Kalmar, part of Cargotec, offers the widest range of cargo handling solutions and services to ports, terminals, distribution centres and to heavy industry. They are the industry forerunner in terminal automation and when Kalmar decided to move forward with the design of their automatic stacking cranes they chose Etteplan. The co-operation in Technical calculation area of engineering started in 2011.
The fully automated cranes operate in the ports by the sea. As the ports are windy and subject to high wind loads, it is critical that the cranes are robust enough to be fully operational in wind speeds up to 25 meters per second. Out-of-service wind speed requirements can be more than 50 m/s. Hence, the design and calculation process has to be extremely precise with relevant safety margins included.
”Traditionally crane wind loads has been calculated manually according to related design rules and standards. The only way to verify these calculations has been the use of wind tunnel testing, but this is a very time-consuming process and the modifications to the physical test model are difficult if several configurations need to be studied” says Matti Paloneva who is R&D Manager for Technical Calculation and Simulation at Kalmar.
Designing the fifth generation ASC 5.0 crane
To advance the design process for their fifth generation Automatic Stacking Cranes, Kalmar decided to move forward with Computational Fluid Dynamics (CFD) calculations.
”Etteplan assisted us with CFD. This method proved to be fast and efficient process to verify the design wind loads. Also the effect of different crane geometries is easy to study. Third point is that the simulation results are very visual and easy to explain to persons who are not so familiar concerning the crane wind loads. The 3D-prints are nice way to visualize the numbers for the loads in presentations”
At Etteplan, Pasi Moilanen was responsible for performing the CFD simulations. Pasi works at Etteplans Centre of Expertise for CFD in Tampere in Finland, one of three offices that conduct the CFD calculations and simulations.
”In this assignment, Kalmar had very high requirements. We had to prepare the calculations with a 5 percent error margin. It is challenging and requires long experience to select the correct parameters to achieve this accuracy.”
The 3D CAD geometry is included in fine detail to achieve the desired 5 percent error level. To meet the set criteria Etteplan needed to consider and evaluate several possible error sources such as wind profile, temperature, pressure, humidity, turbulence, time dependent behavior, wind direction and CFD numerical procedures. It is demanding to predict the behaviour of different parameters, although Pasi Moilanen’s experience of over a hundred of industrial CFD assignments made the parameter screening faster.
One single supplier for the entire CFD process
Kalmar has cooperated with Etteplan earlier on to perform design work and structural analyses, but this time Etteplan was trusted with the CFD as well. The CFD adds the final piece of the puzzle that allow the structural analyzes to be performed more accurately.
”Usually, several suppliers are involved in the design processes but we felt that it was a major benefit for us to work with one single supplier who possess the expertise necessary for all calculations and simulations. One single point of contact is much more efficient and convenient”, says Matti Paloneva.
“The CFD-calculations fulfilled the Kalmar expectations. The goal was to compare the traditional hand calculated wind loads to CFD results instead of expensive and time consuming wind tunnel testing. CFD proved to be efficient and cost effective step. Another important lesson was how we easily can compare different designs in early stages of the R&D project by using CFD."
R&D Manager for Technical Calculation and Simulation at Kalmar