Chapter 33

Bulk Carriers

Hang Sub Urm and Jong Gye Shin

33.1 DESCRIPTION 33.1.3 Types of Bulk Carriers

33.1.1 Definition of Bulk Carriers Types of bulk carriers by size in deadweight are widely
used in the industry. Four typical sizes are classified de-
According to the SOLAS (Safety Of Life At Sea) Chapter
pending on the deadweight. That is, Capesize bulk carriers
XI-Reg.1, a bulk carrier is defined as a ship which is con-
over 80 000 deadweight tons, Panamax bulk carrier be-
structed generally with single deck, topside tanks and hop-
tween 50 000 and 80 000 tons, Handymax bulk carriers be-
per-side tanks in cargo spaces. A bulk carrier is intended
tween 35 000 and 50 000 tons, and Handysize bulk carri-
primarily to carry dry cargoes in bulk, and includes such
ers between 10 000 and 35 000 tons. Handymax and
types as ore carriers and combinations carriers (1). Modern
Handysize bulk carriers are often referred to as Handysize
conventional bulk carriers have been built based on the
bulk carriers.
SOLAS definition.
Bulk cargoes are categorized depending on consump-
Terminology used by the major classification societies
tion sectors. Steel-related, agriculture-related, energy-re-
is that a bulk carrier is a vessel designed for the carriage of
lated, and other sectors. Iron ore, coaking coal, steel, scrap,
bulk cargoes, or a seagoing vessel having single deck with
and pig iron cargoes are included in the steel related sector.
machinery aft for carrying bulk dry cargoes. The SOLAS
Wheat, coarse grains, soyabeans, meal fertilizers, and
definition is relatively limited, and thus general cargo ves-
minor cargoes are categorized as agricultural-related car-
sels, containerships carrying bulk cargoes, and double-
goes. Steam coal is used for energy-related sector, while
skinned bulk carriers are not included in the definition. In
bauxite, alumina, timber, minerals are used for particular
general, a bulk carrier means a ship carrying dry bulk car-
purposes. There are five major dry bulks among them,
goes such as ore, coal, grain, and having topside and hop-
which are iron ore, coal, grain, bauxite and alumina, and
per-side tanks with corrugated transverse bulkheads.
phospahte rock. Iron ore and coal are the raw materials for
making steel. Grain is required for making many food
products and the raw material for farming of cattle. Baux-
33.1.2 History of Bulk Carriers ite and alumina are the raw materials for aluminum mak-
The origin of modern bulk carriers is not known explicitly. ing. Phosphate rock is the bulk fertilizer for crop produc-
It is known that the first modern-type bulk carrier had top- tion. Shipping of the major cargoes has significantly
side and hopper tanks similar to modern dry bulk carriers influenced the types of bulk carriers in the market.
(2). Before the introduction of the modern concept, double As shown in Figure 33.1, bulk carriers of 70 000 dead-
bottom structure was adopted for single deck ships in weight tons and above carry most of the bulk cargoes in-
1890. Triangular-shaped topside tank structure was intro- creasingly in recent years, while handysize bulk carriers
duced for a cantilever-framed ship in 1905. show continuous reduction since 1975. This single com-

33-1
33-2 Ship Design & Construction, Volume 2

Source : Fearnly
Figure 33.1 Cargo Size in the Bulk Carrier Charter Market

modity of bulk cargoes are carried under long-term con- is fitted with hydraulically operated gates. Large size self-
tracts. unloaders can be used at shallow draft in order to transport
As shown in Figure 33.2, Handysize bulk carriers carry cargoes to most ports in the world. The vessel operation is
more other cargoes than iron ore, coal, and grain, while less affected by congested port facilities and unloading
panamax and capesize bulk carriers mostly transport coal rates are very high (3).
and iron ore.
There are some variants of bulk carriers, such as open
hatch bulk carriers, geared bulk carriers having cranes on 33.1.4 List of Bulk Cargoes
deck, self-unloaders, and so on. Open hatch bulk carriers, Bulk carriers transport a wide range of bulk commodities.
having box-shaped midship sections similar to conven- Usually, bulk cargoes are defined in terms of stowage rate,
tional containerships, have been developed for carrying i.e., cubic foot per pound or cubic meter per ton. Stowage
forest products. Onboard gantry cranes are equipped for rate stipulates how many cubic meters of cargo hold will
efficient cargo handling. Since open hatch bulk carriers be used by a ton of any given cargo. Dry bulk cargoes vary
transport damage-prone cargoes such as paper roll, it is from ore of 3.49 ton/m3 to 0.36 ton/ m3 in general. A list of
very important to have smooth surfaces of cargo holds. typical bulk cargoes is shown in Table 33.1 and further de-
Care should be taken to avoid stress concentration on tails can be found in reference 4.
squared hatch corners if rounded corner or necessary Since the density of cargoes varies, ship designers
brackets are not installed. should be careful for cargoes to be carried. For a ship car-
A geared bulk carrier has deck machinery in order to rying heavy ore cargoes, cargo volume is not a primary de-
discharge cargoes. If cargoes are unloaded without shore sign criterion. For a ship carrying grain or light density car-
equipment, a geared bulk carrier may efficiently be used goes, cargo volume becomes an important design
for multi-purpose operation by using grab and crane com- requirement. Repose angle should be considered to calcu-
binations. For loading and unloading operations at smaller late the load acting on internal surfaces of the cargo hold,
harbors, Handysize bulk carriers up to 50 000 deadweight due to the effect of friction within the cargo and inclination
tons are widely employed. of the cargo hold surfaces against which the cargo rests.
Self-unloading bulk carriers were invented for efficient Figure 33.3 shows international sea borne bulk cargoes in
unloading of cargoes over grab methods in case of short 1997 for different sizes of ships.
voyage to specific ports. The vessels have a gravity-fed There are five major dry bulks among them, which are
belt conveyor. The bottom of a hold has hopper tanks and iron ore, coal, grain, bauxite, and phosphate rock. Iron ore
 Chapter 33: Bulk Carriers 33-3

Source : Fearnly
Figure 33.2 Bulk Carrier Fleet Sectors

TABLE 33.I Typical Bulk Cargoes

Commodity Stowage factor, ft3/long ton Stowage factor, m3/long ton Specific gravity, ton/m3

Iron Ore 12–15 0.34–0.42 3–2.42

Coal 42–48 1.2–1.36 0.85–0.75
Grain heavy 42–56 1.2–1.42 0.85–0.72
Grain light 55–60 1.56–1.7 0.65–0.6
Bauxite 28–35 0.79–0.99 1.29–1.03
Phosphate/rock 33–34 0.91–0.96 1.12–1.06
General 24–29 0.69–0.82 1.47–1.24

and coal are the raw materials for steel production. Grain coal, and grain, while Panamax and Capesize bulk carriers
is required for many food products and is the raw material mostly transport coal and iron ore.
for farming of cattle. Bauxite is the raw material for alu- Bulk cargoes are also categorized depending on con-
minum production. Phosphate rock is the bulk fertilizer for sumption sectors, such as steel-related, agriculture-related,
crop production. Shipping of major cargoes has signifi- energy-related, and other sectors. Iron ore, coal, steel,
cantly influenced types of bulk carriers in the market. Coal scrap, and pig iron cargoes are included in the steel-related
and iron ore are usually carried under long-term contracts. sector. Wheat, coarse grains, soybeans, meal fertilizers,
Handysize bulk carriers carry other cargoes than iron ore, and minor cargoes are categorized as agricultural-related
33-4 Ship Design & Construction, Volume 2

Figure 33.3 International Sea Borne Trade in 1997

cargoes. Steam coal is used for energy-related sector, are identical in hull form, general and structural arrange-
while bauxite, timber, and minerals are used for particular ments, and others regardless of their sizes in general.
purposes. Bulk carriers carrying single commodity such as, ore,
and coal are operating between two pre-defined ports
based on a long-term contract. The port condition signifi-
33.1.5 Stowage Rate
cantly influences the ship’s draft and length.
Stowage rate stipulates how many cubic meters of cargo Principal dimensions of bulk carriers are also influ-
hold will be used by a tonne of any given cargo. Since the enced by geographical locations such as canal, draft of
density of cargoes is different, the ship designer is con- port, port facilities, and operation area. Draft of vessels
cerned with cargoes to be carried. For a ship carrying transiting Panama Canal or St. Lawrence Ways is limited
heavy ore cargoes, cargo volume is not a primary design by requirements from the corresponding authorities con-
criterion. However, for a ship carrying grain or light den- trolling the canals.
sity cargoes, cargo volume becomes an important design Figure 33.4 shows possible LBP/B ratios of bulk carri-
requirement. Repose angle should be considered to calcu- ers with respect to deadweight, obtained from feasibility
late the load acting on the internal surfaces of the cargo studies and an actual bulk database. It is found that the ra-
hold, due to the effect of friction within the cargo and in- tios range from 5.0 and 7.0. Figure 33.5 shows possible
clination of the surface against which the cargo rests. Re- LBP/D ratios for different dead weights. The LBP/D ratios
duction of pressure in horizontal direction is normally are located between 11.0 and 12.0. Figure 33.6 shows pos-
taken into account. It is often assumed that the natural re- sible B/D ratios with respect to deadweight. It is seen that
pose angle is the same as internal friction angle and ne- the ratios are scattered between 1.6 and 2.1 with some ex-
glecting the friction between the cargo and the hull surface ceptions.
contacted. Some simplified equations have been used de- Figure 33.7 shows possible cargo capacity of bulk car-
pending on classification societies. riers in m3 with respect to deadweight. It shows a trend that
cargo capacity is almost proportional to deadweight except
33.1.6 Unique Features and Capabilities for few very large size bulk carriers.
33.1.6.1 Characteristics of bulk carriers
Design of bulk carriers is determined by cargo types to be 33.1.6.2 General arrangement
transported. For operation of heterogeneous mixture of The general arrangement of a bulk carrier requires a com-
commodities, multi-port operation is required in a single promise among many conflicting requirements. General
voyage. Dry bulk carriers have been increased in size, but arrangement should satisfy all functions of a ship and
 Chapter 33: Bulk Carriers 33-5

Figure 33.4 Relationship Between Deadweight and LBP/B Ratio

Figure 33.5 Relationship Between Deadweight and LBP/D Ratio

balance various demands within the limited spaces. An op- For dry cargo bulk carriers, required volume of cargo
timized general arrangement enhances the efficient opera- space and required volume and length of machinery space
tion of a ship. Cargo space and machinery space arrange- are basic requirements. Preliminary lines plan is necessary
ments are major arrangement concerns. Crew space of a to check that main engine and machinery space is suffi-
bulk carrier is not different from that of other ship types, cient at the design stage for general arrangement. Required
and the arrangement and facilities largely depend on the volume of fuel oil tanks, ballast tanks, and fresh water
owner’s preference. Watertight subdivision and adequate tanks are also considered to satisfy the minimum draft and
stability are important requirements, while designers maximum cruise range. The minimum number of trans-
should always take into account of structural integrity and verse bulkheads is defined in the classification rules.
easier production. Shipowners usually determine principal dimensions since
33-6 Ship Design & Construction, Volume 2

Figure 33.6 Relationship Between Deadweight and B/D Ratio

Figure 33.7 Cargo Capacity, m3 per Deadweight Tonne

the dimensions are often related to port conditions and the Access is one of dominant design parameters for the
shipowner’s economic feasibility study of the operation. general arrangement to enable the crew to perform their
Cargo space of a dry bulk carrier consists of regular length duties and to escape in an emergency situation. The Mar-
holds having hatches for handling of cargoes by grab or by itime Union of Australia regulations specifically defines
blower for grain cargoes. Lower transverse bulkhead stool the requirements for a means of access in cargo holds of a
is an important parameter to decide uniform length of the bulk carrier, such as clear opening size, ladder dimensions,
cargo space. stairways, cleats, passage ways, and so on.
 Chapter 33: Bulk Carriers 33-7

Figure 33.8(a) General Arrangement of 44 000 DWT Bulk Carrier (Handymax) with Cargo Handling Gear

Figure 33.8(b) General Arrangement of 75 000 DWT Bulk Carrier (Panamax)

Figure 33.8(c) General Arrangement of 170 000 DWT Bulk Carrier (Capesize)

Figure 33.8 shows general arrangement of typical bulk nent inspecting measures due to characteristics of bulk
carrier sizes. carrier.

33.1.6.3 Rules and regulations

Similar to the other types of vessels, bulk carriers should 33.2 SYSTEM DESIGN
be classed by a classification society and must be regis-
tered to a national flag. There are many rules and regula- 33.2.1 Hull Form, Propulsion, and Performance
tions applied to vessels including bulk carriers as compul- 33.2.1.1 Hull form
sory requirements. It is compulsory to comply with Hull forms of bulk carriers have the characteristics of com-
international convention such as International Maritime paratively slow, large block coefficient, long parallel mid-
Organization (IMO) resolutions, International Convention dle body, and rectangular shape of the midship section.
on Load Lines, 1966, SOLAS, MARPOL 73/78, and so on. Simple hull forms with long parallel middle body con-
IMO resolution MSC 23(59), International Code for the tribute to easy manufacturing because of flat and single
Safety Carriage of Grain in Bulk and IMO Resolution curvature lines.
A715, International Code of Safety Practice for Ship’s The installation space for propulsive machinery is usu-
Carrying Timber Deck Cargoes 1991 are major interna- ally secured in aft engine room area. Fuel oil tanks are usu-
tional regulations for bulk carriers in particular. It is re- ally arranged in the engine room area so as to avoid instal-
quired to have an Enhanced Survey Program (ESP) nota- lation of additional piping lines to double bottom tanks in
tion for bulk carriers for proper inspection purposes by the cargo hold region. Most modern bulk carriers have bulbous
classification surveyors, as it is difficult to arrange perma- bows for the reduction of wave resistance.
33-8 Ship Design & Construction, Volume 2

33.2.1.2 Lightweight 33.2.1.3 Main engine

One of most important design step is to estimate light- Main engines are selected by similar criteria as used in
weight and its distribution along the ship length. Figure other types of vessels. Figure 33.10 shows a trend of main
33.9 shows possible lightweights for different ship sizes in engine output with respect to ship size built in between
deadweight tons, based on a feasibility study and actual 1990 and 1996.
bulk carrier database. Lightweight accounts for about 20 Figure 33.11 shows a trend for output of diesel and
percent of deadweight for Handymax size bulk carriers and main-engine driven alternators. For Panamax bulk carriers,
about 12 percent of deadweight of very large bulk carriers. the alternator is designed to produce about 1500 kW.

Figure 33.9 Lightweight – Deadweight Relation of Bulk Carriers

Figure 33.10 Main Engine Output in PS with Respect to Ship Size in Deadweight Tonne.
 Chapter 33: Bulk Carriers 33-9

Figure 33.11 Output of Alternators Driven by Diesel and Main Engines

33.2.2 Payload Related System of double bottom structure. Transverse bulkheads are of
33.2.2.1 Hatch opening size corrugated type with flat upper and lower stools. Shape of
Hatch opening size should be as large as possible. Large corrugation can be determined from both strength and the
size hatch opening contributes easy loading and unloading minimum weight design point of view by changing pitch
of cargoes, while reduction in deck area induces weight in- and depth of the corrugation. Lower and upper stool struc-
crease due to the requirement of hull girder section modu- tures support transverse bulkheads to reduce the span of the
lus. Large hatch length limits the width of deck strip be- bulkhead. Slanted type lower stool is common, but either
tween hatches. For a load condition with two adjacent straight type or slanted type is adopted for upper stool
holds loaded, deck structure between hatches should have mainly depending on the size of bulk carriers. The number
sufficient buckling strength. Hatch size depends on hold of girders is determined according to the allowable mean
length and breadth of the ship. Hatch breadth ranges from shear stress level of each girder, while thickness and num-
approximately 45% to 60% of ship’s breadth and hatch ber of girders also influence sectional properties of the ship.
length ranges from approximately 57% to 67% of hold
length. For bulk carriers having large opening size, tor-
sional stresses due to warping deformation may be taken 33.2.4 Structural Behavior of Bulk Carriers
into account. 33.2.4.1 Hull material
Requirements of hull material for the construction of ma-
rine vessels are well specified in classification societies’
33.2.3 Hull Structures rules. In general, steel for bulk carrier construction is cate-
Figure 33.12 shows a typical mid-body structure of a single gorized as mild steel, higher tensile (HT) steel, casting
side bulk carrier. Ballast tanks are arranged in double bot- steel, and forged steel.
tom, hopper, and topside wing tank structures. Since most For hull structures, mild and HT steels are commonly
cargoes are supported by double bottom and hopper tank used for main structures, while casting steel and forged
structures, the structures should be reinforced extensively. steel have been used for stern frame and rudderstock, re-
A duct keel is arranged for piping and passage in the center spectively. Detailed requirements of material properties
33-10 Ship Design & Construction, Volume 2

Figure 33.12 Typical Midship Section

are defined in the classification societies’ rules. In recent tions, air draft condition if required, and dry docking con-
years, HT steel has been extensively used for hull struc- dition. All of these conditions are considered for departure
tures to minimize lightship weight under competitive in- and arrival states as the typical load conditions.
ternational market environment. Extensive use of higher Usually, the ballast condition and alternate ore load
tensile steel for all longitudinal members and transverse condition generate highest hogging and sagging still water
bulkheads may result in some losses in stiffness of hull and bending moments, respectively. Since vertical wave bend-
less corrosion margin. ing moment follows the International Association of Clas-
It is a usual design practice that higher tensile steel is sification Societies Unified Requirement (IACS UR), the
employed for longitudinal members at deck and bottom ship designers tend to focus on the design criterion that
parts and transverse members where higher stress is ex- the actual still water bending moment should not exceed
pected in order to have maximum benefits of higher tensile the allowable vertical still water bending moment of the
steel. Mild steel has been used for the other structural vessel. In order to reduce the still water bending moment,
members to provide proper stiffness and corrosion margin. ballast adjustment of aft peak and fore peak tanks in the
In view of fracture toughness, there is A to E grades cat- ship is a common approach.
egorized by chemical composition, deoxidization practice,
and thickness (5). Grade C is rarely used for commercial 33.2.4.3 Section modulus calculation
ship construction. Material grade selection for longitudinal Longitudinal strength of bulk carriers is one of the major
members is defined in most classification rules with re- concerns of the bulk carrier design. Once the principal di-
spect to locations and thickness. mensions, configuration of the midship section, structural
arrangement of the cargo holds are determined, longitudi-
33.2.4.2 Longitudinal strength calculations nal strength of each section is to be checked with respect
Longitudinal strength is to be examined with respect to typ- to minimum section modulus requirement of the classifi-
ical extreme load conditions that a vessel will experience in cation society. Local scantling requirements can be satis-
her life. Typical load conditions during the voyage are; light fied for given structural arrangement based on an assumed
ballast condition, normal ballast condition, homogeneous section modulus. Iteration is necessary to minimize the
cargo condition at the design draft, homogeneous cargo difference between the assumed and actual modulus. Usu-
condition at the scantling draft, alternate ore load condi- ally, the section modulus of deck is smaller than that of
 Chapter 33: Bulk Carriers 33-11

bottom due to fact that local scantling requirements for crease. Brackets connected to hold frames should have suf-
bottom structures are severe. In order to increase deck sec- ficient strength to prevent fracture due to rotation of side
tion modulus, it is a common practice to increase deck shell structure.
plate thickness and to use higher tensile steel in the mini- To eliminate fractures at the welding seam lines or deck
mum zone defined by classification rules. corners, abrupt thickness changes between deck plating
and transverse deck strip are to be avoided. Intermediate
33.2.4.4 Shear strength calculations thickness may be inserted if difference in two plate thick-
The side shell is carrying major proportion of vertical ness is more than 18 mm. Additional stiffening of deck
shear force, when the alternate hold loading conditions are strip is sometimes required if buckling is anticipated when
employed. Shear force carried by the side shell plating two adjacent cargo holds are loaded simultaneously.
should be corrected due to high rigidity of double bottom Double bottom connection to lower stool is a very cru-
structures and transverse bulkheads. This correction of cial area since rotation of transverse bulkhead and double
shear force has been examined according to the classifica- bottom cause higher stress concentrations. Soft-toe type
tion society’s requirement. To prevent shear buckling and brackets are fitted at the interconnection between longitu-
to keep the allowable shear stress level of side shell plat- dinals and transverse frames below lower stool.
ing, calculations of the local shear flow are necessary.
33.2.4.7 Direct calculations
A recent trend is that the finite element analysis has in-
33.2.4.5 Heavy cargo loading creasingly been used for the ship structural design. An ex-
Double bottom structures with girders and floors are rein- ample of a finite element model for a cargo hold is shown
forced in way of transverse bulkheads and girders due to in Figure 33.13. Usually, a model for two cargo holds or
shear forces of heavy cargo loading. Bottom plating in three cargo holds is widely used for the examination of
empty holds needs to be reinforced against buckling for the strengths of double bottom and transverse bulkhead struc-
alternate hold loading condition. It is usually found that tures. Depending on the requirements of classification
every third frame is larger than the others for bulk carriers societies, various load conditions must be considered in-
built in the 1970s and hopper transverse webs are matched cluding dynamic pressure. Major classification societies
with transverse webs of topside wing tank. It is a new trend introduce PC-based computer programs to carry out the
that equal-sized hold frames are arranged in cargo holds cargo hold analysis based on their standard procedure of
and side hold frames are independent of the location of direct calculations. The analysis procedure comprises stan-
topside tank transverse webs for modern bulk carriers. dards for finite element modeling, load conditions, bound-
ary conditions, evaluation criteria, and so on depending on
33.2.4.6 Local scantlings the classification societies. Heavy ballast and heavy ore
Since alternate load conditions allow a bulk carrier to carry load with adjacent hold empty are among load conditions
heavy iron ore cargoes, double bottom plating and longitu- to be checked.
dinals are reinforced against heavy cargo loading. Plating Bottom and inner bottom plating are to be checked in
and stiffeners of transverse bulkheads and hopper struc- view of buckling strength when ballast or ore cargoes are
tures within about 1.5 m in the vertical direction are also loaded. Since most cargo weights are transmitted to double
reinforced. Inner bottom structure is reinforced against bottom structures, the shear strength of longitudinal gird-
heavy grab discharge. ers and transverse floors must be sufficient. Higher shear
It is a normal practice that scantlings of inner bottom stresses of floors are usually anticipated near the hopper
plating and longitudinals in ore holds are heavier than those tank. Higher shear stresses are usually found at girders
in adjacent empty holds in the alternate load conditions. near the lower stool of transverse bulkheads.
Floor spacing in duct keel and at the bilge is a half of Buckling strength of deck plating between hatches is to
the ordinary frame spacing for many cases. A bilge keel is be checked when two cargo holds are loaded simultane-
fitted onto bilge strake. Due to welding problems at block ously. Bending strength of transverse bulkhead is primary
joints, usually an intermittent type of bilge keel tends to be concern of designers. When water ballast is loaded in a
adopted. For such a type, ends of the bilge keel should cargo hold, laminar tearing of inner bottom plating near to
carefully be designed to avoid cracks. Side hold frames are lower stool should be taken into account.
usually made with integral brackets to avoid structural dis- Since the cargo hold analysis should check strength of
continuities and have T-type flange to minimize stress in- primary structures, such as double bottom and transverse
33-12 Ship Design & Construction, Volume 2

Figure 33.13 An Example of the Finite Element Cargo Hold Model

bulkhead, stress concentration of local structures such as tures. Small breadth may cause access problems during
double bottom longitudinal connection to lower stool construction and operation stages.
should be checked as well. Although rule scantlings of Figure 33.14 shows a typical ballast piping diagram for
local structural members cover typical local structural be- a 70 000 deadweight tons bulk carrier. It is usual that top-
haviors based on some assumptions, double bottom bend- side ballast tanks are interconnected with bottom ballast
ing, relative deflections between primary structures and ef- tanks via trunk or pipe at side shell for large size bulk car-
fect of brackets should be considered in addition. For this riers. For small size bulk carriers, it is common that sepa-
purpose, the fine mesh analysis of local structures is nec- rate ballast lines are arranged for topside ballast tanks and
essary in way of inner bottom connections to lower stool there is no trunk or pipe between topside ballast tanks and
stiffeners, especially where straight type lower stool is double bottom ballast tanks.
adopted.

33.2.4.8 Machinery arrangement 33.3 DESIGN ISSUES

Piping arrangement depends on the installation of water
ballast line, bilge line, fuel oil transfer line, steam line for 33.3.1 Stability and Damage Safety
fuel oil heating, and valve control line. The size of duct 33.3.1.1 Trim and stability booklet
keel and the depth of inner bottom are influenced by the The trim and stability booklet is prepared by shipyards to
piping system with minimum passage breadth. Pipe diam- give information to ship designers and ship operators. At
eter for water ballast is a primary design point. For exam- the design stages, a preliminary trim and stability booklet
ple, diameter of 300 mm is normally used for a Panamax is made to examine hydrostatic stability, trim, longitudinal
bulk carrier. holds should be considered. strength, and so on.
For Handymax size vessels, the breadth of duct keel is Principal particulars, limitations of operation such as
usually about 1600 mm. The of breadth duct keel is from allowable maximum shear force and bending moment, sta-
2400 to 2600 mm for the other sizes of bulk carriers de- bility criteria, drafts for each load condition, and maxi-
pending on longitudinal spacing of double bottom struc- mum allowable VCG curve are contained in the booklet.
 Chapter 33: Bulk Carriers 33-13

Figure 33.14 Ballast Piping Diagram of a 70 000 Deadweight Tons Bulk Carrier

Tank capacity, cargo hold capacity, hydrostatic tables, • BC-C : for bulk carriers designed to carry dry bulk car-
cross curves, and others are also included. goes of cargo density less than tonne/ m3.
Hull girder vibration may be caused by bow flare slams
33.3.1.2 Typical loading conditions
and unsteady pressure field due to surface waves. The un-
Typical load conditions such as, normal ballast, heavy bal-
steady fluid pressure applying to shell plating of a bulk car-
last, homogeneous load, heavy ore, grain load, and dry
rier in seaways may cause two-node vibration. It is noted
docking conditions are calculated in the trim and stability
that the springing phenomenon affects the fatigue life of a
calculations for departure and arrival states, respectively.
bulk carrier such as lake size bulk carriers. Several efforts
For bulk carriers having an air draft restriction, partial-
have been made to avoid these dynamic problems of ships.
flooding of cargo holds should be considered. Still water
Prediction of wave exciting forces and calculations of ve-
shear force and vertical bending moment distributions are
locity-dependent terms involving derivatives of added
calculated along the ship length.
mass and damping should be made for such vessels.
For scantlings of hull structures, the following standard
loadings in IACS UR are taken into consideration. (7)
33.3.1.3 Damage stability
• BC-A : for bulk carriers designed to carry dry bulk car- Subdivision and stability of cargo ships built before 1992
goes of cargo density 1.0 tonne/m3 and above with should satisfy the International Convention on Safety of
specified holds empty in addition to BC-B conditions. Life at Sea of 1974 (SOLAS74) and the International Con-
• BC-B : for bulk carriers designed to carry dry bulk car- vention on Load Lines of 1966 (ICLL66) as amended for
goes of cargo density of 1.0 tonne/ m3 and above with reduced freeboard vessels. In 1982, IMO introduced a reg-
all cargo holds loaded in addition to BC-C conditions. ulation for freeboard for dry cargo ships based on a proba-
33-14 Ship Design & Construction, Volume 2

bilistic analysis procedure. Furthermore, the SOLAS proper measures should be made for maintenance of ves-
Chapter XII became effective by giving additional safety sels and for level of safety in design. Among the measures,
measures for bulk carriers on or after July 1, 1999. International Society of Classification Societies (IACS) in-
troduced new Unified Requirements, called as IACS UR,
on overloading, transverse bulkhead scantlings, and so on
33.3.2 Comfort, Motion, Noise, and Vibration (7). Compared to oil tankers, bulk carriers have a lack of
33.3.2.1 Springing structural redundancy and operating conditions are severe.
For lake size bulk carriers, operating in Great Lakes in Cargo handling practices during loading and unloading in-
America, have high ratio of length to depth, which is a risk duces damage of hold frames and transverse corrugated
of springing. This is because of lack of stiffness of hull bulkheads by pneumatic hammers, and damage of inner
girder. Springing is defined as the resonant hull girder re- bottom structures by heavy weight grab and bulldozers.
sponse to the unsteady pressure field in the fluid (6). Coal, containing high sulfur, is the cause of corrosion at
bracket ends of side hold frames. Figure 33.15 shows an ex-
ample of severe corrosion in way of side frames.
33.3.3 Environmental Issues One of scenarios for the casualties is that lower end of
33.3.3.1 Recent damages and counter measures brackets attached to hold frame in number 1 cargo hold are
by IACS corroded and damaged. This results in the ingress of sea-
During the past 10 years there have been many losses in water into number 1 cargo hold, which induces sudden in-
lives and cargoes due to casualties of bulk carriers. In some crease in hull girder bending moment and progressive col-
cases, bulk carriers having such damage or corrosion were lapse of watertight transverse bulkheads, which causes
disappeared without any signal and survivors. Several at- sinking of the vessel.
tempts have been made to prevent bulk carrier casualties by The IACS UR require reinforcements for existing bulk
classification societies and IMO. It is widely accepted that carriers having single skin of 150 m in length and carrying

Figure 33.15 Corrosion in Way of Side Frames

 Chapter 33: Bulk Carriers 33-15

bulk cargoes with bulk density of 1.78 t/m3 and above. The goes. Double skinned bulk carriers have advantages over
strength of the after corrugated bulkhead and the double single hull bulk carriers. Damage by grabs, bulldozers, and
bottom structure in way of the foremost cargo hold is given corrosion can be significantly reduced since the inner skin
a special consideration. Damage stability must be exam- of cargo holds is smooth. Coating of holds is a quicker and
ined for the condition that the foremost cargo hold is cheaper solution. The additional longitudinal member con-
flooded. The typical loading sequence should be devel- tributes hull girder strength and protects hold flooding
oped, paying attention to the loading rate, the de-ballasting from side damage. However, higher initial building cost,
capacity, and applicable strength limitation. The sequence some deadweight reduction, and higher port and canal
should be included in the existing loading manual. ICAS dues because of increased measured tonnage, are disad-
requires that a loading computer be installed on board in vantages. As such disadvantages are not of primary con-
order to calculate longitudinal strength for various loading cern over the safety issues of bulk carriers, double skinned
conditions regardless of bulk density or type of side struc- bulk carriers become an alternative to single hull bulk car-
ture. Figure 33.16 shows the locations where the IACS UR riers (8).
is to be applied.

33.3.4 Future Trend of Bulk Carriers 33.4 PRODUCTION ISSUES

One of the weakest points of single hull bulk carriers is the As modern dry bulk carriers have a typical structural shape
side shell structure compared to hopper tank and topside as shown in Figure 33.12, that is, triangular shape of top-
tank structures. A side shell is subject to dynamic pressure side and hopper tanks and corrugated transverse bulk-
in a seaway and damaged from cargo grabs and by hy- heads. The triangular-shape structures require more re-
draulic hammer from the sea. It is also difficult to protect sources for production than rectangular-shape of double
the structure against corrosion from sulfur-rich coal car- bottom. Additional efforts are necessary to support topside

Figure 33.16 Locations where the IACS UR is to be applied

33-16 Ship Design & Construction, Volume 2

structures during the block erection stage. Corrugated during surveys of bulk carriers and oil tankers: Resolu-
bulkheads are usually fabricated by pressing plates into the tion A.744(18) adopted on 4 November 1993, London,
required shapes. It becomes more difficult to press thicker IMO, 1993 (A 18/Res.744)
plates due to the capacity of a press or bending machine. A IMO, 1996 amendments to the guidelines on the enhanced
corrugation length is limited by the capability of the press program of inspections during surveys of bulk carriers
or bending machine. Additional welding seams result in and oil tankers (Resolution A.744(18)) (Adopted in ac-
increase of fabrication costs. Precise control of block joints cordance with article VII of the International Conven-
between two corrugations of different thickness is also a tion for the Safety of Life at Sea, 1974): Certified true
difficult task. copy signed on March 18th, 1997, London, IMO, 1997
IMO, Guidelines on the enhanced program of surveys for
bulk carriers, London, IMO, 1993 (MSC/Circ.628)
IMO, Guidance for planning the enhanced program of in-
33.5 SHIP CHARACTERISTICS spections during surveys of bulk carriers and oil
Table 33.II presents characteristics for typical bulk carriers. tankers, London, IMO, 1994 (MSC/Circ.655)
IMO, Guidelines on the means of access to structures for
inspection and maintenance of oil tanker and bulk car-
riers, London, IMO, 1995 (MSC/Circ.686)
33.6 REFERENCES IMO, Guidelines for the selection, application and mainte-
1. International Maritime Organization, SOLAS Chapter XI, nance of corrosion prevention systems of dedicated
Reg. 1 seawater ballast tanks. Resolution A.798(19) adopted
2. Jacobs, C. L., “Development of Specialized B/Cs,” Marine on 23 November 1995
Technology, Vol. 20, No. 1, January 1983 DET NORSKE VERITAS, Bulk carrier losses. Hovik: Det
3. Vaughan, W. R., “Update on Self-Unloading Dry Bulk Ves- Norske Veritas, 1991
sels,” Marine Technology, Vol.15, No. 3, July 1978 DET NORSKE VERITAS, Cost benefit analysis of exist-
4. Dorman, W. J., “Combination Bulk Carriers,” Marine Tech- ing bulk carriers: A case study on application of formal
nology, October 1996 safety assessment techniques, Hovik, DNV, 1997
5. Alia, B. L. and Wheatcroft, M. F., “Structural Material for
(Paper Series No. 97-P008)
Marine Applications,” Marine Technology, Vol.13, April
1976
INTERNATIONAL ASSOCIATION OF CLASSIFICA-
6. Skjordal, S. O. and Faltinsen, O. M., “A Linear Theory of TION SOCIETIES (IACS), Bulk carriers: Guidance
Springing,” Journal of Ship Research, Vol. 24, No.2, June and information to shipowners and operators, London,
1980 IACS, 1992
7. International Association of Classification Societies, Uni- INTERNATIONAL ASSOCIATION OF CLASSIFICA-
fied Requirements, 2002 TION SOCIETIES (IACS), Bulk carriers: Guidelines
8. International Maritime Organization, Maritime Safety for surveys, assessment and repair of hull structure. 3rd
Committee, 76th Session, MSC 76/23, 16 December 2002 ed., London, Witherby and Co. Ltd, 1995 (ISBN : 1-
85609-135-X)
INTERNATIONAL ASSOCIATION OF CLASSIFICA-
TION SOCIETIES (IACS), Bulk carriers: Guidance
33.7 BIBLIOGRAPHY
and information on bulk cargo loading and discharging
IMO, International code for the safe carriage of grain in to reduce the likelyhood of over-stressing the hull struc-
bulk (International Grain Code), London, IMO, 1991. ture, London, IACS, 1997
(IMO-240) INTERNATIONAL ASSOCIATION OF CLASSIFICA-
IMO, Code of safe practice for solid bulk cargoes (BC TION SOCIETIES (IACS), Bulk carriers: Handle with
Code), 1998 edition (IMO-260E) care, London, IACS, 1998
IMO, BLU Code. Code of practice for the safe loading and INTERNATIONAL ASSOCIATION OF CLASSIFICA-
unloading of bulk carriers. 1998 edition. (IMO-266E) TION SOCIETIES (IACS), Bulk carrier safety. In: In-
IMO, SOLAS – International Convention for the Safety of ternational Association of Classification Societies
Life at Sea, 1974: Resolutions of the 1997 SOLAS (IACS) – The IACS Briefings 1996-1998, London,
Conference relating to bulk carrier safety, 1999 edition. IACS, 1999 ( IACS Briefing No. 5, September 1997)
(IMO-160E) INTERNATIONAL CARGO HANDLING CO-ORDINA-
IMO, Guidelines on the enhanced program of inspections TION ASSOCIATION (ICHCA), The loading and un-
Table 33.II Characteristics of Typical Bulk Carriers

DWT 1 000 Tonnes 41 42 44 65 65 75 114 114 150 150 150 170 170

TYPE B/C B/C O/H B/C B/C B/C B/C B/C B/C B/C B/C B/C B/C
LOA, m 190.0 190.0 190.0 224.0 230.0 230.0 266.0 266.0 274.0 274.0 289.0 289.0 289.0
LBP, m 181.0 181.0 181.0 214.0 220.0 220.0 256.0 256.0 264.0 264.0 278.0 278.0 278.0
Beam m 30.5 30.5 31.5 33.2 36.4 36.0 40.5 40.5 45.0 45.0 47.0 45.0 45.0
Depth m 16.6 16.6 19.5 18.1 16.9 18.8 21.2 21.2 23.2 23.2 24.0 25.0 25.0
Draft m 10.7 10.7 12.0 12.5 11.3 12.8 14.5 14.5 16.9 16.9 15.3 17.9 17.9

Chapter 33: Bulk Carriers

Cb 0.823 0.828 0.793 0.824 0.823 0.843 0.841 0.842 0.821 0.821 0.836 0.837 0.837
Speed knots 14.5 14.2 14.5 14.8 13.5 14.5 14.0 14.3 13.5 13.8 15.0 15.0 15.0
LCB m Forward 3.41 3.0 2.41 3.30 3.41 3.12 3.12 8.52 3.56 0.0 0.0
LWT Tonnes 8500 8200 11 300 11 889 11 300 12 750 16 035 15 305 19 200 19 200 21 500 22 000 22 000
Hatch Size m 18.9 × 18.8 × 18.6 × 16.8 × 16.8 × 14 × 14 × 13.8 × 14.6 × 15.3 × 15.3 ×
16 15.2 26.8 13.8 16 18.6 13.5 15.3 21.4 20.4 20.4
Crew 28 24 26 33 28 36 27 27 26 24 30 30 30
No of Holds 5 5 7 7 7 7 9 9 9 9 9 9 9
Cargo Capacity 1000 m3 56 55.2 60 79.9 80 91 136 136 168 168 190 189.3 189.3
MCR kW/RPM 11 270 × 9700 × 11 640 × 13 000 × 11 000 × 14 340 × 16 200 × 16 200 × 15 450 × 17 450 × 22 920 × 22 920 × 21 300 ×
126 127 127 117 120 90 82 82 80 88 91 91 106
NCR kW/RPM 9580 × 8904 × 9890 × 11 700 × 9350 × 12 200 × 13 770 × 13 770 × 13 910 × 15 710 × 19 480 × 20 630 × 19 220 ×
119 123 120 113 114 86 78 78 75 85 86 88 102
F.O. Consumption 28.9 26.5 29.9 37.1 28.3 36.6 40.8 40.8 41.6 46.9 58 61.6 57.4
Cruising Range 1,000 NM 16.5 18 18 21 22.5 18.5 20 20 21 18.5 23.4 23 23

Legend: DWT: Deadweight tons, O/H: Open hatch carrier, LCB: Longitudinal Center of Buoyancy, LWT: Lightship weight tons, MCR: Max. Continuous Rating, PS × RPM, NCR:
Normal cruise rate, PS × RPM.

33-17
33-18 Ship Design & Construction, Volume 2

loading of solid bulk cargoes, London, ICHCA, 1998. INTERNATIONAL ORGANIZATION FOR STAN-
(ISBN : 1-85330-096-9) DARDIZATION (ISO), Ships and marine technology:
INTERNATIONAL CHAMBER OF SHIPPING (ICS), Bulk carriers: Construction quality of hull structure,
Ship shore safety checklist for loading and unloading Geneva, ISO, 2000. (ISO 15401)
dry bulk cargo carriers, London, ICS, 1996 BES, J., Bulk Carriers: Practical guide to the subject for all
INTERNATIONAL CHAMBER OF SHIPPING (ICS) et connected with the shipping business. 2nd ed. London,
al, Bulk carrier checklists, London, ICS, 1996 Barker & Howard Ltd, 1972