323
1 TASK
The commodity most often shipped in containers
acrossthesevenseasispureair:Approximately20%
of all worldwide shipped containers are empty!
According to estimates related handling costs alone
are more than US$ 15 Billion p.a.! Furthermore
carrierʹs box fleets have to be much bigger than
act
ually needed to satisfy shipperʹs demand. This
results in containers standing empty or idle in
averageapprox.60%ofthetimewhichconsequently
causes additional costs in ports and at depots.
Moreoveremptyboxes void valuable slots on board
the vessels. Hence cost effective container manage‐
menthasbecomethekeyissuefortheprofit
abilityof
container lines! It is estimated that each empty
positioningisvalued atapprox. 450US$/boxmostly
intermsofhandlingcostsinports.
Figure 1. A pair of Tworty Boxes is loaded in Hamburg in
coupledconditiononboardtheʺOOCLMontrealʺ
The high portion of unproductive and costly
emptypositioningsiscausedby:
1 structural imbalances of the general cargo flow
(generaltradeimbalance),
Tworty Box to Improve the Equipment Logistics of
Container Lines
U.Malchow
HochschuleBremen–UniversityofAppliedSciences,Bremen,Germany
ABSTRACT:Amajorshareofallemptycontainerpositioning (deadheading) isresultingfromimbalanceswith
regard to container sizes (20ft/40ft). In order to reduce the shipments ofʹcontainerised airʹ a new type of
container has been developed by the author: The Tworty Boxes can either be used as a standard 20ft or in
coupledcondit
ionasa40ftcontainer.Theoutsideappearanceresemblesanystandard20ftcontainer.However
theTwortyBoxisuniqueinthatithasanadditionaldooratthefrontsidethatopenstotheinside.Thisdoorcan
befixedtotheceilingandbyusingofbondingelementsanot
herTwortyBoxcanbejoinedup,therebycreating
the full 40ft inside space. Operated as a single 20ft box the additional door remains locked, access is only
throughtheexistingstandarddoor.TwortyBoxesdonotrequireanyadditionalcomponentsandfulfilallISO
andCSCrequirements.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 10
Number 2
June 2016
DOI:10.12716/1001.10.02.15
324
2 seasonal impacts of dominating commodities in
specifictrades,
3 imbalances of the 20ft:40ft ratio between both
tradedirections
A significant share of the empty positioning is
resulting from carrierʹs internal imbalances in
containerlogisticswithregardtoboxsizes(20ft/40ft).
Carriers note strong ups and downs in supply
and
demand of different container sizes in certain
areas/ports especially if several services of different
trades are calling the same area. Local dispatchers
often report:ʺToo many 20s, not enough 40sʺ, or
reverse.Notalwaysthesituation canbebalancedin
time.Notseldomthegrotesquesituationoccuresthat
acarrierhastoleaveladen(lowpaying)boxesbehind
in order to reduce the empty stock of a certain size
andpositionthememptytoanotherportoftheworld
where they are urgently needed for high paying
cargo.
Figure2. Frontside with additional door (to beopened to
the inside) and bonding elements adjacent to the corner
castings.
Figure3. Inside view of closed additional front side door
(cablestoopenthedoorarevisible).
2 THETWORTYSOLUTION
In order to significantly reduce the shipments of
ʹcontainerisedairʹtheTwortyBoxhasbeendeveloped.
Its outside appearance resembles any standard 20ft
container.HowevertheTwortyBoxisuniqueinthatit
hasdoorsateachend, theseconddoor openstothe
inside and
can only be locked from the inside. This
doorcanbefixedtothecontainerceilingandwiththe
useofspecial bonding and sealingelementsanother
Tworty Box can be joined up, thereby creating a
watertight40ftunitoffullvalue(withstandarddoors
atbothends).
ThusTwortyBoxes
caneitherbeusedasastandard
ISO20ftorcoupledasa40ftcontainer:
Twenty+Forty=Tworty
IftwoTwortyBoxesarecoupledtoforma40ftbox
the additional doors will be opened supported by
cablesandfixedtothecontainerceilingtoreceivethe
full
40ftinsidespace.Operatedasa20ftboxthisdoor
islocked,accessisonlythroughtheexistingstandard
door.TwocoupledTworty Boxesmakea40ftcontainer
withdoorsatbothends.Thesystemdoesnotrequire
any additional components and the coupled boxes
remainwatertight. The Tworty Boxcomplies
withall
ISOrequirementsforcontainersandhassuccessfully
passedthefullCSCtestingprocedurewithDNV‐GL.
The coupling is carried out by bonding elements
which guarantees that two Tworty Boxes can be
handledlikeasingle40ftcontainer.Theconnectionof
twoTwortyBoxescanonlybereleased
fromtheinside.
Four coupling elements are located adjacent to the
corner castings (Figure 2). Each Tworty Box has two
male and two female bonding elements. They also
keep the distance of 76 mm between the boxes in
ordertocomplywiththeISOregulationforthelength
ofa40ft
container.
The Tworty Box concept is protected by inter‐
nationalpatents.Followingmaindesigntargetshave
beenfollowed:
minimum changes compared to a standard 20ft
container
robustness
easyhandling
(almost)nolooseparts
Compared to single standard 20ft/40ft boxes the
lossesof theTworty Box with
regardtopayloadand
capacity (if any) are marginal (Table 1). The only
loose parts are the flat surrounding sealing ledges
whicharescrewedafterthecouplingprocessfromthe
insideintothegapbetweenbothboxesprovidingthe
necessarywatertightness.AseachTwortyBoxcarriesa
setofsealsunder
theceilingbutonly oneisneeded
forthecouplingoftwoTwortyBoxesthereisenough
redundancy if one sealing element was missing or
damagedleavingenoughtimeforareplacement.The
seal fully complies with international customs
regulations.
325
Table1.Comparisonofpayloadandcapacity.
__________________________________________________________________________________________________
20ft(8ʹ6ʹʹhigh)40ft(8ʹ6ʹʹhigh)
Payload[t] Capacity[m³]Payload[t] Capacity[m³]
__________________________________________________________________________________________________
standardcontainer 21.8…28.2 32.8…33.225.8…26.7 65.3…67.7
TwortyBox27.833.125.263.5
__________________________________________________________________________________________________
By operating Tworty Boxes empty positionings
caused by the need to balance different supply and
demand of 20ft and 40ft container sizes can be
significantly reduced. Even if empty Tworty Boxes
have to be empty positioned (e.g. due to inevitable
imbalances of the general cargo flow) they can be
coupled and
immediately 50% of the lift on/lift off
chargesaresaved.
OnaccountofglobalforwardingcompanyDHLa
pairofprototypeboxeswhichhadbeenstuffedwith
commercialcargohasalreadymadeatrialtripin2013
on board of OOCL and Hapag‐Lloyd vessels from
HamburgtoMontrealand
v.v.tothefullsatisfaction
oftheforwarder.
Figure4. Bolting mechanism with handle for hinged door
(fromtheinside).
Figure5.Boxforbottommalecouplingelement.
3 ECONOMICS
Approx.205MillTEU(TwentyFootEquivalentUnit)
have been shipped across the seven seas in 2011.
Thereof21%wereempty(42MillTEU).
In2011 theworldcontainerfleet consisted outof
30 Mill TEU (of which 27 Mill TEU were standard
20ft/40ft dry cargo boxes), i.e. in
average each
standard TEU has been shipped only 6.8 times
throughouttheyear–thereof1.4timesempty(empty
share of 21%). In average each shipment (full or
empty) has caused 2.9 port handlings (the average
valueofmorethanʹ2ʹiscausedbytranshipments).
Alreadyin2001eachempty
positioninghasbeen
valuedatapprox.400US$/boxmostlyintermsofport
handling costs. It is assumed that this amount has
nowincreasedtoatleast450US$/box.Hencein2011
withaglobal20ft/40ftsplitof1,53TEU/boxwithinthe
standarddrycargoboxfleeteachTEUhadcaused
at
least approx. 410 US$ just for its empty positioning
(1.4x450US$/box:1,53TEU/box≈410US$/TEU).
As the average life time of a container is 8 to 9
years it is obvious that each container causes empty
positioningcostsduringitsentirelifetimewhichare
exceeding
its current newbuild price (approx. 2,000
US$ for a standard 20ft container) by far. Hence
focusingonreducingemptypositioningismuchmore
important than achieving the lowest possible
purchasepriceofstandardcontainerequipment!
3.1 Focusonsingleboxes
Maximumsavingscanbeachievedwhen2xTworties
aresubstituting
2 x20ftand1x40ftstandardboxes
which are normally due to be empty positioned in
opposite trade directions. Table 2 illustrates the
economics of operating Tworty Boxes compared to
standard20ft/40ftcontainers.
Forthecomparisonthreerelevantcostitemshave
been considered whereby the costs of crane
moves
and the costs for coupling/de‐coupling have been
variedwithina realistic bandwidth. Considering the
slightlyhigherinvestmentfortheTwortyBox,itsdaily
capitalcostshavebeensetmorethantwotimes(!)the
value of a standard 20ft box, which is by all means
muchmorethan
theadditionaldoorwillrealistically
cause (this leaves some reserve for an eventually
slightlyhigherdailyM+Rallowance):
dailycapitalcosts:
standard20ftcontainer:0.85US$/box/day
standard40ftcontainer:
1
1.36US$/box/day
TwortyBox: 2.00US$/box/day
(worstcaseassumption)
costspercranemove:100…200US$
costsper(de‐)/coupling:
2
20…100US$

1
Accordingtotheindustrystandardthecapitalcostsofa standard
40ftcontaineraredefinedtobegenerally1.6timeshighercom‐
paredtoastandard20ftcontainer.
2
ThesecostsmayalsocovertheeffortstotracktheTwortyBoxfleet
to ensure that two boxes are always available to be coupled if
needed.
326
Table2.2xTwortyBoxesarereplacing2x20ftand1x40ftstandardcontainer.
3.2 Resultsofsingleboxview
Table2illustratesthemostunfavourablecaseforthe
operation of Tworty Boxes within the given range of
parameters(arrowinFigure6&7),i.e.:
minimumlifton/liftoffrate
maximumcoupling/de‐couplingrate
longestdurationofcontainervoyage
notranshipment
Nevertheless compared to conventional box
operationssavingsof306US$havebeenrevealedfor
a round trip of the boxes, i.e. two shipments. This
amountrepresentssavingsof20%comparedwiththe
operation of standard containers. This magnitude
exceeds by far the industryʹs average profit margin
per
container shipment (especially at present times).
Savedcostsforslotsonboardwhichdonotneedtobe
used for empty positioning have not even been
considered.
Savings would logically increase if costs for
coupling/de‐coupling were decreased. However
considering the wide range of this parameter the
impactontheTworty
Boxprofitabilityisnotdramatic.
ItcanberevealedfromFigure6thattheimpactofthe
duration of the single container voyage is rather
negligible.Itismuchmoretheapplicableaveragelift
on/liftoffratewhichisofsignificantinfluenceonthe
savings. For general guidance the following
rough
amounts can be applied (according to the specific
tradearespectiveaverageoutofbothendshastobe
considered):
Europe: approx.100US$/move
N.America:approx.200US$/move
Asia: approx.300US$/move
As more and more container lines are following
theʺhub‐and‐spokeʺ strategy the influence
of
transhipment has to be considered as well. In the
meantime the share of transhipped boxes in portʹs
global container throughput has risen from 10% in
1980 to more than 30% in 2011! It can be clearly
revealedfromFigure7thatthesavingstheTwortyBox
can provide
become higher the more often the
containers are transhipped! Furthermore savings are
evenmuchhigherifaveragelifton/liftoffchargesin
excess of 100 US$/move meets with the necessity to
transhipemptycontainersatleastonce.
ItcanbeconcludedthattheintroductionofTworty
Boxes can provide dramatic savings
if they are
operatedandkeptincertainimbalancedtradeswhere
theiradvantagescan be fully utilised.Thuscontrary
to standard containers they have to be individually
tracked and treated as special equipment like e.g.
flats,reefersetc.
A simple low scale example as per Figure 8
demonstrates that even
trades with an almost
balancedcargoflowandanidenticalgeneral 20ft:40ft
ratio both ways would very much benefit from the
TwortyBox.Itisassumedthatinahypotheticaltrade
100TEU havetobeshippedeastbound whereas 120
TEU are due to be carried westbound. Contrary to
reality
and not beneficial for Tworty Box operation
bothvolumesshallexactlyhaveanidentical20ft:40ft
ratio(=0.86)ontheiroceanleg.Inrealitythisratiois
however varying more or less around an average
327
figure among the various loading and discharging
portsinvolved
Hence deadheading is not only required to
compensate the general imbalance in required
equipment flow between both regions but also to
balance the various requirements for different
containersizesamongtheportswithinaregion.The
required box fleet is determined
by the dominant
trade direction. In this case for both sizes the
westboundlegisstronger.Henceatleast240TEUof
equipment would be required to ship both volumes
simultaneously.
Just due to the apparent general trade imbalance
additional 20 TEU (6 x 20ft + 7 x 40ft =
13 boxes)
seems only to be necessary to be empty positioned
eastbound (Figure 9). However considering also the
various local imbalances at each port 44 TEU (14 x
20ft+15x40ft=29boxes)haveactuallytobeshipped
empty (also within the regions) in order to
compensate the
imbalanced supply and demand of
containersizes.Thisis120%more(intermsofTEU)
than one would expect from the pure general trade
imbalance, resulting in 123% more empty box
movements!Alsotheboxfleethastobeslightlylarger
thanoriginallyanticipatedasboxeswhichareduefor
an additional intra‐regional deadheading cannot be
immediatelystuffedafterhavingbeenstripped.
Figure6.
Figure7
328
Figure8.Generaltradeimbalance(lowscaleexample).
3.3 Resultofcarrierʹsentirefleetview
Atallportswhichsufferfroma suddenorpermanent
lackofone sizeanda surplus of the other size (e.g.
portʺAʺandʺYʺ)theoperationofTwortieswouldbe
very
advantageous(Figure10).Ifintheexampleonly
4 x Tworties were introduced (replacing 2 x 40ft
standard boxes) and these boxes were kept plying
only between portʺAʺ andʺYʺ just only 40 TEU
(including the Tworties) would have to be empty
positioned(insteadof44TEU).Hencea
Twortyshare
of only 2% (in terms of TEU) within the box fleet
couldtheoreticallyleadtoareductionofdeadheading
costs by 10%! Furthermore the entire fleet could be
reducedby4TEU(‐2%)!
Thus a homogeneous container fleet existing
completelyoutofTwortiesisnotnecessary.Thehuge
majority of the fleet can still consist out of standard
20ft and 40ft boxes. As it can be derived from the
exampleevenasmallnumberofTwortyBoxeswhich
are kept plying between ports where a chronic
surplus of one size meets with the lack of the other
size
can significantly contribute to improved
economicsofacarrierʹscontainerfleet.
Although the Tworty Box cannot supersede all
repositioningnecessities,therearemanytradeswhere
the40ft:20ftratioofequipmentisvaryingamongthe
ports and where the Tworty Box concept can help
substantially.
Because 2 x Tworty Boxes are
destined to replace
approx.2x20ftstandardboxesand1x40ftstandard
box the capital costs of the entire box fleet do not
increaseastheadditionalexpensesforoneTwortyBox
wouldnotexceedhalfthecostsofa40ftstandardbox.
329
Figure9.Emptypositioningcausedbygeneraltradeandlocalimbalance(example).
Figure10.EmptypositioningcausedbygeneraltradeandlocalimbalancereducedbyTwortyBoxes(example).
330
Table3.ExpectedeffectofTwortyBoxoperationoncontainerfleetparameters
__________________________________________________________________________________________________
justbygeneraltrade reality(duetolocally including2%Twortyshare savingsinreality
imbalance(theory)imbalancedsizes)
__________________________________________________________________________________________________
necessary boxes132926‐10%
deadheadings TEU204440‐9%
requiredfleet TEU240240plus236plus‐2%
__________________________________________________________________________________________________
4 CONCLUSIONS
The Tworty Box is most advantageous for container
trades which suffer from a clear imbalance with
regardtothecontainerseizes,i.e.wherethe20ft/40ft
splitofbothtradedirectionsdifferssignificantly.
However the calculations have revealed that
significant savings can even be realised in case of
imbalanceswithregardtothepuretradevolume,i.e.
when coupled Tworty Boxes could replace 2 x 20ft
standard boxes which otherwise would have to be
emptypositionedindividually.ByusingTwortyBoxes
theemptymovementscanberealisedasoneunit,i.e.
the respective handling costs can be cut by
50%
which exceeds the additional expenses for
coupling/de‐couplingbyfar.
Hence the Tworty Box can avoid empty
positioningcausedbyhavingnottherightcontainer
sizes available and even if empty positioning is
unavoidable it can cut the costs for empty
movementsof20ftcontainersalmostbyhalf.
Who
isbenefiting?Itisthecontainerlineswhich
woulddirectlytakeadvantagefromoperatingTworty
Boxes. Presently 53% of the world container fleet is
operated by container lines, thereof 90% are of
standard20ft/40ftdrycargotype.Howeveritisnot
necessary that a container line replaces its entire
container
fleet by Tworty Boxes to gain maximum
savings. Only the portion equivalent to the linesʹ
individual(average)imbalanceneedstobereplaced.
It is not expected that leasing companies which
presently control approx. 44% of the worldʹs
container fleet would be immediately interested to
operate Tworty Boxes. They are
only reacting to the
demand of the container lines and therefore are
expected to be interested only at a later stage.
However big forwarders with shipperʹs owned
containersmightbeinterestedaswellasithasbeen
alreadyprovenbyglobalforwarderDHLwhichhave
successfullytestedtwoprototypeboxes
on occasion
ofatrialtrip.
According to Boedeker, Global Head Ocean
Freight, DHL Global Forwarding, (2013) the Tworty
Box is a very attractive solution which ensures
flexiblecontainermanagementandcostefficiencyby
eliminating empty positioning due to structural
imbalances in the general cargo flow or seasonal
fluctuationsin
thedominantcommoditiesinspecific
sectors. It was quoted to be a smart alternative for
customersthatnotestrongupsanddownsinsupply
and demand of different container sizes in certain
areas,especiallyifseveralservicesofdifferenttrades
arecallingthesamecountryorregion.
Takingthefactthat
21%ofallcontainersshipped
areemptyforreasons ofimbalanceofwhateverkind
itisassumedthatthepotentialmarketvolumeforthe
Tworty Box might be 20% of the existing global
standard20ft/40ftdrycargocontainerfleetwhichis
presently operated by container lines, i.e. presently
27Mill
TEUx0.53x0.2=2.9MillTEU.Hencewith
anaveragelifetimeof8.5years34.000TEUofTworty
Boxeswouldbeneededtobeintroducedannually.
REFERENCES
DHL,PressRelease,June25,2013.
DrewryMaritimeResearch,ContainerMarketReviewand
Forecast,AnnualReport2012/13.
DrewryMaritimeResearch2013.ContainerForecaster.
Drewry Shipping Consultants 2012. Container Census –
2012.
Hapag‐LloydAG2010.ContainerSpecification,Hamburg
Konings, R.& Thijs, R. 2001, Foldable Containers: A New
Perspective on Reducing
Container Repositioning
Costs,TUDelft.
Malchow, U. 2013. Aus zwei mach eins. In: Deutsche
Verkehrs‐Zeitung.Dec.10,2013.
PortofHamburgMagazine,3/2013:34‐39
TWORTY BOX GmbH & Co. KG, Hamburg, website:
www.tworty.com,lastaccessedinFeb.2014.