Stationary Loading Machines: Dragline and Excavator Operations

Item 12: Stationary Loading Machines

1. What is a dragline and what is its function?

The dragline is a stationary loading machine consisting of a bucket (dipper or spoon) that is released and controlled by cables to collect earth. After the collection process, the bucket is suspended, allowing the operator to rotate the machine and deposit the load at any position within the reach of the boom.

2. Dragline terminology and components

Also known as a dragline excavator, its primary components include:

• Chassis
• Movement systems (caterpillars or crutches)
• Boom base
• Boom head pulley
• Bucket (spoon)
• Cables

3. Difference between shovel and backhoe

The primary difference lies in the level of excavation:

• Shovel: Collects material above the level of its caterpillars.
• Backhoe: Operates at a level lower than its caterpillars, making it ideal for digging trenches.

4. Clamshell bucket (gripping jaws)

The clamshell bucket is a gripping device that collects material by dropping from an elevated position. The shells close via cables or a hydraulic system, allowing the material to be lifted without spilling.

Components: Boom and jaw bucket.

5. Drop-ball equipment

This is an attachment for cable excavators that replaces the bucket with a heavy, voluminous mass of special steel or cast iron suspended by a chain or cable.

Primary uses:

• Demolition of walls.
• Breaking large boulders or concrete.

6. Adaptable tools for stationary excavators

Common attachments include:

• Crane
• Hammer
• Hammer breaker
• Drop-ball equipment

7. Composition of the excavator bucket

It consists of an articulated arm that tilts in the vertical plane, supporting a string of endless buckets. The tilt and joint maneuvers are controlled by cables, or more rarely, by hydraulic cylinders or mechanical systems.

8. General rules for operating draglines

• Perform digging in thin, uniform layers to avoid grooves.
• Do not plunge the bucket suddenly, as this may cause cracks in the steel.
• In extreme cold, preheat the bucket before operation to prevent structural failure.
• Maintain the bucket in good condition at all times.
• Ensure the drag cable remains taut against the ground during dredging.

9. Defining the radius of operation

The radius of operation is determined by the length of the boom and the horizontal distance from the axis of the chassis to the projection of the boom head.