Preface
Cold stores and more commonly temperature controlled zones are an essential part of the supply chain in the food & beverage and pharmaceutical industries. Be it meat, vegetables, fish, dairy items or indeed medicine, the products have to be stored, retrieved, sorted or picked in a temperature controlled zone. Without doubt this is an expensive affair to manage and so the correct design and equipment should be considered in order to provide a safe and productive operation. At an age where building and energy costs come at a premium, cold store plan and design should be looked at in great depth in order to keep these high costs to an absolute minimum.
Furthermore working in environments of -20 C and below can easily hinder productivity in which case exposure to these extreme temperatures by your staff should be kept to a minimum. Below we will examine a few basic principles with regards the design and operations of these environments.
What is a temperature controlled zone?
A temperature controlled zone is no more than a room enclosed in insulated panels (thickness varying between 100-300 mm) and operating one or more freezer units inside the chamber, thus keeping the environment at the constant desired temperature. Access to this room is achieved by means of sliding panel doors which can also seal shut when the chamber is not in use by operators.
Typical temperatures in these areas comprise of:
Meat and pastry products @ -18 to - 20 C
Dairy products @ + 5C
Fish and vegetables @ -23 to -25 C
Certain pharmaceutical items @ +2 to +8 C
Order picking/ preparation zones @ 0 to +5C
Make no mistake; to maintain these temperatures in the most cost effective manner is not easy. Below are some pointers that will enable one to minimize building costs, maximize efficiency and at the same time minimize energy losses, which is undoubtedly the most important factor for anyone planning a cold store due to the high on-going expenditure involved.
Construct a marshalling area
It is common practice in cold store design to construct a chill room adjacent to the deep freeze chamber, which will enable staff to arrange and prepare orders in a more comfortable environment and outside of the typical subzero temperatures. Such rooms are usually maintained at around +5 C. It is important to remember that goods in this area have only a limited time available before they start to thaw out so order preparation should be fast and loaded onto the freezer trucks in a timely fashion. Typical time allowance for marshalling areas is about 30 minutes as allowed by HACCP.
Staff operating picking duties in deep freeze environments will not only be less productive, they will also be exposed to health hazards. It is more suitable therefore to have a dedicated driver in a forklift (preferably with a heated cabin) that operates in the deep freeze and feeds pallets to and from the order preparation area.
Note that for the safety of your staff it is advisable to have underfloor heating (especially around the entrance areas to the cold room) as ice build up would be common due to the condensation created from the temperature differences.
High speed doors
High speed doors come in many looks and feels but they all have 2 things in common; their fast open/close speed, and long term durability when it comes to heavy usage. Installing a high speed door as an access from the marshalling to the freezer chamber is crucial, and can offer you invaluable cost savings to your operations.
e specially designed to operate in these severe temperatures. With the traditional 2 door solution, the operator opens the sliding door at the start of the shift and then operates the high speed door throughout the day's activities. These special doors are installed on the cold side and have in built heaters to avoid the build-up of ice. The motors and moving parts have cold resistant oils to stop them from freezing over. The new generation door from Efaflex however can provide a single door solution combining high speed and almost hermetic sealing when closing. With this solution the single door is installed on the warm side. The video below shows details of this door and it is well worth the investment.
Many companies use the freezer's sliding freezer door as a means of going in and out during the daily operations. While this door may open somewhat quickly, energy is still wasted as most of the times the operator will forget or not be bothered to close the door behind him. One can imagine how much air loss this means when done consistently throughout the day. A high speed door on the other hand will be programmed to close automatically the minute the operator passes through and hence he can focus on doing his work instead of having to remember to close doors. Furthermore, sliding freezer doors are not built for numerous open/close cycles and so their lifespan will be shortened considerably.
Another common feature is to see the use of PVC strip curtains in the chamber hatch. This is not as beneficial however as strip curtains do not seal the opening, wear very quickly and curl up at the ends due to the extreme temperatures. They will also accumulate large amounts of condensation and scratches from forklifts over time, hindering visibility and thereby increasing accident risks especially during high traffic periods.
High speed doors are a proven solution for temperature controlled logistics. They ensure the fastest access to the chamber and minimal opening time. Open/ close cycles can be achieved either by pull cord or automatic infrared or laser sensors that can in addition distinguish machine from person. In some instances, crash protection doors are also available making it easy to fit the door curtain back into the frame, on occasions when the forklift accidentally hits it and pops it out of its position.
With an average open time of about 2 seconds followed by automatic closing this means enormous energy savings throughout the day. But the benefits don't stop there; your products reach optimal temperature quickly, temperature fluctuation is minimal and the compressor units don't have to work as hard to maintain constant temperatures. Multiply this daily throughout your year and the door pays for itself very quickly!
What is the most suitable storage system?
Using a suitable storage system is an extremely important factor in maximizing your storage capability in a cold room, as well as decreasing your overall running costs. High density storage is usually the choice here, as it decreases the storage cost per pallet considerably. The more pallets stored the less the cost of energy per pallet. Having a normal pallet racking solution is probably cheap to begin with but you will be freezing plain air due to the need for numerous aisles needed for the forklift's access.
Mobile racking or satellite systems are the most common choice owing to their excellent capability of dense storage as well as the ability of storing and retrieving pallets quickly and efficiently. Depending on whether you need 100% access to your goods or whether you need a small number of SKU's stored in large quantities, will determine which type of system is more suitable. Both systems have been tried and tested for many years in these environments with great success. Although the investment costs are indeed higher, the fast return on investment will be guaranteed.
Mobile racking
Mobile racking is the popular choice for cold stores up to 12m high. The mobile racking system can pack as many pallets as possible (up to 100 % more than a conventional pallet rack system) in any given area and allow for 100% selectivity at the same time. Only room for 1 aisle is needed as the racks move on mobile bases and open up for pallet retrieval and storage. For instances where picking is needed, more than one aisle can be opened simultaneously for immediate picking. Light energy consumption can also be minimised as the roof lighting can be linked into the system control panel and only illuminate the desired aisle, when that aisle is selected and opened up fully. Night parking is another feature whereby all aisles can be opened up equidistant to allow air flow uniformly throughout all products when the shift finishes.
Overall the mobile racking solution is ideal, as the energy consumed per pallet is very low and the building costs much less, due to the lack of aisles that otherwise common pallet racking solutions would require.
Satellite system
The satellite system is a great alternative to drive in and it is the highest density system on the market today. Although it works similarly to drive in and probably closer to pallet live storage, it is much more efficient than drive in and a cheaper solution on a per pallet cost to an equivalent pallet live storage. Available in both FIFO and FILO configurations, the satellite system can store one SKU per channel and operates via a satellite machine utilizing the “goods to man principle”.
The satellite stores and retrieves the pallets in the channel allowing the driver to utilise his time much more efficiently as there is no need for rack entry. This saves a lot of time in labour / forklift usage (and hence repairs) and also minimises damages to the racks, a common and very dangerous and costly issue with drive in systems. Satellite storage is also considerably more dense in its storage capability as opposed to conventional systems, as pallets can be stored up to 40 deep, whereas the drive in or pallet live storage systems have to be split into more manageable blocks for stability reasons.
Add an extra layer of insulation by use of a dock house
Dock houses are another common feature in modern day cold stores. They add another layer of insulation to the marshalling area by isolating the load/unload activities.
Dock houses are nothing but a metal frame that extends the building façade to which normal panel cladding can be applied to. This frame has a provision for a hydraulic dock leveller to be installed into it and can serve the loading and unloading of freezer trucks or vans. The door sits on the building wall as usual (at the back of the dock house) and so it seals the building when no dock activity is present. This door, mostly a normal sectional door will only open after the truck has docked and subsequently opened its doors, thereby minimising cold air loss even further.
Dock doors
For those with a higher budget, it is recommended that here also they install high speed doors with special thermally insulated laths. As loading and unloading means several trips to and from the truck, fast open/ close cycles will prove vastly beneficial. But often you will find that several docks will be required to carry out your goods received/dispatched processes which will drive your budget up considerably if you opt for high speed doors.
In the common situation where you have no choice but to select sectional doors, it is advised that you choose an 80mm thick sandwich panel instead of the standard 40mm one. This will give you double the insulation.
Additionally if seeing outside is a necessary option then choose the peephole over the standard oval window, as shown in the image above.
Dock levellers
Dock levellers usually sit in the aforementioned dock house or if this cannot be achieved, on the edge of the premises, just behind the dock door. Although the dock house is the preferred solution, sometimes it is not feasible to achieve this due to the lack of maneuvering space in the yard for the trucks and containers. In such a situation, the levellers should be recessed so that he door can close in front of it and keep the cold air in. In situations where the dock leveller is recessed, be sure to ask for a telescopic lip 1000mm long, as the distance to the truck is greater than the standard and so the usual swing lip is not likely to reach.
If the chosen way is to position a dock house, ensure that you get special rubber seals to close the gaps between the levellers and its side frames. This will minimise cold air loss at times where the operator is loading or unloading the trucks.
A last tip for the minimisation of cold air loss when it comes to unloading trucks is the ability to dock the truck and then open its doors inside the dock house. As some trucks are lower than others, there will be the need in some instances to lower the leveller and then allow the truck to dock before the doors are then opened inside it. In instances like this a stepped leveller is needed to enable the door opening; often these are also called "meat levellers". An example of a meat leveller is shown in the photo below.
Dock shelters
Dock shelters are placed in front of the dock leveller and provides the sealing between the dock bay and the truck by means of PVC flaps. In the food and beverage industry a dock shelter is mandatory by HACCP.
If however the budget permits, select an inflatable dock shelter. Inflatable dock shelters provide much better sealing by means of perimetric air bags that inflate and "hug" the top and sides of the truck providing perfect sealing (see picture on left). This provides another piece of air loss minimalisation and energy saving.
Protective clothing for your workforce
Equip your pickers with good quality cold store clothes. Cold store clothes that can keep workers comfortable in extreme temperatures such as -25 C are certainly not cheap, but nonetheless essential to the well being and productivity of your employees. Not only should they wear certified jackets, but also cold store trousers, boots, gloves and hoods.
Protect your equipment
Last but not least, it is strongly advised to install strong impact barriers around the hall to protect all the building panels (damages from impacts could cost very dearly), as well as bollards for any expensive equipment such as doors or electrical cabinets that could bring serious downtime in the event of an impact by a forklift. Preventative precautions like these are a must and trying to cut costs here is only going to be a regret at a later stage.
Conclusion
Even though this article has not covered every aspect of the cold store environment (such as the types of freezing units required for example), it should nonetheless be an informative read on what questions to ask and what equipment to consider.
Deep freeze environments have extremely high running costs so professional consultation is highly recommended, should you plan to build one for your business. The benefits achieved when carrying out a carefully thought out design and plan will be following you for years to come. Build a quick and dirty solution without investing in quality equipment from the outset and you will be paying constantly through higher than needed operating expenditures.