Class 2 Naval

8/11/2019 Class 2 Naval

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Ship Construction

1 Enumerate potentially hazardous situations when everywatertight door in a passenger vessel must be closedexcept when a person is passing through it.

1)In the of fog2)when manouvering3)In congested seaways

oors would also be closed in the event of a collision! "reand in #ooding

2 explain how the watertight door control system isdesigned in order to ensure that the crew are not trappedor in$ured by the door when it operates.

%he watertight door system is designed in order toensure that the crew are not trapped or in$ured by thedoor when it operates by means of&'udible and visual alarms when the door is in operation.

%here is also an operating lever by the door which willallow you to stop the doors operation! plus close the doorand open it.

3 sketch in detail a bearing designed to transfer the full weight of the rudder

and stock to the ships structure.sketch


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4 explain why the thrust faces of the rudder carrier are so countered

The thrust faces of the rudder carrier are countered as they assist in the central location ofthe rudder stock.

5 explain why a rudder may tend to lift and how this tendency is countered.A rudder may tend to lift due to heay seas and weather. This is preented by fitting

!umping stops between the upper surface of the rudder and the stern frame.

" #ater ballast tanks of dry cargo ships and cargo tanks of oil tankers may be protected

from corrosion by sacrificial anodes.

describe how anodes preent corrosion$


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Anodes preent corrosion by becoming a sacrificial metal. Anodes are less noble metals

in the periodic table than the cathode% which is steel in this case. The saltwater sets up a

galanic couple% galanic current attacking the sacrificial anodes% which coneys aprotectie coating around the steel work in the tank &the cathode'. The anodes eentually

waste away and hae to be replaced.

( state three suitable materials that can be used for anodes$

These three metals are suitable fore anodes as they are lower in the galanic series than

iron$)inc% *agnesium% Aluminum

+ state any restriction on the use of these materials as anodes in oil tankers

,estriction on these materials as use as an anode in oil tankers is that *agnesium isbanned as there is a risk of sparks% fires and explosion with magnesium . .

- State the purpose of each of the following and describe where they are located in the

ship structure$

a'duct keel$The duct keel is situated in the double bottom of some essels% it runs from the forward

engine room bulkhead to the collision bulkhead% they are used to carry pipework% making

accessible when cargo is loaded. See Sketch.

b'sternframe aft heel$

Sternframe aft heel is where the heel block is placed when the essel is in drydock% this

part of the essel has added strength to support the after end of the ship. See Sketch.

c'forward and after sheer$

orward and after sheer is the rise of the deck at the forward end of the ship and at theafter end% this shape proides added strength% plus keeps water off the deck. See Sketch.

d'round of bilge,ound of bilge is found where the side of the ship meets the bottom% it is rounded to gie

extra strength% plus it also reduces racking .&side motion of the ship ' See Sketch.


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/0 State with reasons% the purpose of each of the following with regard to ship hull forms.

a'bulbous bow

The bulbous bow allows the ship to cut through the water better due to it1s shape% this

gie s the ship more speed and improes fuel economy% also it gies the ship morebouancy. 2t does this by reducing the bow wae.

b'flare

lare is the shape of the ships bow coming up from the water line% it helps keep the bowaboe the water in heay weather% especially on smaller ships when pitching. 2t also

allows the anchor to be lowered without hitting the ships side.

c'bilge keels


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ilge keels hae the prime function of damping the rolling motion of the ship% they also

gie added longitudinal strength at the bilge.

d'sheer

Sheer is the curature of the ships deck from forward to aft% it gies increased strength

and keeps water off the deck.

e'camber

Camber is the curature of the ships deck from port to starboard% it keeps water off thedeck% it also gies added strength to the ships hull.


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// escribe suitable methods for testing each of the following for watertight integrity$

a'a hollow rudder

A hollow rudder would be tested in drydock by filling the rudder with water and checking

it for leaks% a small pressure may be applied to aid this% ie a head of pressure from a standpipe of metres or 0. A, air pressure.


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b'a bulkhead

ulkheads would be tested by means of a simple hose test. 6n construction% bulkheads

are hydrostatically tested.

c'a double bottom tank

ouble bottom tanks are tested by filling them completely with water% including thesounding pipe% by doing this% a small head of pressure is applied to the tank% ad!acent

tanks% cofferdams around the tank being tested would be checked.

d'a watertight door

A watertight door is checked for watertight integrity by means of a simple hose test% but

on construction are hydrostatically tested.

e'shell plating

Shell plating can be tested for watertight integrity by a acuum test% where in drydock% a

sealed box is placed oer welds and eacuated of air% loss of acuum showing leaks%

welds on ships plating may also be x7rayed to check the integrity of the weld.

/ a'explain the purpose of fitting external anodes to a ships hull.The purpose of fitting external anodes to a ships hull is to protect it against corrosion by

using a metal such as aluminum or 8inc to form anode of the corrosion cell% in preference

to the cathodic steel of the ships hull.

b'i'sketch a method of securing external anodes to the ship hull.

sketch

ii'show% with the aid of a sketch % where external anodes are placed. sketch

iii'explain how it may be ascertained that anode replacement is necessary.

2t can be ascertained that anode replacement is necessary by haing an underwaterinspection% and checking the amount of anode material left. ut generally anodes are

designed to last from drydock to drydock% the si8e of anode used is determined by that

length of time.


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/3a'sketch a simple cross section of the machinery space bilge in!ection ale and main

sea in!ection ale% showing$ i'details of how the main sea in!ection ale is fitted to the ship plating$

ii'details of their separate suction and common deliery arrangements$


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b'compare the diameter of the bilge in!ection ale with that of the main sea in!ection

ale.

The diameter of the bilge in!ection ale is not to be less than two thirds the diameter ofthe main seawater in!ection ale.

/4 9ie the reasons why each of the following conditions contribute to an increase in

propeller slip$


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a'essel in ballast condition

#hen the essel is in ballast condition% the propeller will be close to the surface or in

some cases% cutting the surface% thus resulting in an increase in propeller slip.

b'heaily fouled hull

A heaily fouled hull will increase the resistance of the hull in the water and thereforecause drag which will result in an increase of propeller slip.

c'damaged propeller bladesamaged propeller blades will cause an increase in propeller slip as the pitch in the

blades will hae changed.

d'essel going astern:essel going astern will increased the propeller slip as the blades are designed for going

ahead% not astern i.e mismatch between shaft res and most efficient propeller res.

/5 a'Sketch the fwd section of a ship to show the position of the following componentparts of the ships anchorage system$ hawse pipe% cable stopper% windlass and cable lifter%

spurling pipe and chain locker.

b'describe a chain stopper and state it1s purpose.

The chain stopper is used to hold the anchor chain in place once the anchor has beenlowered and it takes the strain on the anchor when the anchor is raised and in place.

c'show by means of a sketch how an anchor cable is attached to the ship.

The final link of the anchor chain is secured to a half shackle which is welded to a securepoint of the ships structure in the chain locker% bulkhead or deck and is known as the ;

bitter end ;.

d'describe how a chain locker is drained of water% sand and mud.

A chain locker is drained of water% sand and mud by means of a bilge eductor which is

normally drien by water from the fire main or general serice main.The reason for using a bilge eductor is that sand and mud mixed with water would

damage a normal pump.


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/" a'*ake a sketch of a watertight door

b'escribe the procedure adopted for testing the watertightness of a watertight door.

The procedure adopted for testing the watertightness of a watertight door is normally to

gie the door a simple hose test.


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ut doors on passenger essels re


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2t may be desirable to fit fin stabilisation to greatly reduce the ship rolling by imposing an

e


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/+ a'Sketch a semi 7 balanced rudder showing

i'etails of the pintles

ii'etails of the rudder carrier ring


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b'State the factors that determine whether a rudder is classed as

i'unbalancedAn unbalanced rudder is where there is no part of the rudder behind the rudder stock

ii'semi 7 balancedA semi 7 balanced rudder is where 5= of the rudder is behind the rudder stock

iii'fully 7 balancedA fully balanced rudder is where 50= of the rudder is on either side of the rudder stock


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/- #ithregard to the roll motion of the ship in seaway$

a'explain why roll motion is considered more serious than pitch motion

,oll motion is considered more serious than pitch motion because with roll motion% the

ship can get into synchroni8ation with the wae and while the wae gets bigger% so will

the roll% also slack tanks can be a problem with roll motion% or can be a shift in cargo.


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b'discuss the basic principles of roll damping utilised in the following anti7roll systems$

i'bilge keels

ilge keels offer a damping effect against roll motion by their surface area acting against

the roll.

ii' actiated fins

Actiated fins work by offering a damping effect against the roll motion by creating anopposite force to the roll% plus using the ships forward elocity to achiee this.

2e% if the ship were to roll to port% the port fin would be sent a signal by a gyroscope to

hae it1s leading edge aboe the axis of tilt% while the stbd fin is sent a signal to hae it1s

fin below the axis of tilt.See sketch

iii'passie roll damping tanks

>assie rolling tanks dampen the roll motion of the ship by using the effect of watermoement in a tank.

The tank contains perforated baffles to slow the motion in the tank from side to side% thususing the force of the water in the tank to act against the motion of roll.


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0 #ith regard to ship construction details for watertight bulkheads

a'state the purpose of this type of bulkhead.

The purpose of a transerse watertight bulkhead is to diide the ship into watertight

compartments% thus restrict the olume of water which may enter the ship due to damage

to the shell plating. They also sere to separate different types of cargo. 2n the eent of a


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fire% they greatly preent the spread. They also increase the strength of the ship

transersely.

b'state how the bulkhead1s are tested for watertightness.

The bulkheads are tested for watertightness by means of a simple hose test. ut initially

on building ship% they are hydrostatically water tested.

/ a'sketch a steel hatch coer of the self7stowing type with rising and falling tracks

b'describe the hatch coer sketched

The sketch is of the *acgreogor rolling hatch coer% each coer is on a set of wheels

which can be !acked up or down% !acked down for opening the hatch coers and !acked up

when hatch coers are in place% the hatch coers are also chained together% so when onecoer is winched along the runway% the other coers follow suit to allow them to be

opened and stowed in the stowage area.

#hen the hatch coers are in place and closed% they are held in position by pins and

wedges. ?6T@ efore remoing any pins or wedges% the wire for opening or closing thehatches must be taut to preent any accidents. Also before opening or closing% the runway

should be checked to be clear.


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a'#ith regard watertightdoors% show details of the fastening arrangements to show

how watertightness is maintained.

b'escribe the procedure adopted for testing the watertightness of a watertight door.


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The procedure adopted for testing the watertightness of a watertight door is normally to

gie the door a simple hose test.

ut doors on passenger essels re


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3a'enumerate three potentially ha8ardous situations when eery watertight door must be

closed.

/'2n the eent of flooding'2n the eent of a collision

3'2n the eent of a fire

Also could be closed on stand7bys and in fog

b'sketch an electricallly operated watertight door

sketch

c'state adantages of a watertight door being operated by electrical means rather than

hydraulic means.

The adantages of haing an electrically operated watertight door oer a hydraulicallyoperated watertight door are$ that there are no chances of burst hydraulic hoses% there are

no hyrdaulic tank leels to keep an eye on% the operation of an electric door is


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4a'sketch a bearing designed to transfer the full weight of the rudder to the ships

structure.

b'describe the conse


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produced when maneuering or testing the gear% extra load would also be generated on

the bearing surfaces.

c'describe the conse


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5 escribe with the aid of sketches% the method of and reasons for the closure of

a'the spurling pipe

The spurling pipe is closed to preent the ingress of water into the chain locker from

heay seas. 2n the past% the spurling pipe was closed with cement% but most ships now use


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" #ith reference to the preention of hull corrosion% describe$

a'surface preparation and painting of new ship plates

?ew ships plates are first shot blast to remoe any rust B corrosion% then a coat of primer

is applied and left to dry completely% note before applying the first coat of primer that the


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plates must be clean and dry. An undercoat is then applied% then a topcoat% the type of top

coat depends if the plates are situated aboe or below the water line.

b'design of the ships structure and it1s maintenance

The structure is designed in such a way as not to collect water% each leel of the structure

including the main deck has scuppers allowing any accumulation of water to drain away.*aintenance inoles remoal of corrosion by chipping% if seere by needle gunning%

then applying a protectie coating of paint% followed by primer% undercoat and topcoat.

asically the structure is painted regulary to preent corrosion. >lus scuppers should bekept free of debris at all time allowing water to drain away.

c'cathodic protection by sacrificial anodes% of the internal and external areas of the ship.

#ith regards internal protection with sacrificial anodes% ships ballast tanks hae anodes topreent corrosion% the anodes being blocks of magnisium or 8inc% they are either bolted or

welded in place in the tanks. Another example of internal protection% are where anodes

are fitted to seawater coolers i.e seawater side of engine lub oil coolers% !acket water

coolers% air coolers etc.

@xternal sacrificial anodes are also fitted to the ships hull below the water line to preentcorrosion% they are fitted all the way around the hull% and also the rudder% they are

normally welded in place.


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(a'state the purpose of cofferdams

The purpose of cofferdams are to preent leakage of one tank or double bottom to anotherie% there would be a cofferdam between fuel tanks and fresh water tanks. They also allow

for inspection of tanks% cofferdams should also be sounded regularly to check for leaks.

b'state where cofferdams are most likely to be found in each of the following$


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i'dry cargo essels

6n dry cargo essels% cofferdams would be found between fuel tanks and cargo % ballasttanks and cargo% also found around the main engine 6 drain tank.

ii'oil tankers6n oil tankers% cofferdams would be found between the oil cargo tanks and the

accommodation or engine room% in some cases this can be the pump room% also there will

be a cofferdam around the main engine 6 drain tank.

c'identify% with reasons% the general precautions which must be obsered before and

during entry to cofferdams and state official guidance on entry into oid spaces is gien$

>recautions taken before entry into an enclosed space are as follows$ An entry permitmust be obtained from a responsible officer% you may be the issuing officer. The space is

to be well entillated and oxygen leels tested by an 0 meter. Safety gear% such as self

contained breathing apparatus sets must be at hand% rescue lines% communications. Also

while anyone is in the enclosed space% someone must be on standby at the entrance whomust be in communication with the people in the space and also must be able to raise the

alarm if they are to get into difficulties.6fficial guidance on entry into enclosed spaces can be found in ;*; notices and also in

the ;Code of

Safe working practices;.

+a'describe with the aid of a sketch% how an oil cargo tank pressure B acuum ale

operates.

The sketch shows a pressure B acuum ale which preents oer pressure or underpressure in cargo tanks. They are usually set to 0./4 A, pressure for lifting and ent to

atmosphere ia a gau8e flame trap. A small drop in pressure inside the tank will cause the

acuum ale to operate% eB: ale % the acuum ale seats inside the pressure ale% the pressure

ale haing more surface area than the acuum ale.

b'explain why the deice sketched is fitted.

The ale is to preent oer pressure and under pressure of the oil cargo tanks% as a

moderate pressure acting on large surface areas of li


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Class 2 Naval

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