Western Cape Business News

Send  Share  RSS  Twitter  09 Feb 2009

FOOD & BEVERAGES: Cold Storage Solution


Recent Western Cape Business News

THE capital cost of putting up a cold store has doubled in just over three years. Running costs have been negatively affected by rising electricity, labour and maintenance costs, and there is little sign that these trends will taper off anytime soon, says James Cunningham, MD of Barpro Storage.

Given these rising costs, it is no surprise that operators want to maximise their storage capacity to the full. In the past this was achieved by block stacking product. This method of storage was successful until the number of product lines started to explode in the late 1980’s. Cold store operators then realised that maximising capacity was useless unless it was also possible to access any pallet quickly.

To achieve accessibility, various types of pallet racking were introduced. Nearly all types of racking can be categorised as being either ‘high density’ or ‘individual access’. In other words, static racking will allow immediate access to every pallet location, but makes dreadful use of the storage volume. Drive-in racking, on the other hand, can give far better utilisation of the storage volume, but accessing individual pallets is time consuming, inefficient and tends to result in higher levels of product damage. In freezer stores which operate at air temperatures of approximately -25 Deg C, ease of pallet access is particularly important as staff cannot be expected to spend time in the cold looking for lost pallets.

Mobile racking is best suited to cold stores as it satisfies the need for both high density storage and immediate pallet access. First installed in South Africa over 20 years ago, mobile racking has proved itself to be the best racking solution for both freezer and chilled stores which have a relatively high product throughput and multiple product lines, says Cunningham.

Where a new cold store is being built, the storage capacity will be enhanced if the store is designed around the mobile racking system. In the design phase for a store in Cape Town, for example, changing one dimension by 400mms increased capacity by 120 pallets or 7%. The higher the proposed cold store, the cheaper the capital cost per pallet location created. In Europe now, clear internal heights are approaching 14 metres. It is primarily reach truck lifting capabilities and not the mobiles that prevent store heights from increasing still further.

A general rule of thumb in designing new cold stores is to achieve a storage capacity of over 3 pallets per sq m of floor space. Where pallets exceed 1.5metres in height the pallets per sq m will obviously fall, but this ratio supplies an indication as to what the capacity of a cold store should be.

Mobile racking systems are designed to cope with the maximum pallet throughput that each cold store can expect. Depending on various factors, a reach truck can be expected to perform between 27 and 35 pallet movements per hour. This rate can be increased to over 50 pallet movements per hour where the reach truck stays in an open aisle and pallets are brought in and removed by a powered pallet jack. The cold store is split up into mobile banks each with its’ own moving aisle to achieve the required pallet throughput. If the store can be designed to facilitate dual cycling then the need for additional moving aisles and reach trucks can be reduced. Dual cycling is where a reach truck can both enter and leave the mobile racking with a pallet on the forks and requires the store pallet entry and exit points to be located close together. Pallet conveyors can be used to achieve this.

While mobile bases can be activated via push button controls, throughput is increased if they can be moved remotely from the reach truck cab. Remote control requires additional safety controls to prevent bases from moving without a visual check that the aisle is clear. The latest systems can count the reach trucks as they enter and leave an open aisle automatically ‘clearing’ the aisle when the reach truck exits in readiness for the bases to move. Actual time taken to move an aisle from one side of a bank of 10 mobiles to the other is approximately 1 minute 20 seconds. Aisle changes take place while the reach truck is taking a pallet to the store dispatch point, thus reducing any time lost in waiting for the aisle to open.

Apart from increasing storage capacities, mobile racking can also improve energy efficiencies by reducing the amount of electricity required for lighting. This is done by automatic light switching so that lights only come on in the open aisles. Lights introduce heat into a cold store. Additional energy is therefore required to remove this heat, making lighting an important component of a cold store’s heat load. The use of automatic light switching and motion sensors can reduce the total energy required for lighting by over 80%.

Mobile racking should therefore be seriously considered when designing a new cold or freezer store. Although more cost effective in larger stores, it has been used locally in stores with a capacity as low as 200 to 300 pallets. Mobiles can also be fitted successfully in existing stores although the store must be taken out of commission for about 5 weeks in order to lay a new floor screed to hold the guide rails. according to Cunningham.

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