The drilling and construction progress in projects depends not only on the machines used, but also quite significantly on reliable tools. For cased pile foundations, a robust drilling grab is essential. LEFFER has developed three robust digging grabs with high impact force for sinking boreholes in rocky, rolling soils and for working under water superimposed loads:
The single-rope pulley grab is particularly characterized by its oil-filled bearings, which remain maintenance-free over the entire service life. The design of the two-rope grab is similar, but does without a pawl carrier and release crown. Lifting and lowering of the grab is controlled by the first rope, the so-called drive rope. The second rope (closing rope) is used for opening and closing.
With this design, the operator can also open and close the grab several times during the drilling process – for example, to loosen the ground or to empty the grab in very cohesive soil. If very large closing forces are required, the use of spherical grabs is recommended. Due to its high intrinsic mass and additional teeth on the spherical shells, the spherical grab can dig into the ground during the closing process and exert very high splitting forces on the ground to be loosened.