A stacker is a large

machine A machine is a physical system using Power (physics), power to apply Force, forces and control Motion, movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to na ...

used in

bulk material handling Bulk material handling is an engineering field that is centered on the design of equipment used for the handling of dry materials. Bulk materials are those dry materials which are powdery, granular or lumpy in nature, and are stored in heaps.http: ...

. Its function is to pile bulk material such as limestone, ores and cereals on to a stockpile. A

reclaimer A reclaimer is a large machine used in bulk material handling applications. A reclaimer's function is to recover bulk material such as ores and cereals from a stockpile. A stacker is used to stack the material. Reclaimers are volumetric mach ...

can be used to recover the material.

Gold dredge A gold dredge is a placer mining machine that extracts gold from sand, gravel, and dirt using water and mechanical methods. The original gold dredges were large, multi-story machines built in the first half of the 1900s. Small suction machin ...

s in Alaska had a stacker that was a fixed part of the dredge. It carried over-size material to the

tailings In mining, tailings are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different to overburden, which is the waste rock or other material that overlie ...

pile. Stackers are nominally rated for capacity in

tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton to distinguish it from the non-metric units of the short ton ( United State ...

s per hour (tph). They normally travel on a rail between stockpiles in the stockyard. A stacker can usually move in at least two directions: horizontally along the rail and vertically by luffing (raising and lowering) its boom. Luffing of the boom minimises dust by reducing the distance that material such as coal needs to fall to the top of the stockpile. The boom is luffed upwards as the height of the stockpile increases. Some stackers can rotate the boom. This allows a single stacker to form two stockpiles, one on either side of the

conveyor A conveyor system is a common piece of mechanical handling equipment that moves materials from one location to another. Conveyors are especially useful in applications involving the transport of heavy or bulky materials. Conveyor systems allow ...

. Stackers are used to stack in different patterns, such as cone stacking and chevron stacking. Stacking in a single cone tends to cause size segregation, with coarser material moving out towards the base. In raw cone ply stacking, additional cones are added next to the first cone. In chevron stacking, the stacker travels along the length of the stockpile adding layer upon layer of material. Stackers and reclaimers were originally manually controlled, with no means of remote control. Modern machines are typically semi-automatic or fully automated, with parameters remotely set. The control system used is typically a

programmable logic controller A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity tha ...

, with a

human-machine interface In the industrial design field of human–computer interaction, a user interface (UI) is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine fr ...

for display, connected to a central

control system A control system manages, commands, directs, or regulates the behavior of other devices or systems using control loops. It can range from a single home heating controller using a thermostat controlling a domestic boiler to large industrial c ...

. Other than stacking, a stacker has three basic movements: * Luffing: This is vertical movement. Stackers use either a winch mechanism with metal wire, or hydraulic cylinders, generally two. Winch mechanisms are highly reliable compared to hydraulic actuators and remain widely used, particularly in large stackers. * Travelling: The stacker moves on a

rail track A railway track (British English and UIC terminology) or railroad track (American English), also known as permanent way or simply track, is the structure on a railway or railroad consisting of the rails, fasteners, railroad ties (sleepers, ...

, which may be

broad Broad(s) or The Broad(s) may refer to: People * A slang term for a woman. * Broad (surname), a surname Places * Broad Peak, on the border between Pakistan and China, the 12th highest mountain on Earth * The Broads, a network of mostly na ...

narrow gauge A narrow-gauge railway (narrow-gauge railroad in the US) is a railway with a track gauge narrower than standard . Most narrow-gauge railways are between and . Since narrow-gauge railways are usually built with tighter curves, smaller structu ...

, enabling it to move around the stockyard as required. For this purpose, traction motors powered by direct current (DC) are connected by

bevel gear Bevel gears are gears where the axes of the two shafts intersect and the tooth-bearing faces of the gears themselves are conically shaped. Bevel gears are most often mounted on shafts that are 90 degrees apart, but can be designed to work at oth ...

s to between 12 and 22 wheels. For manual control, all the controls are in a controller's cabin above the boom conveyor or boom. Modern stackers can be controlled remotely. * Slewing: This is rotation of the stacker around its central axis to align or place the stockpile where required. This works mostly by a slew pinion that rotates around a slew base. This type of gear assembly is called a

sun and planet gear The sun and planet gear is a method of converting reciprocating motion to rotary motion and was used in the first rotative beam engines. It was invented by the Scottish engineer William Murdoch, an employee of Boulton and Watt, but was patente ...

. The axles may be multiple and are driven by DC-powered axle motors which transmit the torque via bevel or

helical Helical may refer to: * Helix, the mathematical concept for the shape * Helical engine, a proposed spacecraft propulsion drive * Helical spring, a coilspring * Helical plc, a British property company, once a maker of steel bar stock * Helicoil A t ...

gears. The

conveyor belt A conveyor belt is the carrying medium of a belt conveyor system (often shortened to belt conveyor). A belt conveyor system is one of many types of conveyor systems. A belt conveyor system consists of two or more pulleys (sometimes referred to ...

s used in stackers may be made of fabric or metal wire, depending upon the material to be handled. They are driven by pulleys, which in turn are driven by

DC motor A DC motor is any of a class of rotary electrical motors that converts direct current (DC) electrical energy into mechanical energy. The most common types rely on the forces produced by induced magnetic fields due to flowing current in the coil ...

s. The motors and gear are coupled by

fluid coupling A fluid coupling or hydraulic coupling is a hydrodynamic or 'hydrokinetic' device used to transmit rotating mechanical power.

. Most stackers are electrically powered by way of a trailing cable. There are basically two types of cable trailing: power cord rotating drum (PCRD) and control cable rotating drum (CCRD). Pendulum adjustments are made to ensure the proper alignment of these cables while the stacker is travelling.

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{{Reflist Bulk material handling Engineering vehicles Mining equipment Articles containing video clips

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