SubscribeCan we imagine the automotive industry without automation? Or the food industry? Can we imagine what a simple glass would cost if it would be hand-blown? The simple answer is NO.
Hop on the automation bus?
The world would be different without automation in manufacturing industry. It guarantees quality, productivity, repetitiveness, and control over operations.
However, when we observe the reluctance and doubt with which automation in the container industry is received, we have to question ourselves why? Container handling has a lot of similarities with manufacturing. Repetition and simplicity of tasks within well-defined physical boundaries seem to be very appropriate for automation. So is the worker-unattractive environment of ports: working 3 shifts, noisy conditions, in industrial, polluted areas, is not the typical boy's dream, is it? Still, unions fight to the last men to secure their position.
No, automation in container terminals has not really taken off. With ECT in The Netherlands (1993), and since recently CTA in Germany (2002), the breed of fully automated terminals is merely a rare species, which leads to more visiting buses to the terminals than workers operating it!
However, something is changing: automation is taken more seriously. In many of the terminal design projects automated handling system components are considered.
In this article we will not try answering the obvious question why automation in our industry is developing so slowly.
Most well-informed terminal operators know that automation will bring substantial cost savings, and will lead to a predictable and controllable operation.
No, the question we will try to answer is whether we can define the best handling system concept for a medium-sized to large terminal, in an business environment that demands high productivity (i.e. berth productivities on main line vessels above 150 - 200 gross moves per hour, and crane productivities of 35 gross moves and beyond) and that suffers from high labour cost, and high societal demands, in terms of environmental friendliness, efficient land utilisation, safety and security?
Do we say that these factors are key for considering automation? Yes and no. Yes in the sense that automation will be easier to sell to the risk averse decision-makers among us when these factors apply, but no in the sense that there are many other reasons for automation. Otherwise, high-tech factories of Philips and Nokia in China would also not exist. Automation offers more, so let's explore which handling system concepts are eligible for implementation in the type of terminals we are talking about.
The remainder of this article will encompass the following sequential topics: first we review the technology at existing automated terminals. Then, we will briefly discuss our methodology of assessing the qualities of the various technologies available, and then focus on yard handling systems. Subsequently we summarize the main results, performance and cost-wise. Finalize we wrap up with some concluding remarks.
Review existing terminals
It's a good habit to look to the past when designing the future. So what can we learn from the two fully automated terminals and their perceived lack of success? First, we immediately want do undermine this last statement: the two terminals - see the introduction - are from our point of view, highly successful, proven by their customers. Both terminals are operating at capacity (up to 90-95% stack density), and are money-makers for their shareholders. Their productivity may not be state-of-the-art, but their cost-efficiency (especially when considering their environment) is exemplary.
What are the details? ECT is operating three terminals on one peninsula, with in total 38 quay cranes, more than 130 automated stacking cranes ("ASC"), and a fleet of 260 automated guided vehicles ("AGV"). The yearly volume is around 3.5 million containers, and the performance typical for the Le Havre Hamburg range (where only Antwerp excels).
Figure 1: I over 3 yard crane at ECT Delta terminals
CTA is smaller, but still a decent size terminal, with 14 quay cranes (of which 12 semi-automated double trolley cranes), with 52 ASCs, and around 70 AGVs. As with ECT's Delta terminals, the terminal operates at capacity, which equals around 1.4 million containers. Special at CTA is the ASC design, which consists of two rail mounted gantries of different size, able to cross each other. Where ECT relies on a single RMG per stack module, CTA has redundancy built in.
What would we change in the design when looking back? ECT now at capacity could use a second ASC since the stacks were heightened (the original design was based on 1 over 1 high only, and meanwhile they are at 1 over 4 high!), thus allowing for simultaneous waterside and landside operations. Also the AGVs are the older (slower) types. Finally, the operation between the QC legs ("in gauge") makes the AGV cycle longer than at CTA, where operation takes place in the crane's backreach. At CTA, we consider the amount of equipment for high peak operations too few to achieve high productivities (40+). Since the land is fully occupied, more ASCs are not an option.
Today's design on new automated terminals embroiders on a theme. This means that we are looking at systems with separated waterside and landside operations, with the storage area in the middle, operated by ASC perpendicular to the wharf (see Figure 2).
Methodology of assessment
So do we think we define the best handling system concept for a medium-sized to large terminal? First, we cannot. But that answer is too simple. We will compare a number of handling systems on their merits, and draw conclusions form those. However, for specific cases, the "best" option maybe another; due to local circumstances, economic reasons, or just as a result of (dis)belief in a particular concept.
The method of assessment is based on comparing the different available systems on their productivity-cost ratio under similar circumstances, simply said: which system offers the best balance between the operational cost and performance, while still meeting today's minimum performance demands, in terms of storage capacity and handling capacity.
In order to answer this question, we first need to define the circumstances under which the comparison will take place, as well as the minimum demands. As we introduced above, we are looking at medium to large terminals, i.e. with an end capacity of 2.0 million TEU+. As state-of-the-art terminal, this terminal will be equipped with 10 quay cranes only, which should be capable of running at least 4,000 hours per year. Berth productivity demands should be a minimum of 200 moves per hour (with 5 - 6 cranes) in order to sustain the coming 10 - 20 years (we think). This translates back to minimum (gross) crane productivities of 35 moves per hour. With gross we mean: including all delays between start operation and end of operation. Adding up all productive crane hours, we easily exceed 2.0 million TEU, assuming a TEU factor of 1.6. The berth length equals 1,000m, and the available space for stacking equals 1,000m x 500m (50 ha), i.e. a nice and rectangular terminal, typical for reclaimed area.
So far, so good. Another important factor for terminal design is the transshipment rate, being a tricky one, since this may be difficult to predict. Therefore, we will analyze the handling systems under different transshipment ratios, in order to find the most robust systems as well.
The transshipment ratio determines to a large degree the peak handling demands at water- and landside, respectively the demand from vessel and gate/rail traffic. In this particular case, we assume gate traffic only. Based on typical conditions, we define the following relation between the transshipment ratio and the peaks at the landside:
Figure 2: Relationship between transhipment ratio and landside peak load
Now we have defined the requirements and circumstances, we continue with the methodology. This consists of two main tools: dynamic simulation to analyze the productivity under realistic operational conditions, as well as cost analysis, translating productivity and working hours into operational costs and investments. The simulation is compiled of two parts: the yard handling systems are compared by analyzing a single stack module under maximum workload (i.e. always a job available); the transportation systems are compared under typical peak conditions in a terminal. Both simulations will be conducted under varying transshipment ratios, i.e. varying balances between waterside and landside demand.
The final step of the comparison is the cost analysis, which consists only of the discriminating factors, as all other things being equal. The cost analysis also has two parts: first the investment side of the medal, then the operational cost side of the medal. Both should be assessed in conjunction, although (again) the risk averse among us, focus on the first and the pay back or NPV method only. We argue that the life-span of a terminal is at least 20 years, so the operational costs have more weight than the short term oriented NPV. Anyway, we have applied both to get the complete picture. The operational cost consists of running costs (energy, maintenance), capital costs and depreciation. Labour costs mainly differentiate the automated transportation systems and the manned ones.
The considered alternatives: stacking systems
We have identified three contesters, the twin-ASC, the cross-over twin-ASC and the cross-over tri ASC. All ASCs, and all shortly deployed or already deployed in real operations (respectively at Euromax in Rotterdam and Antwerp Gateway - the first 4 are running by now -, currently at CTA, and soon at the Burchardkai, also in Hamburg). We have left out the single ASC (ECT like) since we consider it of great importance to have redundancy in the system.
Figure 3: Main properties of the stacking cranes
We have assumed that all small cranes can (potentially) run at the same speeds, acceleration and deceleration (for gantry, trolley, and hoist), although individual suppliers may claim differently, or choose differently. The large cranes are slower because of their dimensions.
All concepts span 10 containers wide, 5 high and 40 TEU long, giving a stacking capacity of 2,000 TEU per block. The width of the twin-ASC equals 35 m, the cross-over ASCs are 42.5 m wide; the additional space being necessary for the cross-over functionality.
Also the interchange zones are similar in terms of design, all equipped with an interchange for AGVs at the waterside (5 lanes), and for road trucks / terminal trucks at the landside (5 lanes).
The results
Comparison ASC systems
In order to determine the maximum capability of a single stack module, we created a model in which there is a continuous demand from the waterside (on average 50% loading, 50% discharge), generated by two quay cranes. The waterside transportation is executed by means of automated guided vehicles. As the number is sufficient, there is no waiting time of the ASC for horizontal transportation.
The landside demand is varied, to represent the different types of cargo flows, from true transshipment - for which this terminal layout is certainly not meant, a parallel layout would be more appropriate - to 100% import/export. In all scenarios the "landside" ASCs are allowed to support the "waterside" ASCs. In the cross-over scenarios, the large ASC can actually access the interchange zone, in the twin configuration, the landside ASC can only "pre-position" the export containers closer to the waterside. Of course, the busier the landside ASCs get (with an increase of landside demand), the lesser the ASCs can support the waterside. In the configuration with 3 ASCs, the small landside ASC only does landside moves (shuffles and productive moves), the large ASC can support both waterside and landside.
The job assignment is a critical component in order to make each of these 3 configurations productive. It considers empty traveling (avoid!), job urgency (sequence), and tries to use idle time for pre-productive moves. Another important control component is the conflict avoidance and the passing algorithm for the cross-over ASCs. When to pass and when to wait is a delicate issue. For more information regarding the actual decision-making we refer to Saanen and Valkengoed (2006).
What it does boil down to is shown in Figure 4, where the productivity of each configuration is shown dependent on the landside demand. In addition, shuffle moves and pre-position moves have been executed, but they are not shown in the graph.
Figure 4: Comparison of productivity of a single stack module in combination with AGVs under maximum load waterside, and a varying load landside. There is always an AGV available. The results are almost similar for the combination with shuttle carriers.
Conclusions
What can we conclude from Figure 4? First, that per stack module the tri RMG is the most productive in all cases. However, the contribution of the 3rd crane is at best 2 productive moves per hour compared to the twin RMG, which does not justify the investment in tracks and cranes. The twin cross-over RMG outperforms the twin RMG by a maximum of 1.2 moves per hour (in case of 100% transshipment). In the range of 55 - 70% transshipment they are almost equal, and below 50% transshipment the twin RMG delivers the higher productivity per stack module.
When we would correct the performance of the twin RMG for the lesser width (15%), the twin RMG would be the best performing one; translating that into a terminal of the described width, we could fit in 21 cross-over modules, and 25 twin modules (19% difference in storage capacity!). This would be important in case the width of the terminal is a limiting factor or where storage capacity is an issue.