What is the Excavators
I. Definition and Basic Structure of Excavators
Definition
An excavator is a type of heavy-duty construction machinery used for earthwork operations such as digging, loading, and unloading. It mainly drives working devices like the boom and bucket through a hydraulic system, enabling it to efficiently complete digging tasks in various complex terrains and working conditions. For example, it can be used to dig foundations in construction projects and to extract ores in mining operations.
Basic Structure
Undercarriage: It is the foundational part of the excavator, used to support the entire machine body and provide the walking function. It includes components such as tracks (or tires) and travel motors. Tracked undercarriages can adapt to rather rugged terrains, providing good stability and traction. They are widely used in mines and large construction sites. Tire-mounted undercarriages are more suitable for driving on relatively flat roads, with higher mobility, and are often used in urban construction and other working environments with better site conditions.
Machine Body: The machine body includes the cab and the engine compartment. The cab is the space where the operator controls the excavator. It is usually equipped with various operating levers, instrument panels, and seats, providing a comfortable and convenient operating environment for the operator. The engine compartment houses the engine, which is the power source of the excavator, providing power for the operation of the entire machine. The power is transmitted to various working components through the transmission system.
Working Devices: They mainly consist of the boom, arm, and bucket. The boom connects the machine body and the arm, and its function is to control the range of digging depth and height. The arm connects the boom and the bucket and can adjust the digging angle and extension distance of the bucket. The bucket is the component that directly performs digging and loading operations. Its shape and size vary according to different operation requirements. For example, there are general-purpose buckets for digging soft soil and heavy-duty buckets for digging rocks.
Hydraulic System: It is a key system of the excavator. It transmits power through the pressure of hydraulic oil to control the movements of various working devices. The hydraulic system includes components such as hydraulic pumps, hydraulic cylinders, and hydraulic valves. The hydraulic pump converts the mechanical energy of the engine into the pressure energy of the hydraulic oil. The hydraulic cylinders convert the pressure energy of the hydraulic oil into mechanical energy to drive the movement of the working devices. The hydraulic valves are used to control the flow direction and pressure of the hydraulic oil, thus achieving precise control of the movements of the working devices.
II. Working Principle of Excavators
Power Transmission
The power generated by the engine is first transmitted to the hydraulic pump through the transmission system (such as belts, chains, or drive shafts). The hydraulic pump converts the rotational power of the engine into the high-pressure flow of hydraulic oil. Under pressure, the hydraulic oil is transported through a series of hydraulic pipelines to various hydraulic cylinders and hydraulic motors.
For the working devices, when the hydraulic oil enters the hydraulic cylinders, it pushes the pistons to move, thus driving the boom, arm, and bucket and other components to perform corresponding movements. For example, when the hydraulic oil enters one side of the piston in the boom hydraulic cylinder, the piston extends outward under the pressure of the hydraulic oil, causing the boom to rise. When the hydraulic oil is discharged from one side of the piston and enters the other side, the piston retracts and the boom descends.
In terms of walking, the hydraulic oil is delivered to the travel motors to drive the tracks (or tires) to rotate, realizing the forward, backward, and turning movements of the excavator.
Control of Digging Movements
The operator controls the opening and closing degree and direction of the hydraulic valves through the operating levers in the cab. Different operating levers control the movements of different working devices. For example, one lever controls the lifting and lowering of the boom, another lever controls the extension and retraction of the arm, and another lever controls the opening and closing of the bucket.
When the operator operates the boom lever to lift it upward, the corresponding hydraulic valve opens, allowing the hydraulic oil to flow into the boom hydraulic cylinder in a specific direction, pushing the boom to rise. When the lever is operated downward, the hydraulic valve changes the flow direction of the hydraulic oil, causing the boom to descend. Similarly, the movements of the arm and bucket are also controlled by operating the corresponding levers and changing the state of the hydraulic valves, thus achieving precise digging movements.
III. Classification of Excavators
Classification by Walking Method
Tracked Excavators: They are characterized by walking on tracks, having good stability and strong traction. They can operate on soft, muddy, and rugged terrains and are widely used in mines, large construction sites, water conservancy projects, and other sites. Due to the large contact area between the tracks and the ground and the small ground pressure, they are not easily sunk when carrying heavy weights. However, the walking speed of tracked excavators is relatively slow, and the maintenance cost of the tracks is relatively high.
Tire-mounted Excavators: They rely on tires to walk, having high mobility and driving speed, and are suitable for driving on relatively flat roads such as urban roads and highways, enabling them to quickly transfer between different working sites. However, the stability of tire-mounted excavators is relatively poor. Especially when carrying heavy loads or operating on soft ground, they are prone to sinking or overturning. Moreover, they exert relatively large pressure on the ground, and their passability in some special terrains (such as muddy areas) is not as good as that of tracked excavators.
Classification by Working Devices
Front Shovel Excavators: The movement direction of the bucket of front shovel excavators is forward and upward for digging. They are mainly used to dig earthwork and materials above the stopping surface. They have relatively large digging force and are suitable for digging relatively hard soil and ores. They are often used in large open-pit mines, large building foundation digging, and other working scenarios. Front shovel excavators have high working efficiency, but their digging range is relatively small, mainly digging in front of the machine body.
Backhoe Excavators: The movement direction of the bucket of backhoe excavators is backward and downward for digging. They are the most common type of excavators. They can dig earthwork below the stopping surface, such as digging ditches and basements. Backhoe excavators have flexible digging movements and can operate in relatively narrow spaces. Moreover, their digging range is relatively wide. Besides in front of the machine body, they can also conduct certain digging operations on the sides.
Dragline Excavators: The bucket of dragline excavators is controlled by cables. They are mainly used to dig large areas of relatively soft earthwork, such as digging river sand and large earthwork stockyards. They have a relatively large digging radius but relatively small digging force. Moreover, their working accuracy is not as good as that of front shovel and backhoe excavators.
Grab Excavators: The working device of grab excavators is the grab, which is mainly used to grab blocky and granular materials, such as ores, wood, and garbage. They have accurate grabbing movements and can adapt to various materials with different shapes and properties. They are often used in port loading and unloading, garbage disposal, and other operations.
IV. Application Areas of Excavators
Construction Engineering Field
In the foundation construction stage of construction projects, excavators are used to dig the foundations of buildings. They can quickly remove the surface soil and obstacles on the ground and dig to the depth required by the design, preparing for subsequent foundation pouring and other work. For example, in the construction of high-rise buildings, excavators can dig large and deep foundation pits in a short time.
In terms of the loading and unloading of construction materials, excavators can unload construction materials (such as sand, gravel, bricks, etc.) from transport vehicles to designated stacking locations or load them into processing equipment such as mixers. Their efficient loading capacity can greatly improve the turnover efficiency of construction materials.
In addition, excavators are also used for site leveling, leveling uneven land into a plane suitable for construction, creating good conditions for the layout and construction of buildings.
Mining Field
Excavators are one of the main equipment in mining. In open-pit mines, excavators are used to dig ores, extracting them from the ore beds. According to the hardness of the ores and the scale of mining, appropriate types of excavators are selected. For example, front shovel excavators are used to dig ores with relatively high hardness, and backhoe excavators are used to dig ores in marginal areas or clean up mine pits.
At the same time, excavators are also used for the loading operation of ores, loading the extracted ores onto transport vehicles (such as mining trucks) so that the ores can be transported to concentrators or other processing locations. Their powerful loading capacity can meet the needs of large-scale mining.
Water Conservancy Engineering Field
In the construction of water conservancy projects, such as building reservoirs, dams, and river regulation projects, excavators play an important role. They can be used to dig river channels, build the foundations of dams, and dig the storage capacity of reservoirs. For example, in river dredging operations, excavators can remove silt and debris in the river channels, widen and deepen the river channels, and improve the flood control and navigation capabilities of the river channels.
For some large water conservancy hub projects, excavators also participate in the loading and unloading of building materials such as concrete and in construction assistance work to ensure the smooth progress of the projects.
Transportation Engineering Field
In highway construction, excavators are used to dig the subgrade of the highway and remove weeds, trees, and rocks and other obstacles within the subgrade range. In railway construction, excavators are also used to dig the ballast bed foundation, creating conditions for the laying of rails.
In addition, in the later maintenance of transportation engineering, excavators can also be used to clean up road collapses and repair the subgrade, ensuring the safety and smoothness of transportation lines.
Agriculture and Forestry Fields
In agriculture, excavators can be used to dig irrigation channels, ponds, and other water conservancy facilities, providing irrigation water sources for crops. They can also be used for land reclamation, developing wasteland or unused land into farmland suitable for cultivation.
In forestry, excavators are used to clear stumps and tree roots in forestlands, creating good site conditions for afforestation. They can also be used to build forest fire prevention belts to prevent the spread of forest fires.
