in manufacturing screw pump stator rubber, so the research of stator rubber formula using performance has become the focus of research. At present, the domestic and foreign scholars have carried out relevant research but there has no reasech on the physical and chemical changes, tribological behaviour and mechanism of friction before and after swelling in medium yet. It will reveal the wear and tear failure mechanism of stator rubber in the working condition of production, provide theoretical and technical support for the reasonable selection of stator rubber, and enrich theory and practice knowledge of rubber tribology.In this paper, the friction pair of metal rotor and stator rubber is research object, and the actual working condition of screw pump is simulated in laboratory. The test analysis program of stator rubber swelling and wear is established, the swelling and wear test can be done under the condition of different media. Several NBR samples with different acrylonitrile content were choosed as test object.Static swelling experiment was carried out in cyclohexane medium, different temperature medium of crude oil and deionized water bubbled into CO₂, etc and the friction and wear simulation test were done under same conditions to measure the coefficient of friction and wear. The change rule of wear volume is obtained by comparison and analysis with test conditions.Then measure the chemical element content, the molecular structure and surface topography of the swelling and aging NBR by using Fourier infrared spectroscopy appearance（FT-IR）, nuclear magnetic resonance analyzer and scanning electron microscope appearance（SEM）. Comprehensive test results in showing that:In cyclohexane corrosive medium with the extension of soaking time the amount of swelling is gradually increased, plasticizer was separated out, surface damage is serious, and mechanical performance degraded. After swelling the rubber sample wear is obvious better the original sample. With the increase of wear and tear load, wear mechanism gradually became to be serious abrasive wear from mild abrasive wear. Under low load, the wear promoted the swelling, but swelling accelerated wear under high load cases.Bubbling CO₂ into deionized water, with the increase of gas flow, swelling ratio increased, the network structure of rubber molecules damaged seriously, the surface appears obvious cracks and holes and mechanical performance declines. The bubbling gases make abrasion loss increase,but the friction coefficient decrease. The existence of the squeezing effect in the process of wear and tear promoted the swelling of rubber.In the increasing temperature of crude oil medium,the swelling quantity of low amount of acrylonitrile in NBR increased and hardness decreased; the swelling quantity of high amount of acrylonitrile in NBR decreased and there was no obvious change in hardness. But the tensile properties of three kinds of rubber samples showed a trend of decline. With the same wear condition, after swelling the rubber sample wear is significantly higher than the no swelling rubber, and there was no significant difference o friction coefficient.In order to comprehensively evaluate the effect of different factors on swelling, aging, friction and wear, screw pump stator rubber friction system is built. On the basis of the screw pump stator rubber friction system, preliminary forecast screw pump stator rubber wear by using the artificial neural network theory to show that the artificial neural network technology applied to multi-factor coupling under the action of the tribological characteristics study of screw pump stator is feasible. There is auxo-actions to improve the service life of pumping system, which lying a foundation for subsequent tribological system theory research.The complexity of stator rubber swelling aging and the friction and wear is expounded in this article and shows the effect on NBR swelling aging, mechanics and friction and wear performance in different swelling medium and acrylonitrile content. And deeply analyzed chemical composition, surface structure and molecular chain change after swelling, aging, friction and wear; cleared the law of swelling and wear mechanisms, as well as the interaction relations between swelling aging and tribological properties. These conclusions provide the experimental data and theoretical basis for making the economy, longevity, reliable oil wells nitrile rubber. It also has guiding significance for rational selection of screw pump stator rubber, and provided an important theoretical basis to prolong working life of the screw pump. That laid the foundation of the stator rubber tribology theory system and new stator rubber material development.