Stackers – fast, effective and reliable handling of bulk materials in a stockyard operation

In any large-scale stockyard operation stackers play a key role as they deposit the bulk materials in pre-set patterns and systems. Stackers are available in a wide variety of configurations depending upon the required throughput and degree of mobility. They may feature a stacking belt that can be raised or lowered, single or twin booms, a semi or fully automatic control system, and other application-specific features. Fully automatic rail-mounted stackers, for example, are ideal for building up stockpiles for storage or blending beds.

Key benefits of our stackers in your stockyard operation

thyssenkrupp stackers combine robustness, fast operation, and high throughputs. They are designed so the user enjoys the benefits of cost effectiveness, reliability, and eco-friendliness. To meet today’s increasingly strict environmental and safety requirements, thyssenkrupp stackers are generally equipped with all the necessary precautionary equipment and systems to minimize the impact of noise, dust emissions, etc. on operators and the surroundings.

Luffing and slewing stacker

This is the most versatile type of stacker since it can slew from one stockpile to another on the other side of the yard, building uniform stockpiles on both sides of the yard feed conveyor. This stacker can build a stockpile in chevron, cone-shell, windrow or strata stockpiling modes. The machine can easily work in combination with each and every type of reclaimer on adjacent rail tracks, as the boom can slew to a position parallel to the rail track, thus allowing other machines to bypass it.

Luffing stacker

A luffing stacker travels along the entire length of the longitudinal stockpile conveyor to build a stockpile on just one side of the conveyor. A luffing stacker is easy to operate and the most cost-effective solution for a stockpile on one side of the conveyor. Thanks to its simple structure it has fewer mechanical components than luffing and slewing stackers. However, only chevron and cone-shell stacking are possible with this type of stacker. Moreover, bypassing machines on adjacent rail tracks is more difficult as the boom cannot be slewed out of the way.

Combined circular stacker-reclaimer

A circular stacker-reclaimer, which is designed for 360° rotation, consists of a slewing and luffing stacker to stack the material, a reclaimer (portal, side or bridge type), and a central column, which includes a feed and discharge hopper. The stacking and reclaiming systems operate independently. Material is fed to the boom conveyor via an overhead feed conveyor.

The substructure or undercarriage is the structural steelwork from above the equalizers up to the slew bearing. It comes in a plate box girder design, with welded constructions on all the major members. The stacker is designed to transfer loads from the stacker superstructure via the portal into the long travel system as efficiently as practicable.

The superstructure is the slewable upper structure mounted above the slew bearing and consisting of the boom, counterweight, masts, and suspension assemblies. The stacker superstructure is designed to support the boom conveyor, luffing system, and counterweights, and to transfer the load into the slew bearing as efficiently as practicable, without excessive stress or instability under all applicable load combinations.

Power and control signal exchanges are supplied to the machine via a flexible trailing cable. When the stacker is moved towards or away from the termination point at the center of the stockyard, this cable is reeled off or onto a reel assembly fitted to the stacker.

A stacker’s travel mechanism consists of travel wheels that are propelled along the rail track by electro-mechanical long travel drives. A stacker requires these long travel assemblies for its travelling motion.

The stacker boom carries the complete boom conveyor belt, conveyor drive, take-up assembly, and counterweight blocks. The stacker boom conveyor carries material from the tail to the head end and discharges it onto the stockpile. The stacker boom is luffed hydraulically and slewed hydraulically or electro-mechanically, enabling the conveyor to discharge at different heights and onto different stockpiles during the stockpile building operation.

Slew drives turn the stacker’s upper slew and boom assembly relative to the undercarriage on a slew bearing mounted between the two structures. The slew drive is mounted on the upper carriage. The slew pinion gear engages the slew bearing with an external gear attached to the undercarriage.

The luffing arrangement consists of one or two hydraulic cylinders and a hydraulic power pack. The cylinders are pin-connected between the slew structure and boom, while the power pack is located in a separate enclosure on the boom rear platform or slew structure. Boom luffing can also be effected using a winch rope system.

The tripper transfers material from the stockyard conveyor belt at ground level to the stacker boom conveyor belt above the stockpile. To this end, the tripper structure progressively increases the yard conveyor angle of elevation. The tripper moves on the same rails as the stacker.

The electrical house (e-house) is where all the electrical switchgear for the stacker, e.g. motor control centers (MCCs), programmable logic controllers (PLCs), variable speed drives (VSDs), etc., is installed.  The e-house is equipped with air conditioning systems to keep it cool and pressurized to ensure dust cannot get in.

How a stacker operates

Stackers are high-capacity machines used for stacking and blending material. Working in two directions, a stacker can pile material onto two parallel stockpiles using a slewing and luffing boom. A rail-mounted stacker travels on two rails between the stockpiles. The stopping and starting sequence for the stacking operation is controlled either from the operator’s cabin control panel or from a central control room.

Stacking methods

Chevron stacking

This method involves the stacker initially building a small pile at the center and along the full length of the stockpile. At the end of the stockpile the stacker is raised by a predetermined height to create a second layer on top of the initial pile by travelling along the rail in the opposite direction.

Cone-shell stacking

The cone-shell method involves a pile being formed by stacking the bulk material in a single cone at the center of the pile until the full height of the stockpile is reached.

Strata stacking

The strata method stacks the bulk material in horizontal layers and creating alternat¬ing layers that enable different grades of the same bulk material to be reclaimed.

Windrow stacking

The stacker initially builds the first small cone along the stockpile length by slewing the boom to make the reach longer or shorter, as required. At the end of the stockpile the stacker boom slews to build a second cone by travelling in the opposite direction.

Technical facts and figures

Installations Over 1,300 installations worldwide
Product characteristics Free-flowing or sticky; lump size up to 250 mm
Throughput Up to 16,000 tons per hour
Boom length Up to 67 m
Pile widths Up to 82 m
Pile heights Up to 31 m

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