EXCAVATOR In Action - 'Skilled Operator At Work' on a Construction Site

EXCAVATORS Excavators are heavy construction equipment consisting of a boom, dipper (or stick), bucket and cab on a rotating platform known as the "house".[1] The house sits atop an undercarriage with tracks or wheels. They are a natural progression from the steam shovels and often mistakenly called power shovels. All movement and functions of a hydraulic excavator are accomplished through the use of hydraulic fluid, with hydraulic cylinders and hydraulic motors.[2] Due to the linear actuation of hydraulic cylinders, their mode of operation is fundamentally different from cable-operated excavators which use winches and steel ropes to accomplish the movements.[3] Terminology: Excavators are also called diggers, JCBs[4] (a proprietary name, in an example of a generic trademark), mechanical shovels, or 360-degree excavators (sometimes abbreviated simply to "360"). Tracked excavators are sometimes called "trackhoes" by analogy to the backhoe.[5] In the UK, wheeled excavators are sometimes known as "rubber ducks."[6] Configurations: Modern hydraulic excavators come in a wide variety of sizes. The smaller ones are called mini or compact excavators.[7] For example, Caterpillar's smallest mini-excavator weighs 2,060 pounds (930 kg) and has 13 hp; their largest model is the largest excavator available (developed and produced by the Orenstein & Koppel, Germany, until the takeover 2011 by Caterpillar, named »RH400«), the CAT 6090, which weighs in excess of 2,160,510 pounds (979,990 kg), has 4500 hp, and a bucket as large as 52.0 m³. Hydraulic excavators usually couple engine power to (commonly) three hydraulic pumps rather than to mechanical drivetrains. The two main pumps supply oil at high pressure (up to 5000 psi, 345 bar) for the arms, swing motor, track motors and accessories while the third is a lower pressure (~700 psi, 48 bar) pump for pilot control of the spool valves; this third circuit allows for reduced physical effort when operating the controls. Generally, the 3 pumps used in excavators consist of 2 variable displacement piston pumps and a gear pump. The arrangement of the pumps in the excavator unit changes with different manufacturers using different formats. The three main sections of an excavator are the undercarriage, the house and the arm (also boom is used). The undercarriage includes tracks, track frame, and final drives, which have a hydraulic motor and gearing providing the drive to the individual tracks. Undercarriage can also have blade similar to that of a bulldozer. The house includes the operator cab, counterweight, engine, fuel and hydraulic oil tanks. The house attaches to the undercarriage by way of a center pin. High pressure oil is supplied to the tracks' hydraulic motors through a hydraulic swivel at the axis of the pin, allowing the machine to slew 360° unhindered and thus provides the left-and-right movement.[8] The arm provides the up-and-down and closer-and-further (or digging movement) movements. Arm consist typically of boom, stick and bucket with three joints between them and the house. The boom attaches to the house and provides the up-and-down movement. It can be one of several different configurations........ https://en.wikipedia.org/wiki/Excavator UNITED STATES (USA) The United States of America (USA), commonly known as the United States (U.S. or US) or America, is a country consisting of 50 states, a federal district, five major self-governing territories, and various possessions.[g] At 3.8 million square miles (9.8 million km2), it is the world's third- or fourth-largest country by total area.[c] Most of the country is located in central North America between Canada and Mexico. With an estimated population of over 328 million, the U.S. is the third most populous country in the world. The capital is Washington, D.C., and the most populous city is New York City....... A highly developed country, the United States is the world's largest economy by nominal GDP, the second-largest by purchasing power parity, and accounts for approximately a quarter of global GDP.[25] The United States is the world's largest importer and the second-largest exporter of goods, by value.[26][27] Although its population is 4% of the world total,[28] it holds 29.4% of the total wealth in the world, the largest share of global wealth concentrated in a single country.[29] Despite income and wealth disparities, the United States continues to rank very high in measures of socioeconomic performance, including average wage, median income, median wealth, human development, per capita GDP, and worker productivity.[30][31] It is the foremost military power in the world, making up more than a third of global military spending,[32] and is a leading political, cultural, and scientific force internationally.[33]...... https://en.wikipedia.org/wiki/United_States

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