Stacking method
Stacking in a Bridge Scraper store is usually done by a ST stacker.
In the longitudinal Bridge Scraper store the stacking method is to stack a large number of layers on top of each other in the longitudinal direction of the pile.
Chevron
With the Chevron method material is deposited by the stacker moving to and from over the centre line of the pile.
The method causes segregation of the material with fine particles in the central part of the pile and coarse particles on the surface and at the bottom of the pile.
To ensure proper blending a Chevron pile must therefore be reclaimed from the face of the pile, working across the entire cross section.
Windrow – open pile
With the Windrow method material is deposited from a number of positions across the full width of the pile.
The method prevents segregation and ensures more even distribution of fine and coarse particles across the pile.
The Windrow method is preferred in cases where segregation would make an open pile base unacceptable – typically in coal stores due to spontaneous ignition.
In order to be able to stack the material according to the windrow method the stacker must be a slewing type stacker.
Reclaiming methods
On/Off mode
Reclaiming capacity is higher than the mill requirement and the reclaimer therefore operates in an On/Off mode, controlled by maximum/minimum level indicators in the feed bin. On leaving the bin the material is proportioned and fed to the mill by weigh feeders.
Direct mode
If the material is difficult to handle it may be an advantage to avoid the intermediate bin between the reclaimer and the mill. This is possible in cases where material from one (or more) store(s) is to be fed to a single mill.
Reclaiming capacity will always match the mill requirement and the reclaimer will operate continuously.
The reclaimer in combination with the transporting belt conveyors acts as a weigh feeder for the reclaimed material.
Special designs
In case of special requirements due to specific material properties or limited space FLSmidth can offer a vide range of special designs.
Live harrow
The Longitudinal bridge Scraper can also be used for applications with “moderately” sticky materials if the harrow is equipped with a live harrow system.