congregating around the crane when in
Safe lifting is paramount! Project
must not interfere with safe crane
The clamshell bucket is an attachment used with a
crane for vertical digging belowground level and for
placing materials at considerable height, depth, or
distance. You can also use it for moving bulk materials
from stockpiles to plant bins, loading hoppers, and
conveyors. It can be used to dig loose to medium
Clamshell operating procedures are as follows:
1. Position and level the crane, ensuring the
digging operation is as close to the radius as the dumping
operation. This prevents you from having to boom up
and down, resulting in a loss of production.
2. Select the correct size and type of bucket for the
3. When lowering the clamshell bucket, if too
much pressure is applied to the closing line brake, the
bucket will close and an excess amount of wire rope will
unwind from the holding line hoist drum. To avoid this,
you should release the holding line and closing line
brakes simultaneously when lowering the open
clamshell into the material for the initial bite. Engage
the closing line control lever to close the bucket.
Control the digging depth by using the holding line
control lever and brake.
4. If, during hoisting, the hoist line gets ahead of
the closing line, the bucket will open and spill the
material. (This could also be caused by having too much
wire rope on the hoist drum.) The operator must hoist
both the closing and holding lines at the same speed to
keep the bucket from opening and spilling material.
5. When the clamshell bucket is raised enough to
clear all obstacles, start the swing by engaging the swing
control lever. Hoisting the bucket can be performed, as
it is swung to the dumping site. The spring-loaded tag
line will retard the twisting motion of the bucket if the
swing is performed smoothly.
6. Dumping and unloading the clamshell is
performed by keeping the holding line brake applied
while the closing line brake is released. Apply the
closing line brake quickly after the load is dumped to
prevent the closing line from unwinding more wire rope
than is needed to dump the material. After the bucket is
emptied, swing the open clamshell back to the digging
site. Then lower the open bucket and repeat the cycle.
The clamshell operating cycle has four steps: filling
(closing) the bucket, raising the loaded bucket,
swinging, and dumping. The boom angle for clamshell
operations should be between 40 to 60 degrees. Be
careful when working with higher boom angles, as the
bucket could hit the boom. A clamshell attachment is
not a positive digging tool.
The height reached by the clamshell depends on the
length of the boom used. The depth reached by the
clamshell is limited by the length of wire rope that the
hoist drum can handle. For the safe lifting capacity for
the clamshell, refer to the operators manual and the
crane capacity load chart.
The dragline is a versatile attachment capable of a
wide range of operations at and belowground level. The
dragline can dig through loose to medium compacted
soil. The biggest advantage of the dragline over other
machines is its long reach for both digging and dumping.
Another advantage is its high cycle speed. The dragline
does not have the positive digging force of the backhoe.
The bucket is not weighted or held in alignment by rigid
structures; therefore, it can bounce, tip over, or drift
sideways when digging through hard materials. This
weakness increases with digging depth.
Dragline operating procedures are as follows:
1. Keep the teeth sharp of the dragline bucket and
built up to proper size.
2. Keep the dump rope short, so the load can be
picked up at a proper distance from the crane.
3. Excavate the working area in layers, not in
trenches, and sloped upward toward the crane.
4. Do not drag the bucket in so close to the crane
that it builds piles and ridges of material in front of the
5. Do not guide the bucket by swinging the crane
while digging. This puts unnecessary side stresses on
the boom. Start the swing only after the bucket has been
raised clear of the ground.
6. A pair of drag chains is attached to the front of
the bucket through brackets by which the pull point may
be adjusted up or down. The upper position is used for
deep or hard digging, as it pulls the teeth into a steeper