Economic and safe deep-freeze store construction using sandwich construction

Europe's largest deep-freeze store now in operation for six years

The smooth supply of consumers with fresh foods and frozen products is no longer conceivable without a freezer chain. Cold stores and deep-freeze stores, along with cold storage and freezing cells, are of crucial importance within this chain. They ensure that foods are stored and presented with optimum refrigeration, so that the required characteristics are preserved until delivery to the consumer. The most modern and economical method of cold store construction is sandwich construction. This provides decisive advantages with regard to construction, building physics, ease of installation and, above all, building costs.

Optimal warehouse design

Over ten years ago, the brand name manufacturer Langnese-Iglo instigated a situation analysis with the aim of optimising its distribution structure. Logistics is of prime importance for brand name manufacturers; they must ensure that the products are available on time and with consistently high quality, but at low cost. Langnese-Iglo's logistics must also meet additional requirements, as the production and distribution of ice cream and frozen food require deep-freeze conditions of approximately -28°C. Ice cream products are also subject to strong season and weather-related sale fluctuations, which must be compensated for by using appropriate logistics for the specific customers. Many different goals and requirements had to be taken into account and integrated into the concept. Various warehouse designs were developed for optimising the distribution structure. A central deep-freeze store was to be implemented at each of the three locations of Heppenheim, Reken and Wunstorf. Goods would be stored in the deep-freeze store closest to the factory producing them, and also be delivered directly from here to the customer. This concept proved to make economic sense. According to this study, the safest and most economical way to implement this concept is with a high-stacking warehouse in silo construction, with its external walls faced with sandwich panels.

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New technological territory

As there are no references to buildings in the deep-freeze storage sector of this size, type and technical specification, it was not possible to be guided by previously implemented projects. Complexity, project size, innovations and execution of such a pioneering project could therefore only be ensured by very professional project management. New requirements for long-term serviceability and the stability of the overall construction called for the development of detailed new solutions. The joining of the sandwich panels at the corners, transverse and longitudinal joints had to be re- designed to cope with the higher requirements. For the building height of 32 m, three sandwich panels had to be installed on top of one another. The resulting transverse joints required a special sealing and joining system. From a static viewpoint, the enormous stresses on the components due to wind strengths and above all thermal effects had to be taken into account. In summer, when the surfaces of the sandwich panels are subject to direct sunlight, temperature differences of 100°C arise between interior and exterior.

The exterior sandwich panels were therefore not to be fastened directly to the supporting framework of the high-stacking warehouse, but using so-called "staples". This fastening method was necessary to reduce the enormous tensions and expansions of the sandwich panels on the building which arise during the cooling phase and in subsequent operation in the event of fluctuations in the external temperature (day and night).

High-stacking warehouse in the construction phase

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Smooth material flow at -28°C

The deep-freeze store in Heppenheim will be used to describe the mode of functioning. The store is in the immediate vicinity of the Heppenheim production centre, and is directly linked to it by a connecting tunnel with an electrical telpher line. Equipped with a total of 16 fully automatic storage and retrieval units, the warehouse is permanently operated at -28°C. This also applies for the forward zone, for its goods-in, quality control, automatic commissioning and goods-out, which is seamlessly connected to the arriving and departing refrigerated lorries. The goods produced in the factory are transported from here, through a 180 m long transport tunnel in insulated gondolas without any refrigeration loss, directly into the -28°C forward zone of the warehouse, where they are then put into storage. The central deep-freeze warehouse is 171 m long, 72 m wide and 32 m high. It can hold 55,800 Euro pallets. Thanks to the silo construction, the shelf structure at the same time also forms the supporting framework for the roof, the walls and for the platforms of the materials-handling technology. The goods are commissioned and loaded in the 108 m long and 40 m wide forward zone, which is also cooled to -28°C.

View of the filled high-stacking warehouse with fully automatic robot for filling and emptying the shelves

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Sandwich for tunnel and thermal booths too

Further rationalisation projects arose as a logical consequence of the development of the warehouse logistics. As already mentioned, these include the tunnel for directly linking production to the central deep-freeze warehouse with an efficient and flexible telpher line system and sealed thermal booths. The tunnel and thermal booths were also manufactured in sandwich construction, using sandwich panels 100 mm thick. A continuous deep-freeze chain has thus been ensured from manufacture all the way through to retail outlet.

Sealed thermal booths with electrical telpher line

Functional architecture

The architects set great store on a clear and clean building, also allowing for a possible extension of the high-stacking warehouse by around 30%.

Building physics and structural constraints, combined with the requirement for optimal volume utilisation with best cooling preservation and low temperature fluctuations, resulted in a really rather unspectacular cube for the high-stacking warehouse.

However, with its clear shape and light-grey colour, it has an almost weightless effect, while meeting all possible building physics requirements. The size can only be estimated, as decorative elements were deliberately omitted.

Heppenheim central deep-freeze warehouse in the immediate vicinity of the factory

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25,000 m² of high-capacity insulation

As the best possible compromise between economy and design requirements, high insulation sandwich panels 170 mm thick were used to face the deep-freeze area. The insulating core of the sandwich panels consists of a CFC-free polyurethane high- resistance foam with an outstanding insulating capacity.

The proven practical k-value for technical operating systems is 0.127 W / m² * K for this panel type. The panel joints were sealed externally by injection of a sealing compound of continuous plastic butyl rubber into the longitudinal keyway of the panels at the factory.

A total of more than 25,000 m² sandwich panels 100 mm and 170 mm thick were used in the Heppenheim building. All sandwich panels used have steel facings 0.6 mm thick on both sides and a 25 µm polyester coating. This complies with corrosion protection class III no. DIN 55928-8.

Joining the sandwich panels

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Wall and ceiling panels for cold and deep-freeze store construction - ROMA quick build insulating panels type P system

Warehouse building with capacity for 56,000 pallets

Short construction time

The first turf was cut for the central deep-freeze warehouse in Heppenheim, with a storage area of 12,000 m² and a storage volume of 386,000 m³, in November 1993. In August 1995, the installation, including all of the extensive technical equipment, was brought into service and tested under deep-freeze conditions. This is an extremely short timescale for a building with such a high degree of automation.

Problem-free operation for six years now: The concept of the deep-freeze warehouse in sandwich construction has been proven correct. The operation of the warehouse has run successfully in all areas from the outset. The result is higher operational reliability combined with lower running costs, in comparison with earlier logistics concepts.

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Continuous cold chain ensured

With the realisation of the three deep-freeze warehouses in sandwich construction and the associated production connections, the Langnese-Iglo logisticians have for the first time realised a continuous cold chain right through to the retail outlet. From production through palleting, storage, commissioning and loading, to the customer, a continuous deep-freeze chain has been created, which does not permit any fluctuation in the normal temperature range. This assures the customer of consistently high quality frozen products, and assures the operator of a continued good market position.

Reken central deep-freeze warehouse

Autor:Erwin Pesch
(Dipl. Ing., FH)
Romakowski GmbH & Co KG, Buttenwiesen

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