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

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

YARD 701

(INSKOLKATA)

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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 –

Multi-function radarHumsa-NG sonar [1] Nagin active towed array sonar

Armament – 1 x 130 mm gun2x8 Brahmos 2 Supersonic Cruise Missiles48 cell Barak 8 SAM32 Barak 1 SAM4 x 30 mm AK-630 rapid fire Gatling guns [1]

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

twin-tube torpedo launchersanti-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 departmentsI. Hull (Structural) Department

II. Engineering DepartmentIII. Electrical DepartmentIV. Weapon Department

HULL DEPARTMENT2. 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-in-ground 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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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).

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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 is used for fire fighting.

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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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 FacePressure Side, Pitch Side. Aft side of the blade (surface facing the stern).

Blade NumberEqual to the number of blades on the propeller.

Blade RootFillet area. The region of transition from the blade surfaces and edges to the hub periphery. The area where the blade attaches to the hub.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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

CavitationCavitation, (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...

CupSmall 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.

DiameterDiameter 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.

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

Leading Edge

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

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.

PitchPitch 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.

RadiusThe distance from the axis of rotation to the blade tip. The radius multiplied by two is equal to the diameter.

RakeRake 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.

RotationWhen 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.

SkewThe 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.

SlipSlip 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 EdgeThe 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.

TrackThe 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.

MECHANICAL ENGINEERING

FATHER AGNEL POLYTECHNIC, VASHI MDL INPLANT TRAINING PROJECT

VentilationVentilation 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.

MECHANICAL ENGINEERING