Inland waterborne pallets - storage, on board handling, transhipment and viability
Prof. Dr. Ir. U. Nienhuis MBA, Ir. C. Dirkse, Dr. Ir. A.J. Klein Breteler
Delft University of Technology Department of Marine and Transport Technology
Mekelweg 2, 2628 CD Delft, The Netheriands tel+31 15 2783882,e-mail secretariaat.scheepsbouw@wbmt.ludelfl,nl
A B S T R A C T
By concentrating the demand for predictable transport of palletised goods a multi-modal transport system should become a possibility. This offers the opportunity to make use of the environmentally friendly alternative of inland shipping.
This alternative should be able to take over a substantial part of inland transport at the lowest rate per pallet, but will require a change in logistics, the
development of a distribution network, an appropriate technical solution, economic viability, etc., all aspects which have been investigated in a broad-oriented research project.
As a part of that research this paper describes an investigation into the
possibilities for the development of a specialised inland ship for the transport of pallets, the storage of these pallets during sailing, the transhipment of the pallets and the ship-shore interface. Furthermore sorting systems were looked into to automatically move pallets during transit into a suitable position for immediate unloading at the next stop.
The analyses have been made on the base of three specific network scenarios. Various concepts for storage and handhng of pallets have been investigated and analysed for use on board, taking into account protection against weather
(covered operation), stability of the ship, ship-shore interface, deformation of the ship, economic viability etc.
The chosen solution is based on the existing Riverhopper concept in combination with an active onboard storage and handhng system. The proposed system is rather unique, which implies that standard components are not immediately applicable and tailor-made additions are required.
Various aspects need further investigation, such as stability during onboard pallet handhng, lashing of pallets and the construction of the cargo roof. Mechanisation and automation of the transhipment system turn out to be key factors for the success of the pallet concept. From the technical and economical point of view the concept looks promising and further developments including a pilot
1. INTRODUCTION
1.1 Background
For transport of pallets roads are used over short, medium and long distances. This contributes to traffic congestion and by that to environmental pollution. But the congestion also has an effect on the cost and the reliability of the road
transport.
By shifting the pallet transport from road to inland shipping cost can be decreased and the reliabihty may be increased.
Especially for dedicated point to point shipping without feeder- and hinterland transport this shift is rather easy and a feasible alternative for medium and long distances.
However, to build a network with more ports, more customers and different cargo including feeder- and hinterland transport is much more complicated. From this starting-point the so-called Distrivaart (Distributed shipping) concept has been developed in The Netherlands in the past two years.
The project was sub-divided in five parts: Economics, Logistic planning and control. Technology, Network development and a Pilot project.
This paper will concentrate on the sub-project Technology only.
1.2 Problem definition
Transport of pallets requires special conditions for the ship and the arrangement of the cargo hold.
Pallets should be kept dry during transport, which implies a covered cargo space. Secondly a storage and transhipment system is required.
Various warehouse systems are available, but a challenge to design a system for application in a ship is the limited space.
Another problem is the interaction between the moving ship and the system, which could lead to restrictions of the position of the cargo due to stability requirements or to undesired displacements of the cargo during sailing.
1.3 Goals of the project
The main goal is the development of design concepts for the storage and transhipment system in the ship including a vahdation of these concepts. A second goal is the development of a cover for the cargo hold.
1.4 Methodology
For development and analysis three scenarios for networks have been drawn up, each representing different stages in the system of distributed shipping now and in the future. The scenarios are following each other logically in such a way that a scenario can grow to a next scenario.
Each scenario will be analysed on its specific aspects, including the most suitable technology.
• Transport network
Simple liner service for various ports. Cargo units are tmckloads of 26 pallets with the same product and the same destination. Pallets inside the truck are exchangeable.
• Distribution network
Liner service with a limited number of ports. Full truckloads; each load may consist of various contingents. Pallets inside contingents are exchangeable. During sailing contingents for the next port have to be combined to new truckloads.
• Collaborative network.
Similar to the distribution network, but the network considers each pallet as unique. This includes also that the destination of specific pallets may change during saihng.
Following steps of the project will be described in the next chapters of this paper: 1. Analysis of the system and terms and conditions
2. Sub-division of the system in functions and components 3. Inventory of system concepts
4. Selection of suitable systems per network 5. Design of cargo roof
6. Elaboration of evaluation criteria 7. For each scenario:
a. Evaluation of selected systems as regards logistics, economics, stability and ship construction;
b. Determination of preferred systems
8. Determination of the most logical migration scenario
2. T E R M S AND CONDITIONS, MORPHOLOGICAL OVERVIEW AND S E L E C T O N OF C O N C E P T
2.1 Terms and conditions; system requirements
Starting point for the design of the system is the so-called Riverhopper concept, an inland ship with following particulars:
Length 63.00 m Breadth 7.20 m Depth 3.05 m Draft loaded 2.75 m Draft empty 0.75 m Draft in ballast L60 m Cargo hold 49.40 x 5.70 x 3.50 m (1 x b x d)
This ship loaded with 575 pallets of beer and 50% of consumables has a GM-value of 0.47 m. Pallet sizes are 1.00 m x 1.20 m x 1.80 m (1 x b x h) with a total weight between 300 and 1000 kg.
Fig. 1. Riverhopper concept (Source: Riverhopper BV)
Minimum requirements have been drafted for the various components of the system and independent of the network scenario as far as possible.
In general the solutions have to f u l f i l national and other legislation. The system should be able to keep running under marine conditions and the cargo should be kept dry and undamaged.
It should be possible to adapt the system for use in another scenario. The system should be able to sustain deformations of the ship caused by the load of the cargo and should be easily accessible in case of failures.
The pallets should be undamaged and have a breadth of 1.20 m. Length may vary and minimum distance between pallets and/or the constmction of the ship is 5 cm, unless automated systems require more.
The stacking svstem should have such a weight that the stability of the ship is safe under all circumstances. Preferably it should be modular for easy
adaptations.
The transhipment svstem should be able to bridge differences in the height of the quay for which a range from 0.60 to 2.60 m has been taken. The system should be able to handle the cargo outside the hold both on port side and on starboard side.
The cover of the cargo hold should be weatherproof and flush inside over the rectangular hold. Openings in the cover should allow horizontal (port and
starboard) and vertical movements of the pallets. The stacking system to be used as constructive support for the cover.
The warehouse management svstem. which determines the loading sequence and the location of the pallets, should be able to take into account stability and
2.2 Morphological overview and criteria
The design of a complex system like the storage and transhipment of pallets it is necessary to investigate many possible solutions in an early stage of the process. This will be done by sub-dividing the system in a number of sub-functions and finding solutions for each sub-function. This matrix of possibihties, the so-called morphological overview, is the basis for further selection by criteria, which have to be drafted as well.
For the storage and transhipment following sub-processes have been determined: Inside the stack:
Shifting of pallets in a stack-lane Transverse movement between lanes Movement in or out a lane
Outside the stack in the ship: Lifting inside the ship Transverse transport Outside the ship:
Shifting from ship to quay and vv Transport on the quay
Shifting into the trailer The ship itself:
Compensation for height of quay
A number of criteria have been drafted to evaluate all possible concepts. Most of them are related to functional constraints or risks, but the most obvious is the economic criterion, expressed by the cost per pallet. This includes all cost of the total transport system, such as capital cost, fuel, crew, maintenance, insurance, etc. and aspects as storage capacity and transhipment speed and cost.
Other criteria are:
- Sorting capacity
- Technical complexity and reliability - Investment risk
- Development cost
- Transhipment time and flexibility - Air draft
- Stability and lashing - Height of quay
- Deflections of the ship - Accessibility of the hold - Safety and environment
2.3 Selection of concepts
To make a sound selection of total concepts a number of aspects has to be
investigated to avoid non-realistic or illogical choices. These aspects are given in the paragraphs below.
2.3.1 Components
Apart from pallet details, various systems and especially standard components need to be investigated, such as hfting systems, vi'arehouse stacking systems, shuttles, stack loading devices (a.o. forklift trucks), etc.
2.3.2 Pallet interspaces
Distances between pallets and the surrounding ship's structure need careful consideration to avoid pallets or its loads being stuck or damaged. Distances will vary from 5 to 10 cm depending of the installed system.
Since the cai-go hold has a free breadth of 5.7 m the stacking system should have two pallets between two columns and additional cross beams. This however will increase the height by 0.4 m.
2.3.3 Capacity of movements in the stack
Based on characteristics of a powered chain or roller conveyor it can be
determined that a capacity of 120 paUets/hr is feasible and sufficient for one lane. This includes handling by the hft.
For a shuttle system - pallets will be handled one by one by a carriage (shuttie) below the pallet - the operation is rather complex and not well suited for sorting. The capacity may be compared with a drive-in system with a forklift truck. Further research on sorting by shutties is required.
2.3.4 Transhipment levels ship-shore
The height of the quay is a key factor in the transfer of pallets from ship to the quay. Starting point was a range of 0.6 - 2.6 m. Another factor is the position of the racking system in relation to the height of the quay. This will depend on the type of the system, but can be influenced by ballasting the ship.
It appears that the level of transhipment should be around the height of the upper rack level and this determines the vertical displacement of the hft.
It should be possible to keep the top of the coaming below the trailer in all circumstances. In that case a lift on the gangway can be placed above the coaming top.
The situation with various levels is illustrated in fig. 2.
3.5 Stability during transhipment
For a number of extreme conditions such as pallet on the gangway, forklift with pallet, crane with load, etc. the angle of heel has been calculated using the traditional formula M = p gVGM(p wherein: M = heeling moment p = density of water g = gravity
V = volume of displaced water GM = initial stability
Fully loaded GM = 0.47 m and by using ballast where necessary and possible the angle of heel can be kept below the safety level of 5 degrees.
Nevertheless the stabihty needs to be kept under control under all circumstances.
Variation to ship of: • depth upper deck
gangway B On r i quay, trailer waterline <N hull
pallets hi_ghes^ and lowest values
St cn s O 15 E CO On rf
Fig. 2. Height of quay and draft
3. P A L L E T S Y S T E M C O N C E P T S AND C A R G O ROOF
Based on common stacking and handhng systems a number of variations have been drafted. The selection of components has been made in such a way that a concept can be composed which will has the best performance for the most suitable scenario.
Numbers and dimensions have been made parametric as far ass possible to ensure a neutral comparison of concepts.
3.1 Inventory of system concepts
Finally 13 concepts were conceived as Hsted below in table 1. One is illustrated in fig. 3 below.
concept type of stacking description
1A Block stacking Pallets transverse; symmetric; direct in trailer 1B Block stacking Pallets transverse; symmetric; direct in trailer 1C Block stacking Pallets longitudinal; symmetric; FLT on shore 2A Powered stack LIFO Symmetric; FLT on shore
2B Powered stack LIFO Asymmetric; FLT on shore
3 Shuttle stack LIFO Symmetric; gangway lift; conveyor with heave 4A Gallery stack Symmetric; 2x SLD on board; FLT on shore 4B Gallery stack Symmetric; 2x SLD on board; lifting table on shore
5 Powered stack; sorting Symmetric; gangway lift; conveyor with heave 6 Powered stack; sorting Crane with pallet cage on board
7A Chain pull stack 2x FLT on shore and on board 7 0 Chain pull stack 3 automatic dischargers
8 Powered stack; sorting One block; both sides automatic dischargers LIFO = Last In First Out
SLD = Stack Loading Device FLT = Fork Lift Truck
Table 1. System concepts
The concept numbers represent a type of stacking. Concepts 1-3 have no sorting capabihty.
The corridors in 4B are transverse and 2 pallets deep; one corridor is used for transfer to shore by chain rollers.
The hfting platform on the quay has a capacity of 120 pallets /hr and the SLD's should be able to f u l f i l that requirement as well. For unfolding the roller
conveyor and setting of the lifting platform 15 minutes should be sufficient. Evaluation of these 13 concepts has resulted in a selection of the most suitable systems for each scenario as indicated in table 2.
concept Transport network Distribution network Collaborative network 1A X I B X 1C X 2A X 2B X 3 4A X X X 4B X X X 5 X X 6 X X 7A X 7B X 8 X X
Table 2. Selection of system per scenario
3.2 Lashing
On certain routes in Holland, especially on the big lakes, the weather conditions may be heavy which might lead to shifting of the pallets. For these circumstances the pallets have to be lashed sufficiently in transverse direction. Several solutions are considered depending on the type of stacking system. Inflatable air cushions, safety fences or a snapping spring system are a few options. It will bring extra cost and possibly some extra effort in operation.
3.3 Cargo roof
In a previous chapter general requirements have been drafted for the construction of a roof to cover the cargo hold. However, the design of the roof will depend on the concept chosen. Within the scope of this paper a solution for concept 5 will be illustrated in fig. 4.
RHS 50x50x4 (EVERY 6Ö0) C O R R U G . PIATE 1,5 R H S 2 6 0 x l 4 a < 6 , 3 ^ (EVERY 2500) \ / e CD
Fig. 4. Roof for cargo hol(d
FREE CLEARANCE 5 4 6 0 C L RS. CD RHS 100x60x4,5 (EVERY 2500) RHS 50x50x4 (EVERY 662) C O R R U G . PLATE 1,5 ( ) d
This construction will have a mass of 50 tons when conventionally constructed in steel and 15 tons i f buih in aluminium. In spite of the higher cost (€ 75K versus € 65K) it turns out that the lightweight construction is necessary.
4. EVALUATION METHOD
In the previous chapter for each scenario a number of concepts with potential have been selected. In this chapter the evaluation method will be elucidated for simulation of operation times, economic performance, stability and deflections of the ship.
4.1 Simulation of operation times
For each concept calculations of run times have been made based on specific cargo packages, detailed stowage plans and assumptions for cargo handhng times.
For the transport network the LIFO principle will be applied. In the distribution and collaborative network shuffle times are introduced for replacement of pallets during sailing. I f the shuffle time is less than the sailing time immediate
4.2 Economic performance
Evaluation of the economic performance will be limited to micro-economic level of the ship, operating in a running company with sufficient availability of cargo and without any development cost or extra investments.
This is a strong simplification of the real situation but for comparison purposes it is acceptable. There will be no fixed schedules, so each ship is able to make its maximum annual number of roundtrips. The operational cost of forklift trucks on board have to be taken in account, but the crew is assumed not to take part in the transhipment work.
Due to the variety of the various technical arrangements of the concepts additional aspects had to be modelled as well, such as feeder- and hinterland transport, geometric usage of the hold, variations of draft, depreciation method, maintenance, fuel cost, transhipment times and crew for fork hft trucks, etc. The economic model is applicable for different ship types and -dimensions, other concepts than used in this project and other sailing routes.
4.3 Stability
The concept of Distrivaart implies that the distribution of the cargo load may change during sailing due to re-arrangement of the pallets. The analysis will focus on the determination of terms and conditions for possible cargo distributions, which are
• Ship particulars "as built" by Damen Shipyards
• Particulars of technical arrangements of the concepts as chosen in the project.
Calculations have been performed by using the PIAS software of SARC bv. Results comprise draft, trim and hydrostatic particulars for various angles of heel and have been used as input for a spreadsheet that calculates the loading
condition.
The outcome of these calculations will be discussed in the next chapter.
4.4 Distortions of the ship's structure
Due to internal and external forces the ship will be distorted and by that also the pallet installation. This may lead to rubbing of pallets, jammed transport
conveyors and ultimately to collapsing of the construction.
The stacking system should therefore be able to sustain some distortions. For a number of characteristic conditions the distortions will be calculated and these distortions will be the input for the supplier of the pallet installation to determine i f and how the installation can accommodate the distortions.
To calculate distortions many data are required which were not all available in this stage of the project. The builder supplied general aiTangement plan,
construction plan and hydrostatic data; other data had to be derived or estimated like the distribution of stiffness (inertia moments), masses of ship, cargo and displacements, the loads, external conditions, etc.
An example of a combination of given and derived/estimated data is the distribution of the lightweight, illustrated in fig. 5.
LW(x): lightweight
60 1 .
frame number
Fig. 5. Typical distribution of lightweight
Three loading conditions have been investigated: empty ship, homogeneously loaded ship and ship with random distributed cargo. These conditions have been considered for the ship in hogging situation with little cargo amidships and in sagging situation with much cargo amidships. Although various assumptions and some simplifications were apphed the calculations showed adequate results.
4.5 Combined evaluation
In chapter 2 the criteria were described for evaluation of the various system concepts. Each concept has been ranked by vahdation of each criterion on a scale from 0-10 and application of a weight factor and then summed up to a total
relative ranking. For different concepts slightly different criteria have been drafted. In table 3 the criteria and weight factors are given for the distribution scenario. Criterion Economic performance weight 7 score prod Shuffle speed Technical complexity Investment risk Development cost
Transhipment time / flexibility Air draft
Stability and lashing Height of the quays Distortions of the ship
Accessibihty of cargo hold at failures Safety and environment
The total evaluation figures for each concept form the basis for the discussion about the best possible solution. This simple mechanism will not result in the only best solution for Distrivaart, because the chosen weights and the given scores are arbitrary, the number of variations is limited and any entrepreneur will make his own business considerations.
5. ELABORATION OF C O N C E P T S - DISTRIBUTION NETWORK
5.1 Principles and scenarios
For all three concepts the criteria have been elaborated and/or calculated. Withm the scope of this paper only the distribution network will be discussed.
The distribution network is a liner service with a limited number of ports. FuU truckloads will be loaded and unloaded; each load may consist of various contingents. Pallets inside these contingents are exchangeable. During saihng contingents have to be combined to new truckloads for unloading in the next port.
In this network sailing is between four inland ports in Holland; the sading schedule is given in table 4.
port Em pty pallets out Full pal ets out Sailing time hrs
| _ Hengelo 234 234 260 286 0 0 0 0 12 Den Bosch 52 78 78 78 130 130 156 156 15 Oosterhout 156 156 156 156 104 104 104 130 3.1 Zwolle 0 0 0 0 208 234 234 234 unknown total 442 468 494 520 442 468 494 520
Table 4. Sailing variations for the distribution network
5.2 Simulation of times
Pallets will be grouped during sailing for minimum transhipment times.
Pallets to be discharged are supposed to be placed in random position. Based on the number of pallets the average shuffle time can be calculated and it is assumed that the pallet with the shortest shuffle time will be selected. The algorithm for the shuffle during saihng is given in fig. 6.
The simulation of the distribution network has been carried out for concepts 4, 5, 6 and 8, based on a homogeneous pallet configuration. For concept 8 only an extra calculation has been made for an extreme pallet configuration to determine the bandwidth of simulated times.
The calculations show that, based on the transhipment speed and the total transport capacity, concept 8 has preference.
A summary of the results for the various concepts of the distribution network is given in table 5.
determine pallet with stiortest shuffle time N bring pallet to lift side of channel stop shuffle process I transport pallet to selected channel
Fig. 6. Flow chart shuffle algorithm
concept capacity - total pallets - effective pallets - trucks change time of trucks (hrs) shuffle time (hrs) transhipment time (hrs) pallet cycle time (sec/pallet) 4A & 4B 2 stacks (see S L D -systenn) 444 pallets 442 pallets 17 trucks 2.8 10.4 7.6 15.4 5 2 stacks of 20 pallets long 480 pallets 468 pallets 18 trucks 3 7.1 8.6 16.5 6 1 stack of 40 pallets long 480 pallets 468 pallets 18 trucks 3 9.1 11.7 22.5 8 1 stack of 42 pallets long 504 pallets 494 pallets 19 trucks 1.6 10.1 4.8 8.7
5.3 Economic performance
In the economic model all relevant cost have been calculated for concepts 4, 5, 6 and 8. These costs will be related to the total number of pallets, the total distance, sailing time, transhipment time and annual number of roundtrips.
The result is that concept 5 has the lowest cost, just shghtly lower than concept 8 and mainly caused by less investment and a better usage of the cargo hold. The differences however are small: only 8 percent between the cheapest and the most expensive option.
5.4 Stability
The loading conditions for each leg of the roundtrip Hengelo-Hengelo have been analysed with a systematic variation of the pallet distribution. Calculations show following results:
• loading over 80% of f u l l pallets is not possible without special measures. • loading below 60% of full pallets aUows random distribution.
• loading between 60% and 80% leads to decrease of random possibilities. • loading from 30% and above may require water ballast in DB.
• loading up to 75 % is safe i f loading distribution can be adapted • Shuffle at the same horizontal level is safe.
• Unrestricted vertical movements are not always possible, which may cause to delay of shuffle time to the next port.
From stabihty point of view concept 5 offers the best opportunities
5.5 Ship's distortions
The analysis of the distortions was focused on longitudinal bending and transverse deformations under various loading conditions and wave patterns. Since the ship initially is in hogging condition all loading conditions and wave patterns that will worsen that condition are the most critical.
Therefore the extreme distortions are found with littie cargo, mainly placed against the sides of the hold, on top of a wave with a length equal to the length of the ship. In this situation vertical deflections were found of 20 mm and transverse displacements of 5 mm. These are of the same magnitude as caused by
temperature differences or torsion.
These distortions have to be considered at the design and engineering of the pallet storage and stacking system.
5.6 Combined evaluation and conclusions
A l l criteria for the concepts have been compared and are summarised for final ranking. The overview of all criteria and the ranking are given in table 6.
Highest ranking is for concept 5, mainly for economic reason, and a good second place for concept 8, which has a good score on transhipment times.
C O N C E P T » 4A 4B 5 6 8 wf Economic performance 0 2 10 4 7 0.259 Shuffle speed 9 9 8 8 8 0.074 Technical complexity 7 6 10 4 8 0.111 Investment risk 4 4 8 1 8 0.037 Development cost 6 5 8 2 8 0.037 Transhipment/flexibility 6 6 5 0 10 0.111 Air draft 0 0 8 10 8 0.074 Stability and lashing 2 2 6 8 6 0.037 Heights of quay 7 6 7 10 7 0.074 Ship's distortions 3 3 8 6 6 0.037 Accessibility at failures 3 3 9 7 7 0.111 Safety and environment 7 8 9 7 7 0.037
Total evaluation 3.78 4.11 8.41 5.22 7.59 1.000
Ranking 5 4 1 3 2
Table 6. Evaluation of the distribution network concepts.
6. T E C H N O L O G Y MIGRATION
Apart from the question "what is the best system" the systems have to be
considered on their possibihty for apphcation in further developments, i.e. further technological migration. This has been done already by the criteria, but in this chapter some directions will be given what the migration path could be for the best concepts of the distribution scenario (distribution network and collaborative network).
6.1 Stacks and lift
The best scoring concepts use a stacking system, either passive with an SLD (concept 4) or a system with powered chain (concepts 2, 5 and 8)
Lifts are used to eliminate FLT's in the hold but only in an automatic system with the stack.
The most important aspect for migration is the extension with a sorting function. A l l stacking systems show sufficient opportunities for migration to a next
distribution scenario. It is not likely that software is available for the operation of 2 hfts, so development of such a system in combination with a warehouse
management system and stability control system is required.
6.2 Shore-ship interface
Man-hour costs for transhipment are a substantial component of the total
transport cost, including cost for a FLT on the quay. A n automatic transhipment system definitely would bring down the man-hour cost, especially when it could be appropriately connected to the system on the ship. This a condition for
migration including a system to control trim, heel and draft during transhipment. For this apphcation no standard technology is available, so substantial time for development should be reserved.
6.3 Components: ready-made or new developing
Due to the special circumstances of waterborne transport by inland ships a number of components are not ready-made available or need special
modifications. Specially developed components should be modular as far as possible to allow extension in a next phase.
6.4 Cargo roof
In general an existing roof could be maintained when migrating to another
distribution concept. May be some changes have to be made in the side-openings.
7. CONCLUSIONS
In this project pallet stacking and transfer systems have been evaluated and ranked for 3 scenarios: transport network, distribution network and collaborative network. For each concept the main conclusions are given, followed by a
statement about the migration and overall conclusions for the technical part of the Distrivaart project.
7.1 Transport network
• The chain pull system is not favourable due to high personnel cost. Observations during the pilot project confirm the theoretical analysis of the transhipment times.
• The block stacking systems with FLT are not satisfactory, neither economical or from migration point of view.
• Shuttle concepts do not satisfy due to lack of redundancy and slow transfer times.
• Concepts with powered stacks have the best score.
• The systems with SLD have critical stabihty since pallets are placed rather high.
• Ship's distortions vary from 20mm deflection for longitudinal bending to 5 mm in transverse direction.
7.2 Distribution network
• Shuffle times are almost independent from the distribution of partial cargos over the hold. Per leg of the route they are not more than 3 hours and therefore sorting is no bottleneck.
• The concepts with SLD systems are less interesting
• The powered stack with shuttle (concept 5) has by far the best score. • Stability scores slightly better than in the transport network but still needs
careful attention.
7.3 Collaborative network
For technical arrangement not much difference in result between distribution network and collaborative network
• Loading and unloading times are equal
• Shuffle times will increase since each pallet is a partial loading instead of groups of pallets
• Concept 5 scores slightly better than the other concepts.
7.4 Migration
Two systems are suited for a good migration path: the SLD and the powered stack system. The latter is the best suited as it misses some disadvantages of the SLD. Mechanisation and automation are key factors for success of Distrivaart. Main problem is the limited availability of components to build the systems
7.5 Overall conclusions
• The most promising concept is based on the powered stack principle • From construction point of view still a number of problems need to be
solved
• Sorting of pallets during sailing is no problem for the distribution and collaborative network. I f the sailing times are not too short there is sufficient time for sorting.
• The evaluation methodology as apphed may also be used for specific situations for individual entrepreneurs.
• Stability might be critical in some concepts. Careful planning in combination with ballasting should be used to overcome this problem
