LHD (load, haul, dump) loaders are similar to conventional

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s 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.
Surface and Underground Excavations, 2nd Edition: Methods, Techniques and ..., By Ratan Raj Tatiya, p. 181

Constructional details

LHDs have powerful Prime mover (locomotive), prime movers, advanced

drive train A drivetrain (also frequently spelled as drive train or sometimes drive-train) or transmission system, is the group of components that deliver mechanical power from the prime mover to the driven components. In automotive engineering, the drive ...

technology, heavy planetary axles,

four-wheel drive A four-wheel drive, also called 4×4 ("four by four") or 4WD, is a two-axled vehicle drivetrain capable of providing torque to all of its wheels simultaneously. It may be full-time or on-demand, and is typically linked via a transfer case pr ...

, articulated steering, and

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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 Mining is the Resource extraction, extraction of valuable geological materials and minerals from the surface of the Earth. Mining is required to obtain most materials that cannot be grown through agriculture, agricultural processes, or feasib ...

, there is a limitation for shifting heavy equipment, and sometimes, an LHD has to be shifted through a shaft while dismantled.

Capacity

An LHD tramming capacity varies from 1 to 17-25

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. Their bucket size varies from 0.8 to 10 m³. Bucket height ranges from 1.8 to 2.5 m.

Drives

LHDs are available in both diesel and

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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 motor An electric motor is a machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a electromagnetic coil, wire winding to gene ...

s 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 pump A hydraulic pump is a mechanical source of power that converts mechanical power into hydraulic energy ( hydrostatic energy i.e. flow, pressure). Hydraulic pumps are used in hydraulic drive systems and can be hydrostatic or hydrodynamic. They gen ...

s and

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s 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.

Safety provisions

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). For electric shock safety, these LHDs' power source (gate end box) is equipped with earth conductivity protection using pilot core in electric trailing cable, which isolates complete power when earth continuity is broken.

Latest developments

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. Two LHD OEM's (

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and

Sandvik Sandvik AB is a Swedish multinational corporation, multinational engineering company specializing in products and services for mining, rock excavation, drilling rig, rock drilling, rock processing (crusher, crushing and mechanical screening, scre ...

) have developed commercial auto-tramming systems - called Minegem and Automine respectively.

Constructional details

Capacity

Drives

Safety provisions

Latest developments

See also

Footnotes

Further reading