Special Hammer Grabs

Special Hammer Grab

LEFFER’s robust free-fall grabs with high closing force are ideally suited for boring in detritus soils and for water logged pile foundations. The pulleys are equipped with oil-filled, maintenance-free lifetime bearings.

The LEFFER hammer grab can be utilized in the recommended double rope operation, as well as in single rope operations for which a grab cover with latches and simple chandelier is necessary.

Double Rope – During the double rope operation, the first rope is attached to the locking mechanism and the second is attached to the chain suspension tackle of the hammer grab unit. When lowering the hammer grab into the casing hole, the first rope is lifted and thus the grab jaws are closed. At the required location, the second rope is lifted and the grab jaws are opened by means of the heavy spring. The brakes of both cable dredger winches are opened, the hammer grab drops with open grab jaws and penetrates deep into the strata.

In order to obtain maximum filing capacity of the grab jaws, the hammer grab can be lifted several times using the second rope in order to penetrate deeper into the hard strata with opened grab jaws. This creates a chisel effect before being withdrawn with closed jaws by means of the first rope.

Single Rope – In the single rope operation the grab is suspended at the closing mechanism and is driven into the casing with opened grab jaws. It drops freely at the required location and into the casing bottom with the jaws open. When hitting the casing bottom, the latches in the grab cover are falling to the outside and the jaws are closed when pulling the rope attached to the closing mechanism. After withdrawl from the casing, the grab is guided into the chandlier and slowly lowered. The catch hooks grip on the hammer grab neck below the retaining ring and the grab jaws strike open due to the heavy spring force, which enables even adhesive bore medium to loosen quickly. In order to release the grab from the chandelier, it is pulled up until the chandelier is lifted slightly and then is lowered with the jaws open.

Both the double rope and single rope operation are quick, reliable and highly economical.

View product brochure at the bottom of the page.

Special Hammer Grab (L Series), Cable Type

LEFFER L Series Special Hammer Grabs are ideal for boring fully cased pilings in detritus soils and below-water pile foundations. These are a free-fall, pulley type grabs that feature robust design and high closing forces. A broad selection of LEFFER special hammer grab models are available for use with casing diameters that range from 600 to 3000 mm. Models are available in single rope pulley grab (SK designation), single rope pulley grab with teeth (RK designation), double rope pulley grab (SZ), or double rope pulley grab with teeth (RZ designation. Like other LEFFER machinery and grabs, the L Series Special Hammer grabs are precision engineered, constructed from the finest materials, and proven through decades of service with leading foundation construction firms. When use in conjunction with LEFFER hydraulic casing rotator/oscillator pile boring equipment, these special hammer grabs deliver rapid and efficient pile construction for large and deep projects in any, including the most difficult, of soil conditions.

LEFFER Special Hammer Grab (L Series), Cable Type – Model and Type Overview

Range of Casing Diameters	Models/ Types	Single Rope pulley grab	Single rope pulley grab with teeth	Double rope pulley grab	Double rope pulley grab with teeth
600-1000 mm	L 490-L 890	SK	-	SZ	-
900-1600 mm	L770-L 1460	SK	RK	SZ	RZ
1500-2500 mm	L 1350–L2250	SK	RK	SZ	RZ
2500-3000 mm	L2170-L2750	-	RK	-	RZ

LEFFER Special Hammer Grab (L Series), Cable Type – Features and Benefits

Features	Benefits
Four frame sizes cover all diameters when using individual kits	Greater performance and flexibility at less cost
Design incorporates maximum mechanical advantage. Force multiplication is increased for larger sized grabs	Optimal closing force for each frame size
Fully enclosed and sealed bearings	Low maintenance. High durability.
Double rope grabs can chop to penetrate	Flexibility in firm soils. Improved productivity by ensuring a full load on each cycle.

View product brochure at the bottom of the page.

Spherical Grab (LKG Series)

LEFFER LKG Series Spherical Grabs are for drilling/excavating bored pilings. The LKG Series includes 18 individual models sized for excavating cased bores or drilled shafts from 880 to 3800mm in diameter. The LEFFER Spherical Grabs incorporate a double rope grab with high closing force that makes it suitable for vibration free boring in hard soil conditions, and in cobble and boulder soil conditions as well.

LEFFER Spherical Grab (LKG series) – Features and Benefits

Features	Benefits
Optimized grab kinematics and jaw design	High shearing forces at the jaw edges and low movement ensure full loading- delivering increased
Four frame sizes cover all diameters when using individual kits	Greater performance and flexibility at less cost
Design incorporates maximum mechanical advantage. Force multiplication is increased for larger sized grabs	Optimal closing force for each frame size