Storage synergy
April 1st 2004

Synergy between storage and materials handling equipment is an essential factor in establishing a professional warehouse operation and improving efficiency, says Nick Robinson, Director of Locators Storage Systems

When designing a new warehouse or making alterations to an existing facility, it is essential to take a holistic approach. Often the client/user will start out with either a storage or materials handling concept in mind and work one around the other rather than in conjunction.

A common scenario is that a warehouse has been identified and a company needs to know the storage/pallet capacity. Or, there is a specific storage/pallet capacity requirement and the company needs to know what footprint is required.

In either case it is important to consider a number of factors: how the stock is stored; the required selectivity of stock; importance of stock rotation; current and future stock levels and throughputs; order picking requirements; available height in the building; whether new or existing handling equipment will be used.

Storage medium

Once these have been considered, a decision can be made as to the most appropriate storage medium. Assuming conventional adjustable pallet racking (APR) is selected, the capacity of the warehouse or required footprint can now be calculated by taking into account the MHE needs.

Generic operating aisle widths can be used to determine the basic racking layout:

Counterbalance truck: 3500 4000mm

Reach truck: 2800 3000mm

Articulating truck: 1800 2200mm

Very Narrow Aisle truck: 1600 1800mm

It is important to remember that storage equipment specifiers normally quote rack face to rack face dimensions as the aisle width, whereas MHE specifiers and suppliers will quote a truck operating aisle width which is actually the load face to load face dimension. Under SEMA guidelines there will normally be a pallet overhang of 50mm, thereby reducing the available aisle for the MHE by 100mm overall. This is often overlooked and leads to aisle widths being tighter than originally envisaged.

The approximate area needed to store 2000 pallets, based on 4 high, with 15% marshalling area, standard 1200mm x 1000mm pallet, stored 1000mm in depth is: counterbalance 2400m2; reach 2000m2; articulating 1700m2; and VNA 1550m2

The relative merits of both truck type and storage solution need to be considered alongside operational and financial considerations. The most appropriate solution is often a combination of different storage and handling techniques.

For example, order picking from pallets may constitute a large part of distribution function, so VNA for this reason may be inappropriate due to throughputs. Equally, the increase in storage capacity offered by VNA may not justify the additional capital and maintenance costs of the equipment.

Once the MHE has been selected, the detailed design specification can be completed. It is paramount that careful attention is given to the full specification of the forklift trucks, including the specific model, as variations of up to 200mm in operating aisles can apply from manufacturer to manufacturer. It is also important to be aware of the full specification of the mast, battery, sideshift, etc., as all have a significant effect on the trucks operating aisle width.

Once these points have been confirmed, the racking can be designed to maximise the use of available space. However, there are other factors to be considered before a final design is submitted for approval:

a) Sprinklers are they being used within the pallet racking? This is important, as the flue between double-sided runs will normally be a minimum of 250mm (cf 200mm). Sprinklers will also affect the beam spacing, which in turn may affect the required lift height on the forklift truck.

b) Access routes need to comply with Fire Regulations.

c) Allowance in aisle widths for any upright protection, operational flexibility, order picking activity and future developments.

Unless these points are taken into account there could be serious financial implications due to the sprinkler and lighting being in the wrong position. All of which underlines the need to ensure that storage and MHE work in synergy.

Integrated solution

In summary, it is important that the following criteria are met when designing an fully integrated storage and materials handling system:

Look at both the storage and materials handling equipment in conjunction from the start of the design process, not separately. If a company can advise on both there is a much better chance that a fully integrated solution will be achieved.

Confirm specific make, model and specification of handling equipment to be used. Finalise the detailed storage layout taking the specification of the mast, battery, sideshift, etc., into account, along with other relevant factors from interested parties, such as lighting and sprinkler contractors.

Avoid selecting a truck supplier or model before confirming the warehouse layout. There may be benefits in consulting alternative suppliers who have a different range of equipment to offer. Likewise do not settle on a racking layout and then look to choose an equipment supplier.