LHD (load, haul, dump machine)

LHD loaders are similar to conventional front end loaders but developed for the toughest of hard rock mining applications, with overall production economy, safety and reliability in mind. They are extremely rugged, highly maneuverable and exceptionally productive. More than 75% of world's underground metal mines use LHD for handling the muck of their excavations.[1]

Constructional details

LHD 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 application where height and width is limited. As the length is not a limitation in underground tunnel and decline LHD 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 limitation for shifting heavy equipment. Sometimes, an LHD has to be shifted through a shaft while dismantled.[2]

Capacity

Their tramming capacities varies from 1 to 17-25 metric tons. Their bucket size varies from 0.8 to 10 m3. Bucket height range from 1.8 to 2.5 m.

Drives

LHD are available in both diesel and electric versions. Diesel version is easily transportable from one location to another and have diesel engines as power drive of 75 to 150 HP or more. Engines are either water or air cooled.

LHD with electric motors as drives have general capacity of 75 to 150 HP. These are operative at medium voltage of 380 to 550 volts. Flexible trailing cable are provided with reeling/unreeling facility to feed power.

These drives operate hydraulic pumps and hydraulic motors for further operation of various movement of bucket and vehicle traction/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, two-stage gear box and, drive lines.[3]

Safety provisions

Service, emergency and parking brakes with fire resistant hydraulic fluid is used . Head lights, audible warning signal, back up alarm and portable fire extinguisher are provided. Special cabin/canopy is also provided for safety of operator. A safety device is provided to shut off the engine if exhaust gases exceed temperature of 85 °C (or as per set value).[4]

For electric shock safety these LHD's power source(gate end box) are equipped with earth conductivity protection using pilot core[5] in electric trailing cable, which isolate complete power when earth continuity is broken.

Latest developments

LHDs are available with remote controls. These are essential to remove the material where the stope is unprotected from top. There can be fall of loose muck from top. There are LHD available with remote tramming facility and these can handle 8000 tons of ore per day.[6]

See also

Footnotes

  1. ↑ , Surface and Underground Excavations, 2nd Edition: Methods, Techniques and ..., By Ratan Raj Tatiya, p. 181
  2. ↑ , Surface and Underground Excavations, 2nd Edition: Methods, Techniques and ..., By Ratan Raj Tatiya, p. 181
  3. ↑ , Reliability modelling and performance, by B. Samanta*, B. Sarkar†, and S.K. Mukherjee‡
  4. ↑ , Surface and Underground Excavations, 2nd Edition: Methods, Techniques and ..., By Ratan Raj Tatiya, p. 181
  5. ↑ ; Electrical Engineer's Reference Book, M A Laughton, M G Say - 2013 - Technology & Engineering, p.32/18 mining;
  6. ↑ , Surface and Underground Excavations, 2nd Edition: Methods, Techniques and ..., By Ratan Raj Tatiya, p. 183

Further reading

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