... steel hoisting level,vertical hoisting 2.Clamping force control by hydraulic 3.Load:RYY (6-12t),RYYL( 20-28t) High ... adjust the size of clamping force , In the hydraulic cylinder oil by hydraulic lock in and out of the mouth, ensure malfunction, ... can keep hydraulic cylinder pressure. 4. The hydraulic cylinder, valve body and hydraulic ...