If cold stores have one most important lesson to teach it is that given their much higher construction and running costs compared with ambient warehouses it is critical to get the design right first time, and that design has three aspects: 1) the building 2) the most appropriate passive storage medium, i.e. racking/shelving and 3) the dynamic handling equipment, like forklifts, stacker cranes and conveyors.
The building will include all the refrigeration machinery and doors and not least the insulation sandwich panels because a common problem within the cold storage industry is the degradation of these insulation panels, with critical consequences if the problem is not solved in time.
Issues from such degradation are fourfold. 1) The panels lose their thermal insulation value, resulting in higher energy costs. 2) Water will seep through into the cold store, causing ice formation on floors and stored products, creating safety concerns. 3) The ceiling panels will increase their weight and lose their structural integrity and strength, normally via delamination, posing yet more dangerous hazards. 4) The increased weight on the panels will impose larger loads on the steel structure, often taking the structure beyond it design limit. The six principal causes of these panel problems are: 1) inadequate ventilation, 2) inadequate roofing insulation 3) roof leaks, 4) refrigeration pipework, 5) refrigeration valve stations, 6) poor vapour sealing. A history of these systems has found that insulation panel deterioration is a frequent event, and caused primarily by poor total design of the cold stores.
Given that energy can account for 25% of cold store running costs, the smaller the store envelope to do the required storage operation the better, and this is where the need to consider the right type and mix of racking needs careful thought. Conventional adjustable pallet racking (APR) rarely provides the lowest storage cost because the floor utilisation is low so it may be worth considering the alternative forms of racking, like double-deep, mobile, drive in/drive through, push-back, satellite and flow through (live or dynamic). Leading forklift companies can ease the decision process with their software programmes that will help to achieve the right balance between storage density and product selectivity, but one should not leave out the safety issue because drive in racking, for example, is inherently more accident prone.
Cold storage operations are one of the toughest materials handling challenges so it is important to choose a forklift manufacturer with a long track record of adapting trucks for harsh conditions. Subzero temperatures affect battery capacity, electronics, lubrication and drivers’ ability to operate the trucks. A forklift’s capacity can be reduced by 1% per degree below 20 deg C. Very cold temperatures will make the metal, especially the welding joints, more brittle, a problem that can include racking if it is welded rather than bolted or boltless. One should also consider which would be the most cost effective type of cold store forklift.
In the past reach trucks have been a favourite but they are not as space efficient as articulated forklifts because they require minimum aisle widths of 2.6 mt as opposed to 1.8 mt for the artics. Choosing the latter could mean saving considerable energy and building costs. It is also now possible to fit conventional counterbalance forklift, suitably adapted for cold store conditions, with attachments like the SpaceMate that will convert them to VNA capability at a small fraction of the cost of a new articulated truck.
At any temperature below 6 deg C forklifts will be affected by condensation. To avoid the issues this raises operators should keep a truck in the cold store, even when charging them. If trucks have to leave the cold store then keep the truck out for as long as feasible for it to dry out completely. The drying out can be hastened by blowing hot air over them. If frequent ingress and egress is unavoidable try to make the stay inside as short as possible so that the truck temperature does not fall below 0 deg C. If this is difficult try reversing the operation so the truck stays inside as long as possible. Driver comfort should not be overlooked. Fitting them out with warm clothing will still mean they should take breaks about every 15 minutes, so placing a driver inside a warm cab would be much more productive. Such comfort also means truck operation is easier.
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