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CH 2 : NAUTICAL TERMS

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Harbour

A sheltered area of the seaVessels can be launched here / taken for repair /

seek refuge in time of storm

Types of Harbour:

Natural (eg Mumbai and Kandla)

Semi Natural (eg. Visakhapatnam) Artificial (eg. Chennai)

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TYPES OF HARBOURS

NATURAL

SEMI NATURAL

ARTIFICIAL

Harbour Area

Harbour Area

Harbour Area

Breakwater

Breakwater

WindWind

Breakwater

Wind

WindWind

Wind

Shore

Shore

Shore

Pierhead

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Breakwater

Constructed to protect the enclosed area of water

from storm waves

The monolithic structure at the tip of a breakwateris called the Pierhead

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Port

It is a harbour where terminal facilities such as

handling of stores, landing of passengers and

cargo, etc. are added to itEvery port is a harbour; the converse is not true.

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Tides

They are periodic movements in the level of the

surface of the sea due to the periodical forces

(differential in gravitational pull) of Sun and MoonTides with a period of about a day are called

diurnal tides; those with 12 h period are called

Semi-diurnal tides

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Bores

The sudden rise of water up a channel

It is an extreme case of the shallow water effect

(eg. Tsunami)

The water wall may be 0.3m to 4.5m high

Wharves or Quays

Constructed parallel to shore or Breakwater within

the harbour

Meant to permit berthing of vessel alongside for

cargo working

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Jetties and Piers

Solid/ open structures with wide platform on top to

permit cargo handling of vessels

Locked Basin

An enclosed basin where a No of vessels can beberthed

Their entrance is controlled by gates

The water level within the basin can be

independent of outside water level changes

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Ballast

It is the weight added to improve the stability of the

ship when unloaded

Separate Ballast compartment are provided for the

purpose, in whichballasting is being done (water ispumped in)

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Dry Dock

Provided for construction, repair and maintenance

of ships

Types:

Graving Dry Dock

Floating Dry Dock

Marine Railway Dry Dock

The bottoms of ships require scraping and cleaningto maintain speed

(contd)

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Dry Dock (contd..)

The docking arrangements expose the ships

exterior fully and keep it out of water

The ship enters the dock, then the dock gate is

closed. The dock is raised by unballasting

(pumping out of water)

(Esquimalt Dry Dock in British Columbia has a

length of 350m and width of 41m. It is constructed

with concrete and granite altars. The 3 pumps have a

capacity of 2,70,000 litres/ min each; and the dock

can be emptied in 4h)

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LOADING TERMS FOR SHIPS

Load Line / Plimsoll Line

Indicated by a line or set of lines out5side merchant

ships

It is the water level upto which the ship can be

legally loaded

Displacement Load

The weight of ship and cargo loaded to the LoadLine

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LOADING TERMS FOR SHIPS

Displacement Light

The weight of ship in kN without cargo, fuel and

stores

Dead Weight Tonnage

It is the Displacement Load less Displacement Light

It represents the carrying capacity of a ship

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Littoral Drift

It is a zig zag deposit of sand along the shore after

erosion along the shore due to tides

On such exposed shore, if a harbour is constructed in

the path of Littoral Drift, there will be accumulation

of sand on one side and erosion on the other side

Entrance Locks

These are the arrangements for accessibilityrestrictions into a harbour

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Jetties

These are the structures in the form of piled

projections

Built out from the shore to deep water

Provided where harbour entrance is affected by

Littoral Drift or the sea is shallow for a long distance

Used to berth vessels alongside

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Trestles

Light piers designed to withstand only vertical loads

Moles These are the structures formed by rock filling and extending

from shores

Similar to Trestles, but constructed where water depth is lessthan 3m

Dolphins

These are used for anchorage purpose in the sea

Fenders

These are cushioning units to prevent damage due to

collision between the vessel and the pier/ buoy/ jetty, etc.

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LOADING TERMS FOR SHIPS

Gross Tonnage

It is the carrying capacity, expressed in volume

(units of 100 cum)

Net Tonnage

It is the Gross Tonnage minus the space provided for

crew, machinery, engine room and fuel

Cargo Tonnage

The commercial expression for the cargo carrying

capacity in the vessel (measured in volume / wt)

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BASIN WITH PROTECTIVE BREAKWATER

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BUILT DRY DOCK

ALTARS

KEEL

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CONTAINER SHIP

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ENTRANCE LOCK

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CROSS SECTION OF A LOCK

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DOCK AND BASIN

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DRY DOCK

ENLARGED CROSS SECTION

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MARINE RAILWAY DOCK

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OFF SHORE TYPE FLOAGING DOCK

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ROCK MOLE

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2-BERTH PIER

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WIND EFFECT ON SHORE LITTORAL DRIFT

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FLEXIBLE DOLPHIN

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FENDERS