[icedcappucino]

1) What is the purpose of subdivision of ships.
– The purpose of subdivision is “To provide the ship into water tight compartments, therefore reducing the risk of sinking, when damaged.”
– Effectiveness depends upon the bulkhead height and spacing.
– It can also prevent the spread of fire to certain extent.

2) List the function of
A) Transverse bulkhead
B) Longitudinal bulkhead.

A) Transverse bulkhead
– contains longitudinal extent of flooding.
– maintains transverse form
– limits length of cargo
– end compartments could cause large trim and could cause loss of stability, therefore they are divided with transverse bulkhead to make them small.
– prevent the spread of fire to certain extent.
B) Longitudinal bulkhead
– contains transverse extent of flooding.
– adds additional strength
– prevents excessive list due to free surface effect.
– prevent the spread of fire to certain extent.

3) State the minimum number of bulkheads permissible for a cargo vessel fitted with machinery space amidships.
– the minimum numbers of bulkheads which must be fitted are stipulated under the Classification Society Rules.
– a collision bulkhead must be fitted.
– an aft peak bulkhead must be fitted.
– watertight bulkhead must be provided at each end of the machinery space.
– a vessel with the machinery space amidships, a minimum possible number of watertight bulkheads is four.
– with machinery space at the aft, this could be reduced to three, the aft peak bulkhead being at the aft of the machinery space.

4) Give the requirements relating to the collision bulkhead.
– in respect of location on passenger ship and cargo ship.
– conditions under which the variations are modified in respect of i) cargo ships ii) passenger ships
Collision bulkhead on Cargo ship
– collision bulkhead is fitted at a distance of not less than 5% of the ship length or 10m (whichever is less),
Not more than 8% of the ship’s length abaft the stem at the load waterline.
Collision bulkhead on Passenger ship
– collision bulkhead on passenger ship is governed by the Merchant Shipping Act and is as follows,
– at a distance from the forward perpendicular at not less than 5% of the length of the ship and not more than 3m + 5% of the length of the ship.
Variation in the position of collision bulkhead on cargo ships and passenger ships.
Variation in the position of collision bulkhead is modified under the following conditions,
A) where any part of the ship below the waterline extends forward of the forward perpendicular Eg. Bulbous bow , the distance stipulated above is measured from a point either.
– at the mid length of such an extension. OR
– at a distance 1.5% of the length of the ship forward of the forward perpendicular, OR
– at a distance 3m forward of the forward perpendicular
Which ever gives the smallest measurement.
B) where a long structure is fitted, the forepeak or collision bulkhead shall be extended weathertight to the deck next above the bulkhead deck. The extension need not be fitted directly above bulkhead below.
C) Where bow doors are fitted and a sloping loading ramp forms part of the extension of the collision bulkhead above the bulkhead deck, the part of the ramp which is more than 2.3 m above the bulkhead deck may extend forward of the limits prescribed for bulkheads on passenger ships.

5) Define the following and explain their significance in the subdivision of passenger ships.
A) Bulkhead deck
B) Margin line
C) Watertight
D) Weather tight

A) Bulkhead deck
– The deck to which the main bulkheads extend watertight is called the bulkhead deck.
– It is normally the freeboard deck.
– But it could be a superstructure deck or a deck below the freeboard deck.

B) Margin line
– this is an imaginary line, drawn parallel to and three inches below the bulkhead deck at side.
– The ship is deemed to remain afloat after flooding if calculation shows that the margin line is not submerged.

C) Watertight
– if the compartments, fitting are able to withstand a head of pressure, they are said to be watertight.
– for a bulkhead to be watertight it is required to withstand a head of water pressure to the bulkhead deck.
– testing is done by a water pressure test.

D) Weather tight
– means any sea condition water will not penetrate into the ship.

6) List three methods of testing acceptable/used by classification societies.
Three methods of testing
– Air pressure test, if any suspect joints are then subjected to soapy liquid solution test.
– Hose test
– Head of water test

7) List the requirements relating to testing of
A) Water tight bulkhead
B) Forepeak tanks
C) Double bottom tanks
D) Deep tanks

A) Testing of Water tight bulkheads
– all water tight bulkhead should be tested with the method of hose test.
– for collision bulkhead (the forepeak bulkhead and aft peak bulkhead), if they are formed boundaries of the tank, then “head of liquid” test should be done by filling the peaks with water up to the load waterline.

B) Testing of Forepeak tanks
– subject to hose test.
– “head of liquid” test also should be done, by filling the peaks with water up to the load waterline.

C) Testing of Double bottom tank
– tested to max water head in service (to the top of air pipe),
– test can be done alternately by air pressure test. (before any protective coatings are applied) air pressure may be raised up to 0.21 kg/cm2 and then lowered to a test pressure 0.14 kg/cm2.
– any suspect joints are then subjected to a soapy liquid solution test.
– water head pressure tests will also be carried out in conjunction with air test.

D) Testing of Deep tank
– tested to max water head in service (to the top of the air pipe).
– this should not be less than 2.5 m above the crown of the tank.

8) Describe with the aid of a sketch (s) the construction of a watertight bulkhead and its attachments to sides, deck and tanktop.

– Bulkhead is a plating welded as horizontal strakes.
– plate thickness increases with depth
– they can be intercoastal between decks.
– Stiffeners are attached to the plain bulkhead.
– Stiffeners are normally bracketed but could also be directly welded to the tank top.
– they could also be supported by horizontal stringers (normally found on tank boundaries). This permits an increase in stiffeners spacing.
– Swedges and corrugated bulkheads are now common, they are normally vertical. They are used in liquid carrier to reduce free surface effect in the tanks.
– Boundaries of bulkheads are welded with double fillet welded.
– Shelf plates fitted on bulkheads on ships that have tween decks. (tween deck will be welded on that plate)
– Passage of piping and ventilation trunks on bulkheads must be avoided, however if required, pipes must be flanged, and a WT shutter provided for trunks.

9) State the regulations in relation to the penetration of watertight bulkheads.
– where frames or beams pass through a bulkhead, such a bulkhead shall be made structurally water tight without using wood or cement.
– pipes piercing the collision bulkhead shall be fitted with suitable valves operable from the above the freeboard deck and the valve chest shall be secured at the bulkhead inside the forepeak.
– the valve may be fitted on the after side of the collision bulkhead provided that the valves are readily accessible under all service conditions and the space in which they are located is not a cargo space.
– all valves shall be steel, bronze or other ductile material. Valves of ordinary cast iron or similar material are not acceptable.
– two pipes may be allowed to pierce the collision bulkhead if the forepeak is divided into two compartments. These compartments must be designed to hold two different liquids.
– No door, manhole, ventilation duct or other opening shall be fitted on the collision bulkhead.
– pipes passing through bulkheads are either welded, or fastened to the bulkhead by studs or bolts screwed through clear holes in the plating.
– this ensure that, if the bolt breaks, part of it will be left in the bulkhead, otherwise a clear hole might be left in the plating.
– where a ventilation trunk passes through, a watertight shutter is to be provided.

View post on imgur.com

[Author]

Posts