Slewing bearing can simultaneously support larger combined load including axial load, radial load and tilting moment etc. General slewing bearing all has mounting holes, oil holes and sealing apparatus, can meet categories of main machine operating under various different conditions. In addition, slewing bearing possess the characteristics of compact structure, guiding rotation convenient, easy installation and easy to maintenance, and widely applied to large size slewing equipment in the industries of engineering, mining, metallurgy, wind power generation, vessel, seaport, petroleum, chemical industry, light industry, medical appliance, foodstuff, vehicle, robot, aerospace, radar and war industry etc. According to different structural style, slewing bearing can be divided into four point contact ball slewing bearing, cross cylindrical (taper) roller slewing bearing, double row four point ball slewing bearing, double row different diameter ball slewing bearing, ball and roller combined slewing bearing and tri-row cylindrical roller combined slewing bearing etc. Above mentioned slewing bearings can also be divided into different structures of no gear type, external gear type and internal gear type as per if exist gear and gear teeth distributing position. According to different structural feature, slewing bearing can respectively meet main machine requirements under various load conditions. Among them, four point contact ball slewing bearing has higher dynamic load capacity, cross cylindrical roller slewing bearing has higher static load capacity. Tri-row cylindrical roller combined slewing bearing is a kind of high carrying capacity slewing bearing, due to leading raised carrying capacity to direction of bearing height, various loads can be respectively supported by different raceways and roller sets, so raceway diameter greatly decrease under the same stress condition, it has the character of making main machine more compact. Zsj standard packing