Railroad operation in permafrost

17 twin shuttles connect incoming goods and dispatch with internal warehouse logistics in the high-bay pre-zone of a deep-freeze warehouse at a large bakery. At minus 24 degrees, they move 660 pallets per hour, around the clock, seven days a week. Anyone who has to come in for maintenance wants to get out again quickly: at double-digit sub-zero temperatures, service calls in the cold store are freezing cold challenges. It is understandable that malfunctions or even breakdowns should remain the absolute exception. This is a key requirement for warehouse logistics in the cold storage sector: Automated systems must function reliably, reliably and with low maintenance even at extremely low temperatures.

High-throughput material flow system

Eisenmann electric monorail systems are primarily used where standardized packaging units need to be moved quickly and at high throughput rates. EMS systems can be flexibly adapted to the respective transport volume via the number of vehicles used. The ground remains largely free of disruptive infrastructure. The guaranteed availability is over 98 percent. Twin shuttles can handle double the load and take up to two tons of payload. With the help of their support structure conveyors, it is possible to pick up or drop off individual or both pallets at the same time. With a transport speed of two meters per second, the shuttles move quickly. They accelerate quickly and stop gently and with millimeter precision at the respective transfer point. Collisions between the closely timed shuttles are impossible.

"Unplanned breakdowns that result in repair work and downtime must not occur in practice."

Sebastiano Sardo Vice President Conveyor Systems, Eisenmann

Low-maintenance solutions are in demand

But does the material flow also work when the room temperature is minus 24 degrees? The proportion of frozen goods in total food sales has increased steadily. The demand for storage capacity and suitable logistics systems is increasing accordingly. In cooperation with the planning partner of the food production group, Eisenmann demonstrates that electric monorail systems can also be operated reliably in cold storage over the long term. Legal regulations such as Directive 89/108/EEC and Regulation (EC) No. 37/2005 for monitoring the temperatures of deep-frozen foodstuffs in means of transport, storage and warehousing facilities apply. Technical applications in the deep-freeze sector require in-depth know-how, particularly with regard to the suitability of the materials used for refrigeration and foodstuffs. Permanent freezing in a fully automated warehouse requires smooth interaction. "The demands on the reliability of the automation systems are high: they must be designed to meet the requirements of extreme sub-zero temperatures. Unplanned failures that result in repair work and downtime must not occur in practice," emphasizes Sebastiano Sardo, Vice President Conveyor Systems at Eisenmann.

Adapted to cold applications

In the multi-storey, 40-metre-high refrigerated warehouse of a baked goods manufacturer supplying a well-known discounter, EMS Twin Shuttles from Eisenmann connect the interfaces between incoming goods and dispatch with intralogistics over a distance of around 200 meters. How does extreme cold affect the properties and functionality of different materials? Support and rail systems made of metal shrink in extremely cold conditions, while greases and oils change their flow behavior.

Over the past few years, Eisenmann engineers have carried out a series of tests both internally and in cooperation with external testing institutes to investigate the behavior and interaction of individual components at different temperatures. "With technical expertise, in-depth materials research and the findings from a recently completed project in Italy, Eisenmann has provided proof that it can meet the requirements," says Rainer Melles, the responsible Head of Logistics Planning.

Twin with food approval

A shuttle can carry a payload of up to two tons.

The Eisenmann EHB Twin Shuttle trolleys are equipped with freely programmable trolley controls. Frequency-controlled drives ensure adapted acceleration and deceleration behavior. Even in tight bends, the intelligent distance control ensures contact-free accumulation. Electric monorail systems for deep-freeze applications are set up at ambient temperature. After a few days of cooling, the cold store reaches the target temperature. Only then do the driving tests begin.

"To compensate for shrinkage in the rail material, expansion joints are applied at regular intervals," explains Sebastiano Sardo. The Eisenmann expert explains how the technology defies the adverse ambient temperature in the deep-freeze warehouse: "Harder wheels made of Vulkalon cope better with the low temperatures and dampen the running noise. In addition, temperature-adapted oils and greases with food approval are used in the drives. For cable tows, the material must be resistant to cold and breakage."

But that's not all: the current sensors used to supply power are equipped with cold-resistant carbon brushes. The position sensors and mirrors at the 16 goods transfer interfaces must not fog up when the roller shutters are opened. To ensure functionality, the actuators/sensors and the moving switch boxes with their sensitive circuit boards must therefore be heated in some cases.

Failure-free in regular operation

The system went into regular operation in the industrial bakery in March 2017 and has been running smoothly ever since. In the high-bay warehouse with its 16 aisles, 17 twin shuttles handle 15,800 pallets every day. "Eisenmann has thus proven that specially equipped SRM systems also work reliably in the cold storage area," summarizes Rainer Melles. One reason why Eisenmann is already planning two further projects for large refrigerated warehouses with EMS Twin-Shuttles.

www.eisenmann.com