vol2_section23

7/27/2019 Vol2_Section23

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Section 23 – Strengthenings for Heavy Cargo, Bulk Carriers, Ore Carriers B 23 - 1

Section 23

Strengthenings for Heavy Cargo, Bulk Carriers, Ore Carriers

A. Strengthenings for Heavy Cargo

1. General

1.1 For ships, occasionally or regularly carrying heavy

cargo, such as iron, ore, phosphate etc., and not intended

to get the notation "BULK CARRIER" (see B.) or "ORE

CARRIER" (see C.) affixed to their character of

classification Strengthenings according to the following

regulations are recommended.

1.2 Ships complying with these requirements will get

the following notation affixed to their character of classification "STRENGTHENED FOR HEAVY CARGO".

1.3 It is recommended to provide adequate strengthening

or protection of structural elements within the working range

of grabs.

2. Double bottom

2.1 Where longitudinal framing is adopted for the double

bottom, the spacing of plate floors should, in general, not

be greater than the height of the double bottom. The

scantlings of the inner bottom longitudinals are to be

determined for the load of the cargo according to

Section 9, B.

For the longitudinal girder system, see Section 8, B.7.5.

2.2 Where transverse framing is adopted for the double

bottom, plate floors according to Section 8, B.6. are to be

fitted at every frame in way of the cargo holds.

2.3 For strengthening of inner bottom, deep tank tops

etc. in way of grabs, see B.4.3.

2.4 In the drawings to be submitted, details are to be

given regarding the loads resulting from the cargo, upon

which the calculations are based.

3. Longitudinal strength

The longitudinal strength of the ship must comply with

the requirements of Section 5 irrespective of the ship's

length.

B. Bulk Carriers

1. General1.1 For hull structural design of bulk carrier with L

90 m IACS Common Structural Rules for Bulk

Carrier are applicable.

1.2. Bulk carrier means a ship which is constructed

generally with single deck, double bottom, top-side tanks

and hopper side tanks in cargo spaces, and is intended

primarily to carry dry cargo in bulk.

Such a ship is considered in this Section a "Single Side

Skin Bulk Carrier" when one or more cargo holds are bound

by the side shell only or by two watertight boundaries, one

of which is the side shell, which are less than 1000 mm

apart. The distance between the watertight boundaries is

to be measured perpendicular to the side shell.

When the distance is above 1000 mm or above in cargo

area, such a ship is considered a “ Double Side Skin Bulk

Carrier “.

For accessibility see Section 1, D.1.

1.3 Bulk carriers built in accordance with the following

requirements will get the notation "BULK CARRIER"

affixed to their character of classification. Entries will be

made into the certificate as to whether specified cargo holds

may be empty in case of alternating loading. Additional

indications of the types of cargo for which the ship is

strengthened may be entered into the certificate.

1.4 The requirements of Sections 1 to 22 apply to bulk

carriers unless otherwise mentioned in this Section. A.1.3

is also to be observed.

1.5 For bulk carriers carrying also oil in bulk also

Section 24, G. applies.

1.6 Where reduced freeboards according to LLC 66

shall be assigned, the respective requirements of the Load

Line Convention are to be observed.

1.7 The scantlings of the bottom construction are to be

determined on the basis of direct calculations according

to Section 8, B.8.

1.8 For corrosion protection for cargo hold spaces see

Section 35, G.

1.9 For dewatering requirements of forward spaces of

bulk carrier, see Volume III Rules for Machinery

Installations, Section 11, N.

1.10 For water ingress detection system of bulk carrier,

see Volume IV Rules for Electrical Installations, Section

18.



Section 23 – Strengthenings for Heavy Cargo, Bulk Carriers, Ore Carriers B23 - 2

2. Longitudinal strength

The requirements of A.3. apply.

For alternate loading conditions Section 8, B.8.2.2 is to

be observed.

3. Definitions

k = material factor according to Section 2, B.2.

tK = corrosion allowance according to Section 3, K.1.

p bc = bulk cargo pressure as defined in Section 4,

C.1.4.

4. Scantlings of bottom structure

4.1 General

The scantlings of double bottom structures in way of thecargo holds are to be determined by means of direct

calculations according to Section 8, B.8.

4.2. Floors under corrugated bulkheads

Plate floors are to be fitted under the face plate strips of

corrugated bulkheads. A sufficient connection of the

corrugated bulkhead elements to the double bottom structure

is to be ensured. Under the inner bottom, scallops in the

above mentioned plate floors are to be restricted to those

required for crossing welds. The plate floors as well as the

face plate strips are to be welded to the inner bottom

according to the stresses to be transferred. In general, single bevel T-joints or double bevel T–joints are to be used.

4.3 Inner bottom and tank side slopes

4.3.1 The thickness of the inner bottom plating is to be

determined according to Section 8, B.4.

When determining the load on inner bottom pi, a cargo

density of not less than 1 t/m3 is to be used.

For determining scantlings of tank side slopes the load pi

is not to be taken less than the load which results from an

angle of heel of 20 .

4.3.2 Where the plating has been designed according to

the following formula, in connection with 9. the notation

"G" may be entered into the Certificate behind the character

of classification:

tG = [mm]0,1 L 5 k

The thickness, however, need not exceed 30 mm.

Note

The stressing of the inner bottom plating depends mainly

on the use of grabs, therefore, damage of plating cannot

be excluded, even in case of compliance with the above

recommendation.

4.3.3 Sufficient continuity of strength is to be provided

for between the structure of the bottom wing tanks and the

adjacent longitudinal structure.

5. Side Structures

5.1 Side longitudinals, longitudinal stiffeners, main

frames

The scantlings of side longitudinals are to be determined

according to Section 9, B. The longitudinal stiffeners at

the lower tank side slopes are to have the same section

modulus as the side longitudinals. Their scantlings are also

to be checked for the load according to 4.3.1. For the

longitudinal stiffeners of the topside tanks within the upper

flange Section 9, B.1.5 is to be observed.

5.2 Main frames and end connections

The section modulus of main frames of single side skin

bulk carrier is to be increased by at least 20% above the

value required by Section 9, A.2.1.1

The section modulus W of the frame and bracket or integral

bracket, and associated shell plating, at the locations shown

in Fig. 23.1, is not to be less than twice the section modulus

WF required for the frame midspan area.

The dimensions of the lower and upper brackets are not

to be less than those shown in Fig. 23.2.

Structural continuity with the upper and lower end

connections of side frames is to be ensured within topsides

and hopper tanks by connecting brackets as shown in

Fig. 23.3.

Frames are to be fabricated symmetrical sections with

integral upper and lower brackets and are to be arranged

with soft toes.

The side frame flange is to be curved (not knuckled) at the

connection with the end brackets. The radius of curvature

is not to be less than r, in [mm], given by:

r = 0,4

bf 2

tf

where bf and tf are the flange width and thickness of the

brackets, respectively, in [mm]. The end of the flange is

to be sniped.

In ships with L < 190 m, mild steel frames may be

asymmetric and fitted with separate brackets. The face plate

or flange of the bracket is to be sniped at both ends. Brackets

are to be arranged with soft toes.

The web depth to thickness ratio of frames is not to exceed

the following values:

= for symmetrically flanged frameshw

tw60 k




= for asymmetrically flanged 50 k

frames

The outstanding flange b1 is not to exceed 10 timesk

the flange thickness, see Fig. 23.1.

In way of the foremost hold, side frames of asymmetrical

section are to be fitted with tripping brackets at every two

frames according to Section 9, A.5.5.

Where proof of fatigue strength according to Section 20

is carried out for the main frames, this proof is to be based

on the scantlings which do not include the 20 per cent

increase in section modulus.

For bulk carrier ship configurations which incorporate

hopper and topside tanks the minimum thickness of frame

webs in cargo holds and ballast holds is not to be less than:

tw,min = [mm]C (7,0 0,03 L)

C = 1,15 for the frame webs in way of the

foremost hold

= 1,00 for the frame webs in way of other holds

where L need not be taken greater than 200 m.

The thickness of the brackets at the lower frame ends is

not to be less than the required web thickness tw of the

frames or tw,min + 2,0 mm, whichever is the greater value.

The thickness of the frame upper bracket is not to be less

than the greater of tw and tw,min.

5.3 Minimum thickness of side shell plating

The thickness of side shell plating located between hopper

and upper wing tanks is not to be less than t p,min , in [mm],

given by:

t p,min = [mm]L

5.4 Weld connections of frames and end brackets

Double continuous welding is to be adopted for the

connections of frames and brackets to side shell, hopper

and upper wing tank plating and web to face plates.

For this purpose, the weld throat is to be (see Fig. 23.1):

S 0,44 t in zone “a”

S 0,40 t in zone “b”

where t is the plate thickness of thinner of the two connected

members.

Where the hull form is such to prohibit an effective filletweld, edge preparation of the web of frame and bracket

may be required, in order to ensure the same efficiency

as the weld connection stated above.

6. Topside tanks

6.1 The plate thickness of the topside tanks is to be

determined according to Section 12.

6.2 Where the transverse stiffening system is applied

for the longitudinal walls of the topside tanks and for the

shell plating in way of topside tanks, the stiffeners of the

longitudinal walls are to be designed according to

Section.12, the transverse frames at the shell according

to Section 9, A.3.

6.3 The buckling strength of top side tank structures

is to be examined in accordance with Section 3, F.

6.4 Sufficient continuity of strength is to be provided

for between the structure of the topside tanks and the

adjacent longitudinal structure.

7. Transverses in the wing tanks

Transverses in the wing tanks are to be determined

according to Section 12, B.3. for the load resulting from

the head of water or for the cargo load. The greater load

is to be considered.

The scantlings of the transverses in the lower wing tanks

are also to be examined for the loads according to 4.3.1.

8. Cargo hold bulkheads

The following requirement apply to cargo hold bulkheads

on the basis of the loading conditions according toSection 5, A.4.

8.1 The scantlings of cargo hold bulkheads are to be

determined on the basis of the requirements for tank

structures according to Section 12, B., where the load p bc

according to Section 4, C.1.4 is to be used for the load p.

8.2 The scantlings are not to be less than those required

for a watertight bulkhead according to Section 11. The plate

thickness is in no case to be taken less than 9,0 mm.

8.3 The scantlings of the cargo hold bulkheads are to

be verified by direct calculations.

8.4 Above vertically corrugated bulkheads, transverse

girders with double webs are to be fitted below the deck,

to form the upper edge of the corrugated bulkheads. They

are to have the following scantlings:

S web thickness= thickness of the upper plate

strake of the bulkhead

S depth of webB

22

S face plate = 1,5 times the thickness of the

(thickness) upper plate strake of the bulkhead.



Section 23 – Strengthenings for Heavy Cargo, Bulk Carriers, Ore Carriers B23 - 4

8.5 Vertically corrugated transverse cargo hold bulkheads

are to have a plane stiffened strip of plating at the ship's

sides. The width of this strip of plating is to be 0,15 H where

the length of the cargo hold is 20 m. Where the length of

the cargo hold is greater/smaller, the width of the strip of

plating is to be increased/reduced proportionally.

Fig. 23.1 Side frame of single side skin bulk carrier

Fig. 23.2 Dimensions of the upper and lowerbracket of the side frames .

Fig. 23.3 Connecting bracket in the hopper tank




9. Hatchway coamings, longitudinal bulkheads

9.1 Coamings

The scantlings of the hatchway coaming plates are to be

determined such as to ensure efficient protection against

mechanical damage by grabs. The coaming plates areto have a minimum thickness of 15 mm. Stays shall be

fitted at every alternate frame. The longitudinal hatchway

coamings are to be extended in a suitable manner beyond

the hatchway corners.

ln way of the hatchway corners full penetration welding

by means of double bevel T-joints or single bevel T-joints

may be required for connecting the coaming with the deck

plating.

9.2 Longitudinal bulkheads

Where longitudinal bulkheads exposed to grabs have got

a general corrosion allowance according to Section 3,

K.2. of tK = 2,5 mm in connection with 4.3.2 and 9.1

the notationG may be entered into the Certificate behind

the character of classification.

10. Loading information for Bulk Carriers, Ore

Carriers and Combination Carriers

10.1 General, definitions

10.1.1 These requirements are additional to those specified

in Section 5, A.4.3 and apply to Bulk Carriers, Ore

Carriers and Combination Carriers of 150 m length and above, and are minimum requirements for loading

information.

10.1.2 All ships falling into the category of this Section

are to be provided with an approved loading manual and

an approved computer-based loading instrument.

10.1.3 The following definition apply:

Loading manual is a document which in addition to the

definition given in Section 5, A.4.1.3 describes:

– which cargo hold(s) or combination of cargo holds

might be empty at full draught. If no cargo hold

is allowed to be empty at full draught, this is to

be clearly stated in the loading manual.

– maximum allowable and minimum mass required

of cargo and double bottom contents of each hold

as a function of the draught at mid hold position.

– maximum allowable and minimum required mass

of cargo and double bottom contents of any two

adjacent holds as a function of the mean draught

in way of these holds. This mean draught may be

calculated by averaging the draught of the two

mid-hold positions. – maximum allowable tank top loading together with

specification of the nature of cargo for cargoes

other than bulk cargoes.

– maximum allowable load on deck and hatch covers.

If the vessel is not approved to carry load on deck

or hatch covers, this is to be clearly stated in the

loading manual.

– the maximum rate of ballast change together with

the advice that a load plan is to be agreed with the

terminal on the basis of the achievable rates of

change of ballast.

Loading instrument is an approved computer system which

in addition to the requirements given in Section 5, A.4.1.3

shall be capable to ascertain that:

– allowable mass of cargo and double bottom contents

in way of each cargo hold as a function of the ship's

draught at mid-hold position

– allowable mass of cargo and double bottom contents

in any two adjacent cargo holds as a function of the mean draught in way of these holds, and

are within permissible values.

10.2 Conditions of approval of loading manuals

In addition to the requirements given in Section 5, A.4.2

the following loading conditions, subdivided into departure

and arrival conditions as appropriate, are to be included

in the Loading Manual:

– alternate light- and heavy cargo loading conditions

at maximum draught, where applicable.

– homogeneous light and heavy cargo loading

conditions at maximum draught.

– ballast conditions including those conditions, where

ballast holds are filled when the adjacent topwing-,

hopper- and double bottom tanks are empty.

– short voyage conditions where the vessel is to be

loaded to maximum draught but with limited amount

of bunkers.

– multiple port loading/unloading conditions.

– deck cargo conditions, where applicable.

– typical loading sequences where the vessel is loaded

from commencement of cargo loading to reaching

full dead weight capacity, for homogeneous

conditions, the relevant part load conditions and

alternate conditions, where applicable. Typical

unloading sequences for these conditions shall also

be included. The typical loading/ unloading

sequences shall also be developed to not exceed

applicable strength limitations. The typical loading

sequences shall also be developed paying due

attention to loading rate and the deballasting

capability1).

1) Reference is made to IACS recommendation no. 83 (August 2003),

“Note to Annexes to IACS unified Requirements S1A on Guidance for

Loading/ Unloading Sequence for Bulk Carriers.



Section 23 – Strengthenings for Heavy Cargo, Bulk Carriers, Ore Carriers D23 - 6

S typical sequences for change of ballast at sea,

where applicable.

10.3 Condition of approval of loading instruments

The loading instrument and its operation manual aresubjected to approval. In addition to the requirements

given in Section 5, A.4.5.1 the approval is to include:

– acceptance of actual hull girder bending moment

limits for all read out points.

– acceptance of actual hull girder shear force limits

for all read out points.

– acceptance of limits for each mass of cargo and

double bottom contents of hold as a function of

draught.

– acceptance of limits for mass of cargo and double

bottom contents in any two adjacent holds as afunction of the mean draught in way of these

holds.

C. Ore Carriers

1. General

1.1 Ore carriers are generally single-deck vessels with

the machinery aft and two continuous longitudinal

bulkheads with the ore cargo holds fitted between them,

a double bottom through out the cargo length area and

intended primary to carry ore cargoes in the centre hold

only.

1.2 Ships built in accordance with the following

requirements will get the notation "ORE CARRIER"

affixed to their character of classification. Entries will

be made into the Certificate as to whether specified cargo

holds may be empty in case of alternating loading.

Additional indications of the types of cargo for which

the ship is strengthened may be entered into the

Certificate.

1.3 For ships subject to the provisions of this paragraph

the requirements of B. are applicable unless otherwise

mentioned in this sub-section.

1.4 For ore carriers carrying also oil in bulk also

Section 24, G. applies.

1.5 Where reduced freeboards according to LLC 66

shall be assigned, the respective requirements of the Load

Line Convention are to be observed.

2. Double bottom

2.1 For achieving good stability criteria in the loaded

condition the double bottom between the longitudinal

bulkheads should be as high as possible.

2.2 The strength of the double bottom structure is to

comply with the requirements given in B.4.

3. Transverse and longitudinal bulkheads

3.1 The spacing of transverse bulkheads in the side tanks

which are to be used as ballast tanks is to be determined

according to Section 24, as for tankers. The spacing of

transverse bulkheads in way of the cargo hold is to be

determined according to Section 11.

3.2 The scantlings of cargo hold bulkheads exposed to

the load of the ore cargo are to be determined according

to B.8. The scantlings of the side longitudinal bulkheads

are to be at least equal to those required for tankers.

D. Fitting of Forecastle of Bulk Carrier, Ore Carriers

and Combination Carriers

1. Application

All bulk carriers, ore carriers and combination carriers are

fitted with an enclosed fore castle on the freeboard deck.

The structural arrangements and scantlings of the fore castle

are to comply with the requirements of Section 16.

2. Dimensions

The forecastle is to be located on freeboard deck with itsaft bulkhead fitted in way or aft of the forward bulkhead

of the foremost hold (see Fig 23.4 )

The forecastle height, HF ( m), above the main deck is not

to be less than the grater of:

S the standard height of a superstructure as specified

in the LLC 66, or

S HC + 0,5 (m)

HC = height of the forward transverse hatch coaming

of cargo hold No.1 (m)

In order to use the reduced design load for the forward

transverse hatch coaming ( see Section 17, B.1.14 ) and

hatch cover stoppers ( see Section 17, B.4.7 )of the foremost

cargo hold, the distances between all points of the aft edge

of the forecastle deck and the hatch coaming plate, F (m),

are to comply with the following ( see Fig 23.4 ):

F = 5 (m)HF

HC

A breakwater is not to be fitted on the forecastle deck for

the purpose of protecting the hatch coaming or hatch covers.

If fitted for other purposes, the distance between its upper

edge at centre line and the aft edge of the forecastle deck,B ( m ),is comply with the following ( see Fig 23.4 ):

B 2,75 HB (m )



Section 23 – Strengthenings for Heavy Cargo, Bulk Carriers, Ore Carriers D 23 - 7

HB = is the water height of the breakwater above the

forecastle.

Fig. 23.4 Dimensions of forecastle

vol2_section23

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