Class 4 Safety Oral Ship Construction & Naval File
Class 4 Safety Oral Ship Construction & Naval File
Class 4 Safety Oral Ship Construction & Naval File
7. Draught extreme : The distance from the bottom of the keel to the waterline. The load draught is
the maximum draught to which a vessel may be loaded.
8. Draught' moulded : The draught measured from the top of the keel to the waterline.
9. Freeboard: The distance from the waterline to the top of the deck plating at the side of the deck
amidships.
Freeboard represents the safety margin showing to what depths a ship may be loaded under various
service conditionse.g., the type of cargo, the waters to be navigated, and the season of the year.
Purpose of Freeboard
To ensure that she can not be loaded beyond her strength.
To provide ship with adequate Reversed Buoyancy
To keep the deck high enough from water, to enable the crew to navigate and handle her in
all weather condition.
10. Camber or round of beam: The transverse curvature of the deck from the centreline down to the
sides. This camber is used on exposed decks to drive water to the sides of the ship. Other decks are
often cambered. Most modern ships have decks which are flat transversely over the width of the
hatch or centre tanks and slope down towards the side of the ship.
11. Sheer:The curvature of the deck in a fore and aft direction, rising from midships to a maximum at
the ends. The sheer forward is usually twice that aft. Sheer on exposed decks makes a ship more
seaworthy by raising the deck at the fore and after ends further from the water and by reducing the
volume of water coming on the deck.
12. Rise of floor: The bottom shell of a ship is sometimes sloped up from the keel to the bilge to
facilitate drainage. This rise of floor is small, 150 mm being usual.
13. Bilge radius: The radius of the arc connecting the side of the ship to the bottom at the midship
portion of the ship.
14. Tumble home: In some ships the midship side shell in the region of the upper deck is curved slightly
towards the centreliie, thus reducing the width of the upper deck and decks above. Such tumble
home improves the appearance of the ship.
15. ARCHIMEDES' PRINCIPLE: If a solid body is immersed in a liquid there is an apparent loss in weight.
This loss in weight is the upthrust exerted by the liquid on the body and is equal to the weight of the
volume of liquid which the body displaces.
16. Displacement: When a ship is floating freely at rest the mass of the ship is equaI to the mass of the
volume of water displaced by the ship and is therefore known as the displacement of the ship.
17. T.P.C: The tonne per centimetre immersion (TPC) of a ship at any given draught is the mass required
to increase the mean draught by 1 cm.
T.P.C: A w (waterplane area) X
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100
18. Metacentre: The point where a vertical line through a centre of buoyancy of an inclined ship
intersects the vertical line through the centre of gravity when it is floating in equilibrium.
19. Water plane area coefficient: (Cw): is the ratio of the area of the waterplane to the product of the
length and breadth of the ship.
20. Midship section area coefficient ( Cm ): the ratio of the area of the immersed portion of the
midship section to the product of the breadth and the draught.
21. Block coefficient (Cb): is the ratio of the volume of displacement to the product of the length,
breadth and draught.
22. Prismatic coefficient (Cp): is the ratio of the volume of displacement to the product of the length
and the area of the immersed portion of the midship section.
23. Wetted surface area: The wetted surface area of a ship is the area of the ship's hull which is in
contact with the water. This area may be found by putting the transverse girths of the ship, from
waterline to waterline, through Simpson's Rule and adding about f per cent to allow for the
longitudinal curvature of the shell. To this area should be added the wetted surface area of
appendages such as cruiser stern, rudder and bilge keels.
DENNY s EQUATION
TAYLO s EQUATION
24. Centre of gravity: The centre of gravity of an object is the point at which the whole weight of the
object may be regarded as acting. If the object is suspended from this point, then it will remain
balanced and will not tilt.
25. Centre of buoyancy: the point through which the total force of buoyancy is considered to act.
26. Metacentric height: distance between C.O.G and transverse metacenter (M).
27. Pitch of propeller: one revolution of the shaft the propeller will move forward a distance.
28. Diameter of propeller: diameter of the circle or disc cut out by the blade tips.
29. Pitch ratio: it is the face pitch divide by diameter.
30. Theoretical speed (Vt): distance the propeller would advance in unit time if working in an ungielding
fluid. Thus if the propeller turns N rev/min.
Vt=P x N m/min
= P x N x 60 knots
1852
31. Wake: ater hi h is i otio at the ster of a ship as a result of a ship s o e e t, the o i g
water known as wake.
32. Wake fraction: ratio of the wake speed to the speed of advance.
33. Speed of advance: speed of ship relative to the wake is termed the speed of advance Va.
34. Real slip or True slip: difference between theoretical speed and the speed of advance.
Real slip = Vt -- Va X 100%
Vt
35. Skew: offset of a propeller blade from the vertical in the plane od rotation, it is always a distance in
the direction opposite to rotation.
36. Slip: the difference between the actual distance travelled by a ship and the theoretical distance
given by the product of the propeller pitch and the no. of revolution. It is usually expressed as a
percentage and can have a negative value if a current or following wind exists.
37. Apperent slip: the propeller work in water the ship speed V will normally be less than theoretical
speed, or
the difference between the two speed known.
38. Longitudinal Centre of Flotation: it is the point about which the ship will Trim when weight are
loaded or discharged, if the weight added at L.C.F point, trim will not change only draft change.
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39. Permeability (): ratio of volume with the space which is assumed to be occupied by water to the
total volume of that compartment. for M/C space: 85%, for accommodation: 95%, for cargo hold
average: 60%
40. Buoyancy: the upthrust exerted by the water on the ship. If the ship float freely the buoyancy is
equal to the weight of ship.
41. Reserve buoyancy: it is the potential buoyancy of a ship and depends upon the intact watertight
volume above the waterline of ship. If the mass added to ship or buoyancy lost due to bilging the
reserve buoyancy is converted into buoyancy by increasing draught.
42. Strake: external hull of a ship consists of bottom shell, side shell and deck which are formed by
longitudinal strips plating called strake. Or continue range of plate forming the side of vessel, or
etal plate e te di g ship s hull fro ste to ster .
43. Bilge strake: strake at the turn of the bilge called.
44. Stealer strake: No.of adjacent strakes fitted at the end of ship called.
45. Garboard strake: strake adjacent to the keel on each side of ship called.
46. Sheer strake and its importance: it is largest continue strake at the top og the side of vessel on
maindeck. Or uppermost strake of side plating which meet the upper deck. It is 10-20% thicker than
other side plating.
IMPORTANCE: when vessel is bending to forces from tension to compression and sheer strake is
subjected to maximum compressive and tensile stress. Which is contribute to the strength of the
hull.
47. Stringer: the stiffners used to strengthening the sides surface of the ship called, without stringer the
hull shape doesnot formed.
48. Coffin plate: used to connect stern frame to the flat plate keel.
49. Shoe plate: used to connect stem to the flat plate keel.
50. Margin plate: at bilges, the tank top may be either continued straight out to the shell by means of a
tank margin plate. Which is water tight and set an angle of about 45 0 to the tank top and meeting
the shell almost at right angle.
51. Bulwark: It is solid wall that extends above the weather deck or any other deck to exposed to
weather and fitted for the safety of the crew. Atleast 1 m in height spacing of stays and is not
exceed 1.2 m on the forecastle.
52. Freeing port: the area of freeing port on each side depend on the length of well deck, the lower
edge of the port must be as near to the deck as possible and opening are to be protected by rails
spaced approx. 230 mm apart. When hinged flaps are fitted the hings must be of non-corrodible.
53. Gunwale: the upper edge of a ship s side here the sheer strake eets the de k plati g alled.
54. Margin line: is a line drawn at least 76 mm below the upper surface of the bulkhead deck at side.
It is the imaginary line, which is drawn 76mm below the uppermost continuous deck. It
denotes the limit, up to which ship can be flooded/ loaded without sinking.
For a ship which has a continuous bulkhead deck, the margin line is to be taken as a line
drawn not less than 76 mm below the upper surface of the bulkhead deck at side, except that where
there is a variation in the thickness of the bulkhead deck at side the upper surface of the deck
should be taken at the least thickness of deck at side above the beam.
If desired however, the upper surface of the deck may be taken at the mean thickness of the
deck at side above the beam as calculated for the whole length of the deck, provided that the
thickness is no greater than the least thickness plus 50 mm.
55. Trsnsom space: situated in S.G. room there you can find manhole door near Rudder Trunk this
purpose is to inspect Rudder Trunk condition, Lubrication etc.. you can enter inside this place for
carried out inspection in Port only and in calm weather or sea.
56. Buttock line: It is equidistant transverse section line from the midship to fwd of the ship, such that
they give you the cross section are at various station at all possible draft and trim.
They are mainly used for knowing the light weight displacement at the time of end of
construction phase of a ship.
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Q 31: Explain inclining experiment? Why it is carried out? Define calculation? Draw tender and
stiff ship?
A 31:
INCLINING EXPERIMENT
This is a simple experiment which is carried out on the completed ship to determine the
metacentric height, and hence the height of the centre of gravity of the ship.
If the height of the centre of gravity of the empty ship is known, it is possible to calculate its
position for any given condition of loading.
It is therefore necessary to carry out the inclining experiment on the empty ship (or as near to
empty as possible).
The experiment is commenced with the ship upright.
A small mass m is moved across the ship through a distance d.This causes the centre of gravity to
move from its original position G on the centreline to G1.
If A = displacement of ship
Then GG1 = m x d
A
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tan = __ a__
L
and GM = m x d x L
x a
The height of the transverse metacentre above the keel may be found from the metacentric
diagram and hence the height of the centre of gravity of the ship may be determined.
KG = KM GM
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Tender ship: small metacentric height GM, will have small Righting lever GZ, at any angle and will roll
easily.
GM is said to be POSITIVE when G is lies below M
and vessel is stable.
Stiff ship: large metacentric height GM, will have large righting lever GZ, at any angle resistance to rolling.
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Q 33: what is Free Surface Effect? And method to reduce it? How it will effect on GM?
A 33:
Free Surface Effect: When a tank on board a ship is not completely full of liquid, and the vessel heels, the
liquid moves across the tank in the same direction as the heel.
C.O.G moves away.
Reduce metacentric height GM.
Reduce righting lever GZ.
Increase angle of heel.
RESULT: SHIP is UNSTABLE.
without division
GG2 =
POCKETING
Free Surface Effect can be reduced, to some extent, by creating pocketing. Pocketing occurs when
the surface of the liquid contacts the top or bottom of the tank, reducing the breadth (B) of the free
surface area.
Since the effects of pocketing can not be calculated, it is an indeterminate safety factor.
The Free Surface correction will therefore indicate less overall stability than actually exists.
SURFACE PERMEABILITY
Impermeable objects (engines, pumps, piping
systems, etc) inside a flooded space project
through and above the liquid surface.
These objects inhibit the moving water and the
"shifting of the wedge" may or may not be
complete, thus reducing Free Surface Effect.
The impermeable objects also occupy volume,
reducing the amount of flooding water (movable
weight) that can fill the space.
SLUICE VALVES
Sluice valves allow opposing tanks to be
cross-connected.
When large, partially filled tanks are
connected, Free Surface Effect increases,
and the vessel becomes less stable.
Ships like oilers and tenders use these
valves to create long, slow roll periods
during ammunition handling and refueling
Sluice Valve Closed: Sluice Valve Open:
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Q 34: Explain Angle of loll? How you will correct it? And lot more question asking from this
theory.
A 34:
ANGLE OF LOLL
ANGLE OF LOLL:
It is the angle at which the ship with initial negative
Metacentric height will lie at rest in still water. If the
ship is further inclined to an angle less than angle of
loll, the ship will sink.
An initially unstable ship heels to a certain angle and
ends up in neutral stability. That angle is called angle
of loll
At angle of loll ., GM = 0 OR KG = KM
CORRECTIVE ACTION
First check if the vessel is listed or lolled.
Always presume it is lolled for safety and work
accordingly.
Calculate the vol of all tanks check for any slack
tanks if any for the reason listed .
If the port and starboard listing moments are same
then confirm its lolled
In a listed condition always try to lower the centre of gravity by discharging the high side of the
ballast first
start filling low side of the tanks (prefer smaller
tanks to minimise free surface effect during filling )
(coz if you fill the other side of the tank, the listing
moment will be enough to capsize).
gradually start filling the mid tank and then the
port side tank.
now the vessel should be upright , even if it is not .,
try ballasting other tanks in the same method
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Q 35 : GZ and GM curves, Explain stability in it, at what angle will vessel lose its stability?
A 35:
ANGLE OF CRONTRAFLEXURE:
The angle till which the rate of GZ increases with increase in heel. Though after this GZ may
increase, the rate of increase is slower ANGLE AT WHICH MAX GZ occurs.
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WORK:
it reduce the hull wave making resistance of a ship, which is the major residuary frictional
resistance of a ship.
when water will be cut by Bulbous bow there is two type of wave will generate.
Primary wave which formed by bow just in front of Bow will cut the Secondary Wave formed by ship
hull and will reduce dragging.
So hull wave making resistance is reduced so more efficient and lesser fuel oil consumption.
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Q 38 : How many type of keel used in ship construction? Explain all of them?
A 38:
Runs along the centreline of the bottom plate.
For most ships it is of flat plate construction
Centre Girder a watertight longitudinal division which runs along the centreline from fore peak to
aft peak bulkhead.
Types Of Keel:
FLAT KEEL
BAR KEEL
DUCT KEEL
FLAT KEEL:
Used in all types of sea going vessels
Flat keel would basically mean a single bottom
In the olden days, above the floors, a wooden plank was placed to facilitate cargo carriage. (now u
might wonder that makes it a sort of double bottom right ? ans is , its ot, oz if it s a dou le
bottom, it should be water tight
BAR KEEL:
A bar is placed in the center of the keel called bar keel.
These consist one or more solid bar which are supported by frames running around the vessel.
The either side of the hull attached to the bar keel is called Garboard strake
These types of keels are incorporated in ferries or boats that are to be grounding.
Keelson plate: longitudinal beam on top of the keel of a vessel for strength & stiffners.
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DUCT KEEL:
Some double bottoms have a duct keel fitted along the centreline
Internal watertight passage running along the length of the ship, usually from collision bulkhead
/forepeak to for d a hi er spa e ulkhead.
Used to carry pipework along the length of the ship to various holds/tanks.
Prevent any construction which could occurs if pipe rupture with cargo.
Usuall a essed a a atertight a hole at the for d e d of a hi er spa e
Not required in machinery space or further aft pipework runs along top of E/R double bottom and
along shaft tunnel
Two longitudinal girders not more than 1.83 m apart. Ensures girders rest on docking blocks
Keel Plate and tank top above duct keel must have increased scantlings to compensate for
reduced strength of the transverse floors
Stiffeners are fitted to shell and bottom plating at alternate frame spaces and are bracketed to
the longitudinal girders
Also called as BOX KEEL, allows pipes and other services throughout the keel length.
This is fitted from the FWD of the E/R bulkhead to the aft of the collision bulkhead.
AFT side e a t e ui ed Du t keel oz pipe ill pass th ough to the HAFT TUNNEL
This keel facilitates pipe passing through the cargo holds and thus isolating piping from cargo
contact
This enables lines to pass through that facilitate draining.
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Q 39 : Expalin Bilge Keel? How it is connected ? How much length it is? Purpose of it?
A 39:
BILGE KEEL
PURPOSE:
Dump the rolling motion of the vessel.
Protected of bilge on grounding.
Increase the longitudinal strength.
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The forward ends of the cant beams are connected to a deep beam extending right across the
ship.
At the lower ends, the cant frames are connected to a solid floor.
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Stern is flat which reduce the production costs, while at some time reducing the bending moment
on the after structure.
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Corrugations (or swedges) are formed on a corrugated bulkhead to eliminate the need to fit the
vertical stiffener, as in those of the plain bulkhead.
The elimination of vertical stiffeners also results in saving in steel weight and cost of stiffeners.
The angle of corrugation is normally about 45 degrees.
The troughs are vertical on transverse bulkheads but must be horizontal on continuous
longitudinal bulkheads, which form part of the longitudinal strength of the ship.
Diaphragm plates or horizontal stringers are fitted on the bulkhead to keep the corrugation in
place.
This B/H form very smooth surface in oil tanks allowed improve drainage and easy of cleaning.
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CONSTRUCTION:
Longitudinal deck girders and deck longitudinals are supported at the bulkheads which therefore act
as pillars, while at the same time they tie together the deck and tank top and hence reduce vertical
deflection when the compartments are full of cargo.
it is found that a bulkhead required to withstand a load of water in the event of flooding will
readily perform the remaining functions.
The number of bulkheads in a ship depends upon the length of the ship and the position of the
machinery space.
In ships more than 90 m in length, additional bulkheads are required, the number depending upon
the length.Thus a ship 140 m long will require a total of 7 bulkheads if the machinery is amidships
or 6 bulkheads if the machinery is aft, while a ship 180 rn in length will require 9 or 8 bulkheads
respectively.
Each ship must have a collision bulkhead at least one twentieth of the ship's length from the
forward perpendicular, which must be continuous up to the uppermost continuous deck.
The stern tube must be enclosed in a watertight compartment formed by the sternframe and the
after peak bulkhead which may terminate at the first watertight deck above the waterline.
A bulkhead must be fitted at each end of the machinery space although, if the engines are aft, the
after peak forms the after boundary of the space. In certain ships this may result in the saving of
one bulkhead.
These bulkheads must extend to the freeboard deck and should preferably be equally spaced in the
ship.
The bulkheads are fitted in separate sections between the tank top and the lowest deck, and in the
'tween decks.
Watertight bulkheads are formed by plates which are attached to the shell, deck and tank top by
welding.
Since water pressure increases with the head, and the bulkhead is to be designed to withstand such
a force, it may be expected that the plating on the lower part of the bulkhead is thicker than that at
the top.
The bulkheads are supported by vertical stiffeners spaced 760 mm apart. Any variation in this
spacing results in variations in size of stiffeners and thickness of plating.
The ends of the stiffeners are usually bracketed to the tank top and deck although in some cases the
brackets are omitted, resulting in heavier stiffeners.
The bulkheads are tested for watertightness by hosing them using a pressure of 200 kN/m 2.
If hose test is not practicable bcoz of possible damage to M/C, Electrical equipment insulation, it
may be replaced by careful visual examination of welded connection.
Tank which are intended to hold liquids, and which form part of the watertight subdivision of the
ship shall be tested for tightness and structural strength with water head. The water head is in no
case to less than top of the air pipes or to a level of 2.4 m above the top of the tank whichever is
greater.
We can do by dye penetrant test or an ultrasonic test.
The test is carried out from the side on which the stiffeners are attached.
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It is usual to provide one hatch per hold or 'tween deck, although in ships having large holds two
hatches are sometimes arranged.
The length and width of hatch depend largely upon the size of the ship and the type of cargo Iikely
to be carried.
General cargo ships have hatches which will allow cargoes such as timber, cars, locomotives and
crates of machinery to be loaded.
A cargo tramp of about 10 000 tonne deadweight may have five hatches, each 10 m long and 7 m
wide, although one hatch, usually to No. 2 hold, is often increased in length.
Large hatches also allow easy handling of cargoes. Bulk carriers have long, wide hatches to allow the
cargo to fill the extremities of the compartment without requiring trimming manually.
chains and wedges in operational condition at all time Keep clean hatch cover tops
and all drainage holes to be kept clear
Look for any broken or missing gasket and replace it immediately.
The length of renewed gasket must be minimum 1 m
Before renewing rubber gasket, check and rectify steel to steel fault
Gasket rubber to be of approved type by class
Grease all the moving parts
Check for any hydraulic system leakage if cover is oil operated
Oil test to be performed for hydraulic system
Call surveyor after any major repair in the cover and its concerned parts
The limitation or drawbacks of this test is that it requires two persons and hatch cover to be tested
must be empty.
The leakage if very minimal cannot be identified by naked eye and cannot be performed in sub zero
or cold weather.
2. Ultrasonic Test:
The Ultrasonic testing is a more accurate method of testing water tightness of hold and its cover.
In this system an ultrasonic generator is kept inside a closed and intact cargo hold.
A sensor of that unit is passed all over the compression joint and any low pressure area or point
detected by the instrument can be a leakage point.
An ultrasonic test is carried out using type-approved, efficient and reliable testing equipment.
This equipment consists of two parts: an ultrasound multi-transmitter and a hand-held detector.
The multi-transmitter is placed in the hold in a central position. It produces a uniformly distributed
omnidirectional sound throughout the hold space.
The sound energy is measured by the hand-held detector.
The transmitter sound is produced in a narrow frequency (kHz) band, and the detector is only tuned
to filter out this band. As inspectors wear headphones and read data off a digital display, they are
not hampered by surrounding noise and can detect any leaks.
The dete tor s uilt-in memory function also records the dB values, making the data downloadable
to a PC, so that it can be safely logged for reports.
For swift, clean and easy testing, ultrasonic technology can be used to check any opening on board
a ship that needs to be sealed
Few drawbacks of this instrument is it is not normally kept onboard and qualified person is
required to perform this test.
3. Chalk Test:
This is the oldest or most traditional method for testing hold cover compression, but it cannot test
the water tight integrity of the hold.
A layer of chalk powder is applied all over the steel back of the hatch and then the hatch cover is
closed and tightened to its normal values.
The impression of chalk on the rubber packing is then studied to check lack of compression point
shown by gap in the chalk marks.
HATCH COAMING
The hatches are framed by means of hatch coamings which are vertical webs forming deep
stiffeners.
The heights of the coamings are governed by the International Load Line Rules.
On weather decks they must be at least 600 mm in height at the fore end and either 450 mm or 600
mm aft depending upon the draught of the ship.
Inside superstructures and on lower decks no particular height of coaming is specified.
it is necessary, however, for safety considerations, to fit some form of rail around any deck opening
to a height of 800 mm.
It is usual, therefore, at the weather deck, to extend the coaming to a height of 800 mm.
In the superstructures and on lower decks portable stanchions are provided, the rail being in the
form of a wire rope.
These rails are only erected when the hatch is opened.
The weather deck hatch coamings must be 11 mm thick and must be stiffened by a moulding at the
top edge. Where the height of the coaming is 600 mm or more, a horizontal bulb angle or bulb plate
is fitted to stiffen the coaming which has additional support in the form of stays fitted at intervals of
3 m.
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If the double bottom is transversely framed, then transverse solid plate floors, and bracket floors
with transverse frames, provide the principal support for the inner bottom and bottom shell plating.
Solid plate floors are fitted at every frame space in the engine room and in the pounding region.
Also they are introduced in way of boiler seats, transverse bulkheads, toes of brackets supporting
stiffeners on deep tank bulkheads, and in way of any change in depth of the double bottom.
Where a ship is regularly discharged by grabs, solid plate floors are also fitted at each frame.
Elsewhere the solid plate floors may be spaced up to 3.0m apart, with bracket floors at frame
spaces between the solid floors.
The plate brackets of bracket floors are flanged and their breadth is at least 75 percent of the
depth of the center girder at the bracket floors.
To reduce the span of the frames, which should not exceed 2.5 meters, at the bracket floor,
vertical angle or channel bar struts may be fitted.
Vertical stiffeners usually in the form of welded flats will be attached to the solid plate floors, which
are further strengthened if they form a watertight or oil tight tank boundary.
One intercostal side girder is provided port and starboard where the ship s eadth e eeds
ut does ot e eed a d t o a e fitted po t a d sta oa d he e the ship s eadth is
greater.
In way of the bracket floors a vertical welded flat stiffener is attached to the side girder.
Additional side girders are provided in the engine room, and also in the pounding region.
As the unsupported span of the bottom longitudinal should not exceed 2.5m, vertical angle or
channel bar struts may be provided to support the longitudinal between widely spaced solid
floors.
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Q 50: Panting and Pounding effect? How to resist Panting and Pounding? Draw Sketch?
A 50:
PANTING
Panting:
As the waves pass along the ship they cause fluctuations in water pressure which tend to create
an in-and-out movement of the shell plating. The effect of this is found to be greatest at the ends
of the ship, particularly at the fore end, where the shell is relatively flat.
Such movements are termed panting and, if unrestricted, could eventually lead to fatigue of the
material and must therefore be prevented. The structure at the ends of the ship is stiffened to
prevent any undue movement of the shell.
The structure of the ship is strengthened to resist the effects of panting from 15% of the ship's
length from forward to the stem and aft of the after peak bulkhead.
In the fore peak, side stringers are fitted to the shell at intervals of 2 m below the lowest deck.
Panting beam are fitted FWD of the Collision B/H below the lowest deck.
Panting beam connected to Beam knee.
Panting beam fitted alternate frame.
Beam space not more than 2 m apart vertically and supported by pillars.
POUNDING
Pounding:
When a ship meets heavy weather and commences heaving and pitching, the rise of the fore end
of the ship occasionally synchronize with the trough of a wave. The fore end then emerges from
the water and re-enters with a tremendous slamming effect, known as pounding.
While this does not occur with great regularity, it may nevertheless cause damage to the bottom of
the ship forward. The shell plating must be stiffened to prevent buckling.
Pounding also occurs aft in way of the cruiser stern but the effects are not nearly as great.
Solid floor are fitted at every frame space and are attached to the bottom shell by continue welding.
Longitudinal framed:
If bottom shell of a ship longitudinally frame the spacing between longitudinal are reduced 700 mm
and are continue as FWD as practicable to the collision B/H.
Transverse floor are fitted alternate frame.
Side girder fitted not more 2.1 m apart.
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Watertight door is fitted to any access opening in a watertight bulkhead. Such openings must be cut
only where necessary for the safe working of the ship and are kept as small as possible, 1.4 m high
and 0.75 m wide being usual.
The doors may be mild steel, cast steel or cast iron, and either vertical or horizontal sliding, the
choice being usually related to the position of any fittings on the bulkhead.
The means of closing the doors must be positive, i.e., they must not rely on gravity or a dropping
weight.
Some suitable packing is fitted round the door to ensure that it is watertight., six clips being fitted to
the frame.
Watertight doors are tested using a pressure Weather tight doors are also designed to
tank where a hydrostatic pressure can be withstand brief submersion experienced from
applied to the door. green seas. This means a weather tight door
can withstand a small head of water
(generally no higher than the height of the
door).
The door is generally pressurized form the A weather tight door is generally tested with
inside as this is worst case scenario. a high pressure hose, which is directed at the
seal.
=======================================================================================
They have also proved to be of considerable benefit to larger vessels such as oil tankers and bulk
carriers, where the tug requirement has been reduced.
CONSTRUCTION:
In all cases the necessity to penetrate the hull forward causes an increase in ship resistance and
hence in fuel costs, although the increase is small.
A popular arrangement is to have a cylindrical duct passing through the ship from side to side, in
which is fitted an impeller which can produce a thrust to port or to starboard.
The complete duct must lie below the waterline at all draughts, the impeller acting best when
subject to a reasonable head of water and thus reducing the possibility of cavitation.
The impeller may be of fixed pitch with a variable-speed motor which is reversible or has reverse
gearing.
Alternatively a controllable pitch impeller may be used, having a constant-speed drive.
Power may be provided by an electric motor, a diesel engine or a hydraulic motor.
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Propeller drop.
the propeller shaft in the after peak tank is provided with inboard and outboard seals.these seals
contain nitrile rubber or viton lip seal which seals against the bronze liner shrunk fit around the cast
iron propeller shaft.
after a few years it creates grooves on them and naturally looses sealing and sea water can easily
find its way inside.this reduces the lubrication effect and creates wear if the bronze liner.
now as there is enough clearance the shaft will come down by certain amount because of the
propeller weight.this drop in propeller shaft is termed as propeller drop and is measured by POKERS
gauge.
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lubricators is fitted, and the grease used for lubrication is of a water resistant type (calcium soap
based with graphite)
Wear down
A small allowance is made for wear down,
which must be periodically checked.
This may be measured either between pads
welded on top of the rudder and onto the
rudder horn, or between the top of the
rudder stock and a fixed mark on the inner
structure of the steering gear flat.
The latter generally involves the use of a
'Trammel gauge' which takes the form of a 'L'
shaped rod made to fit the new condition of
the gear.
As wear down occurs it can easily be checked
with this gauge.
The rudder is prevented from jumping by
rudder stops welded onto the stern frame.
These limits refer to rudders of traditional design and are governed by both the physical layout of
the rudder and actuator but also due to the stall angles of the rudder. i.e. the angle at which lift (
turning moment ) is reduced or lost with increasing angle of attack.
There are designs of rudder such as Becker flap which have increased stall angles up to 45 o
At docking:
1)Bouncing clearance: measured between top of rudder and jumping bar.
2)Wear down clearance: between the bottom of rudder and reference mark.
Rudder wear
down refers to the measurements taken generally during a docking period to indicate excessive
wear in the steering gear system particularly the rudder carrier.
This wear down or rudder drop is measured using a special L shaped instrument called Tramel.
When the vessel is built a distinct centre punch mark is placed onto the ruder stock and onto a
suitable location on the vessels structure, here given as a girder which is typical.
The trammel is manufactured to suit these marks As the carrier wears the upper pointer will fall
below the centre punch mark by an amount equal to the wear down.
Rudder Clearance
Pads are welded to the hull and rudder. A clearance is given ( sometimes refered to as the jumping
clearance). As the carrier wears this clearance will increase
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The tops of the stools are lined up accurately to suit the height of the shaft, although adjustments to
the height of bearings are made when the ship is afloat.
The stools are constructed of 12 mm plates, riveted or welded together, the latter being the most
usual.
They are attached to the tunnel rings to prevent movement of the bearings which could lead to
damage of the shaft.
The loads from the bearings are transmitted to the double bottom structure by means of
longitudinal brackets.
Manholes are cut in the end plates to reduce the weight and to allow inspection and maintenance
of the stools.
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2) Bilge keel
When ships were first built of iron instead of wood a bar keel was fitted, one of its advantages being
that it acted as an ant rolling device.
With the fitting of the flat plate keel the ant rolling properties were lost. An alternative method was
supplied in the form of bilge keels which are now used in the majority of ships.
These projections are arranged at the bilge to lie above the line of the bottom shell and within the
breadth of the ship, thus being partially protected against damage.
The depth of the bilge keels depends to some extent on the size of the ship but there are two main
factors to be considered;
(a) the web must be deep enough to penetrate the boundary layer of water travelling with
the ship
(b) if the web is too deep the force of water when rolling may cause damage.
Bilge keels 250 mm to 400 mm.in depth are fitted to oceangoing ships.
The keels extend for about one half of the length of the ship amidships and are tapered gradually at
the ends.
3) Tank stabilizer
There are three basic systems of roll-damping using free surface tanks:
(a) Passive Tanks
(b) Controlled Passive Tanks
(c) Active Controlled Tanks
These systems do not depend upon the forward movement of the ship and are therefore suitable
for vessels such as drill ships.
In introducing a free surface to the ship, however, there is a reduction in stability which must be
considered when loading the ship.
(a) Passive Tanks
The principle of action is the same as for the previous system, but the transverse movement of the
water is controlled by valves operated by a control system similar to that used in the fin stabiliser.
The valves may be used to restrict the flow of water in a U-tube system, or the flow of air in a fully-
enclosed system.
The mass of water required in the system is about 2% to 2+% of the displacement of the ship.
Careful design of the tank in terms of its shape , water capacity and vertical positioning in the ship
allows control to be exercised with respect to rolling.
With correct design of tank the water oscillating period will equal the roll period of the ship but its
motion will lag behind that of the ship by one quarter of the roll period and behind the wave by half
of the roll period.
Water in the tank thus opposes the wave action producing the roll. Water movement between the
tanks is regulated to some extent by the air valves.
With the valves closed the system is put out of action. With this arrangement, known as the
controlled passive system, the mass of water to about 2 to 2.5% of the ships displacement.
=======================================================================================
Q 57: Explain & Draw Torsion Box? Location of it? (most imp question for container ship)
Q 57 a: what is Racking and how to resist it?
Q 57 b: Why in Tanker there is no Torsion Box?
A 57, 57 a, 57 b:
TORSION BOX
LOCATION : Runs from Collision B/H to AFT peak B/H in both PORT & STBD side.
PREVENT:
Torsional bending on ships due to the torsional moment on ship caused by the dynamic
movement of the wave.
To avoid Racking Effect caused by the Sheer Stress on the vessel.
RACKING EFFECT:
When a ship is rolling, the deck tends to move laterally relative to the bottom structure, and the
shell on one side to move vertically relative to the other side. This type of deformation is referred
to as a ki g .
When a ship rolls there is a tendency for the ship to distort transversely in a similar way to that in
which a picture frame may collapse. This is known as racking.
It is reduced or prevented by the beam knee and tank side bracket connections together with the
transverse bulkheads, the latter having the greatest effect.
Transverse bulkheads primarily resist such transverse deformation, the side frames contribution
being insignificant provided the transverse bulkheads are at their usual regular spacings.
THEORY:
TORSION: When anybody is subject to a twisting moment which is commonly referred to as torque,
that od is said to e i torsio .
A ship heading obliquely (45) to a wave will be subjected to righting moments of opposite direction
at its ends twisting the hull a d putti g it i torsio .
In most ships these torsional moments and stresses are negligible but in ships with extremely wide
and long deck openings they are significant.
A particular example is the larger container ship where at the topsides a heavy torsion box girder
structure including the upper deck is provided to accommodate the torsional stresses.
OIL TANKER has many transverse bulkheads which act as a main stiffening member as a racking
and twisting along with we have the uppermost continue deck hi h does t ha e a ope i g
hat h o pare to dr argo ship. o OIL TANKER did t ha e additio al stiffe i g e er like
Torsion box.
IN BULK CARRIER have small hatch opening and it has sufficient deck space or deck stiffening
member which are sufficient to counteract the twisting moment.
=======================================================================================
Q 58: What is Standard Fire test? Explain Class of Bulkhead also called Thermal Bulkhead?
A 58 :
STANDARD FIRE TEST
A standard fire test is a test in which specimens of the relevant bulkheads or decks are exposed in a
test furnace to temperatures corresponding approximately to the standard time-temperature curve
in accordance with the test method specified in the Fire Test Procedures.
Specimen shall have an expose surface not less than 4.65 m2 and height 2.44 m including atleast
one joint.
CLASS A BULKHEAD:
A" lass di isio s are those di isio s for ed ulkheads a d de ks hi h o pl ith the
following criteria:
they are constructed of steel or other equivalent material;
they are suitably stiffened;
they are insulated with approved non-combustible materials such that the average
Temperature of the unexposed side will not rise more than 140C above the original temperature,
nor will the temperature, at any one point, including any joint, rise more than 180C above the
original temperature, within the time listed below:
Class A-60 60min
Class A-30 30Min
Class A-15 15Min
Class A-0 0Min
They are constructed as to be capable of preventing the passage of smoke and flame to the end of
the one-hour standard fire test.
CLASS B BULKHEAD:
"B" class divisions are those divisions formed by bulkheads, decks, ceilings or linings which comply
with the following criteria:
They are constructed of approved non-combustible materials and all materials used in the
construction and erection of "B" class divisions are non-combustible.
They have an insulation value such that the average temperature of the unexposed side will not
rise more than 140C above the original temperature, nor will the temperature at any one point,
including any joint, rise more than 225C above the original temperature, within the time listed
below:
Class B-15 15 min
Class B-0 0 min
They are constructed as to be capable of preventing the passage of smoke and flame to the end of
the first half hour standard fire test.
CLA C BULKHEAD:
"C" class divisions are divisions constructed of approved non-combustible materials. They need
meet neither requirements relative to the passage of smoke and flame nor limitations relative to
the temperature rise.
=======================================================================================
Out of the three reasons, the most common cause is uneven cargo loading and unloading.
Anti-heeling System
The anti heeling system of a ship automatically detects the heeling angle of the ship and
compensates the same.
This allows the vessels to have continues loading and unloading cargo operation without stopping in
between for list correction.
This saves considerable amount time on the port.
In this system, ballast tanks are internally connected to each other by means of pipe lines,
automatic valves and control systems.
When the ship heels to any of the sides, the heeling sensor sends the signal for change of ships
a gle ith respe t to the ship s upright positio to the aster o trol pa el.
This change in heeling angle is compensated by methods of auto transferring the water from the
heeled side to the other side of the ship, making the vessel upright.
Level control switches are also installed in the ballast tank involved with the anti-heeling system to
avoid low level or over filling and hence over pressurizing of the tanks.
=======================================================================================
Permit to work is to be valid only for a certain time period. If time period expires then again new
permit is to be issued and checklist is to be filled out.
Permit to work has to be checked and permitted by the Master of the ship in order to work in
confined space.
Proper signs and Men at work sign boards should be provided at required places so that person
should not start any equipment, machinery or any operation in the confined space endangering life
of the people working.
Duty officer has to be informed before entering the enclosed space.
The checklist has to be signed by the person involved in entry and also by a competent officer.
One person always has to be kept standby to communicate with the person inside the space.
The person may also carry a life line with him inside.
The person should carry oxygen analyzer with him inside the enclosed space and it should be on all
the time to monitor the oxygen content.
As soon as level drops, the analyzer should sound alarm and the space should be evacuated quickly
without any delay.
No source of ignition has to be taken inside unless the Master or competent officer is satisfied.
The number of persons entering should be constrained to the adequate number of persons who are
actually needed inside for work.
The rescue and resuscitation equipment are to be present outside the confined space. Rescue
equipment includes breathing air apparatus and spare charge bottles.
Means of hoisting an incapacitated person should be available.
After finishing the work and when the person is out of the enclosed space, the after work checklist
has to be filled.
The permit to work has to be closed after this
The above mentioned procedure is extremely important to entering an enclosed space. These points are
i perati e to risk a re e ers life hile e teri g a o fi ed spa e.
=======================================================================================
Q 61: How you will clean Bilge Holding tank with following safety ? and what are they ?
A 61:
BILGE HOLDING TANK CLEANING WITH SAFETY
First you make sounding of the tank.
Now inform to bridge for discharging water from the tank via OWS, and note down your position
of the ship, if should be outside of the special area.
Discharge as much as possible bilge water to overboard.
PREPARED BY : KUNJAL S. SHAH Page 64
*MEO CLASS 4 SAFETY(COSCPOOL)ORAL PREPARATION FILE PART 3*
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2. Bearing check:
Before installing your new prop ensure that the shaft bearing is not worn.
A worn bearing or shaft will not be suitable for any propeller, so if it is worn, replace it. If there is
too much play of the shaft in the bearing, the bearing must be replaced or vibration and damage to
the shaft can occur.
Please note that certain types of bearings require some clearance.
If not sure contact the manufacturer and ask them what the maximum allowable clearance is.
4. Propeller fit:
Dry fit the propeller to the shaft, without the key in place first. Check that the propeller does not
rock on the taper.
Mark the shaft at the forward end of the propeller hub.
This is most is important - to first fit the new prop onto the shaft withoutthe key in place and to
mark the shaft at the forward edge of the prop hub. Remove the prop and place the key into the
shaft keyway.
Slide the prop back onto the shaft and check that the forward edge of the hub comes to your shaft
mark.
If not then it is likely that the key is too large, and the propeller is not seated to the shaft taper
correctly.
Remove the prop and file the top of the key down until the prop will slide on to the shaft and reach
the mark.
This will ensure that the prop is now correctly seated on the shaft taper.
7. Install propeller:
Install the propeller with the key fitted to the shaft. Some people prefer to use a lubricant on the
shaft, we do not recommend this.
Che k that the propeller goes up to the ark o the propeller shaft. If it does t, the propeller is
sitting on the key and you must reduce the height of the key to overcome this problem.
Draw the propeller up the taper using the propeller locking nut, then lock this nut with the second
nut.
Don't forget to fit a new cotter pin.
8. Painting propellers:
Painting your propeller will degrade the performance. Barnacles, on the other hand will degrade
the performance more than properly applied paint.
If you use the boat often painting is not necessary. If you have the bottom regularly cleaned then
painting is also not required.
On the other hand, if you are like most of us and use the boat not as often as you would like, then
painting may be helpful. A good alternative is the specialized silicon propeller coatings
e.g.PROPSPEED which works because they are slick;- any marine growth slides off the metal surface
when moving through the water.
Here is one procedure for painting propellers:
A. The propellers will be clean when you receive them apart from a light coat of oil. Remove this oil
film using alcohol or acetone.
B. Choose a good quality Zinc Chromate primer and lightly coat the propellers.
C. The anti-fouli g pai t to use o the propellers is sold u der arious trade a es as Outdri e
Anti-fouli g Pai t i spra a s. pra -3 light even coats of paint on the propellers taking care not
to get any paint into the bore of the hub.
D. Allow at least 48 hours drying time before putting the propellers into service.
E. It is best not to apply standard anti foul paint with a brush as it tends to "spin off" the propellers
quickly and cannot be applied as evenly as spray paint.
9. Alignment check:
After the boat has been in the water for 24 hrs, the engine alignment should be checked.
=======================================================================================
Sweet Crude:
Crude which has Hydrogen Sulphate ( H2S ) less than 25 ppm
Crude which has sulphur is between 0.42-0.50 % .
Crude contain small amount of H2S and CO2 and is commonly used in process into Gasoline,
kerosene and High quality diesel.
Sour Crude:
Crude which has Hydrogen Sulphate ( H2S ) more than 25 ppm
Crude which has sulphur is more than 0.50 % .
Crude contain small amount of H2S and CO2 but impurities are more and to remove impurities more
processing charge. and is commonly used in process into heavy fuel oil.
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It is fitted with the parallel plug with an arrangement which gets open on being loaded and gets
automatically closed when released to avoid the damage in case a person forget to close the
sounding cap.
It is always located close to the suction pipe to get the correct sounding for the pump to take the
suction.
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Q 65: Tell me about dimension of International Shore coupling, Sewage Coupling, and Bilge line
coupling?
A 65 :
Dimension International Shore Coupling Bilge Coupling Sewage Coupling
( 500 GT and above have at least one )
O.D 178 mm 215 mm 210 mm
I.D 64 mm According to O.D of pipe According to O.D of pipe
Bolt Circle Dia 132 mm 183 mm 170 mm
Flange Thick 14.5 mm 20 mm 16 mm
Slot in Flange 4 6 4
Dia of Slot 19 mm 22 mm 18 mm
Bolt & Nuts 4/4 6/6 4/4
Dia of Bolt 16 mm 20 mm 16 mm
Length of Bolt 50 mm Suitable length Suitable length
Pipe inner dia ------------------------ --------------------- 100 mm
o Frie d these are all a out HIP CONTRUCTION AND NAVAL ARCHITECTURE , I hope ou ill
u dersta d easil a d if ou ha e a dou t just go through the REED, PUREY, et et ook, or a
reference if you have. I just share what I know from my side.
Co e tio A epted
I e t page ou ha e THE MOT IMPORTANT PART OF THI AFETY ORAL OLA & MARPOL ,
and surveyor most most most important topic also this. I will try to explain each and
everything, also about RULES AND REGULATION .