people fromoperation.NOTE:completionoperations.congregating around the crane when inSafe lifting is paramount! Projectmust not interfere with safe craneCLAMSHELL OPERATIONSThe clamshell bucket is an attachment used with acrane for vertical digging belowground level and forplacing materials at considerable height, depth, ordistance. You can also use it for moving bulk materialsfrom stockpiles to plant bins, loading hoppers, andconveyors. It can be used to dig loose to mediumcompacted soil.Clamshell operating procedures are as follows:1. Position and level the crane, ensuring thedigging operation is as close to the radius as the dumpingoperation. This prevents you from having to boom upand down, resulting in a loss of production.2. Select the correct size and type of bucket for thecrane.3. When lowering the clamshell bucket, if toomuch pressure is applied to the closing line brake, thebucket will close and an excess amount of wire rope willunwind from the holding line hoist drum. To avoid this,you should release the holding line and closing linebrakes simultaneously when lowering the openclamshell into the material for the initial bite. Engagethe closing line control lever to close the bucket.Control the digging depth by using the holding linecontrol lever and brake.4. If, during hoisting, the hoist line gets ahead ofthe closing line, the bucket will open and spill thematerial. (This could also be caused by having too muchwire rope on the hoist drum.) The operator must hoistboth the closing and holding lines at the same speed tokeep the bucket from opening and spilling material.5. When the clamshell bucket is raised enough toclear all obstacles, start the swing by engaging the swingcontrol lever. Hoisting the bucket can be performed, asit is swung to the dumping site. The spring-loaded tagline will retard the twisting motion of the bucket if theswing is performed smoothly.6. Dumping and unloading the clamshell isperformed by keeping the holding line brake appliedwhile the closing line brake is released. Apply theclosing line brake quickly after the load is dumped toprevent the closing line from unwinding more wire ropethan is needed to dump the material. After the bucket isemptied, swing the open clamshell back to the diggingsite. 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 clamshelloperations should be between 40 to 60 degrees. Becareful when working with higher boom angles, as thebucket could hit the boom. A clamshell attachment isnot a positive digging tool.The height reached by the clamshell depends on thelength of the boom used. The depth reached by theclamshell is limited by the length of wire rope that thehoist drum can handle. For the safe lifting capacity forthe clamshell, refer to the operator’s manual and thecrane capacity load chart.DRAGLINE OPERATIONSThe dragline is a versatile attachment capable of awide range of operations at and belowground level. Thedragline can dig through loose to medium compactedsoil. The biggest advantage of the dragline over othermachines is its long reach for both digging and dumping.Another advantage is its high cycle speed. The draglinedoes not have the positive digging force of the backhoe.The bucket is not weighted or held in alignment by rigidstructures; therefore, it can bounce, tip over, or driftsideways when digging through hard materials. Thisweakness increases with digging depth.Dragline operating procedures are as follows:1. Keep the teeth sharp of the dragline bucket andbuilt up to proper size.2. Keep the dump rope short, so the load can bepicked up at a proper distance from the crane.3. Excavate the working area in layers, not intrenches, and sloped upward toward the crane.4. Do not drag the bucket in so close to the cranethat it builds piles and ridges of material in front of thecrane.5. Do not guide the bucket by swinging the cranewhile digging. This puts unnecessary side stresses onthe boom. Start the swing only after the bucket has beenraised clear of the ground.6. A pair of drag chains is attached to the front ofthe bucket through brackets by which the pull point maybe adjusted up or down. The upper position is used fordeep or hard digging, as it pulls the teeth into a steeperangle.12-34
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