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8/10/2019 GA Lecture

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General Arrangement Lecture Notes - by Prof. S.C.Misra

1

Draw outline of profile, upper deck, forecastle deck. If upper deck is stepped show it that

way. Forecastle deck should have a height more than 2.3m such that the required bow height

as per ILLC rules is obtained (normally takes upto 3.0 m). Longitudinally, it should extend

from forward end till the fore peak bulkhead or to the next bulkhead. The reason for a

forecastle deck are:

Minimum bow height as per ILLC (reduction of probability of deck wetness)

Forecastle deck area for anchoring and mooring equipment

Adequate volume underneath for storage and chain locker etc.

Provide additional cargo space.

Fix frame spacing (IRS):

1.3 Frame spacing

1.3.1 The normal frame spacing between aft peak and 0.2 L form F.P. may be taken as :

450 + 2L [mm] for transverse framing

550 + 2L [mm] for longitudinal framing. However, it is generally not to exceed 1000

[mm].


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1.3.2 Elsewhere, the frame spacing is generally not to exceed the following :

- In peaks and cruiser sterns:

600 [mm] or as in 1.3.1, whichever is lesser.

-

Between collision bulkhead and 0.2L from F.P.:

700 [mm] or as in 1.3.1, whichever is lesser.

Fix collision bulkhead and aft peak bulkhead (easy to erect) and determine number of

bulkheads (IRS):

2.1 Number of bulkheads

2.1.1 The following transverse watertight bulkheads are to be fitted in all ships:

-

A collision bulkhead;- An afterpeak bulkhead;

-

A bulkhead at each end of the machinery space.

For ship without longitudinal bulkheads in the cargo region transverse watertight bulkheads

are to be fitted so that the total number of bulkheads is not less than that given in table 2.1.1.

Table 2.1.1. : Total no. of bulkheads

Engine Room Location

Ship length [m] Aft* Elsewhere

L 65 3 3

65 < L85 4 4

85 < L105 5 5

105 < L115 5 6

115 < L125 6 6

125 < L145 6 7

145 < L165 7 8

165 < L190 8 9

L > 190 Specially considered

* with aftpeak bulkhead forming after boundary of machinery

Space

2.1.2. The ordinary transverse watertight bulkheads in the holds should be spaced at

reasonably uniform intervals. Where non-uniform spacing is unavoidable and the

length of a hold is unusually large, the transverse strength of the ship is to maintain by

providing additional web frames, increased framing etc.

2.1.3. Proposals to dispense with one or more of these bulkheads will be considered, subject

to suitable structural compensation, in case they interfere with the requirements of a

special trade.


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2.2 Position of collision bulkhead

2.2.1 For passenger ships, the position of the collision bulkhead will normally be

determined in accordance with the requirements of the International Convention for

safety of Life at Sea (SOLAAS).

2.2.2.

For ships other than passenger ships, the distanceC

X from the forward perpendicular

to the collision bulkhead is to be between the following limits:

Xc,min = 0.05LL-XR[m] for L < 200 [m].

=10XR[m] for L 200 [m].

Xc, max = 0.08 LLXR[m].

For ships with ordinary bow shape;

XR= 0

For ships having any part of the underwater body extending ford of the forward

perpendicular e.g., a bulbous bow;

XR= the least of:

- G/2;

- 0.015 LLand

- 3.0 [m]where,

G = the distance from forward perpendicular to the forward end of the protruded part [m]

LL= the load line length of the vessel [m], as per International Load line Convention (see

Ch.1)

Fix the position of engine room aft bulkheadmost of the times it is the aft peak bulkhead.

Fix the position of engine room forward bulkhead.


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Divide the cargo space into holds by placing the remaining bulkheads. The principle of

placing the bulkheads may be based on cargo requirement:

Equal length holds

Alternate large and small holds (bulk carriers/ products tankers/ container ship (as

shown in the beginning )

A single large hold (for large cargo in a multipurpose carrier)

Decide on longitudinal bulkheads - in double hull tankers, container ships etc. Discuss why in

container shipsballast requirement and box girder.

Decide on sloped bulkheads on top and bottom wing tanks in a bulk carriertop tank slope

should be more than angle of repose of cargonormally 300

. Bottom tank slope is normally450. Discuss why sloping bulkheads are provided in bulk carriers.

The longitudinal and sloped bulkheads have a good relationship with cargo and ballast

capacity; so this requires to be checked.

Decide on double bottom height which should be more than centre girder height d as given

below (IRS):

d = 250 +20 B + 50 T

where d is in mm and B and T are in m. The tank capacity below db should be adequate.

Decide on height of tween deck(s). Ships carrying packaged cargo, such as multipurpose

ships, non-standard cargo sizes such as refer cargo or some other cargoes such as cars etc.,

require large floor space. So, to provide more deck area, a number of tween decks are to be

provided. The height of each tween deck should be adequate for the maximum height of

cargo in that deck space. This is not required for volume based cargo such as tankers and bulk

carriers. In container ships, the top of a container serves as the floor for the next higher

container. So container ships do not require tween decks.

Hatch openings and hatch covers.


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Ballast Tank capacities and tank distribution.

Balast water is required for empty voyage to have proper sinkage, trim and stability.

Excessive ballast capacity is bad since it is expensive and takes up useful space. Ballast

capacity should be such that full propeller immersion is obtained at the aft end and forward

draught is not too low to avoid the harmful effects of slamming. To avoid excess scantlingIRS recommends a minimum forward draught of 0.04LBP (=TF). For

BPFBP LTL 04.0025.0 , the ford scantlings are to be increased. For a TF< 0.025 LBP, direct

calculations are to be submitted for approval.

Approximately in a ballast voyage, displacement is 0.5 of fully loaded displacement which is

about 0.55 of full draught.

Ballast distribution should be such that excessive hogging moment is avoided in this

condition. Segregate the B.W. tank from any other liquid tank.

The following points may be considered while making tank arrangements:

1. No access is required except for cleaning and maintenance. Minimum two manholesare to be provided on top preferably at diagonal corners.

2. Tanks and pipes carrying a particular type of liquid must be segregated from those

carrying another type of liquid.

3. FW tank should not have any tank adjacent to itself. So an FW tank and any other

tank must be separated by a cofferdam. For the same reason, FW tanks cannot be

placed below LWL.

4. Since total liquid carried relatively low, the tanks may conveniently be situated in the

lower portions to increase transverse stability.5. To simplify piping arrangements

FW tanks should be near E.R. as well as accommodation

D.O. & H. F. O. tanks should be near the E.R. for reducing piping length. D. O. can

conveniently be stored in E.R. double bottom.

B.W. tanks should be well distributed all over the length and breadth of ship to help

stability and trim requirements. Pipes should not run inside tanks carrying another

liquid, i.e. FO pipe should not run in B.W. tank.

Consumable tanks (HFO, D.O. & F.W.) should be so located that their consumption

does not cause unnecessary adverse trim.

They should not cause unduly adverse free surface effects. So these tanks should bedivided into smaller tanks with reduced breath. Too many small tanks, however, will

make complicated piping system.

B.W. tanks are either fully pressed or empty.

B.W. tanks should be distributed all over the length of ship with sufficient capacity in

the peak tanks to adjust for required trim and stability.

Tanks should be distributed symmetrically about C. L. so that advice heel effects are

not felt. If there is any such effect (damage stability) cross-connection between port

and starboard tanks may be provided.


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6.

The boundaries of d.b. tanks, deep tanks etc. should be designed to withstand

hydrostatic pressure.

7. The tank distribution should not adversely affect the longitudinal strength of hull

girder.

ACCOMODATION PHILOSOPHY

Consideration for accommodation layout in merchant ships:

PrivacyIndividual

Group

Privacy is status based

[ bed rooms, living rooms, lobby etc.]

FacilitiesSpace per person

Galley, pantry and dining spaces

Toilet and WC (attached or common)

Recreation

Facilities and fittings as per status

ServicesLaundry and drying room

Linen stores

Lockers

Deck stores etc.

Provision and stores

Cold provision stores [diary, meat and vegetables]

Duty mess

Change room and wash space

HabitabilityControl of interior environment

Ventilation

Air conditioningAcoustic

Vibration

Aesthetic

SafetyConstruction

Fire zones

Passages and staircases

LSA arrangement

FFA arrangement

Fire alarms


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Production, operation and Maintenance aspectsRoom size standardization

Fittings and furnishing standardisation

Simple and easy to maintain

Long term habitability

Comparative Manning Levels in Indian and Foreign Flag Vessels (1990)

INDIAN FLAG VESSEL WITH INDIAN MANNING FOREIGN FLAG VESSEL WITH INDIAN MANNING

OFFICERS OFFICERS

Master 1 Master 1

Chief Officer 1 Chief Officer 1

Second Officer 1 Second Officer 1

Third Officer 1 Third Officer 1

Radio Officer 1 Radio Officer 1

Chief Engineer 1 Chief Engineer 1

Second Engineer 1 Second Engineer 1

Third Engineer 1 Third Engineer 1Fourth Engineer 1 Fourth Engineer 1

Fifth Engineer 1 Electrical Officer 1

Electrical Officer 1

Nautical Cadet 1

Sub Total + Cadet 12 Sub Total 10

PETTY OFFICERS PETTY OFFICERS NIL

Catering Officer 1

Petty Officer 1

Maintenance Fitter 1

Assistant Fitter 1

Wireman 1

Sub Total 5

CREW CREW

DECK GENERAL PURPOSE

Deck Serang 1 Bosun 1

Seaman/Helmsmen 3 AB/GP -1 3

Seaman -1 4 ORD SN/GP -2 2

Seaman -2 3 Motorman/GP -1 3

Deck Utility Hand 1 Wiper/GP -2 1

Crew Cook 1 General Cook 1

Crew Cook 1

Messman /GP -2 2

Sub Total 13 Sub Total 14

ENGINE ROOMEngine Serang 1

Donkey Greasers 3

Engine Room Ratings 3

Sub Total 7

CATERING

Chief Cook/Baker 1

Second Cook 1

Pantryman 1

General Stewards 4

Saloon Utility Hand 1

Sub Total 8

TOTAL CREW 28 TOTAL CREW 14

TOTAL (OFFICERS TOTAL (OFFICERS+ P.O.S + CREW) 45 + CREW) 24


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Additional for Tankers Additional for Tankers

Pumpman 1 Fitter 1

Asst. Pumpman 1 Pumpman 1

Total For Tankers 47 Total For Tankers 26

Ref.: INDIAN SHIPPING, Vol. 45, Nos. 1-2

Manning of Typical Medium size Cargo Vessels in India (2005)

Complement

Senior Officers

Captain 1 Ch. Engineer 1Ch. Officer 1 2

ndEngineer 1

Officers2

ndOfficer 1 3

ndEngineer 1

3rdOfficer 1 4thEngineer 1

Owner 1Pilot 1

Petty officers 4Crew 10

Total complement 24

Depending on Cargo and Ship type, specialist crew and officers may be added.

Norms of Accommodation

Crew:

Max 4 persons / room - 2.8m2/ personor

10m2/ person - Single room not including toilet

Toilet: at least1 for 8 person (Common)or attached

Officers:14m

2and attached toilet and WC

CE & Captain :37m

2and attached toilet and WC

Clear head room in all accommodation rooms: 191 cm.

Hospital: required in ships having crew > 128 & voyage >3 days withat least 1berthfor every 12 persons


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