Interroll has produced a White Paper entitled “Key Factors and Performance Indicators in the Choice of a ‘Core Storage System’”. It is available to download by readers of SHD Logistics by following the link at the end of this story.
The White Paper has been jointly authored by:
Prof. Dr.-Ing. habil. Lothar Schulze
Head of Department, Planning and Controlling of Warehouse and Transport Systems, Leibniz University, Hanover, Germany. Guest professor at the Southeast University Nanjing, China, and the SP Jain Center of Management, Dubai and Singapore.
Dr.-Ing. Li Li, PhD
Scientific researcher with the Department of Planning and Controlling of Warehouse and Transport Systems, Leibniz University, Hanover, Germany. Lecturer at the Ostwestfalen-Lippe University.
Dipl.-Ing. oec. Daniel Knopp
Scientific researcher with the Department of Planning and Controlling of Warehouse and Transport Systems, Leibniz University, Hanover, Germany.
Process stability through flow storage
Over the past few years, flow storage systems have continued to advance. They represent an attractive logistical and economic alternative to conventional rack storage systems.
Growth is the fundamental goal of any company. This tends to lead to inadequate storage capacity and the subsequent need for expansion. Frequently, the existing structure of the building can only be revamped or adapted to the changing requirements at considerable expense. Day-to-day experience in the field of operational planning shows that the existing volume of space must therefore be maximised to ensure it is put to the best possible use. An ideal alternative is to convert a conventional rack-storage system into a compact warehouse solution. Wherever a high degree of process quality and durability is also required, flow storage systems are increasingly becoming a recognised and popular solution.
The channel structure is a defining feature of flow storage systems. Inclined channels are fitted with non-powered rollers. The flow of unit loads, from the moment they enter to the moment they leave the channel, is ensured by harnessing the power of gravity. Speed controllers regulate the throughput speed of the units. A separator at the end of the channel ensures that even several heavyweight units gradually make their way down through the channel as soon as one of the units has been removed.
A key feature of flow storage systems is their scalability. The number of unit loads with identical sets of characteristics can be increased by lengthening the channels. Channel depths for up to 50 pallets have already been achieved. When unit loads with different sets of characteristics need to be handled, the number of channels can simply be increased. The characteristics of unit loads include the item itself, its best-before date, the supplier, the destination, transportation route, sequencing, and the height or weight of the unit load or category of goods.
Because standard components are generally used in flow storage systems, maintaining and replacing them is relatively simple. When quality components are used for the various parts, the system can be expected to have a long service life. The basic rule of thumb in the logistics world also applies here, that quality comes with a certain price, but any extra investment pays off for the owner in terms of the ROI in the medium to long term.
The design of the conveyor rollers used in flow storage modules is of crucial importance. They have to ensure parallel and steady progression of the unit loads through the channels. At the same time, the benefits of a slight incline or decline in storage racks can only be exploited in full if particularly lightweight rollers are used. The lighter models also have the advantage of being quieter to run.
The issue of energy efficiency is no longer restricted to specific areas of internal logistics; it has now become a prevailing factor throughout. Designing an energy-efficient storage system means taking account at the planning stages of a host of factors that will affect its subsequent operation. Apart from using certain materials, rack types and control technology, the overall dimensions of the whole system play a crucial role.
It is therefore particularly important to consider the volume of the building. The crucial point is that energy requirements are primarily dictated by the need to heat or cool the building. Flow storage systems lead to a high space utilisation ratio and low energy requirements for heating, cooling and lighting the building. In addition, less investment in the building itself and its interior fittings is required. As well as shorter pathways within the warehousing system and reduced energy consumption, savings in personnel costs may also be achievable.
All forms of manned forklift vehicles are suitable for operating such a flow storage system. They can be used to operate both the dynamic storage and the internal transportation system, which means there is no need to invest in a costly and time-consuming interface between the warehouse control and internal transportation system.
It is possible to improve throughput rates by increasing upstream and downstream control technology. In certain cases, the number of manned or automated forklift trucks working together will increase, or several sections of the route can be completed by automated units such as storage and retrieval machines.
In order to highlight economic areas of use for flow storage systems, the relevant factors were collated as part of a research project, and the flow storage system was compared with the conventional, single-location rack method. For the purposes of making that comparison, the usual investment and cost factors applicable within Western Europe were assumed.
The object of the study was to determine the optimal storage facility cubature, i.e. the ideal length, width and height of the core storage unit, depending on the rack technology applied. Total enumeration was used as the method of calculation, whereby all possible solutions were calculated and the optimal solution selected.
The optimisation targets significant to the planning of any warehouse were determined. As well as minimal running costs, the minimum sized cubature and required investment were also investigated. Both the necessary storage capacity and hourly warehouse movements served as key factors in drawing the relevant comparisons.
Other influential factors include the warehouse control technology used, the warehouse temperature, the size and weight of the unit loads to be stored, the operating times, the workforce and energy costs and the price of land on which the building is constructed and the warehouse structure itself.
With the help of computer modelling, a host of practical combinations of dimensions and factors were calculated to determine the key factors and performance indicators. They offer planners and decision-makers the advantage of not presenting a single operating situation but rather highlighting a range of processes and trends. This means that future trends such as increasing warehouse movements can be taken into account in any decision-making process.
Despite the relatively high investment required in a flow storage system, it offers economic benefits over the single-bay rack method, when the overall costs are compared. Wherever there are high numbers of warehouse movements, and no large storage capacity with short channels are required, a flow storage system should be considered in the decision-making process. For energy-intensive warehousing tasks such as the storage of fresh and frozen goods, flow storage systems offer equally ecologically and economically sound benefits. These advantages have led to major companies opting for a flow storage system as the solution to their logistics challenges.
For some years now, the Department of Planning and Controlling of Warehouse and Transport Systems at Leibniz University in Hanover has developed comprehensive design and practical experience with computer-assisted warehouse planning tools. This was the impetus for developing a customised planning tool for flow storage technology. Once the relevant project-specific data is inputted, it will highlight options for optimising storage concepts. The full extent of planning-related outcomes such as investment, overall cost and required floor space will be made available in a timely manner.
To download the full White Paper, please click on the links below.
Interroll White Paper (2.8MB .pdf)
Supporting graphics (2.5MB .ppt)