Case study

What are VNA racking pick and deposit stations?

Pick and deposit stations (P&Ds) may be an optional extra but they can be fundamental to an operation using narrow aisle racking. The combination of tall racks and very narrow aisles enable a significant increase in storage capacity however, an aisle width as little as 1.6 metres does require the service of a specialist Narrow Aisle (VNA) fork lift truck. Using wire or rail guidance these very slim, high reaching trucks navigate the aisles safely in a forward and backward motion and although they operate effectively within the aisles, beyond the aisles they are less practical with limited flexibility. For some operations this can cause a degree of limitations when it comes to the transportation of pallets between Goods-In and the racking.

P&Ds play a crucial role that enables the VNA trucks to remain in the rack aisles where they are the most productive whilst the more flexible Counterbalance/Reach trucks (std FLT) handle the pallets outside the rack structure. Located at the end of the narrow aisle racking in the form of pallet shelves projecting from the end of the racks, P&Ds offer temporary accommodation to pallets leaving or entering the structure. The pallets can be loaded or retrieved from Goods-In and P&Ds by the std FLT which has the ability to move faster and with greater manoeuvrability in the area between the pallet racking and Goods-In. The VNA truck can extend travel slightly further whilst still being guided to access the P&Ds to either deposit or retrieve pallets.

 

Narrow aisle racking with castllated P&Ds

The design variants of P&Ds

There are two different types of P&Ds:

Cantilevered – The one pallet deep racking shelf is located at the end of the narrow aisle rack and there can be one per level on every row. The floating robust shelves are without uprights at the end of the rack so visibility and access is unrestricted.

Cantilevered P&Ds2

 

Castellated – The pallet shelves are an extension of the pallet racking beams that can extend enough to match the length of a full bay that can accommodate multiple pallets per level. To enable std FLT access, the extensions are added to alternate racking rows forming a castellated pattern to the aisle ends.

castllated Narrow Aisle

It’s important to consider the pattern in which your pallets are picked and transported from the HGV during delivery before you decide between the cantilever and castellated P&Ds. A pallet doesn’t measure equal at all sides so whilst being positioned in line with the none-turning wire guided VNA truck the pallet must also be angled correctly when placed on the P&Ds. The width of a narrow aisle racking bay is often 1100mm, perfect for accommodating both UK and EU pallet sizes without the need for decking, as UK & Euro pallets have a common dimension of 1200mm. However UK pallets are 1200mm x 1000mm and EU pallets are 1200mm x 800mm so when placing the pallets onto the racks they must be placed so the 1200mm side sits over the 1100mm beams.

 

When working with a cantilevered P&D station the counterbalance truck can only access the P&Ds from the outfacing side therefore the forks enter the pallet on the 1200mm side when picking and placing. The narrow aisle truck will then access the pallets the smaller side (UK 1000mm/EU 800mm) where the position is kept whilst transporting it between the P&Ds and racks. When working with castellated P&Ds the std FLT can access the pallets from the same side as the narrow aisle.

 

P&Ds can be fitted on both ends of the narrow aisle racking system however in some operations just one end is more efficient where both delivery and despatch are on the same side of the building. For the most efficient P&D system, locating them nearest the external doors is ideal. If despatch and goods in are located at opposite ends of the building with a narrow aisle system running centrally then P&Ds would be beneficial on both ends of the structure.  Although the std FLT is unable to reach the highest points of P&Ds, these locations can be use to store pallets to ease pressure during peak times or to store the less frequently picked products.

Narrow Aisle cantilevered

Save time and money using P&Ds

Although P&D stations create a two stage deposit and retrieval process, there’s opportunity to create a sequenced pattern involving of both truck types to speed up the journey of inbound and outbound pallets. In addition, the introduction of a Warehouse Management System (WMS) can enable dual cycling to prevent an empty travelling VNA truck and a pick up in efficiency. Using WMS technology, the VNA truck can multi task by locating required pallets as it travels between pick ups and drop offs.

Would P&Ds be suited to your operation?

Prior to adding P&Ds to your narrow aisle racking, it’s advisable you carry out a full assessment of your inventory flow. This includes the volume, speed and frequency of both inbound and outbound pallets and this should be measured against the number of P&D stations, the number of std FLT and VNA trucks. The process of putting away and picking pallets has an extra element when using P&Ds, so the right balance is crucial. To ensure the operation remains streamlined and timely without throughput disruption even at peak times it’s important to ensure enough resource both within and outside the pallet racking system. A fair number of aisle serving trucks will be especially crucial to the management of a varying product picking frequency. This will prevent a build up of pallets at the P&Ds as there will be enough trucks to handle regular pallet traffic and increased traffic at the same time.

P&Ds may add more visual character to your narrow aisle pallet racking system, but to know whether this addition is right for your operation, call on the expertise of WSL. During a free site survey, our highly experienced and knowledgeable Design Technicians will take time to get to know your operation, understand your needs and assess your space. If it’s concluded that P&Ds would benefit your operation we can advise you on the most effective configuration for your particular facility and processes. Why not give us a call on 0113 2045350 or email sales@wslmail.co.uk to arrange a site visit at your convenience.

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