Tonnage & Launching Ppt

7/23/2019 Tonnage & Launching Ppt

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FREEBOARD

• Freeboard is the distance from the waterline to the top of the deck platingat the side of the freeboard deck amidships.

•

The freeboard deck is the uppermost continuous deck having means ofclosing all openings in its weather portion.

• The minimum freeboard is based on providing a volume of reservebuoyancy which may be regarded as safe, depending upon the conditions ofservice of the ship. In deep sea ships,, sucient reserve buoyancy must beprovided to enable the vessel to rise when shipping heavy seas.

•

Load Line Rules give a tabular freeboard which depend upon the typeof ship, the length of tie ship and is based on a standard vessel having ablock coecient of 0.68, length divided by depth of ! and a standard sheercurve.

"orrections are then made to this value for variations from the standard,together with deductions for the reserve buoyancy a#orded by weather tightsuperstructures on the freeboard deck $ne further point is consider is thelikelihood of water coming onto the fore deck. This is largely a function of thedistance of the fore end of the deck from the waterline. %or this reason aminimum bow height is stipulated. This value depends upon the lengthof the ship and the block coecient and may be measured to the forecastledeck if the forecastle is &' or more of the ship(s length. )hould the bowheight be less than the minimum then either the freeboard is increased or

the deck raised by increasing *the sheer or +tting a forecastle.



Type of ships for free Board computation

• Two basic types of ship are considered (ie A & B) :

• Type A ships

These are designed to carry only liuid cargoes and hencehave a high integrity of e-posed deck, together with e-cellentsubdivision of the cargo space. ecause the hatches are oiltight and heavy seas are unlikely to cause /ooding to cargospace or accommodation , these vessels are allowed to loadto a comparatively deep draught . hile these ships have ahigh standard of watertight deck , they have a comparativelysmall volume of reserve buoyancy and may therefore beunsafe if damaged. It is necessary therefore, in all suchvessels over !0 m in length, to investigate the e#ect ofdamaging to the underwater part of the cargo space and, inlonger ships, the engine room. 1nder such conditions thevessel must remain a/oat without e-cessive heel and havepositive stability.



Type B ship

Type ships cover the remaining types of vessel

and are assumed to be +tted with steelhatch covers. In older ships having wood covers

the freeboard is increased.

)hould the hatch covers in Type ships be

gasketted with ecient securing arrangements,then their improved integrity is rewarded by areduction in freeboard of 60' of the di#erencebetween the Type 2 and Type tabular freeboards.

If, in addition, the vessel satis+es the remainingconditions for a Type 2 ship 3e.g. /ooding ofcargo spaces and engine room*, 00' of thedi#erence is allowed and the vessel may beregarded as a Type 2 ship



The tabuar Freeboards

• The tabular freeboards for Types 2 and ships are given in the 4ules forlengths of ship varying between 5 m and 76! m. alues are as below 9

Typical values are as follows9 :ength of ship Type 2 Type ;i#erence

m %reeboard in mm

5 500 500 <

00 7! 5& 76

500 565 756 6!5

700 7565 670 768

76! 777 !707 8&0

• The freeboard calculated from the tabular freeboard and corrected is termedthe )ummer %reeboard and corresponds with a Summer Load Line S.

• In the tropics the weather is usually kind and a deduction of = of the )ummer

draught may be made to give the Tropical Load Line T.• )imilarly there is a Winter Load Line W which is a penalty of = of the

summer draught. In ships 00 m and less in length there is a further penaltyof !0 mm if the vessel enters the orth Atlantic in the winter !WA*

The above is based on the assumption that the ship /oats in water density05!kg >m 7.



Tabuar Freeboards (!ont)

If the vessel /oats in fresh water withthe same displacement, then it will lie ata deeper draught.

The fresh water allowance isdisplacement in sea dater at summerdraught divided by T 3where T is thetonne per cm at the same draught*.

F represents the freshwater line in thesummer ?one and TF the euivalentmark in the tropical ?one.



Tonna"e #ar$in"s



Tonnage @arkings

• The freeboard markings 3%ig.* are cut into the shellplating with the centre of the circle at midships. Theletters :4 on the circle indicate that the load line hasbeen assigned by :loydAs 4egister of )hipping.

• If the vessel has a radiused gunwale, the deck line iscut at a convenient distance below the correct positionand this distance is then deducted from the freeboardstated in the certi+cate.

• !onditions of Assi"nment

The :oad :ime 4ules are based on the very reasonableassumption that the ship is built to and maintained at

a high level and the structural strength and will sail in aseaworthy condition.



%oad ine Annua ur'eys

• To ensure that the vessel is maintained at thesame standard of safety, annual surveys are

made by the 2ssigning 2uthority . 2ninspection is made of all those items whicha#ect the freeboard of the ship and areincluded in the "onditions of 2ssignment.

•

The accuracy of the freeboard marks ischecked and a note made if any alterations tothe ship which could a#ect the assignedfreeboard.



B6& Tonnage 4ules

• In B6& the Tonnage 4ules were completely revised in an attempt to improvethe safety of dry cargo ships.

•

A register ton represents 00 cubic feet of volume .• The Tonnage "eck deck is he second deck e-cept in single deck ships .

• The tonnage length is measured at the level of the tonnage deck here animaginary line is drawn inside the hold frames or sparring, the tonnagelength being measured on the centre line of the ship to this line.

• Tonna"e depths are measured from the top of the tank top or ceiling to the

underside of the tonnage deck at the centre line, less one third of the camber. There is, however, a limitation on the height of the double bottom considered.

• Tonna"e breadths are measured to the inside of the hold frames orsparring.

• The tonnage length is divided in to a number of parts. 2t each cross<sectionthe tonnage depth is similarly divided and tonnage breaths measured. The

breaths are put through )impson(s 4ule to give cross<sectional areas. Thecross<sectional areas are in turn, put through )impsonAs 4ule to give avolume. This volume, divided by 00 # is the $nder deck Tonnage.

• The %ross Tonnage is found by adding to the 1nder deck tonnage, thetonnage of all enclosed spaces between the upper deck and the second deck,the tonnage of all enclosed spaces above the upper deck together with any

portion of hatchways e-ceeding ' of the gross tonnage.



B6& tonnage rules 3 "ont*

The et Tonnage or Register Tonnage is obtained by deducting from the Cross Tonnage,the tonnage of spaces which re reuired for the safe working of the ship 9

3a* masterAs accommodation

3b* crew accommodation and an allowance for provision stores r 3c* wheelhouse, chartroom, radio room and navigation aids room

3d* chain locker, staring gear space, anchor gear and capstan space

3e* space for safety euipment and batteries

3f* workshops and storerooms for pump men, electricians, carpenter, boatswains and the lamproom

3g* donkey engine and donkey boiler space if outside the engine room

3h* pump room if outside the engine room3i* in sailing ships, the storage space reuired for the sails, with an upper limit of 5 .! ' of the

gross tonnage

3g* water ballast spaces if used only for that purpose. The total deduction for water ballast,

including double bottom spaces, may not e-ceed B' of the gross tonnage

• 3k & 'ropelling 'ower Allowance. This forms the largest deduction and is calculated as follows9

•

If If the @achinery )pace Tonnage is between 7' and 50' of the Cross Tonnage, the DropellingDower allowance is 75 ' of the Cross Tonnage .

• If the @achinery )pace Tonnage is less than 7' of the Cross Tonnage , the propelling allowanceis proportion of 75' of the Cross Tonnage. Thus an actual tonnage of 5' would give a DropellingDower 2llowance of 5 > 7 E 75 ' of the Cross Tonnage .

• If the @achinery space allowance is more than 50 ' of the Cross Tonnage, the Dropelling power2llowance is $ne and three forth times the machinery space Tonnage with an upper limit of !!'e-cept for tugs.



#odied tonna"e

@any ships are designed to run in service at a loaddraught which is much less than that allowed by the

:oad :ine 4ules. If the freeboard of a vessel is greaterthan that which would be assigned taking the seconddeck as the freeboard deck than reduced Cross and Fet Tonnages may be allowed. In this case the tonnage of

the space between the upper deck and the seconddeck is not added to the 1nder deck Tonnage and istherefore not included in the Cross Tonnage or Fet Tonnage, both are conseuently considerably reduced.

2s an indication that this modi(ed tonnage has

been allocated to the ship , a tonnage mark must becut in each side of the ship in line with the deepest loadline !0 mm aft of the centre disc . If any cargo iscarried in the tween decks , it is classed as deck cargoand added to the tonnage. .



B85 4ules

• The B6& and earlier Tonnage rules in/uenced the design of ships andintroduced features which were not necessarily consistent with the safety

and eciency of ships.

• In B6Ban international convention on tonnage measurement of ships washeld and new tonnage 4ules were produced . These rules came into force

in B85 for new ships, although the B6& 4ules still be applied to

e-isting ships until BB.

• Drinciple behind the new 4ules was to produce similar to the previous rulesfor gross and net tonnage using a simpli+ed method which re/ected moreclosely the actual si?e of the ship and its earning capasity withoutin/uencing the design and safety of the ship .

• The gross tonnage is calculated from the formula

• Cross tonnage (T)

• G H

• G total volume of all enclosed spaces in ship in m7

• H G0.5 0.05 log 0



4esults of B85 4ules

• 2ll shelter deck ship carrying dual tonnage andtonnage mark will disappear from the scene

• 2 uni+ed system of measurement will be used byall nations with no variations in interpretation.

• Fet tonnage will be used to determine canal dues,light dues ,some pilotage dues , and some harbourdues.

• Cross tonnage will be used to determine manning

levels, safety reuirements such as +re+ghtingreuirements ,some pilotage and harbour dues ,towing charges an graving dock charges.



)hipyard :ayout

• 2n ideal layout for a modern shipyard is based on a production /owbasis, with the yard e-tending back from the river or shore at which the

berths or building dock are located. The furthest area from the berths isreserved for the material stockyard, and between the two are arrangedin seuence the consecutive work and shop processes. Too oftene-isting shipyards follow the river bank, and are restricted by theirlocation in a built up area or the physical river bank slope frome-tending back from the river so that modi+ed production /ow lines are

reuired.

• Dlanning a new shipyard, or re<planning an e-isting one, will involvedecisions to be made on the following9

• )i?e and type of ship to be built.

• @aterial production per year to be achieved.

• @aterial handling euipment to be supplied.

• @achining processes to be installed.

• 1nit si?e and weight to be fabricated and erected.

• 2mount of out+t and engine installation to be undertaken.

• "ontrol services to be supplied.

• 2dministration facilities reuired.



hipyard %ayout



hipbuidin" *rocess



hip Buidin" *rocess• "esign selection

•

"rawing o)ce < :ines Dlan, 7 ;imensionalrepresentation of shell plating , )hell e-pansionand loft work

• loft work < )crieve boards , 0 > )cale lofting

,"2; > "2@ :oft work• 'late and section 'reparation J )tock yard,

@angles, )hot blasting, Driming Daint,Dlatehandling in @achine )hop

•

'late and section *achining J Dlate Dro+lers, Dlaning @achines ,;rilling @achines,

Cuillotines, Dresses, Dlate rolls, Keatlinebending, %rame ending, 4obotics



Drefabrication

• )ub assemblies

• 1nit fabrication

• $ut +t modules• 1nit erection

• Loining ship sections a/oat



ulk "arrier )ide lock units



:aunching

:aunching involves the transference of theweight of the ship from the keel locks ,shores, etc., on which it was supported during

construction, to a cradle on which it is

allowed to slide into the water. Formally thevessel is launched end on, stern +rst, but a

number of shipyards located on river or $thernarrow channels are obliged to launch the

vessel sideways. essel Kave been launchedbow +rst, but this is a rare occurrence as thebuoyancy and weight moments, also the

braking force, are generally more favorable

when the vessel is launched stern +rst.



@ethods of :aunching

• Mnd :aunching

• :aunching ways and cradle

•

)ide launches• uilding docks

• )hip :ifts



uilding locks



%aunchin" +ays



Reease arran"ement for ship %aunch



%aunch arrestin" arran"ements



%aunchin" se,uence

Tonnage & Launching Ppt

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