Stackers is one of yard equipments used in bulk material handling applications for the iron and steel industry, power industry, port terminals, mining industry, petrochemical and fertilizers industries. Stackers is to pile bulk material such as limestone, ores and cereals onto a stockpile for stacking circular, kidney or longitudinal stockpiles as well as for homogenization and blending.

Stackers normally travel on a rail between stockpiles in the stockyard with the main operation performed on a fixed place. A stacker can usually move in at least two directions typically: horizontally along the rail and vertically by luffing its boom. Luffing of the boom minimizes dust by reducing the height that the coal needs to fall to the top of the stockpile. The boom is luffed upwards as the stockpile height grows.

With the slewing the boom, it allows a single stacker to form two stockpiles, one on either side of the conveyor.

Stackers are used to stack into 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. Raw cone ply stacking is when additional cones are added next to the first cone. Chevron stacking is when the stacker travels along the length of the stockpile adding layer upon layer of material.

Stackers and reclaimers were originally manually controlled manned machines with no remote control. Modern machines are typically semi-automatic or fully automated, with parameters remotely set.

The controlling system used is typically a PLC (programmable logic controller) with an HMI (human-machine interface) for display connected to a central control system.

Other than stacking, the stacker does three basic movements: luffing, traveling and slewing.

The conveyors used in the stackers may be fabric or metal wire type, depending upon the material being handled. The conveyors are in turn driven by pulleys. The pulleys are driven by DC motors. The motor and gear are coupled by fluid coupling.

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