DRAGLINE OPERATIONS

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 crane.

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 angle.

7. The drag cable can be reversed end for end to prolong the life of the wire rope, reduce early wire rope replacement, and keep wire rope cost down. Remember, the drag cable should not be lubricated.

8. When lowering the dragline bucket into the area to be worked, release the drag brake to tip the cutting edge down and then release the hoist brake. You do not have to drop the bucket to force the teeth into the material. The bucket is filled as it is dragged toward the crane by engaging the drag control lever. The cutting depth is controlled by releasing tension from the hoist brake. The dragline is NOT a positive digging tool.

9. The dragline cycle is filling the bucket, lifting the bucket, swinging the loaded bucket, and dumping the load.

10. Since the dragline is not a rigid attachment, it will not dump materials as accurately as do other excavators. When a load is dumped into a haul unit or hopper, you need more time to position the bucket before dumping it.

NOTE: When you are dumping into a haul unit, NEVER load over the cab. Additionally, make sure the operator is out of the cab and clear of the dragline or clamshell bucket.

11. The boom angle for dragline operations should normally be from 25 to 35 degrees. However, check the crane load chart to ensure this low boom angle does not exceed the capacity of the crane. At this relatively low boom angle, you must be careful when excavating and dumping wet, sticky materials, because the chance of tipping the crane is increased because the material tends to hang in the bucket.

Dragline Employment

The dragline can be used in dredging where the material handled is wet and sticky. It can dig trenches, strip overburden, clean and dig road side ditches, and _{slope embankments.} When the dragline is handling mud, it is the most practical attachment. Its reach enables it to handle a wide area of excavation while sitting in one position, and the sliding action of the bucket eliminates trouble with suction.

Other uses of the dragline include the following:

_{1. In-line approach.} When excavating a trench with the dragline, ensure the dragline and carrier unit are centered on the excavation (fig. 12-48). The dragline cuts or digs to the front and dumps on either side of the excavation. The crane moves away from the face as the work progresses.

2. Parallel approach. The dragline can slope an embankment better by working it from the bottom to the top. The crane is positioned on the top with the carrier parallel to the working face, so it can move the full length of the job without excessive turning.

3. Drainage. A dragline is ideal if earthwork materials have to be removed from a trench, canal, gravel pit, and so forth, containing water. Plan the work to begin at the lowest grade point, so drainage will be provided as the dragline progresses towards higher levels.

NOTE: Digging underwater or in wet materials increase the weight of the materials and frequently prevent carrying heaped bucket loads.

Ditching the excavation through swamps or soft terrain is common. Under these conditions the excavated material is normally cast onto a levee or spoils bank.

4. Loading haul units. When the job requires excavated material to be loaded into hauling units, the excavation should be opened up so loaded hauling equipment can travel on high, dry ground or on better grades. The spotting of trucks and dragline should be planned for minimum boom swing with the truck bed under the boom point and the long axis of the bed parallel with the long axis of the boom or at right angles to the boom. More spillage is to be expected from a dragline than from a front-end loader.