The brewery distribution center has a volume of 71,600 cubic meters and contains about 8,000 pallets. Every day 1,800 pallets are handled in or out of the system, and the object of this study was to verify the functionality of the automated storage and retrieval system and integrated conveyor system— including elevators connecting five levels of the distribution center. The complex system is modeled with the powerful Arena simulation software.
The brewery distribution system is required to store beverage bundles (supplied from production, train, or trucks) and to consign for delivery via train and trucks. The core of the distribution center is a four-level conveying system, conveying up to 800 different products into and out of a 7,600 pallet AS/RS system. The conveyor system is designed for a daily performance of 1,800 pallets in normal operation. Four automatic narrow-aisle cranes are installed in two aisles, each moving 300 pallets an hour. Ten rail wagons and 30 trucks are loaded and unloaded every day. With such a high volume, an efficient storage and retrieval system was needed to reduce delays in transportation.
From the main level, where the scanner is positioned, the pallets move in pairs via two elevators to the next two levels above, feeding the four pick-up points for the narrow-aisle crane. For each aisle, two pickup and two dropdown stations are placed asymmetrically on each of the levels. Each of the aisles are divided into two sections, each with a narrow-aisle crane and individual unloading and loading stations. After unloading two pallets, the narrow aisle crane has to move vertically to load the next pair of pallets for storage.
Individual animated statistics are placed on the overall layout. These include histograms for the usage of each individual narrow-aisle crane, the number of pallets in the system in different sections, and the congestion level of different conveyor units and rail-guided vehicles.
With Arena, all complex situations could be modeled easily. The results of the simulation study surprised the end user and the main contractor. Although the system design could handle the required throughput of pallets, bottlenecks at different times of the day occurred in unexpected areas.
The simulation project provided them a greater understanding of the system characteristics through the need to collect more detailed information, and analyzing the performance thus reduced the risk of unexpected problems in the design. After installation, a comparison of simulation results with real output was found to be 100 percent accurate.
- The narrow-aisle cranes were underused
- The input and output pallets could be processed in the required time span; however, during breakdowns, pallets coming from the production, train, and truck areas should be handled alternately for maximum throughput
- The buffer sections, with a few exceptions, have sufficient capacity
- The rail-guided vehicle QVW2 will be a bottleneck unless a higher velocity can be obtained
- The elevator SF3/4 will be a bottleneck during breakdowns of other units, and breakdown strategies need to be developed
- One I-point (scanner) is sufficient, but strategies for building pallet pairs are necessary
- Elevator SF1 will be a bottleneck if only one pallet can be handled at a time