Excavator
Overview
 
Excavators are heavy construction equipment consisting of a boom
Backhoe
A backhoe, also called a rear actor or back actor, is a piece of excavating equipment or digger consisting of a digging bucket on the end of a two-part articulated arm. They are typically mounted on the back of a tractor or front loader...

, stick, bucket
Bucket (machine part)
A bucket is a specialized container attached to a machine, as compared to a bucket adapted to the form of a human being...

 and cab on a rotating platform (known as the "house"). The house sits atop an undercarriage with tracks
Caterpillar track
Continuous tracks or caterpillar tracks are a system of vehicle propulsion in which modular metal plates linked into a continuous band are driven by two or more wheels...

 or wheel
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

s. A cable-operated excavator uses winches and steel ropes to accomplish the movements. They are a natural progression from the steam shovel
Steam shovel
A steam shovel is a large steam-powered excavating machine designed for lifting and moving material such as rock and soil. It is the earliest type of power shovel or excavator. They played a major role in public works in the 19th and early 20th century, being key to the construction of railroads...

s and often called power shovels. All movement and functions of a hydraulic excavator are accomplished through the use of hydraulic fluid
Hydraulic fluid
Hydraulic fluids, also called hydraulic liquids, are the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water...

, with hydraulic cylinder
Hydraulic cylinder
A Hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in engineering vehicles.- Operation :...

s and hydraulic motor
Hydraulic motor
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement . The hydraulic motor is the rotary counterpart of the hydraulic cylinder....

s.
Encyclopedia
Excavators are heavy construction equipment consisting of a boom
Backhoe
A backhoe, also called a rear actor or back actor, is a piece of excavating equipment or digger consisting of a digging bucket on the end of a two-part articulated arm. They are typically mounted on the back of a tractor or front loader...

, stick, bucket
Bucket (machine part)
A bucket is a specialized container attached to a machine, as compared to a bucket adapted to the form of a human being...

 and cab on a rotating platform (known as the "house"). The house sits atop an undercarriage with tracks
Caterpillar track
Continuous tracks or caterpillar tracks are a system of vehicle propulsion in which modular metal plates linked into a continuous band are driven by two or more wheels...

 or wheel
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

s. A cable-operated excavator uses winches and steel ropes to accomplish the movements. They are a natural progression from the steam shovel
Steam shovel
A steam shovel is a large steam-powered excavating machine designed for lifting and moving material such as rock and soil. It is the earliest type of power shovel or excavator. They played a major role in public works in the 19th and early 20th century, being key to the construction of railroads...

s and often called power shovels. All movement and functions of a hydraulic excavator are accomplished through the use of hydraulic fluid
Hydraulic fluid
Hydraulic fluids, also called hydraulic liquids, are the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water...

, with hydraulic cylinder
Hydraulic cylinder
A Hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in engineering vehicles.- Operation :...

s and hydraulic motor
Hydraulic motor
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement . The hydraulic motor is the rotary counterpart of the hydraulic cylinder....

s. Due to the linear actuation of hydraulic cylinders, their mode of operation is fundamentally different from cable-operated excavators.

Terminology

Excavators are also called diggers, JCBs (a proprietary name
J. C. Bamford
JCB is a global construction, demolition and agricultural equipment company headquartered in Rocester, United Kingdom. It is the world's third-largest construction equipment manufacturer. It produces over 300 types of machines, including diggers , excavators, tractors and diesel engines...

) or 360-degree excavators (sometimes abbreviated simply to 360). Tracked excavators are sometimes called "trackhoes" by analogy to the backhoe
Backhoe
A backhoe, also called a rear actor or back actor, is a piece of excavating equipment or digger consisting of a digging bucket on the end of a two-part articulated arm. They are typically mounted on the back of a tractor or front loader...

. In the UK, wheeled excavators are sometimes known as "rubber ducks."

Usage

Excavators are used in many ways:
  • Digging of trench
    Trench
    A trench is a type of excavation or depression in the ground. Trenches are generally defined by being deeper than they are wide , and by being narrow compared to their length ....

    es, holes, foundations
    Foundation (architecture)
    A foundation is the lowest and supporting layer of a structure. Foundations are generally divided into two categories: shallow foundations and deep foundations.-Shallow foundations:...

  • Material handling
  • Brush cutting with hydraulic attachments
  • Forestry work
  • Demolition
    Demolition
    Demolition is the tearing-down of buildings and other structures, the opposite of construction. Demolition contrasts with deconstruction, which involves taking a building apart while carefully preserving valuable elements for re-use....

  • General grading/landscaping
  • Heavy lift, e.g. lifting and placing of pipes
  • Mining
    Mining
    Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...

    , especially, but not only open-pit mining
    Open-pit mining
    Open-pit mining or opencast mining refers to a method of extracting rock or minerals from the earth by their removal from an open pit or borrow....

  • River
    River
    A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

     dredging
  • Driving piles
    Deep foundation
    A deep foundation is a type of foundation distinguished from shallow foundations by the depth they are embedded into the ground. There are many reasons a geotechnical engineer would recommend a deep foundation over a shallow foundation, but some of the common reasons are very large design loads, a...

    , in conjunction with a pile driver
    Pile driver
    A pile driver is a mechanical device used to drive piles into soil to provide foundation support for buildings or other structures. The term is also used in reference to members of the construction crew that work with pile-driving rigs....


Configurations

Excavators come in a wide variety of sizes. The smaller ones are called mini or compact excavator
Compact excavator
A compact or mini excavator is a tracked or wheeled vehicle with an approximate operating weight from 0.7 to 8.5 tonnes. It generally includes a standard backfill blade and features independent boom swing....

s. Caterpillar's
Caterpillar Inc.
Caterpillar Inc. , also known as "CAT", designs, manufactures, markets and sells machinery and engines and sells financial products and insurance to customers via a worldwide dealer network. Caterpillar is the world's largest manufacturer of construction and mining equipment, diesel and natural gas...

 smallest mini-excavator weighs 3549 pounds (1,609.8 kg) and has 19 hp
Horsepower
Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the...

; their largest model weighs 187360 pounds (84,985.1 kg) and has 513 hp
Horsepower
Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the...

. The largest excavator available is the Orenstein & Koppel RH400, it weighs in excess of 2160510 pounds (979,990.9 kg), has 4500 hp and has a bucket size of about 52.0 m³.

Engines in excavators drive hydraulic pump
Hydraulic pump
Hydraulic pumps are used in hydraulic drive systems and can be hydrostatic or hydrodynamic.Hydrostatic pumps are positive displacement pumps while hydrodynamic pumps can be fixed displacement pumps, in which the displacement cannot be adjusted, or variable displacement pumps, which have a more...

s; there are usually 3 pumps: the two main pumps are for supplying oil at high pressure (up to 5000 psi
Pounds per square inch
The pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units...

) for the rams
Hydraulic cylinder
A Hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in engineering vehicles.- Operation :...

, swing motor, track motors, and accessories, and the third is a lower pressure (700 psi
Pounds per square inch
The pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units...

) pump for Pilot Control, this circuit used for the control of the spool valves, this allows for a reduced effort required when operating the controls.

The two main sections of an excavator are the undercarriage
Undercarriage
The undercarriage or landing gear in aviation, is the structure that supports an aircraft on the ground and allows it to taxi, takeoff and land...

 and the house. The undercarriage includes the blade (if fitted), tracks, track frame, and final drives, which have a hydraulic motor
Hydraulic motor
A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement . The hydraulic motor is the rotary counterpart of the hydraulic cylinder....

 and gearing providing the drive to the individual tracks, and the house includes the operator cab, counterweight
Counterweight
A counterweight is an equivalent counterbalancing weight that balances a load.-Uses:A counterweight is often used in traction lifts , cranes and funfair rides...

, engine, fuel and hydraulic oil tanks. The house attaches to the undercarriage by way of a center pin, allowing the machine to slew 360° unhindered.

The main boom attaches to the house, and can be one of several different configurations:
  • Most are mono booms: these have no movement apart from straight up and down.
  • Some others have a knuckle boom
    Knuckle boom
    A knuckleboom crane appears similar to a standard crane, except that the boom articulates at the 'knuckle' near the middle, letting it fold back like a finger...

     which can also move left and right in line with the machine.
  • Another option is a hinge at the base of the boom allowing it to hydraulically pivot up to 180° independent to the house; however, this is generally available only to compact excavator
    Compact excavator
    A compact or mini excavator is a tracked or wheeled vehicle with an approximate operating weight from 0.7 to 8.5 tonnes. It generally includes a standard backfill blade and features independent boom swing....

    s.
  • There are also triple-articulated booms (TAB).


Attached to the end of the boom is the stick (or dipper arm). The stick provides the digging force needed to pull the bucket through the ground. The stick length is optional depending whether reach (longer stick) or break-out power (shorter stick) is required.

On the end of the stick is usually a bucket
Bucket (machine part)
A bucket is a specialized container attached to a machine, as compared to a bucket adapted to the form of a human being...

. A wide, large capacity (mud) bucket with a straight cutting edge is used for cleanup and levelling or where the material to be dug is soft, and teeth are not required. A general purpose (GP) bucket is generally smaller, stronger, and has hardened side cutters and teeth used to break through hard ground and rocks. Buckets have numerous shapes and sizes for various applications. There are also many other attachments which are available to be attached to the excavator for boring, ripping, crushing, cutting, lifting, etc.

Before the 1990s, all excavators had a long or conventional counterweight that hung off the rear of the machine to provide more digging force and lifting capacity. This became a nuisance when working in confined areas. In 1993 Yanmar
Yanmar
is a Japanese diesel engine manufacturer with more than 90 years of history. The engines are used in a wide range of applications, including seagoing vessels, construction equipment, agricultural equipment and generator sets.-Company description:...

 launched the world's first Zero Tail Swing excavator, which allows the counterweight to stay inside the width of the tracks as it slews, thus being safer and more user friendly when used in a confined space. This type of machine is now widely used throughout the world.

Excavator attachments

In recent years, hydraulic excavator capabilities have expanded far beyond excavation tasks with buckets. With the advent of hydraulic powered attachments such as a breaker
Breaker (hydraulic)
A breaker is a powerful percussion hammer fitted to an excavator for demolishing concrete structures or rocks. It is powered by an auxiliary hydraulic system from the excavator, which is fitted with a foot-operated valve for this purpose...

, a grapple or an auger
Auger
An auger is a drilling device, or drill bit, that usually includes a rotating helical screw blade called a "flighting" to act as a screw conveyor to remove the drilled out material...

, the excavator is frequently used in many applications other than excavation. Many excavators feature a quick coupler
Quick coupler
Quick couplers are used with construction machines to allow the rapid change of buckets and attachments on the machine. They remove the need to use hammers to manually drive out and insert the mounting pins for attachments...

 for simplified attachment mounting, increasing the machine's utilization on the jobsite. Excavators are usually employed together with loaders
Loader (equipment)
A loader is a heavy equipment machine often used in construction, primarily used to load material into or onto another type of machinery .-Heavy equipment front loaders:A loader A loader is a heavy equipment machine often used in construction, primarily used to load material (such as asphalt,...

 and bulldozers. Most wheeled, compact
Compact excavator
A compact or mini excavator is a tracked or wheeled vehicle with an approximate operating weight from 0.7 to 8.5 tonnes. It generally includes a standard backfill blade and features independent boom swing....

 and some medium sized (11 to 18 tonne) excavators have a backfill (or dozer) blade. This is a horizontal bulldozer-like blade attached to the undercarriage and is used for levelling and pushing removed material back into a hole.

Notable manufacturers

See also

Types of excavator
  • Compact excavator
    Compact excavator
    A compact or mini excavator is a tracked or wheeled vehicle with an approximate operating weight from 0.7 to 8.5 tonnes. It generally includes a standard backfill blade and features independent boom swing....

  • Dragline excavator
    Dragline excavator
    A dragline excavator is a piece of heavy equipment used in civil engineering and surface mining.In civil engineering the smaller types are used for road, port construction, and as pile driving rigs. The larger types are used in strip-mining operations to move overburden above coal, and for...

  • Long reach excavator
    Long reach excavator
    The long reach excavator or high reach excavator is a development of the excavator with an especially long boom arm, that is primarily used for demolition. Instead of excavating ditches, the long reach excavator is designed to reach the upper stories of buildings that are being demolished and pull...

  • Steam shovel
    Steam shovel
    A steam shovel is a large steam-powered excavating machine designed for lifting and moving material such as rock and soil. It is the earliest type of power shovel or excavator. They played a major role in public works in the 19th and early 20th century, being key to the construction of railroads...

  • Power shovel
  • Suction excavator
    Suction excavator
    A suction excavator or vacuum excavator is a construction vehicle that removes earth from a hole on land, or removes heavy debris on land, from various places, by powerful suction through a wide suction pipe which is up to a foot or so diameter...



Other
  • Bulldozer
    Bulldozer
    A bulldozer is a crawler equipped with a substantial metal plate used to push large quantities of soil, sand, rubble, etc., during construction work and typically equipped at the rear with a claw-like device to loosen densely-compacted materials.Bulldozers can be found on a wide range of sites,...

  • Civil engineering
    Civil engineering
    Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings...

  • Heavy equipment
  • Mining simulation
    Mining Simulation
    A mining simulator is a system used to replicate elements of mining operations, for training or efficiency analysis. Mining simulation application can range from pure statistical analysis, to scale models, all the way to replica cabins of mining machinery mounted on pneumatic actuators surrounded...

  • Bucket-wheel excavator
    Bucket-wheel excavator
    Bucket-wheel excavators are heavy equipment used in surface mining and mechanical engineering/civil engineering. The primary function of BWEs is to act as a continuous digging machine in large-scale open pit mining operations...


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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