Merchant Ship Construction - D. A. Taylor

Acknowledgements 1 wish to lhank the many firms, organisations and individuals who have provided me with assistance and malcrial during the writing of lhis book. For guidance provided in their specialist areas I would like (0 thank Me W. Cole, Welding Manager and Mr I. Waugh, Ship Manager, both of Swan Hunter Shipbuilders.

To the firm of Swan Hunter Shipbuilders, now a member of British Shipbuilders, I wish 10 extend my thanks for their permission to use drawings and information based on their current shipbuilding practices. The following firms and organisations contributed drawings and information for various sections of this hook, for which I thank them: AGA Welding Ltd Austin and Pickergill Ltd Blohm and Voss, A.G.

DOC CUlling Machines Brown Brothers & Co. Ltd Cammcll Laird Shipbuilders Cape Boards and Panels Ltd Clarke Chapman Ltd Dookin and Co. Ltd F.A. Hughes and Co. Ltd Flakt Ltd (S.F. Review) Glacier Metal Co. Ltd Hempel's Marine Paints Hugh Smith (Glasgow) Ltd International Maritime Organisaton Uoyd's Register of Shipping

MacGregor Centrex Ltd Moss Rosenberg Verft, AS. Odense Steel Shipyard ltd Philips Welding Industries Phoceenne Sous-Marine, S.A. Power Blast ltd Rockwool Co. (UK) ltd Sigma Coatings Ltd Stone Manganese Marine LId Stone Vickers Strommen Staal, A.S. Taylor Pallister and Co. ltd The DeVilbiss Co_ Ltd The Ntn'aJ Architect Voith GmbH Wilson Walton International ltd

Contents The ship - its functions, featutes and types 2 Ship stresses and shipbuilding materials

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3 Shipbuilding 4 Welding and cutting processes 5 Major structural items A Keel and bottom construction 72 B Shell plating, framing systems and decks 77 C Bulkheads and pillars 85 D Fore end construction 92 E Aft end construction 101 F Superstructures and accommodation 116 6 Minor structural items 7 Outfit 8 Oil tankers, liquefied gas carriers and bulk carriers 9 Ventilation 10 Organisations and regulations II Corrosion and its prevention 12 Surveys and maintenance 13 Principal ship dimensions and glossary of terms

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72

125 134

165 185 197 213 223

229

Index 235

1

The Ship- its Functions, Features and Types Merchant ships exist 10 carry cargoes across the waterways of the world safely, speedily and economically. Since a large pan of the world's surface. approximately three·fifths. is covered by water. it is reasonable 10 consider that the merchant ship will continue to perform its funclion for many centuries 10 come. The worldwide nalure of this function involves the ship, its cargo and its crew in many aspects of inll~rnational life. Some It:atures of this international transportation. such as weather and climatic changes, availability of cargohandling facilities and international regulations. will be considered in later chapters. The ship, in its various forms. has ~volved to accomplish its function dqxnding upon three main factors - the type of cargo carried. the type of construction and materials used. and the area of operation. Three principal cargo-carrying Iypes of ship exisl loday: Ihe general cargo ftSSel, !he lanker and the passen~r ve~1. The general cargo ship functions today as a general carrier and also, in several particular forms, for unit-based or unitised cargo carrying. Examples include container ships, pallet ships and 'roll· on, roll-ofr ships. The tanker has its spedalised forms for the carria~ of crude oil, refined oil products, liquefied gases, etc. The passenger ship includes, senerally speaking, the cruise liner and some ferries. The type of construction will affect the cargo carried and, in some generally internal aspects, !he characteristics of !he ship. The principal types of construction refer to the framing arrangement for stiffening the outer shell plating, the three types being longitudinal, transverse and combined framing. The use of mild steel, special steels, aluminium and other materials also influences the characteristics of a ship. General cargo ships are usually of transverse or COmbined framing construction using mild steel sections and plating. Most tankers employ longitudinal or combined framing systems and the larger vessels utilise high tensile steels in their construction. Passenger ships, with their large areas of superstructure, employ lighter metals and alloys such as aluminium to reduce the weight of the upper regions of the ship. The area of trade, the cruising ra.nge, the climatic extremes experienced, must all be borne in mind in the design of a particular ship. Ocean-going vessels reqUire several tanks for fresh water and oil fuel storage. Stability and trim Irrangemenu musl be satisfactory for the weather conditions prevailing in the

2

Th~

Ship - 111 Functions, Features and Types

3

area of operation. The strength of the structure. its ability to resist the effects of waves, heavy sus. etc., must be much greater for an ocean-going \'essel than for an inland waterway vessel. Considerations of safety in all aspects of ship design and operation must be paramoun!. so The ship must be seaworthy. This term relates to many aspects of the ship: it must be capable of remaining anoat in all conditions of wC3ther; it Inust remain alloat following all but the most serious damage: and it musl remain stable and behave well in the various sea states encountered. Some of the constructional and regulatory aspects of seaworthiness will be dealt with in later chapters. Stability and other design aspects are explaincd in dt'uil III .VOl'o/ Architecture {or Marine Enginccrs. by W, Muckle (Bulterworths, 1975). The development of ship types will continue as long as there IS a sufficient demand to be met in a particular area of trade. Recent ynrs ha\'c seen such developments as very large crude carriers (VlCCs) for the transport of oil. and the liquefied natural gas and liquefied petroleum gas tankers for the bulk carriage of liquid gases. Can tainer ships and \ roriou5 barge o.:arriers have developed for general cargo transportation. Bulk carriers and combination bulk cargo carriers are also relatively modern developments. Seveul basic ship types wiJI now be conSidered in further detail. The particular features of appearance. construction. layout. size. etc. will be examined for the following ship types:

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(I) General cargo ships. (2) Tankers. (3) Bulk carriers. (4) Container ships. (5) Passenger ships.

Many other types and minor \~.triations exist. but the above selection is considered to be representative of the major part (If the world's merchant neeL

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J General cargo ships The general cargo ship is the 'maid of all work', operating a worldwide 'go anywhere' service of cargo transportation. II consists of as large a clear open carga

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Ship Stresses and Shipbuilding Materials The ship at sea or lying in still water is being constant!)' subjected \0 :I wide variety of sueues and strains. which result from the action of (orces from outside and within the ship. Forces within the ship result from structural weight. cargo. machinery weight and the ef(ects of operating machinery. Exterior forces include the hydrostatic pressure of the water on the hull and the action of the wind and waves. The ship must at all times be able to resist and withstand these messes and strains throughout its struClUre. II mUSI therefore be conslrucled in a manner, and of such materials, that will provide the necessary strength. The ship must also be able to function efficiently as a cargo-carrying vessel. The various forces acting on a ship are constantly varying as to their degree and frequency. For simplicity. however. they will be considered individually and the particular measures adopted to counter each type of force will be outlined.

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The fmallink of the anchor cable is secured to the ship's structure by a clench pin. On most modem ships this pin is positioned on the outside of the chain

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plating. The vertical stiffeners are bracketed to the floor and to the deck heams which nm transversely across the stem. A deep hmizontal stringer can provide additional stiffening to the >hen plating if required. A deep centre girder runs beneath each of the deck:; at tlte stern and is bracketed EO the deep web at the centreline of the after shell plating. This web is likewise bracketed to the various floors in the stern and finally 10 the solid-plate floor construction below.

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Rudder trunk The rudder trunk is an open section which is left in the stern for the elltry of the rudder stock into the steering flat (Figure 5.34). A horizontal platform is some_ times fitted midw.ay up the trunk to fit a watertight gland. The (runking above i, then constructed to be watertight and access to this upper section and the gland is provided bya manhole. FIMr

The shell plating at the after end is temtinated by the stemframe (Figure 5.34). This is usually a casting, but fabrications and forgings are sometimes used. In single-screw shi ps the ste-rnframe has a boss on the cen treline for the tailshaft to pass through and an adequate aperture is provided for the propeller to operate in. 1f sufficient clearance at the blade tips were not allowed then serious vibrations would be set up in the after end of the ship. The lower part of the sternframe may provide a support for the rudder post or an overh.anging section may provide gudgeons for the rudder pintles. Figures 5.34, 5.41 and 5.42 show different arrangements. Various sections of the sternframe, particularly above the arch, provide- connecting points to the individual floors of the after end construction. The transom post and vibration post are two particular connections (Figure 5.34). Sound connections at these points ensure that propeller-induced vibntions are kept to a minimum. Twin-screw ships have a sternframe which is only required to support the rudder pintles and is thus much reduced in size. Larger stemframes, particularly those of cast constmction, are manufactured in two parts with provision made for bolting together and, after careful alignment, welding at the suitably prepared joint.

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Strum boxes are filled on all bUI machinery and tunnel space suction pipes. Perforations of 10 mm maximum diameter are made in the plate to provide a suction area at least twice that of the suction pipe. In the machinery and tunnel space bilge !ines, mud boxes are fitted. The mud box fits between lengths of piping and has a perforated centreplate. The use of strum and mud boxes prevents the entry of large objects to the pipeline and safeguards the internal parts of the pump (Figure 7.15). Suction valves for the individual compartments must be of the screw-down non-return (SNDR) type to prevent reverse now. All other valves must be of the

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On·return (NR) type. The port Jnd stathOard hoLd bilge valves are usually ~ouped ill distribution chests a.t the forward end of the machinery spa.:e. Bilge iping is made up of the fore arld aft mains and suction branches to the ldividu.al compartments. Piping is arranged, where possible, in pipe tunnels. o( uct keels to ,avoid penetrating watertight double-bottom tanks. Bilge ripes are Ide-pendent of piping for any other duties such as hallasl or fre-sll water. a"se-nge-t "hip bilge main:. romt mn at lea:.t 20'% of the ,hip's beam i.nsioe of the de shell; in addition, any brandIeS further outboard must have a non-return alve fitted. Bil,gc pipe suction lines are sized according to ail empirical formula. Minimum ranch and main siz:e-s -are 50 mm and 65 mm, respectively, and the maximum ile is 100 rnm for both. Bilge piping may be constructed Qf cast iron, steel, opper or other suitable approved ma.terials. It is usual to employ galvanised teel piping in bilge s}'~tems. At \cast foU( inclepelldent puwel-dri'fe,n pump'" must be conn.ected to the lilge main. Mmt ships employ two bilge pumps and have bilge main c-onnec.1ions III the ballast and main circulating pumps. \Vhere POSSible these pumps should )e loc,Hed in separa~e- watertight compartments. One bilge system pump must )e capable of operation under reason;.

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W paSsenger sllips of 4000 gross tonnes and above mllst have at least three Jower-driven fire pumps. All cargo ships in excess of 1000 gross tonnes must lave at least two independently driven fire pUmps. Where these two pumps are .ceated in one area -an eme[gen.cy fiI~ pump must be pmvided and located remote from the machinery space. The emergency fire pump must be independently driven by a compression ignitiun engine or other approved means. Water mains of sufflcient diameter to provide an adequate Water supply for the ,imu.ltaneous operation {)f two fire hoses must be Connected to the fire pumps. An isolating valve :is fitted tQ the machinery space fire main to enable the ~me[gency fire pump to supply the deck lines, if the machinery spaCe main is 'rokea or the pump is out of action. A di.agIamm .. ,,> CL. ~ ......

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Acoustic insulation Sound results from the movement of air particles and travds in the form of waves away from the source. There arc many sources of sound on board ship. such as propulsion engines. auxiliary engines. large fans and ventilation plants. These would have a cumulative disturbing affect on p(rsonnel if allowed 10 continue unchecked. Various countries now have either codes of practice for noise levels in ships. or regulations relating to noise levels in ship spaces. Maximum noise levels are given for particular spaces using a weighted sound pressure level or db{A) value. Most ships at sea, however, would not meet these criteria. New ship designs will require consideration of noise levels in the very early stages if an acceptable noise environment is to be obtained. Two approaches are made to the solution of the problem. First, rooms and areas which are occupied for any length of time are fitted out in such a manner as to be as sound absorbing as possible. The second method is to isolate or silence the sound from occupied spaces. Increasing the sound·absorption capacity of a room is achieved by using a variety of sound absorbers. These include membrane absorbers such as lhin panels, resonant absorbers such as perforated ceiling boards and porous absorbers such as mineral wool. Sounds can be isolated by the use of nexible connections in ducting. nexible mountings on machinery, and sound insulating the surroundings of a noisy space. Air-.'"er

iquc-fic-d natural gas is continually boiling in tanks when lr;msporto.:d by S('8. be-re is therefore a lll::e-d to (eleasl:: this gas tu ;II/uid a pr~'s,ure nuild-up ill the Ink. It may be n'"nte-d dire-c!iy to atillosphere or bum( in boilers or in sT,cc'";:llly darted dual fL1ele[lgines. Barningthe hoil-(Iffg-ilsin a flare mounted on a hO(lill .:mote from the ship is another possible solution. Rc-liqud,tCiio!l is 110t ~onomical because of the- large- p'Jwer and IllJ~e cost rn,n9

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fr:am.... to the hopper hmk. At the end~ of the hupper tank region a considerable change in section lKcurs. The construction used to reduce the effect of tl1is discontinuity is snown in Fignn> 8.17. A large tapered bracket is used wnich is connected to tile surrounding transversely framed structure as shown, A section through an upper hopper t.:mJ,; or saddle tank is shown in Figure 8.18, The longitudinal framing under the deck can be seen as well as the bracket connecting the aprer edge of the transverse frame to the tanL The side shell pmtion of the tank is transversely framed by offset bulb plates with plate webs, as shown in Figure 8./8. fitted at every fourth frame. A deep-flanged bracket joins the inuer tank side to the hatch side girder. Details of a bulkhead stool are shown in Figure 8.19. With a corrugated trausverse hulkhc:ad as :shown, the stool arrangement is used to shape the forward and after lower regions of the , of tne United Natious . 1shippin, amI t e seOl I\'Uer '" ,1 concemlllg S1IPS, " ,_ ' .. I (1~'10} fOfll11Orly 1\-leO was forme", the Illterllatiolw] \1.antlll1( Orgdnlsall~1 th nrst assembly mel in London in Following its formal approval by 21 stale" e I

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. in out many studies, producing detailed recom[MO, IS responSIble for carry d' d o'Nding fonowing conventions, mand eloving standu ~ an pr.. , Ih. d . men a Ions, ev , clion outfitting and operation. e reqUlIe1959.,

datol}' requirements f7 ~l.~~~~~::::eIflationa1Convention for the Safety of Li~e men ts ~uch as those 0 t ~ hen ado ted by the government of the vessel s at Sea only become mandator)' W P f involvement by IMO can be seen Iegi~tered country. Some of the many areas 0 in the following list: (I) (2) (3) (4) (5) (6)

Navigationale-quipment. Ufe·saving equipment, Personnel tf-aining. . Tanker construction and equipment. Fire s-afety in ships. Radio comll1unkatiorls. (7) Search and rescue techniques. (8) Suhdivision and stability, (9) Carriage of dangerous goods. (IQ} Marine pollution.

Items (4) and (5) will now be examined in some detail, since they embody many aspects affecting the construction of merchant ships.

Tanker construction and equipment , ' o f oil tankers will continue to be a source of The constructlon i!,nd eqUipment ,",., of oil ha" h,en and are still being, , " . elargequanlts , much mvestlgatlon SlnC f d d hips Efforts are being made with the discharged fJllm damage~ o.r. oun ~:ti S of' the sea (and shore} by oil Two ohie(t of preventmg or limIting po on

200

OrganiHltion and Regulation

panicular avenues of , 16 nyugcnic, 25, 2& fini~hing tre~tm~nt, 21 furgings,26 l1it:her tensile, 24, 2:6 producti{ln, 2: I propertiC.l, 22:, 24 shi-p-lJ.uilding.23 ~\aTHlald ~eoCti()m, }1 "tern, 92, 93 Stern, cruiser, 102, 103 tramom, 103,104 iternframe, Hill 104 examinati()'l,226 ,terntube, 1G6, J 07 ,tiffener, 75, 30, 233

Stiffening, bulld,,,ad,87 de~k, I'll

local luading:, 83 Still water bending mument (S-\\'BM), i5 Strain, 29, 3() Strake, 72, 77--78, 8.2: Stress,28 30 compres,iw,28 proof, 3\ shea,. 28 tenslk,28Stress-strain gr