Akshay dhumal

FATHER AGNEL POLYTECHNIC, VASHI

MDL INPLANT TRAINING PROJECT

MAINTENANCE SHOP
It is very small shop in mazagon dock and it is in south yard. In this shop there is various
types of lathe machine and the workers do various jobs on it. If in any shop there is
problem in any machine the workers of maintenance shop go there and repair it in any
cost.
LATHE MACHINE :
A metal lathe or metalworking lathe is a large class of lathes designed
for precisely machining relatively hard materials. They were originally designed to
machine metals; however, with the advent of plastics and other materials, and with their
inherent versatility, they are used in a wide range of applications, and a broad range of
materials. In machining jargon, where the larger context is already understood, they are
usually simply called lathes, or else referred to by more-specific subtype names (toolroom
lathe, turret lathe, etc.). These rigid machine tools remove material from
a rotating workpiece via the movements of various cutting tools, such as tool bits and drill
bits.

Contents
1 Construction
o

1.1 Headstock

o

1.2 Beds

o

1.3 Feed and lead screws

o

1.4 Carriage


1.4.1 Cross-slide



1.4.2 Compound rest



1.4.3 Toolpost

o

1.5 Tailstock

o

1.6 Steady, follower and other rests

2 Types of metal lathes
o

2.1 Center lathe / engine lathe / bench lathe

o

2.2 Toolroom lathe

o

2.3 Turret lathe and capstan lathe

MECHANICAL ENGINEERING

o

2.4 Gang-tool lathe

o

2.5 Multispindle lathe

o

2.6 CNC lathe / CNC turning center

o

2.7 Swiss-style lathe / Swiss turning center

o

2.8 Combination lathe / 3-in-1 machine

o

2.9 Mini-lathe and micro-lathe

o

2.10 Wheel lathe

o


2.11 Brake lathe

3 Feed mechanisms
4 References
5 Bibliography
6 External links

Construction
The design of lathes can vary greatly depending on the intended application; however,
basic features are common to most types. These machines consist of (at the least) a
headstock, bed, carriage, and tailstock. Better machines are solidly constructed with broad
bearing surfaces (slide-ways) for stability, and manufactured with great precision. This
helps ensure the components manufactured on the machines can meet the required
tolerances and repeatability.

Head stock




The headstock (H1) houses the main spindle (H4), speed change mechanism (H2, H3), and
change gears (H10). The headstock is required to be made as robust as possible due to the
cutting forces involved, which can distort a lightly built housing, and induce harmonic
vibrations that will transfer through to the work piece, reducing the quality of the finished
work piece.
The main spindle is generally hollow to allow long bars to extend through to the work area.
This reduces preparation and waste of material. The spindle runs in precision bearings and
is fitted with some means of attaching work holding devices such as chucks or faceplates.

Beds

:

The bed is a robust base that connects to the headstock and permits the carriage
and tailstock to be moved parallel with the axis of the spindle. This is facilitated by
hardened and ground bedways which restrain the carriage and tailstock in a set track. The
carriage travels by means of a rack and pinion system. The leadscrewof accurate pitch,
drives the carriage holding the cutting tool via a gearbox driven from the headstock.
Types of beds :
Inverted ―V‖ beds
Flat beds
Combination ―V‖ and Flat beds
"V" and combination beds are used for precision and light duty work, while flat
beds are used for heavy duty work.

Feed and lead screws

:

The feedscrew (H8) is a long driveshaft that allows a series
of gears to drive the carriage mechanisms. These gears are located in the apron of the
carriage. Both the feedscrew and leadscrew (H7) are driven by either the change gears (on
the quadrant) or an intermediate gearbox known as aquick change gearbox (H6) or Norton
gearbox. These intermediate gears allow the correct ratio and direction to be set for
cutting threads or worm gears. Tumbler gears (operated by H5) are provided between the
spindle and gear train along with a quadrant plate that enables a gear train of the correct
ratio and direction to be introduced. This provides a constant relationship between the
number of turns the spindle makes, to the number of turns the leadscrew makes. This ratio
allows screwthreads to be cut on the workpiece without the aid of a die.




Carriage :
In its simplest form the carriage holds the tool
bit and moves it longitudinally (turning) or
perpendicularly (facing) under the control of
the operator. The operator moves the carriage
manually via the handwheel (5a) or
automatically by engaging the feed shaft with
the carriage feed mechanism (5c). This
provides some relief for the operator as the
movement of the carriage becomes power
assisted. The handwheels (2a, 3b, 5a) on the
carriage and its related slides are
usually
calibrated, both for ease of use and to assist in making reproducible cuts. Calibration
marks will measure either the distance from center (radius), or the work piece's diameter,
so for example, on a diameter machine where calibration marks are in thousandths of an
inch, the radial handwheel dial will read .0005 inches of radius per division, or .001 inches
of diameter. The carriage typically comprises a top casting, known as the saddle (4), and a
side casting, known as the apron (5).

Cross-slide :
The cross-slide (3) rides on the carriage and has a feedscrew that travels at
right angles to the main spindle axis. This permits facing operations to be performed, and
the depth of cut to be adjusted. This feedscrew can be engaged, through a gear train, to the
feed shaft (mentioned previously) to provide automated 'power feed' movement to the
cross-slide. On most lathes, only one direction can be engaged at a time as an interlock
mechanism will shut out the second gear train.
Compound rest

:

The compound rest (or top slide) (2) is usually where the tool post is
mounted. It provides a smaller amount of movement (less than the cross-slide) along its
axis via another feedscrew. The compound rest axis can be adjusted independently of the
carriage or cross-slide. It is used for turning tapers, to control depth of cut when
screwcutting or precision facing, or to obtain finer feeds (under manual control) than the
feed shaft permits. Usually, the compound rest has a protractor marked in its base (2b),
enabling the operator to adjust its axis to precise angles.
Toolpost :
The tool bit is mounted in the toolpost (1) which may be of the
American lantern style, traditional four-sided square style, or a quick-change style such as
the multifix arrangement pictured. The advantage of a quick change set-up is to allow an
unlimited number of tools to be used (up to the number of holders available) rather than
being limited to one tool with the lantern style, or to four tools with the four-sided type.
Interchangeable tool holders allow all tools to be preset to a center height that does not
change, even if the holder is removed from the machine.




Tailstock

The tailstock is a tool (drill), and centre mount, opposite the headstock. The
spindle (T5)does not rotate but does travel longitudinally under the action of a leadscrew
and handwheel(T1). The spindle includes a taper to hold drill bits, centers and
other tooling. The tailstock can be positioned along the bed and clamped (T6) in position as
dictated by the work piece. There is also provision to offset the tailstock (T4) from the
spindles axis, this is useful for turning small tapers, and when re-aligning the tailstck to the
axis of the bed.
The image shows a reduction gear box (T2) between the handwheel and spindle, where
large drills may necessitate the extra leverage. The tool bit is normally made of HSS, cobalt
steel or carbide.

Steady, follower and other rests

Long workpieces often need to be supported in the middle, as
cutting tools can push (bend) the work piece away from where
the centers can support them, because cutting metal produces
tremendous forces that tend to vibrate or even bend the
workpiece. This extra support can be provided by a steady
rest (also called a steady, a fixed steady, a center rest, or
sometimes, confusingly, a center.




A lathe machine is used for the shaping and machining of various work pieces. There are
many different types depending on the material you are working on.

Engine lathes

:

These are probably the most popular among the lathe machines. In fact,
no machine shop is seen without this type of lathe. The good thing about engine lathes is
that it can be used in various materials, aside from metal. Moreover, the set-up of these
machines is so simple that they are easier to use. Its main components include the bed,
headstock, and tailstock. These engine lathes can be adjusted to variable speeds for the
accommodation of a wide scope of work. In addition, these lathes come in various sizes.
Fig.1. Engine Lathe

Turret Lathes :
These types of lathes are used for machining single workpieces
sequentially. This means that several operations are needed to be performed on a single
work piece. With the turret lathes, sequential operations can be done on the work piece,
eliminating errors in work alignment. With this set-up, machining is done more efficiently.
Correspondingly, time is saved because there is no need to remove and transfer the work
piece to another machine anymore.
Fig.2. Turret Lathe

Special Purpose Lathes :
As the name implies, these lathes are used for special purposes
such as heavy-duty production of identical parts. In addition, these lathes also perform
specific functions that cannot be performed by the standard lathes. Some examples of
special purpose lathes include the bench-type jewelers’ lathes, automatic lathes,
crankshaft lathes, duplicating lathes, multispindle lathes, brakedrum lathes, and production
lathes among others.




YARD
701
(INSKOLKATA)




Important characteristics are as follows:
Name –

INS Kolkata

Namesake –

Kolkata

Operator –

Indian Navy

Builder –

Mazagon Dock Limited

Laid down –

September 2003

Launched –

30 March 2006

Commissioned –

2012

Displacement –

6,800 tons[1]

Length –

163 meters[1]

Speed –

17.4 meters[1]

Beam –

30+ knots

Sensors & Processing
Systems –
Armament –


Multi-function
Humsa-NG
Nagin active towed array sonar

1
2x8
48
32

x
Brahmos
cell

2
Barak

radar
sonar[1]

130
Supersonic
Barak

mm
Cruise
8
1

gun
Missiles
SAM
SAM


4 x 30 mm AK-630 rapid fire Gatling guns[1]
twin-tube
torpedo
launchers
anti-submarine rocket launchers[1]

Aircraft carried –

2 Sea Kind or HAL Dhruv helicopters

1. stern is called the weather deck. The main deck area over the stern is called the fantail or poop
deck. The flat part of the bottom of the ship is

The Ship Is divided in to 4 departments
I. Hull (Structural) Department
II. Engineering Department
III. Electrical Department
IV.
Weapon Department

HULL DEPARTMENT
2. What is hull?

HULL:
The hull is the main body of the ship below the main outside deck. The hull consists of an
outside covering (or skin) and an inside framework to which the skin is secured. The skin
and framework are usually made of steel and secured by welding. However, there may still
be some areas where rivets are used. The steel skin may also be called shell plating.
Marine vehicles are categorized as either displacement craft or dynamic-lift craft.
Displacement craft derive their lift from buoyancy (displacement). Dynamic-lift craft derive
their lift dynamically, such as by hydrofoils or planning surfaces. The drag of displacement
craft is primarily frictional and wave making. The drag of dynamic-lift craft is primarily
frictional and induced (drag induced by lift). In high-speed craft of either type, frictional
drag is normally more than half the total drag. It is important to reduce frictional drag,
although all types of drag are reduced to achieve a large lift-to-drag (L/D) ratio. The
following are dynamic-lift: hydrofoil ships, air cushion vehicles (ACV), seaplanes, wing-inground effect (WIG) craft, planning hydrofoil ships, surface effect ships (SES) and ram wing
craft. Displacement craft include: slender monohull ships, catamaran ships, SWATH (Small
Water plane Area Twin Hull) and displacement hydrofoil ships.
To achieve high speeds, i.e. speeds greater than 30 knots, various types of hull have been
developed, some making use solely of hydrostatic support like monohulls but by
increasing the number of hulls, as with catamarans and trimarans in particular;
hydrodynamic support has also been used by means of underwater "wings" which serve to
lift the load-carrying hull out of the water above a certain speed; other principles have been
developed, in particular those using aerostatic support, such as air cushion vehicles.




Vessels constructed with two, three, or more hulls are referred to as catamarans, trimarans,
or generally as multihull vessels. Multihull vessels have the advantage of more lateral
stability than a monohull vessel, but with a wetted surface area that is normally higher than
that of a monohull vessel of similar size.
The term "tumblehome" (alternatively spelled "tumble homes" or "tumble-home") refers to
a property of a water vessel's hull wherein its topside or some portion thereof, is inclined
inward. Generally according to conventional tumblehome-type monohull designs, the two
sides of the vessel are sloped, above the maximum beam (widest width or breadth), toward
the middle or center of the vessel.
Monohull tumblehome hull designs typically are beset with certain undesirable
characteristics. They have a poor righting arm, since the tumblehome feature decreases
the water plane area as the ship heels (tilts to one side; lists). They have poor damage
stability, because the above-water volume is limited by the tumblehome feature. They have
restricted useable superstructure volume and width at the deck level. They are
characterized by unusual sea-keeping responsiveness along with ongoing concern
regarding the dynamic stability in a seafaring way; this is probably attributable to the broad
transom (which has large above-water volume associated therewith) in combination with
the wave-piercing bow (which has limited above-water volume associated therewith).
The coatings applied to the hulls of modern commercial vessels are maintained, they act as
a deterrent to the settlement of marine organisms on vessel surfaces below the water line.
Studies have shown that there are areas on the hull where the coatings are compromised,
thus allowing settlement of marine fouling organisms. Fouling organisms have also been
noted to exist in sheltered areas around rudder posts, and within sea chest intakes. Sea
chest intakes tend to harbor a diverse community that is sheltered from the turbulence
created by movement through the water. Even properly maintained vessels can transport
fouling organisms when these factors exist. Slow moving vessels that have long residence
times in port are more likely to develop fouling organisms, than those that have short
residence times, and are transiting more often. Towed vessels, such as, overseas cargo
barges, floating dry docks, vessels from decommission yards, or any floating platform, are
examples of this type of dynamic.
The main centerline structural part of the hull is the keel, which runs from the stem at the
bow to the sternpost at the stern. The keel is the backbone of the ship. To the keel are
fastened the frames, which run athwart ship. These are the ribs of the ship and gives shape
and strength to the hull. Deck beams and bulkheads support the decks and gives added
strength to resist the pressure of the water on the sides of the hull.
3.Different parts of hull structure?
This diagram shows the key structural elements of a ship's main hull (excluding the bow,
stern, and deckhouse).



1. Deck structure
2. Bulkhead
3. Inner bottom shell plating
4. Hull bottom shell plating
5. Transverse frame
6. Keel frame
7. Keelson
8. Longitudinal stiffener
9. Hull side beam

1) Deck structure





The decks aboard ship are the same as the floors in a house. The main deck is the
first continuous watertight deck that runs from the bow to the stern. In many
instances, the weather deck and the main deck may be one and the same. Any
partial deck above the main deck is named according to its location on the ship. At
the bow it is called a forecastle deck, amidships it is an upper deck, and at the stern
it is called the poop deck. The term weather deck includes all parts of the forecastle,
main, upper, and poop decks exposed to the weather. Any structure built above the
weather deck is called superstructure.

2) Bulkhead

The interior of the ship is divided by the bulkheads and decks into watertight
compartments. A vessel could be made virtually unsinkable if it were divided into
enough small compartments. However, too many compartments would interfere with
the arrangement of mechanical equipment and the operation of the ship. Engine
rooms must be large enough to accommodate bulky machinery. Cargo spaces must
be large enough to hold large equipment and containers.

3) Inner bottom shell plating
Inner bottom shell plating provides water-tightness. The plates, the principal strength
members of a ship, have various thicknesses. The heaviest plates are put on amidships.
The others are put on so that they taper toward both ends of the ship (from the keel toward
the bilge and from the bilge toward the upper row of plates). Using plates of various
thickness reduces the weight of the metal used and gives the vessel additional strength at



its broadest part. The plates, put on in rows from bow to stern, are called strakes. They are
lettered consecutively, beginning at the keel and going upward.

4) Hull bottom shell plating
Hull bottom shell plating provides water-tightness. The plates, the principal strength
members of a ship, have various thicknesses. The heaviest plates are put on
amidships. The others are put on so that they taper toward both ends of the ship
(from the keel toward the bilge and from the bilge toward the upper row of plates).
Using plates of various thicknesses reduces the weight of the metal used and gives
the vessel additional strength at its broadest part. The plates, put on in rows from
bow to stern, are called strakes. They are lettered consecutively, beginning at the
keel and going upward.

5) Transverse frame
Though this hull design is outdated, it is still used for smaller ships of length less
than 120 meters. In this design there is a plate floor every 3.05 meters and a frame
every 1 meter. The frames run transversally to the hull structure. The frames are
joined together with the help of floor angle iron transverse. In this design every floor
plate will have 3 frames. The frames are attached to the margin plates with the help
of flanged bracket as shown in the figure.
Iron transverse is attached between two floor plates to provide additional support
and increase structural strength. Refer the diagram for a better understanding of the
design.

6) Keel frame
The main central member along the length of the bottom of the boat. It is an
important part of the boat's structure which also has a strong influence on its
turning performance and, in sailing boats, resists the sideways pressure of the wind
In boats and ships, keel can refer to either of two parts: a structural element, or a
hydrodynamic element. These parts overlap. As the laying down of the keel is the
initial step in construction of a ship, the construction is dated from this event, with
only the ship's launching considered more significant in its creation.

7) Keelson
An internal beam fixed to the top of the keel to strengthen the joint of the upper
members of the boat to the keel




8) Longitudinal stiffener
Inter coastal plates that are used to join two floor plates.
9) Hull side beam
Triangular shaped Iron brackets that are welded where the two frames meet. They are
attached to the margin plates to resist excessive bending stress.

10)EXTERNAL PARTS OF THE HULL
The waterline is the water-level line on the hull when afloat. The vertical distance from
the waterline to the edge of the lowest outside deck is called the freeboard. The vertical
distance from the waterline to the bottom of the keel is called the draft. The waterline,
draft, and freeboard will change with the weight of the cargo and provisions carried by
the ship. The draft of the ship is measured in feet and inches. Numbered scales are
painted on the side of the ship at the bow and stern.

The relationship between the drafts at the bow and stern is the trim. When a ship is
properly balanced fore and aft, she is in trim. When a ship is drawing more water
forward than aft, she is down by the head. If the stern is too far down in the water, she is
down by the stern. If the vessel is out of balance laterally or athwart ship (leaning to one
side) she has a list. She may be listing to starboard or listing to port. Both trim and list
can be adjusted by shifting the weight of the cargo or transferring the ship’s fuel and
water from one tank to another in various parts of the hull.
The part of the bow structure above the waterline is the prow. The general area in the
forward part of the ship is the forecastle. Along the edges of the weather deck from bow
to stern are removable stanchions and light wire ropes, called life lines. Extensions of
the shell plating above the deck are called bulwarks. The small drains on the deck are
scuppers. The uppermost deck running from the bow to the called the bilge. The curved
section where the bottom meets the side is called the turn of the bilge.
Below the waterline are the propellers or screws which drive the ship through the
water. The propellers are attached to and are turned by the propeller shafts. A ship
with only one propeller is called a single-screw ship. Ships with two propellers are
called twin-screw ships. On some ships (especially landing craft) there may be metal
frames built around the propellers (called propeller guards) to protect them from
damage. The rudder is used to steer the ship.




3.Loads on Ship Hulls
The hulls of ships are subjected to a number of loads.


Even when sitting at dockside or at anchor the pressure of surrounding water
displaced by the ship presses in on its hull.



The weight of the hull and of cargo and components within the ship bears down on
the hull.



Wind blows against the hull, and waves run into it.



When a ship moves, there is additional hull drag, the force of propellors, water driven
up against the bow.



When a ship is loaded with cargo, it may have many times its own empty weight of
cargo pushing down on the structure.

If the ships structure, equipment, and cargo are distributed unevenly there may be large
point loads into the structure, and if they are distributed differently than the distribution of
buoyancy from displaced water then there are bending forces on the hull.
When ships are dry-docked, and when they are being built, they are supported on regularly
spaced posts on their bottoms.

Primary Hull Loads, Strength, and Bending
Diagram of ship hull (1) Sagging and (2) Hogging under loads. Bending is exaggerated for
demonstration purposes.
The primary strength, loads, and bending of a ship's hull are the loads that affect the whole
hull, viewed from front to back and top to bottom. Though this could be considered to include
overall transverse loads (from side to side within the ship), generally it is applied
to Longitudinal loads (from end to end) only. The hull, viewed as a single beam, can bend
1. down in the center, known as sagging
2. up in the center, known as hogging.



This can be due to:


hull, machinery, and cargo loads



wave loads, with the worst cases of:


sagging, due to a wave with length equal to the ship's length, and peaks at the bow
and stern and a trough amidships



hogging, due to a wave with length equal to the ship's length, and a peak
amidships (right at the middle of the length)

Secondary Hull Loads, Strength, and Bending
The secondary hull loads, bending, and strength are those loads that happen to the skin
structure of the ship (sides, bottom, deck) between major lengthwise subdivisions
or bulkheads. For these loads, we are interested in how this shorter section behaves as an
integrated beam, under the local forces of displaced water pushing back on the hull, cargo
and hull and machinery weights, etc. Unlike primary loads, secondary loads are treated as
applying to a complex composite panel, supported at the sides, rather than as a simple
beam.
Secondary loads, strength, and bending are calculated similarly to primary loads: you
determine the point and distributed loads due to displacement and weight, and determine
local total forces on each unit area of the panel. Those loads then cause the composite
panel to deform, usually bending inwards between bulkheads as most loads are
compressive and directed inwards. Stress in the structure is calculated from the loads and
bending.
Tertiary Hull Loads, Strength, and Bending
Tertiary strength and loads are the forces, strength, and bending response of individual
sections of hull plate between stiffeners , and the behavior of individual stiffener sections.
Usually the tertiary loading is simpler to calculate: for most sections, there is a simple,
maximum hydrostatic load or hydrostatic plus slamming load to calculate. The plate is
supported against those loads at its edges by stiffeners and beams. The deflection of the
plate (or stiffener), and additional stresses, are simply calculated from those loads and the
theory of plates and shells.

3. Modes of failure & causes of hull.
Modes of Failure:
From the loading point of view, a ship is essentially an elastic beam floating on the water
surface and subjected to a range of fluctuating and steady loads. These loads will generate
bending moment and shear force which may acting on the ship.




Forces on the hull include:
Action of sea
Force acting on the heavy items composed of gravity forces and the dynamic forces
due to acceleration imparted by the ship's motion
Thrust due to main propulsion forces on the hull
Failure is said to occur when the structure can no longer carry out its intended function
Although most structural components are designed in such a manner that if one element
fails, it sheds its load on to another element which can withstand this additional load,
hence normally this does not lead to an immediate catastrophe but immediate remedial
action is certainly necessary to prevent further damage .
However there is a phenomenon known as the "domino" effect, wherein the surrounding
structural elements fail in succession and the result can be loss of the ship, hence the
necessity of immediate action mentioned above

Causes of Failure
Listed below are three reasons as to why the ship's hull may fail.
1. Failure may occur due to the hull structure becoming distorted on being strained beyond
the yield point. This will lead to a permanent set and distortion of the structure
2. Failure may also be caused due to cracking of the hull structure. This occurs when the
material can no longer sustain the load applied on it various sections. The loading may
exceed the ultimate strength of the material or more likely the failure is due to fatigue of the
material leading to a cracking and ultimate fracture
Even if the cracks in the hull do not lead to complete fracture, they can prove disastrous as
it can lead to leakage and thus cause flooding and consequent sinking of the vessel
3. Failure may also be due to the structural instability. Very large deflections can occur
under relatively lighter loads, and the structure behaves like a crippled strut.




ENGINEERING DEPARMENT
PROPULSION SYSTEM:The ships propulsion system consists of a 2 gas turbine one at AFT and other at FWD
which gives the working force to the propeller. As the speed given to the shaft is 1.4 lacs
rpm a reduction gear box is fitted which reduces the speed to 240 rpm, thus increasing the
torque required for moving the propeller. Between the propeller and the gear box there is a
thrust bearing which supports the propeller shaft and also reduces the vibrations produced
by the propeller from reaching the gear box and gas turbine. The propeller shaft is also
fitted with plummer block whose main function is only to support the shaft. There is also a
shaft break which prevents its movement in stationary state.

Pumps used in ships:-

1: Fire pump – The outlet lines of this pumps run through the entire ship. It
fire fighting.

is used for

2: Fuel transfer pump – The main function of this pump is to transfer fuel from the storage
tank to the gas turbine and diesel engine continuously.

3: Luboil pump – The main function of this pump is to transfer the lubricating oil around the
gas turbine to reduce friction and for cooling purpose.

4: Bilge pump – It is a high capacity pump which can pump out 5 tonnes of water per hour
in case of leakage or missile attack
.
5: Centrifugal pump – The main function of this pump is to purify the lubricating oil of its
impurities like seawater, metal chips etc.

6: Salvage pump – It removes the leak lubricating oil and fuel from the gas turbine into sea.




Systems used on ships

Refrigeration system: It is a normal Carnot cycle air conditioning system consisting of
a compressor – condenser – receiver – expansion valve – evaporator. It also includes other
auxiliary equipments like heat exchanger, absorber, oil separator. The main function of this
system is to serve the cold storage and weaponary storage rooms.

Air-conditioning system: The system used here is an year round AC system consisting
of a air purifier, humidifier, dehumidifier, heater, cooler.
Its main function is to serve the entire 10 deck and control rooms.

Reverse osmosis system: Reverse osmosis (RO) is a filtration method that removes many
types of large molecules and ions from solutions by applying pressure to the solution when
it is on one side of a selective membrane. The result is that the solute is retained on the
pressurized side of the membrane and the pure solvent is allowed to pass to the other side.
To be "selective," this membrane should not allow large molecules or ions through the
pores (holes), but should allow smaller components of the solution (such as the solvent) to
pass freely.
Reverse osmosis is most commonly known for its use in drinking water purification from
seawater, removing the salt and other substances from the water molecules
the main function of this system on shipis to convert the sea water into soft water required
for drinking and other daily needs.

Stabilizer system: Ship stabilizers are fins mounted beneath the waterline and emerging
laterally. In contemporary vessels, they may be gyroscopically controlled active fins, which
have the capacity to change their angle of attack to counteract roll caused by wind or
waves acting on the ship.




Radar system:

Radar is an object detection system that uses electromagnetic waves to
identify the range, altitude, direction, or speed of both moving and fixed objects such as
aircraft, ships, motor vehicles, weather formations, and terrain. The term RADAR was
coined in 1940 by the U.S. Navy as an acronym for Radio Detection And Ranging. A radar
system has a transmitter that emits radio waves. When they come into contact with an
object they are scattered in all directions. The signal is thus partly reflected back and it has
a slight change of wavelength (and thus frequency) if the target is moving. The receiver is
usually, but not always, in the same location as the transmitter. Although the signal
returned is usually very weak, the signal can be amplified through use of electronic
techniques in the receiver and in the antenna configuration. This enables radar to detect
objects at ranges where other emissions, such as sound or visible light, would be too weak
to detect.

Sonar system: Sonar (originally an acronym for SOund Navigation And Ranging) is a
technique that uses sound propagation (usually underwater, as in Submarine navigation) to
navigate, communicate with or detect other vessels. Two types of technology share the
name "sonar": passive sonar is essentially listening for the sound made by vessels; active
sonar is emitting pulses of sounds and listening for echoes. Sonar may be used as a
means of acoustic location and of measurement of the echo characteristics of "targets" in
the water. Acoustic location in air was used before the introduction of radar. Sonar may
also be used in air for robot navigation, and SODAR (an upward looking in-air sonar) is
used for atmospheric investigations. The term sonar is also used for the equipment used to
generate and receive the sound. The acoustic frequencies used in sonar systems vary from
very low (infrasonic) to extremely high (ultrasonic).

PROPELLER:- A propeller is a type of fan which transmits power by converting rotational
motion into thrust. A pressure difference is produced between the forward and rear
surfaces of the airfoil-shaped blade, and air or water is accelerated behind the blade

Types of propeller:Controllable pitch propeller
This type of propeller is used in spite of its low efficiency due to the smooth and easy
maneuverability it provides, especially when the ship has to often move in the confined
waters. This propeller is also used when the ship has to continuously operate at one speed
or for fuel efficiency reasons where the ship has to move of different speeds and
displacement. This propeller is often used in war ships where the cruising speed is half the




full speed. A controllable pitch propeller prevents the over-torquing of the cruise propeller
that might be caused by fixed pitch propeller.
An alternative to two pitch propeller will be a two speed gear box.

Highly skewed propeller
A highly skewed propeller can be a fixed pitch propeller or a controllable propeller.
Skewing contributes negligibly to increase the efficiency of the propeller but plays an
important role in reducing the propeller forces on the hull. This type of propeller is mainly
fitted on cruise ships or passenger ships where the avoidance of vibration is of utmost
importance.

Self Pitching propellers
These types of propellers are generally used for low power vessels. They are highly
found in yachts or smaller vessels, as there are higher chances of facing mechanical errors
when they are used in heavy and high powered vessels. An interesting point is that the
open water efficiency obtained at astern is same as that at ahead.




Other propeller types
There has been a massive advancement in the innovation and development of the
propellers for increasing efficiency. Some of the newly developed propellers are tip vortex
free(TVF) and balanced thrust loading(BTL) propellers. They are not so extensively used as
they do not provide the kind of efficiency that they promise.
One more type of propeller is contra-rotating propeller which reduces the rotational losses
and thus increases the efficiency. This type of propeller is generally used in a direct
electric drive propeller where the usage of gear box can be avoided. They are generally
fitted on smaller ships. This type of propellers if used in bigger ships gets confronted with
problems such as high mechanical complexity, high cost of gear box and shafting and
propeller limits. Thus they are used in smaller ships with less power and higher steering
performance requirement.

TERMINOLOGY OF PROPELLER

Blade Back
Suction side. Forward side of the blade (surface facing the bow ).

Blade Face
Pressure Side, Pitch Side. Aft side of the blade (surface facing the stern).
Blade Number
Equal to the number of blades on the propeller.
Blade Root
Fillet area. The region of transition from the blade surfaces and edges to the hub periphery.
The area where the blade attaches to the hub.




Blade Tip
Maximum reach of the blade from the center of the hub. Separates the leading and trailing
edges.

Cavitation
Cavitation, (which is often confused with ventilation), is a phenomena of water vaporizing
or "boiling" due to the extreme reduction of pressure on the back of the propeller blade.
Many propellers partially cavitate during normal operation, but excessive cavitation can
result in physical damage to the propeller's blade surface due to the collapse of
microscopic bubbles on the blade. There may be numerous causes of cavitation such as
incorrect matching of propeller style to application, incorrect pitch, physical damage to the
blade edges, etc...
Cup
Small radius of curvature located on the trailing edge of the blade. This curved lip on the
propeller allows it to get a better bite on the water. This results in reduced ventilation,
slipping, and allows for a better hole shot in many cases.

Diameter
Diameter is the distance from the center of the hub to the tip of the blade x 2. It can also be
looked at as the distance across the circle that the propeller would make when rotating. It
is the first number listed when describing a propeller.

Hub
Solid cylinder located at the center of the propeller. Bored to accommodate the engine
propeller shaft. Hub shapes include cylindrical, conical, radius, & barreled.

Leading Edge




The edge of the propeller blade adjacent to the forward end of the hub. The leading edge
leads into the flow when providing forward thrust.

Pitch
Pitch is defined as the theoretical forward movement of a propeller during one revolution —
assuming there is no "slippage" between the propeller blade and the water.
Pitch is the second number listed in the propeller description.
Radius
The distance from the axis of rotation to the blade tip. The radius multiplied by two is equal
to the diameter.
Rake
Rake is the degree that the blades slant forward or backwards in relation to the hub. Rake
can affect the flow of water through the propeller.
Aft Rake helps to trim the bow of the boat upward, which often results in less wetted surface
area and therefore higher top end speed.
Forward, or negative rake, helps hold the
bow of the boat down. This is more common in workboat type applications.
Rotation
When viewed from the stern (facing forward): Right-hand propellers rotate clockwise to
provide forward thrust. Left-hand propellers rotate counter-clockwise to provide forward
thrust.
Skew
The transverse sweeping of a blade such that when viewing the blades from fore or aft
shows an asymmetrical shape.
Aft Skew: Positive skew. Blade sweep in the direction opposite of rotation.
Forward Skew: Negative skew. Blade sweep in the same direction as rotation.
Slip
Slip is the difference between actual and theoretical travel of the propeller blades through
water. A properly matched propeller will actually move forward 80 to 90 percent of the
theoretical pitch.
Trailing Edge
The edge of the propeller adjacent to the aft end of the hub. When viewing the propeller
from astern, this edge is closest. The trailing edge retreats from the flow when providing
forward thrust.
Track
The absolute difference of the actual individual blade rake distributions to the other blade
rake distributions. Always a positive value and represents the spread between individual
blade rake distributions.




Ventilation
Ventilation is a situation where surface air or exhaust gasses are drawn into the propeller
blades. When this situation occurs, boat speed is lost and engine RPM climbs rapidly. This
can result from excessively tight cornering, a motor that is mounted very high on the
transom, or by over-trimming the engine.


Akshay dhumal

Recommandé

Recommandé

Contenu connexe

Tendances

Tendances (20)

En vedette

En vedette (19)

Similaire à Akshay dhumal

Similaire à Akshay dhumal (20)

Dernier

Dernier (20)

Akshay dhumal