DOUBLE BOTTOM TANKS

Volume enclosed between the ship's bottom up to the turn of the bilge, abaft the collision bulkhead and forward of the aft bulkhead and tank top in the cargo holds is termed as double bottom tanks. Double bottom tanks are identified numerically from forward to aft.

Double bottom tanks do not extend in way of the peak tanks and Main Engine room space.

Double bottom tanks are sub-divided longitudinally to form Port and Starboard Tank by water tight girders or walls of the duct keel, Double bottom tanks are divided by water tight floors.

Double bottom tanks are strengthened by bracket floors, solid floors, tank side brackets, inter coastal girders, center girder, longitudinal members which are located under the tank top and on the inner surface of the bottom plating, all these members jointly contribute in strengthening longitudinal and transversely the bottom structure of the ship.

Tank side brackets are fitted along the length of the double bottom tanks in way of the turn of the bilge.

Double bottom tanks are generally used for ballast water, fuel, fresh water / boiler feed water.

Every double bottom tank must be provided with air pipes, sounding pipes, filling and suction pipe line arrangements. 

SHIP’S TANKS

PEAK TANKS :

Tanks located at the extreme end of the ship are termed as peak tanks. Tanks at the fore end of the ship is termed as Fore Peak tank, tank at the aft end of the ship is termed as Aft Peak

Tank.

Fore peak tank is the volume enclosed between the Collision bulkhead, ship’s hull plating, and the fore peak tank top.

Aft peak tank is the volume enclosed between the Aft Bulkhead, Ship’s hull plating, and the Aft peak tank top.

These tanks are located in the high stress regions of the ship, hence they have to be fitted with special strengthening arrangements termed as panting arrangements.

Fore peak and aft peak tank is generally used as Ballast water tank and fresh water tank respectively.

Access to these tanks is provided through manhole located on the tank top.

Since both theses tanks are used for storing liquid, these tanks must be provided with air pipes for intake and expulsion of air during liquid movements to avoid vaccumization, sounding pipes for calculating quantity of liquid present in the tank, filling and pumping out pipe line arrangements.

General Information on Each plan

In general each of the ship plan will have the following information: 

1. Name of the plan
2. Name of the ship, endorsement in-case of change of ship name
3. Principal Dimensions
4. Name of ship building Yard
5. Year and place of built
6. Plans drawn and verified by
7. Plans Approved by
8. Ship owners Name
9. Scale of projection

SHELL AND DECK PLATING

General: Seams, or ‘Edge Laps’, are joints which run fore and aft; that is, along the longer edges of the plates.

Butts, or ‘End Laps’, are joints which run athwartships, or vertically; that is, along the shorter edges of the plates.

Strakes are continuous, fore and aft, lines of plates.

Garboard strakes are the strakes of shell plating next to the keel on either side (i.e. the ‘A Strake’).

Sheerstrakes are the upper strakes of shell plating on either side, next to the upper deck. (The ‘J strake’ in the sketch opposite.)

The Deck Stringer is the outboard strake of deck plating, which is connected to the sheerstrake. (Strake ‘E’ on the deck plan, opposite.)

Stresses on Plating: The obvious purpose of plating is to keep out water and to tie together the ship’s framework. It also plays an important part in resisting longitudinal bending stresses, so it needs to be stronger amidships than at the ends, particularly at the deck and bottom. In long ships, it may

also be necessary to strengthen the shell plating against shearing stresses at about the half-depth of the ship, in the region of about one-quarter of the ship’s length from either end.

Shell Expansion and Deck Plans: These are plans which show all the plates in the hull, drawn to scale. They also show many other details, including frames, floors, deck edges, stringers, etc. The partial plans shown in the plate, opposite, are simplified and are merely intended to illustrate the fitting of shell and deck plating.

Identifying Plating: Strakes of shell plating are distinguished by letters from the keel outwards, the garboard strake being strake ‘A’. The plates in each strake are usually numbered from aft to forward. For example, plate D5 would be the fifth plate from aft in the fourth strake from the keel.

Strakes of deck plating are lettered from the centre line, outboard; whilst deck plates are numbered from aft to forward.

Stealer Plates: The girth of the ship decreases toward the ends and so the width of plates must be decreased in these parts. To save making the plates too narrow at the ends of the ship, it is usual to run a number of pairs of adjacent strakes into one. This is done by means of a stealer plate.

This can be seen in the upper shell expansion plan, given here; in which Plate B4 is a stealer, since it runs the B and C strakes into each other. Note how the stealer and the plates beyond it, always take the name of the lower of the strakes which are run together.

PUMPIMG AND PIPE LINE ARRANGEMENTS PLAN

A copy of the plan is always displayed in conspicuous locations accessible and frequented by the ship's crew

This plan will familiarizes the seaman with the location of various Pumps i.e Bilge, Ballast, Cooling water circulating, Lubricating, Fresh water, Cargo Fuel oil, Fire and emergency fire pump etc.

This plan familiarizes the seaman with the pipe line layout on Deck, through Double Bottom tanks or duct keel of various systems i.e Steam, hydraulic, ballast, fuel oils, fresh water, cooling water, hold

bilge.

In case of tankers, cargo loading and discharge lines, associated valves and valve chest, pressure relief valves for various systems on board.

This plan is used for tracing pipe lines for purpose of safe and smooth operations, repairs and maintenance.

The Pumping and pipe line system is in colour code indicated in the key plan.

Further details of pipes size, valves, associated valve chests can be obtained from the appropriate plans.

LIFE SAVING APPLIANCES PLAN

            A Copy of the L.S.A plan is always displayed in conspicuous locations accessible and frequented by the ship’s crew.

This plan will familiarize the seaman with the location of various Life Saving Appliances on board.

Information available on F.F.A plan will be as follows:

1. Quantity and Location of Life Boats, Life Rafts indicating their carrying capacity.
2. Quantity and location of Life Buoys and their attachments
3. Quantity and location of Adult and child size life jackets.
4. Location of SART AND EPIRB
5. Location and quantity of thermal protective suits.
6. Location of blankets, stretcher and first aid box.
7. Location of rescue boat
8. Quantity and location of hand flares and distress rockets
9. Quantity and location of Line throwing apparatus.

FIRE FIGHTING APPLIANCES PLAN

A Copy of the F.F.A plan is always displayed in conspicuous locations accessible and frequented by the ship’s crew.

This plan will familiarize the seaman with the location of various Fire Fighting Appliances on board. Information available on F .F.A plan will be as follows:

1. Location, quantity and type of portable and mobile fire fighting extinguishers on board. Location of fixed fire fighting installation i.e CO battery, high expansion Foam, inert gas plant, the pipe line layout, remote control operation location, exit nozzles of the fire fighting agent etc
2.  Location of general / fire alarm buttons.
3.  Location of International shore connection and coupling.
4.  Location of Fire Hoses, types of nozzle, fire axe, fireman suit, SCABA, SOPEP locker, emergency head-quarters, emergency light, stretcher, blankets etc.
5.  Location of sand box, emergency fire pump, emergency escape routes.
6.   Location of line throwing apparatus, distress rocket parachutes etc.
7.   Location of emergency cut out for forced and emergency ventilation.
8.   A copy of this plan is always placed in a fire proof and water tight steel tube case near the gangway under an emergency light

All the above information will be indicated by a key index on the plan.

CONTENTS OF GENERAL ARRANGEMENT PLAN

A copy of the G.A plan is always displayed in conspicuous locations accessible and frequented by the ship’s crew. The general layout is displayed through a side profile, mid-ship section and Arial view of decks on board a ship. 

The general arrangement plan will familiarize the seaman with the Following information:

1. No. of Hatches, No. of cargo compartments on the ship.
2. Location of various double bottom tanks, topside tanks, peak tanks, Cofferdams etc.,
3. No. and location of fuel oil tanks.
4. Location of various decks, engine room, saloon and store rooms etc.
5. Salient features of lift gear.
6. Location of emergency machinery i.e steering gear, generator, fire pump etc.
7. Location of Crew and Master’s accommodation.
8. Location of Navigation Bridge, chart room, monkey island etc.
9. Salient of deck fittings, lifting gear, deck machinery, gangway etc.

 More details of any particular space, fittings must be refereed to appropriate plan.