Abstract: Aiming at seal extrusion, seal damage, increased oil mist and frequent starts of the pressure-oil pump at the joint between the rotating sleeve of the oil distributor and the upper operating oil pipe, field maintenance records and stroke measurements were analyzed. A sealing pressure plate with separated axial static sealing and radial dynamic sealing is proposed. Application results show that the improved step seal and O-ring combined structure reduces extrusion and shear risks and improves oil-system operation.