... ,Tower Crane,Truck crane,and so on.3. Single-Row Crossed Roller Slewing Ring( 11 series) The ... Machinery. 4. Three-Row Roller Slewing Ring( 13 series) Three-Row Roller Slewing Ring has 3 seat-rings,Upper ... Orbit,Nether Orbit and Radial Orbit are separated individually,it makes the load of each row ... -duty Truck Crane,and so on. 5.Single-Row Four Point Contact Ball Slewing Ring( QU,QW ...