LHD (load, haul, dump) loaders are similar to conventional front end loaders but developed for the toughest of hard rock mining applications, keeping overall production economy, safety, and reliability in consideration. They are extremely rugged, highly maneuverable, and exceptionally productive. More than 75% of the world's underground metal mines use LHD for handling the muck of their excavations. [1]
LHDs have powerful prime movers, advanced drive train technology, heavy planetary axles, four-wheel drive, articulated steering, and ergonomic controls. Their narrower, longer, and lower profile make them most suitable for underground applications where height and width are limited. As the length is not a limitation in a tunnel and decline, LHD loaders are designed with sufficient length. The length improves axial weight distribution and bucket capacity can be enhanced. The two-part construction with central articulation helps in tracking and maneuverability. In mining, there is a limitation for shifting heavy equipment, and sometimes, an LHD has to be shifted through a shaft while dismantled. [1]
An LHD tramming capacity varies from 1 to 17-25 tonne. Their bucket size varies from 0.8 to 10 m3. Bucket height ranges from 1.8 to 2.5 m.
LHDs are available in both diesel and electric versions. The diesel version is easily transportable from one location to another and has diesel engines with a power drive of 75 to 150 HP or more. Engines are either water- or air-cooled.
LHD with electric motors as drives have a general capacity of 75 to 150 HP. These are operative at a medium voltage of 380 to 550 volts. Flexible trailing cables are provided with a reeling/unreeling facility to feed power.
These drives operate hydraulic pumps and hydraulic motors for further operation of the various movements of buckets and vehicle traction and steering. The speed of the vehicle is controlled mechanically. The transmission is controlled by a hydrostatic drive; in hydrostatic transmission, the motor drives a variable displacement pump hydraulically connected to a hydro-motor driving the axle via a gearbox. The speed is controlled by changing the displacement volume of the axial pump. The power train consists of a closed-loop hydraulic transmission, parking brakes, a two-stage gearbox, and drive lines. [2]
Service, emergency, and parking brakes with fire-resistant hydraulic fluid are used. Headlights, audible warning signals, backup alarms, and portable fire extinguishers are provided. A special cabin is also provided for the safety of the operator. A safety device is provided to shut off the engine if exhaust gases exceed a temperature of 85 °C (or as per the set value). [1]
For electric shock safety, these LHDs' power source (gate end box) is equipped with earth conductivity protection using pilot core [3] in electric trailing cable, which isolates complete power when earth continuity is broken.
Most LHDs come equipped with remote control capabilities, which are crucial for clearing materials in areas where the stope lacks top protection, preventing loose muck from falling off. Some LHD models offer remote tramming functionality, enabling them to handle a daily ore capacity of 8000 tons. [4] Two LHD OEM's (Caterpillar and Sandvik) have developed commercial auto-tramming systems - called Minegem and Automine respectively. [5]
Underground hard-rock mining refers to various underground mining techniques used to excavate "hard" minerals, usually those containing metals, such as ore containing gold, silver, iron, copper, zinc, nickel, tin, and lead. It also involves the same techniques used to excavate ores of gems, such as diamonds and rubies. Soft-rock mining refers to the excavation of softer minerals, such as salt, coal, and oil sands.
An elevated passenger ropeway, or chairlift, is a type of aerial lift, which consists of a continuously circulating steel wire rope loop strung between two end terminals and usually over intermediate towers, carrying a series of chairs. They are the primary onhill transport at most ski areas, but are also found at amusement parks and various tourist attractions.
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A loader is a heavy equipment machine used in construction to move or load materials such as soil, rock, sand, demolition debris, etc. into or onto another type of machinery.
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Joy Global Inc. was a company that manufactured and serviced heavy equipment used in the extraction and haulage of coal and minerals in both underground and surface mining. The company had manufacturing facilities in Alabama, Pennsylvania, Texas, Wisconsin, Australia, Canada, China, France, South Africa, Poland and the United Kingdom. In 2017, Joy Global was acquired by Komatsu Limited and was renamed Komatsu Mining Corp.
Strataca is a salt mine museum in Hutchinson, Kansas, United States. It was previously known as the Kansas Underground Salt Museum. The museum is built within one of the world's largest deposits of rock salt, formed 275 million years ago, and provides the opportunity to go 650 feet (200 m) beneath the Earth’s surface. The museum is located in the Hutchinson Salt Company mine which began operation in 1923 as Carey Salt Company. There are 14 other salt mines in the United States, but Strataca is the only one accessible to tourists.
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