Study on factors influencing the sealing performance of a polished-rod sealing device for a pumping unit
To identify the key factors affecting the sealing performance of a polished-rod sealing device under typical operating conditions, a beam pumping unit polished-rod sealing device was investigated in this study. Uniaxial tensile tests were performed on nitrile butadiene rubber, and the material constants of the two-parameter Mooney–Rivlin model were determined as C10=2.05411 and C01=0.10236. A two-dimensional axisymmetric finite element model was then established to analyze the effects of axial pressure, temperature, and friction coefficient on the contact pressure, stress, strain, and deformation of the sealing packing. The results show that axial pressure is the dominant factor affecting sealing performance. Within the axial pressure range of 2–12 MPa, the contact pressure increased significantly with increasing axial pressure. When the axial pressure reached 4 MPa, the average contact pressure at the sealing interface was 1.63 MPa, exceeding the wellhead pressure of 0.5 MPa and satisfying the sealing requirement. The recommended axial pressure range is 4–10 MPa. Within the temperature range of 20 °C–100°C, temperature had little effect on the contact pressure, stress, and strain distributions. In the friction coefficient range of 0.02–0.2, the contact pressure changed only slightly, while the friction force increased with increasing friction coefficient; when the friction coefficient reached 0.2, the maximum friction force was 1.0821 N. These results provide a theoretical basis for the structural optimization, material selection, and operating parameter design of polished-rod sealing devices.