Astec Conveyors has completed a project at the TNT Preston depot following the success of an earlier installation in Birmingham. Astec, in conjunction with TNT, designed a concept based on the same principles as Birmingham, providing a reversible materials handling system that could be operated by three warehouse shifts.
A mezzanine floor was installed to reduce ground floor congestion. The upper level provides a segregated area with a sortation conveyor system and an area for processing small packages and documents. This created an efficient ground level workflow for bulk items.
TNT Preston operates three shifts and the objective of this project was to install a reversible straight-line conveyor system, which would support both the Night and Back shifts plus the regional sortation.
The new system allows up to four inbound trailers at a time to be unloaded, therefore speeding up the flow of freight into the depot. Assuming average parcel dimensions, the system was designed to handle a minimum throughput rate of 1,800 items an hour across the system.
Outbound goods are off-loaded from collection vehicles onto line-shaft conveyors to be transferred and indexed up to a checkpoint, where they are checked, weighed and then labelled with a detailed, printed delivery / routeing label.
Following this procedure, parcels are then merged and transported onto the “main line” – along a common close pitched powered roller conveyor and then up a reversible inclined belt conveyor, feeding into the upper level system located on the mezzanine floor.
The upper and lower level systems have an inline barcode reader station which was designed and installed to function in both directions.
The barcode scanner checks and communicates information to the host TNT “Universe” computer system and the sortation PLC system to ensure traceability, while performing the updates in real time.
From the mezzanine, items are discharged down designated inclined / declined belt conveyors onto telescopic boom conveyors and into awaiting trailers to be delivered to the hub for further sorting.
The Astec sortation system is designed to run both forwards and backwards.
Returning inbound parcels from TNT sortation hubs are unloaded from trailers, via telescopic conveyors and back up the inclined / declined belt conveyors to the mezzanine floor and upper level sort system.
Barcode routeing labels are scanned and consignments can sort to spiral chutes prior to being transported back to floor level and diverted down designated lanes for outbound trailers.
There is also the option of feeding inbound parcels directly to the lower system, when the upper level is being used in Regional Sortation mode.