Floating Cranes for Container Handling Ben-Jaap A. Pielage, Joan C. Rijsenbrij, Han Ligteringen Abstract Floating cranes could be used to increase the berth capacity for the largest container vessels, making it possible to reduce the vessel berth time. By adding floating cranes on the waterside of a berthed container vessel, the berth productivity could be increased without disturbing the landside operations. Containers would be loaded directly into barges, which could transport the containers to an inland barge terminal. This would not only reduce the pressure on the deep sea terminals and connecting road infrastructure, but could possibly also reduce the total handling costs for containers to and from the hinterland. This paper presents the findings of a study focusing on the feasibility of such a floating crane concept. The paper discusses the conceptual design of the crane itself, as well as its integration in the current logistic processes and its potential market. T I. INTRODUCTION HE container terminal of the future will have to service increasingly larger vessels within relatively short times at competitive costs. Furthermore, there are increasing service demands on the landside for handling the trucks, trains and barges. Earlier studies [1] suggest that by using floating cranes on the water-side of a berthed container vessel, the berth productivity could be increased without disturbing the shore-side operations (see Fig.1). Moreover, there would be no demand for storage or internal transport on the port terminal, as the containers would be transported directly to an inland barge terminal. Furthermore, it was expected that the total handling costs for container to and from the hinterland could be reduced. This paper presents the findings of a follow-up study Floating cranes for Container Handling [2]. The aim was to better assess the feasibility of this floating crane concept. The study focuses on the potential market for the floating crane, the possible integration of the floating crane in the current logistic processes, the conceptual design of the floating crane, and includes a first assessment of the dynamics(movements) and costs. Fig. 1. First sketch of the floating crane concept (Source: Jan van Beemen, Royal Haskoning) [1]. II. POTENTIAL MARKET To better assess the potential market for the floating crane, seven large ports in Europe are analyzed: Le Havre (France), Antwerp (Belgium), Rotterdam (the Netherlands), Amsterdam (the Netherlands), Bremen-Bremerhaven (Germany), Hamburg (Germany) and Constantza (Romania) [3]. These ports are considered based on their ability to service large container vessels and their inland waterway connections. For the deployment of floating cranes, space is required on the waterside of the vessel. Furthermore, the vessels should be able to navigate the basins. The selection criteria for suitable terminals were therefore: nautical access, water depth and basin width. Figure 2 shows the terminals analyzed for Maasvlakte 1 (right) and Maasvlakte 2 (left, currently in development) in the port of Rotterdam. Of the 6 terminals investigated, 5 would be suitable for floating crane deployment. Manuscript received March 27, 2008 Dr.ir. B.A. Pielage is with the department of Maritime and Transport Technology, Faculty 3ME, Delft University of Technology, the Netherlands (phone: +31 15 2785292; fax: +31 15 2781397; e-mail: B.A.Pielage@tudelft.nl Prof.ir. J.C. Rijsenbrij is with the department of Maritime and Transport Technology, Faculty 3ME, Delft University of Technology, the Netherlands (J.C.Rijsenbrij@tudelft.nl). Prof.ir H. Ligteringen is with the department of Hydraulic Engineering, Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands (H.Ligteringen@tudelft.nl) Fig. 2 Rotterdam Maasvlakte Terminals (Source: Rotterdam Port authority)
In the seven European ports, a total of 33 terminals were reviewed. Floating cranes could be deployed in 14 of the 33 terminals. Table I shows an overview of the results. TABLE I PORTS & TERMINALS FOR FLOATING CRANES Port Number of Terminals Number of terminals Investigated with potential Le Havre 6 1 Antwerp 4 3 Rotterdam 6 5 Amsterdam 4 1 Bremerhaven 2 0 Hamburg 6 3 Constantza 5 1 The current vessel stowage planning process does not easily include the option of grouping containers for direct barge transport in one bay. This limitation must be taken into account when considering possible implementation of floating cranes. B. Introducing the Floating Crane One of the main advantages of introducing floating cranes would be the increase in berth capacity. The number of quay cranes that can simultaneously work on a vessel is limited by their base dimensions. Two quay cranes working side by side will leave at least one 40 foot bay between them, as shown in Figure 4. This leaves potential for floating cranes to increase the berth capacity. Total 33 14 III. LOGISTICS & OPERATIONAL ASPECTS One of the main concerns from an operational point of view was whether the floating crane could be integrated in the current logistic processes. This section first briefly discusses the current vessel stowage planning and introduces how the floating crane can be integrated in the current operations. Five cases are studied [4]. A. Current Vessel Stowage Planning A container vessel typically travels on so-called string routes, where at each port of call containers are discharged and additional containers destined for subsequent ports are loaded. Determining a viable arrangement of containers to facilitate this process in a cost effective way, makes up the vessel stowage problem [5]. Ideally all containers to be discharged at a certain port should be on top of containers that are destined for a subsequent port on the route. Whereas it is sensible to group cargo with the same destination in the same bay, a good distribution of this cargo between bays will permit multiple cranes to work on the vessel. The vessel stowage planner takes into account how many cranes will be made available at each port and aims to maximize their use. Furthermore the vessel stowage planner must take into account many other aspects, such as the size and weight of the container, and whether they are reefers or contain hazardous cargo. Figure 3 shows an example of a vessel stowage planning. Fig. 3. Example of vessel stowage planning (Modified from [2]) Fig. 4. Crane positions during loading/unloading (Modified from [6]) By introducing floating cranes, the total handling costs could also be reduced. The decrease in vessel mooring time and bypassing of the expensive deep sea terminal could reduce costs. However, there are also additional costs at the so called barge hub terminals further inland (see Figure 5). These and other costs are further analyzed in the case studies. Fig. 5. Container flow containers to and from the hinterland [4]. C. Five Case Studies To better assess whether floating cranes could indeed be integrated in the logistic processes, increase the berth capacity and reduce costs, five cases have been studied [4]. The focus was on possible implementation of the floating crane in current operations without changing the vessel stowage planning (only Case 5 involves changes in the vessel stowage planning). All cases were based on data from an actual vessel, with an existing vessel stowage planning. A 7 quay crane split (distribution) of containers on the vessel would be the point of departure. The crane planner would then integrate 2 additional floating cranes into the schedule, resulting in a combination of 7 quay cranes and 2 floating cranes working on the vessel. For the example vessel, the
vessel handling time could thus be reduced from 17 hours (with 7 quay cranes) to 15 hours (with 7 quay cranes and 2 floating cranes). The cost implications of adding the floating cranes are further discussed per case. In Case 1: Floating cranes are presumed to handle only those containers that are known to continue by barge, without changing the vessel stowage planning. This would however be practically impossible. Even if the final destination and mode of transport for all containers would be known (which is not the case), the vessel stowage planning does not take the final destination or mode into account. Therefore the so called barge containers are randomly scattered throughout the bays to be unloaded. Floating cranes that handle only barge containers with the current vessel stowage planning is therefore considered unfeasible. In Case 2: Floating cranes handle all containers in the bay it is working on, the barges remain at the terminal and the containers are second handled onto the terminal by the quay (barge) crane. In this case, all containers remain within the control of the terminal. The vessel mooring time will be reduced (2 hours), but the total costs will be higher, mainly due to the second handling of the containers. First cost calculations show that the total cost would increase from approx. 641000 Euro with 7 quay cranes to 647000 Euro with 7 quay cranes and 2 floating cranes. This case could however still be of interest for terminals that want to increase their service (berth capacity) at a price. In Case 3: Floating cranes handle all containers in the bay it is working on, the barges transport all the containers to the barge hub terminal, where all containers are second handled. Although this could reduce the transport costs for the so called barge, rail and road containers, the so-called transshipment containers will need to return to the deep sea terminal. Again the vessel mooring time will be reduced, but the total costs are expected to be higher (645 k versus 641 k), amongst others due to the return of transshipment containers. In Case 4: Floating cranes handle all containers in the bay it is working on, the transshipment containers are put into one barge which remains at the terminal (similar to Case 2), and all other containers are transported by barge to the barge hub terminal (similar to Case 3). In this barge split case, the vessel mooring time will again be reduced. Furthermore, the first cost calculations show that the total costs could be reduced (from 641000 Euro with 7 quay cranes to 630000 Euro with 7 quay cranes and 2 floating cranes). Of the four cases without changes to the vessel stowage, this case is considered most promising from a total cost point of view. However, it should be noted that these are only preliminary cost estimates and based on one example vessel. In Case 5: Floating cranes handle only barge containers which have been grouped by the vessel stowage planners to allow for an efficient handling by floating cranes. In this case, it is assumed the vessel stowage planning will be adapted. Although this case shows the larges potential cost savings (from 641k tot 622k) the feasibility of changing the vessel stowage planning is still unclear. Aspects such as availability of information, last minute changes, possible decrease in transport and handling efficiency are still to be considered. IV. CONCEPTUAL DESIGN To better assess the technical feasibility and investment costs of the floating crane, a conceptual design was developed [7]. The philosophy was to develop a concept based on existing (proven) designs and standard (reliable) components, using the knowledge and experience of the partners involved in the research. The main requirements for the floating crane were that it would be able to reach across the whole width of the largest container vessels, work on a bay directly adjacent to a bay where a quay crane is working, be able to (re)position itself along the vessel, have a productivity of 25 moves per hour, be able to perform twin lifts, and service two barges simultaneously. The main parts of the floating crane are: the deep sea crane, the barge crane, the pontoons, and the foundation structure (connecting the pontoons and supporting the barge and deep sea cranes). Figure 6 shows the main parts of the floating crane. The machine room, with a buffer for containers, is positioned on the front pontoon. Fig. 6. Main parts of the floating crane [7]. The maximum outreach is 60 meters, and the maximum height under the spreader is 55 meters (to water level), making it possible to service the largest container vessels. The base of the crane is approximately 52 by 52 meters, and the distance between the pontoons is approx. 27 meters, making it possible to service 2 normal sized barges or one large (Class VI / 400 TEU) barge. Figure 7 shows the floating crane in its working environment. The floating crane is positioned between 2 quay cranes, unloads the containers from the vessel, and positions the containers in the buffer. The barge crane handles the containers between the buffer and the barges.
The mass and mass-distribution of the different crane parts were derived from the conceptual design. The total mass of the crane was calculated to be approx. 2600 tons. For simulating a (maximum) load case, both the deep sea crane and barge crane are assumed to perform their load cycle simultaneously, both with maximum load (twin lift: two 30 Ton containers under the spreader). The maximum accelerations and velocities are shown in Figure 10. Fig. 7. Impression of the floating crane in its working environment [7]. The floating crane has two thrusters for propulsion, one on each pontoon, as shown in Figure 8. For loading/unloading operations, the crane is attached to the deep sea vessel using cables and winches. This secures the crane to the vessel, but also makes it possible to move the crane alongside the vessel. Winches are also used to secure and position the barges under the barge crane. Fig. 10. Maximum accelerations and velocities for crane cycles [8]. The resulting heave, surge and sway movements of the boom tip are presented in Figure 11. The maximum heave would be between approx. -1.8 and +1.8 meters, the maximum surge between -1.1 and +1.2 meters and the maximum sway between -0.6 and 0.7 meters. Heave Fig. 8. Top view of positioning and propulsion systems on the floating crane [7]. Surge V. DYNAMICS OF THE CRANE In order to assess the dynamic behavior of the crane under certain load conditions, a model was developed in a multi body dynamics program [8]. The first assessments focused on the dynamic movements of the tip of the boom. Figure 9 shows the defined movements: heave, surge and sway. Fig. 9. Heave, Surge and Sway movements of the boom tip [8]. Sway Fig. 11. Heave, Surge and Sway of the boom tip during a oad cycle [8].
Although the heave and surge have relatively large ranges, the time between peaks is also relatively large. These movements could be (partly) compensated by the crane driver. The sway movement is relatively low, but is difficult to control. Furthermore, the sway movements are most critical when considering possible collision between the boom of the floating crane and the booms of the quay cranes. If a floating crane is working on a bay directly adjacent to a quay crane, the distance between the booms is estimated at approx. 4 meters. The maximum sway displacement of 0.7 meters is well within this margin. However, the simulation does not take waves and wind into account. Further research is required. Similar analyses were performed for the movement of the deep sea spreader and barge spreader. From the analyses it could be concluded that the dynamic responses of the floating crane seem to be within allowable limits. However, special attention should be paid to the sway of the boom tip and the (corresponding) sway of the deep sea spreader. In any case, using a floating crane on a bay directly adjacent to a quay crane does require operational restrictions to avoid collisions between spreaders/containers. cost calculations should be regarded as first estimates. A more in depth business case is required to better assess the costs and possible cost savings. TABLE III ESTIMATED YEARLY OPERATIONAL COSTS Cost Type of costs (million Euro) Fixed costs Depreciation & interest (linear, 15 years, rest value 1 million Euro, Intr. 6%) 1.7 Maintenance cost (5% of investment) 0.9 Insurance (0,5% of investment) 0.09 Personnel costs Indirect (Admin. etc) 0.16 Variable costs (for 2600 hours) Personnel costs Direct (5 people at total 250 euro/hour*2600 hours) 0.65 Energy costs (2600 hours) 0.25 Miscellaneous 0.25 Total Yearly Costs (for 2600 hours (approx.30%) utilization) 4.0 VI. COST ESTIMATES The investment costs for the floating crane were estimated using the conceptual design and the experience of the participants (see Acknowledgements) in the project. Table II presents the cost breakdown. The total investment costs are estimated at 18 million euro. TABLE II ESTIMATED INVESTMENT COSTS Part Cost (million Euro) Deep sea crane 7.5 Barge crane 2.2 Structure connecting pontoons 1.2 Pontoons 3.6 Engine room & Thrusters 2.0 Winches 0.5 Miscellaneous 1.0 Total Investment Costs 18.0 The estimated yearly operational costs were calculated for 2600 hours (approx. 30%) utilization. Table III shows the results of the calculations, adding up to approx. 4 million euro per year for 2600 hours operation. Assuming an average production of 25 containers per hour, the costs per container can be calculated at 62 euro/container. Although the handling cost per container by floating crane can be lower than the handling costs per container by quay crane, the potential to reduce the total handling costs greatly depends on the type of operation, as discussed in the section on Logistics and Operational Aspects. In that section is was argued that Case 4, with the so called barge split, would be most promising from a total cost point of view. However, the VII. CONCLUSIONS The aim of this study was to better assess the feasibility of floating cranes for container handling. The following conclusions are drawn: The floating crane is considered technically feasible. The main parts of the crane are based on existing designs, and the conceptual design shows no technological show stoppers. The floating crane can be integrated in the current logistic operations without changing the current vessel stowage planning. However, using a floating crane on a bay directly adjacent to a quay crane does require operational restrictions in order to avoid collisions between spreaders/containers. The first assessment of the dynamics show that the distance between the booms of the cranes should be sufficient to avoid collisions between the booms themselves. A more in depth study on the operation and dynamics of the crane is however required. Using floating cranes can reduce the container vessel berth time and may reduce total handling costs. Without changing the vessel stowage planning, Case 4 seem most promising from a total cost point of view. In Case 4 the floating cranes handle all the containers in the bay they are working on; the transshipment containers are put into one barge which remains at the terminal to be second handled back onto the terminal; and all other containers are transported by barge to the inland Barge Hub Terminal, where they are second handled onto the Barge Hub Terminal. The first cost estimates show possible cost savings of approx. 11.000 euro for one vessel (from 641000 Euro with 7 quay cranes to 630000 Euro with 7 quay cranes and 2 floating cranes). However, it should be noted that these are only preliminary cost estimates, and based on one example vessel.
Furthermore, this case assumes a Barge Hub Terminal to be available approx 50 kilometers inland. A more in depth business case is required to better assess the total costs and benefits, as well as implementation issues. The floating crane concept greatly depends on the availability of an inland Barge Hub Terminal, at least as a possible cost saving alternative. In return, a Barge Hub Terminal can benefit from the floating crane concept as it will provide more containers. Combining the floating cranes with a direct barge connection to a Barge Hub Terminal will furthermore reduce the pressure on the deep sea terminals handling and storage capacity, as well as the connecting road infrastructure. So apart from possible cost reductions, floating cranes could also be of interest to terminals reaching their maximum capacity, and/or as a method to reduce road congestion in port areas. Floating cranes can be used at the Maasvlakte in Rotterdam, but also in many other ports. Of the 7 European ports and 33 terminals reviewed, 14 terminals appear to have the qualities required for deployment of floating cranes. 80% of the potential terminals are located in the three major container ports in Europe: Antwerp, Hamburg and Rotterdam. Although the study shows positive preliminary results with regard to the technical, operational and financial feasibility, there are several aspects to be considered in more detail. To better assess the costs and possible cost savings, a business case is required. The business case should not only focus on the cost and benefits themselves, but also on possible issues with regard to the distribution of the costs and benefits among the parties involved. The question who is going to invest, and who is going to operate should also be considered. To better assess the operational aspects and to ensure a safe working environment, a further analysis of the operation and dynamics is required, and should also be included in a next phase. Finally, it is recommended to investigate the possibilities for adapting the vessel stowage planning to allow for concentration of barge containers in specific bays. REFERENCES [1] H. Ligteringen, J.C. Rijsenbrij, B.A. Pielage, W.F. Molenaar, M. van Schuylenburg, A.M. Vaes-Van de Hulsbeek Container terminal of the future Port Research Centre Rotterdam-Delft, 2004 (in Dutch) [2] B.A. Pielage, J.C. Rijsenbrij, W. van den Bos, H. Ligteringen, J. van Beemen, Floating Cranes for Container Handling Port Research Centre Rotterdam-Delft, ISBN: 978-90-5638-189-9, 2007. [3] R. Obrer Marco Logistical and Economical Aspects of the Floating Container Crane within a Netwok Terminal, Master of Science Thesis, Delft University of Technology, Faculty of Civil Engineering and Geosciences, Department of Hydraulics, Delft, 2007. [4] H.A. ter Horst, Vessel Stowage Planning for the Floating Crane Concept, Literature Assignment, Delft University of Technology, Faculty of Mechanical, Maritime and Materials Engineering, Department Marine and Transport Technology, Report Number 2006.TL.7086, Delft., 2006. [5] I.D. Wilson,, P.A. Roach, J.A. Ware. Container stowage pre-planning: using search to generate solutions, a case study, Knowledge-Based Systems 14, pp. 137-145, 2001. [6] I.D.Wilson, P.A. Roach. Container stowage planning: a methodology for generating computerised solutions, Journal of the Operational Research Society 51, pp. 1248-1255, 2000. [7] J.H. Reus, Structural design of the floating container crane concept, Design Assignment, Delft University of Technology, Faculty of Mechanical, Maritime and Materials Engineering, Department Marine and Transport Technology, Report Number 2007.TL.7121, Delft, 2007. [8] M. Barends, Dynamic behaviour of a floating container crane, s for container Handling, Master of Science Thesis, Delft University of Technology, Faculty of Mechanical, Maritime and Materials Engineering, Department Marine and Transport Technology, Report Number 2007.TEL.7207, Delft, 2007. ACKNOWLEDGMENT This paper presents the finding of the Port Research Centre project Floating Cranes for Container Handling. The Port Research Centre (PRC) is a cooperation between the Port of Rotterdam and the Delft University of Technology. It mission is to generate, coordinate and execute innovative, strategic research projects aimed at application in the Rotterdam port and industrial area. Participants in the project were Delft University of Technology, the Port of Rotterdam, APM Terminals, Kalmar Industries, Gottwald Port Technology, Ravestein, Siemens Netherlands, IDEA Heavy Equipment and Royal Haskoning.