Monday, November 10th, 2008
Excavators are heavy equipment used in civil engineering and surface mining. An excavator, also called a 360-degree excavator or digger, sometimes abbreviated simply to a 360, is an engineering vehicle consisting of a backhoe and cab mounted on a pivot (turntable is a more apt description) atop an undercarriage with tracks or wheels. The term excavator is sometimes used as a general term for any piece of digging equipment.
Roles of Excavators
Excavators are used in many roles:
1- Digging of trenches, holes, foundations
2- Demolition
3- General grading/landscaping
4- Heavy lift, e.g. lifting and placing of pipes
5- River dredging
6- Mining, especially, but not only open-pit mining
7- Brush cutting with hydraulic attachments
Varieties of Excavators
Excavators for sale come in a wide variety of sizes. The smaller ones are called a mini-excavator or compact excavator. One manufacturer’s largest model weighs 84,980 kg (187,360 lb) and has a maximum bucket size of 4.5 m³ (5.9 yd³). The same manufacturer’s smallest mini-excavator weighs 1470 kg (3240 lb), has a maximum bucket size of 0.036 m³ (0.048 yd³) and the width of its tracks can be adjusted to 89 cm (35 inches). Another company makes a mini excavator that will fit through a doorway with tracks that can be adjusted to only 70 cm (28 inches) wide.
Examples of Excavators
1- Compact excavator
A compact hydraulic excavator is a tracked or wheeled vehicle with an approximate operating weight of 6 metric tons (13,228 lbs). It generally includes a standard backfill blade and features independent boom swing. The compact hydraulic excavator is also referred to as a mini excavator.
2- Dragline excavator
Dragline excavation systems are heavy equipment used in civil engineering and surface mining. In civil engineering the smaller types are used for road and port construction. The larger types are used in strip-mining operations to extract coal and these are amongst the largest mobile equipment (not water-borne), and weigh in the vinicity of 2000 metric tonnes, though specimens weighing up to 13,000 metric tonnes have also been constructed.
3- Bucket-wheel excavator
Bucket-wheel excavators are heavy equipment used in surface mining and civil engineering. The excavation component itself is a large rotating wheel mounted on an arm or boom. On the outer edge of the wheel is a series of scoops or buckets. As the wheel turns, the buckets remove soil or rock from the target area and carry it around to the backside of the wheel, where it falls onto a conveyor, which carries it up the arm toward the main body of the excavator. Additional conveyors then may carry it further; in some cases, several long conveyors are placed end-to-end, each supported by a large vehicular base.
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Tuesday, October 7th, 2008
Excavator is a machine used for excavating the earth for the foundation of building. There are different types of new and used excavator for sale for different purpose. Depending on different functions different parts of the excavator are made differently in order to execute the work.
A bucket wheel excavator is equipment used by the civil engineers for mining the surface of the earth. It is a very weighty machine and perhaps it is the most enormous automobile ever constructed. In the human history MAN Takraf RB293 is the biggest vehicle. It has its name in Guinness book of world record as the largest machine ever made. The excavator comprises of a large wheel that rotates on the arm of the machine.
The outer part of the wheel consists of a number of buckets. As the wheel rotates the bucket fixed on it starts removing the soil from the earth and throws it into a conveyor. Sometimes many conveyors are placed one after the other which are supported by the base of vehicle. The largest bucket wheel excavator is about 100 meters high and 200 meters long. It weighs about 13,000 tons and has the capacity of 12,000 m.These heavy machinery equipments are very costly. It costs around $100 million and needs five people to operate the machine. In addition to these it also needs five years to assemble this machine.
There are some other well known excavators which are much smaller in size. Compact hydraulic excavator is one such excavator weighing about .7 to 7.5 metric tons. It consists of a free swing and a standard blade that is backfill. This excavator is also known as mini excavator. The mini excavator is quite different from other excavator and has some uncommon function. In this machine all the works are performed by the relocation of the hydraulic fluid. It is for this reason it is known as hydraulic excavator. The blade of the machine starts functioning with the pressure of hydraulic fluid on the hydraulic cylinder.
The back fill of the blade of mini excavator comprises of workgroup, house and undercarriage. The workgroup of the mini excavator further comprises of dipper also known as arms, boom and attached auger, breaker, bucket etc. These attachments are linked to the structure of the house of the excavator through a frame. The second part of the blade is house. It comprises of hydraulic pump, engine compartment, etc. The movement of the workgroup and house together allows the slew to rotate, which is situated in the undercarriage. The moving house assembly of the excavator is commonly known as slew.
Undercarriage of the excavator is composed of rubber, rollers, drive sprockets and related structure. The main function of under carriage is to support workgroup and house structure. Free swing is another important part of an excavator. The main function of this part is to maintain a balance during digging. It can also be used in a narrow area where the rotation of the cab is not possible.
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