Bme notes

Q1. Main components of reciprocating IC engines:
Q2. Difference between the principle and operation of four stroke and two stroke engine
Q3.Thermal power plants
Q4. Differences between Impulse and Reaction Turbines:
Q5. Describe rolling operation and also describe various types of rolling mills.
Q6. Describe the function of air compressor with neat sketch
Q7. Vapour compression refrigeration system
Q8. What are the advantages of AC and DC power supply in welding?
Q9. Friction Clutch
Q10. Couplings
Q11. Difference between Centrifugal Pump and Reciprocating Pump:
Q12. Centrifugal pump
Q13 . Reciprocating pump
Q14. CASTING
Q15. Modes of heat transfer
Q16. Bernoulli's Theorem.
Q17. Venturimeter
Q18. Construction ofpitot tube
Q19.WELDING
Q20. TURNING

Cylinder: It is the main part of the engine inside which piston reciprocates to and fro. It should have high strength to
withstand high pressure above 50 bar and temperature above 2000 o
C. The ordinary engine is made of cast iron and
heavydutyenginesare made of steel alloysoraluminumalloys.Inthe multi-cylinderengine,the cylinders are cast in one
block known as cylinder block.
Cylinderhead:The topend of the cylinderis covered by cylinder head over which inlet and exhaust valve, spark plug or
injectorsare mounted.A copperor asbestosgasketis provided between the engine cylinder and cylinder head to make
an air tight joint.
Piston:Transmit the force exertedbythe burningof charge to the connectingrod.Usuallymade of aluminiumalloywhich
has good heat conducting property and greater strength at higher temperature.
Figure 1 showsthe differentcomponentsof IC engine. 2000 oC. The ordinary engine is made of cast iron and heavy duty
engines are made of steel alloys or aluminum alloys. In the multi-cylinder engine, the cylinders are cast in one block
known as cylinder block.
Cylinderhead:The topend of the cylinderis covered by cylinder head over which inlet and exhaust valve, spark plug or
injectorsare mounted.A copperor asbestosgasketis provided between the engine cylinder and cylinder head to make
an air tight joint.
Piston:Transmit the force exertedbythe burningof charge to the connectingrod.Usuallymade of aluminiumalloywhich
has good heat conducting property and greater strength at higher temperature.
Figure 1 shows the different components of IC engine.
Piston rings: These are housed in the circumferential grooves provided on the outer surface of the piston and made of
steel alloys which retain elastic properties even at high temperature. 2 types of rings- compression and oil rings.
Compressionringisupper ring of the piston which provides air tight seal to prevent leakage of the burnt gases into the
lowerportion.Oil ringislower ring which provides effective seal to prevent leakage of the oil into the engine cylinder.
Connecting rod: It converts reciprocating motion of the piston into circular motion of the crank shaft, in the working
stroke. The smaller end of the connecting rod is connected with the piston by gudgeon pin and bigger end of the
connectingrod is connected with the crank with crank pin. The special steel alloys or aluminium alloys are used for the
manufacture of connecting rod.
Crankshaft: It convertsthe reciprocatingmotionof the pistonintothe rotarymotionwiththe helpof connecting rod. The
special steel alloys are used for the manufacturing of the crankshaft. It consists of eccentric portion called crank.

Crank case: It houses cylinder and crankshaft of the IC engine and also serves as sump for the lubricating oil.
Flywheel: It is big wheel mounted on the crankshaft, whose function is to maintain its speed constant. It is done by
storing excess energy during the power stroke, which is returned during other stroke.
Four stroke engine:
- Cycle of operation completed in four strokes of the piston or two revolution of the piston.
(i) Suctionstroke (suction valve open, exhaust valve closed)-charge consisting of fresh air mixed with the fuel is drawn
into the cylinder due to the vacuum pressure created by the movement of the piston from TDC to BDC.
(ii) Compressionstroke (bothvalvesclosed)-freshcharge iscompressedintoclearance volumebythe return stroke of the
pistonandignitedbythe spark for combustion. Hence pressure and temperature is increased due to the combustion of
fuel
(iii) Expansionstroke (bothvalvesclosed)-highpressure of the burntgasesforce the pistontowardsBDCand hence power
is obtained at the crankshaft.
(iv) Exhaust stroke (exhaust valve open, suction valve closed)- burned gases expel out due to the movement of piston
from BDC to TDC.
Two stroke engine:
-No piston stroke for suction and exhaust operations
-Suction is accomplished by air compressed in crankcase or by a blower
-Induction of compressed air removes the products of combustion through exhaust ports
-Transfer port is there to supply the fresh charge into combustion chamber
Figure 3 represents operation of two stroke engine

Q2. Difference between the principle and operation of four stroke and two stroke engine
Q3.Thermal power plants these powerstations,steamisproducedby burning some fossil fuel (e.g. coal) and then used
to run a steamturbine.Thus,a thermal power station may sometimes called as a Steam Power Station. After the steam
passes through the steam turbine, it is condensed in a condenser and again fed back into the boiler to become steam.
Thisis knownas ranking cycle. This article explains how electricity is generated in thermal power plants. As majority of
thermal power plants use coal as their primary fuel, this article is focused on a coal fired thermal power plant.

Coal: In a coal based thermal power plant, coal is transported from coal mines to the generating station. Generally,
bituminouscoal orbrowncoal isusedas fuel.The coal isstoredin either'deadstorage'orin 'live storage'.Deadstorage is
generally40days backupcoal storage whichisused when coal supply is unavailable. Live storage is a raw coal bunker in
boilerhouse.The coal iscleanedinamagneticcleanertofilteroutif any ironparticlesare present which may cause wear
and tearin the equipment.The coal fromlive storage is first crushed in small particles and then taken into pulverizer to
make it in powdered form. Fine powdered coal undergoes complete combustion, and thus pulverized coal improves
efficiency of the boiler. The ash produced after the combustion of coal is taken out of the boiler furnace and then
properly disposed. Periodic removal of ash from the boiler furnace is necessary for the proper combustion.
Boiler:The mixture of pulverizedcoal andair (usuallypreheatedair) istakenintoboilerandthenburntinthe combustion
zone.Onignitionof fuel alarge fireball isformedat the center of the boiler and large amount of heat energy is radiated
from it. The heat energy is utilized to convert the water into steam at high temperature and pressure. Steel tubes run
along the boiler walls in which water is converted in steam. The flue gases from the boiler make their way through
superheater, economizer, air preheater and finally get exhausted to the atmosphere from the chimney.
 Superheater:The superheatertubesare hangedat the hottest part of the boiler. The saturated steam produced
in the boiler tubes is superheated to about 540 °C in the superheater. The superheated high pressure steam is
then fed to the steam turbine.
 Economizer: An economizer is essentially a feed water heater which heats the water before supplying to the
boiler.
 Air pre-heater: The primary air fan takes air from the atmosphere and it is then warmed in the air pre-heater.
Pre-heatedairisinjectedwithcoal inthe boiler.The advantage of pre-heating the air is that it improves the coal
combustion.
Steam turbine: High pressure super heated steam is fed to the steam turbine which causes turbine blades to rotate.
Energy in the steam is converted into mechanical energy in the steam turbine which acts as the prime mover. The
pressure andtemperature of the steam falls to a lower value and it expands in volume as it passes through the turbine.
The expanded low pressure steam is exhausted in the condenser.

Condenser: The exhausted steam is condensed in the condenser by means of cold water circulation. Here, the steam
loses it's pressure as well as temperature and it is converted back into water. Condensing is essential because,
compressing a fluid which is in gaseous state requires a huge amount of energy with respect to the energy required in
compressing liquid. Thus, condensing increases efficiency of the cycle.
Alternator: The steam turbine is coupled to an alternator. When the turbine rotates the alternator, electrical energy is
generated. This generated electrical voltage is then stepped up with the help of a transformer and then transmitted
where it is to be utilized.
Feedwater pump: The condensedwaterisagainfedtothe boilerbya feed water pump. Some water may be lost during
the cycle, which is suitably supplied from an external water source.
This was the basic working principle of a thermal power station and its typical components. A practical thermal plant
possess more complicated design and multiple stages of turbine such as High Pressure Turbine (HPT), Intermediate
Pressure Turbine (IPT) and Low Pressure Turbine (LPT).
Advantages and Disadvantages of a Thermal Power Plant
Advantages:
 Less initial cost as compared to other generating stations.
 It requires less land as compared to hydro power plant.
 The fuel (i.e. coal) is cheaper.
 The cost of generation is lesser than that of diesel power plants.
Disadvantages:
 It pollutes the atmosphere due to the production of large amount of smoke. This is one of the causes of global
warming.
 The overall efficiency of a thermal power station is low (less than 30%).
Q4. Differences between Impulse and Reaction Turbines:
S.No Impulse Turbine Reaction Turbine
1
In impulse turbine all hydraulic energy is converted
into kinetic energy by a nozzle and it is is the jet so
produced which strikes the runner blades.
In reaction turbine only some amount of the available
energy is converted into kinetic energy before the fluid
enters the runner.
2
The velocity of jet which changes, the pressure
throughout remaining atmosphere.
Both pressure andvelocitychangesas fluid passes through
a runner. Pressure at inlet is much higher than at outlet.
3
Water-tight casing is not necessary. Casing has no
hydraulicfunctiontoperform.Itonlyservestoprevent
splashing and guide water to the tail race.
The runner must be enclosed within a watertight casing.
4
Water is admitted only in the form of jets. There may
be one or more jets striking equal number of buckets
simultaneously.
Water is admitted over the entire circumference of the
runner.
5
The turbine doesn’trunfull and air has a free access to
the bucket.
Water completelyfillsat the passages between the blades
and while flowing between inlet and outlet sections does
work on the blades.

6
The turbine is always installed above the tail race and
there is no draft tube used.
Reaction turbine are generally connected to the tail race
through a draft tube which is a gradually expanding
passage. It may be installed below or above the tail race.
7
Flow regulation is done by means of a needle valve
fitted into the nozzle.
The flow regulation in reaction turbine is carried out by
means of a guide-vane assembly. Other component parts
are scroll casing, stay ring runner and the draft tub.
8 Example of impulse turbine is Pelton wheel.
Examples of reaction turbine are Francis turbine, Kaplan
and PropellerTurbine,DeriazTurbine,TubulerTurbine,etc.
9 Impulse turbine have more hydraulic efficiency. Reaction turbine have relatively less efficiency.
10 Impulse turbine operates at high water heads. Reaction turbine operate at low and medium heads.
11 Water flowistangential directiontothe turbine wheel. Water flows in radial and axial direction to turbine wheel.
12 Needs low discharge of water. Needs medium and high discharge of water.
13 Degree of reaction is zero.
Degree of reactionismore than zeroand less than or equal
to one.
14 Impulse turbine involves less maintenance work. Reaction turbine involves more maintenance work.
Q5. Describe rolling operation and also describe various types of rolling mills.
Types of Rolling mills
Rolling mills may be classified according to the number and arrangement of the rolls.
(a): Two high rolling mills
(b): Three high rolling mills
(c): Four high rolling mills
(d): Tandem rolling mills
(e): Cluster rolling mills
two high rolling mills
Two high rolling mills may further classified as
· Reversing mill
· Non reversing mill
A two high rolling mill has two rolls only.
Two high reversing mill:
In twohighreversingrollingmillsthe rollsrotate istinone direction and then in the other, so that rolled metal may pass
back and forth through the rolls several times. This type is used in pluming and slabing mills and for roughing work in
plate , rail , structural and other mills.

These are more expensive compared to the non reversing rolling mills. Because of the reversible drive needed.
Two high non reversing mill:
In twohighnon reversingmillsastworollswhichrevolvecontinuouslyin same directiontherefore smaller and less costly
motive powercanbe used.Howevereverytime material istobe carriedback overthe top of the mill for again passing in
through the rolls. Such an arrangement is used in mills through which the bar passes once and in open train plate mill.
2: Three high rolling mill:
It consistsof a roll stand withthree parallel rollsone above the other.Adjacentrollsrotatesinopposite direction. So that
the material may be passed between the top and the middle roll in one direction and the bottom and middle rolls in
opposite one.
In three highrollingmillsthe workpiece isrolledonboththe forwardandreturn passes.Firstof all the work piece passe s
through the bottom and middle rolls and the returning between the middle and the top rolls.
So that thickness is reduced at each pass. Mechanically operated lifted tables are used which move vertically or either
side of the stand. So that the work piece fed automatically into the roll gap.
Since the rolls run in one direction only a much less powerful motor and transmission system is required. The rolls of a
three high rolling mills may be either plain or grooved to produce plate or sections respectively.
3: Four high rolling mill:
It has a roll standwithfour parallel rollsone above the other.The topand the bottomrollsrotate inopposite direction as
do the twomiddle rolls.The twomiddle are smallerinsize thanthe topand bottomrollswhichare calledbackup rollsfor
providing the necessary rigidity to the smaller rolls.
A four high rolling mill is used for the hot rolling of armor and other plates as well as cold rolling of plates, sheets and
strips.
4: Tandem rolling mills:
It isa setof twoor three standsof roll set inparallel alignment.Sothata continuouspassmaybe made through each one
successively with change the direction of material.

5: Cluster rolling mills:
It is a special type of four high rolling mill in which each of the two working rolls is backup by two or more of the larger
backup rolls for rolling hard in materials. It may be necessary to employ work rolls of a very small diameter but of
considerable length. In such cases adequate of the working rolls can be obtained by using a cluster mill.
Q6. Describe the function of air compressor with neat sketch
It isa mechanical component(machine) tocompressthe airwithraise itspressure.The air compressor sucks air from the
atmosphere andcompressesitthenfurtherdelivers with a high pressure to a storage vessel. From the storage vessel, it
may be transmit by the channel (pipeline)
to a place where the supply of compressed air is required. Afterward the compression of air requires some work to be
done on it; therefore a compressor must be driven by some prime mover.
Application of Air Compressor:
It is used for operating pneumatic drills, riveters, road drills, paint spraying, in starting and
supercharging of internal combustion engines, in gas turbine plants, jet engines and air motors,
etc. It is also employ in the operation of lifts, rams, pumps etc.
Classification of Air Compressors:
1. According to working:
 Reciprocating compressors
 Rotary compressors
2. According to action:
 Single acting compressors
 Double acting compressors
3. According to number of stages:
 Single stage compressors
 Multi-stage compressors
Important Definitions:
1. Inlet pressure: It is the absolute pressure of air at the inlet of a compressor.
2. Discharge pressure: It is the absolute pressure of air at the outlet of a compressor.
3. Compression ratio (or pressure ratio): It is the ratio of discharge pressure to the inlet pressure.
Since the discharge pressure is always more than the inlet pressure, therefore the value of
compression ratio is more than unity.
4. Compressor capacity: It is the volume of air delivered by the compressor, and is expressed in

m3/min or m3/s.
5. Free air delivery: It is the actual volume delivered by a compressor when reduced to the normal temperature and
pressure condition. The capacity of a compressor is generally given in terms of free air delivery.
6. Swept volume: It is the volume of air sucked by the compressor during its suction stroke.
Mathematically the swept volume or displacement of a single acting air compressor is given by
Vs = (π/4) X D2
X L
Where D = Diameter of cylinder bore, and
L = Length of piston stroke.
7. Mean effective pressure. As a matter of fact, air pressure on the compressor piston keeps on changing with the
movementof the pistoninthe cylinder.The mean effective pressure of the compressor is found out mathematically by
dividing the work done per cycle to the stroke volume.
Working of Single Stage Reciprocating Air Compressor:
Components: It consists of a cylinder, piston, inlet and discharge valves etc.
Working: when the piston moves downwards (suction stroke), the pressure inside the cylinder
fallsbelowthe atmosphericpressure.Due to this pressure difference, the inlet valve gets opened and air is sucked into
the cylinder, at inlet pressure until the piston completes the suction stroke. Then the piston moves upwards (delivery
stroke), the pressure inside the cylinder goes on increasing till it reaches the discharge pressure. At this stage, the
discharge valve getsopenedandairisdeliveredtothe container.Atthe end of delivery stroke, a small quantity of air, at
highpressure,isleftinthe clearance space.Asthe pistonstartsitssuctionstroke,the aircontainedinthe clearance space
expands till its pressure falls below the atmospheric pressure. At this stage, the inlet valve gets opened as a result of
which fresh air is sucked into the cylinder, and the cycle is repeated.
It may be noted that in a single acting reciprocating air compressor, the suction, compression and delivery of air takes
place in two strokes of the piston or one revolution of the crankshaft
Advantages
 Each type of air compressor comes with different definition because it offers different types of feature that
impresses all of air compressor users. But all in all, an air compressor is an equipment that adds air inside a
container and compresses it, which makes the air pressure inside the tank higher than the air outside of the
tank.
 Differenttypesof aircompressorprovidesdifferentlevelsof power,butitstill dependsonwhatlevel youneed,
whetheritisfor airin spraypaintingor an air compressor that fills air to a car tire. Each type of air compressor
doesa specificjobsoreadingitsdescriptionwill helpyou a lot. You will know the capacity of power that it can
provide.
 Unlike otherequipment,the machines,aircompressorsdoesn’tneedmeticulousmaintenance. But regular but
easymaintenace canbe done to avoidminorproblemsthatcan leadtomajor damage like engine malfunction,
but other than that, it provides good performance.

Disadvantages
Air compressorsare verynoisy.Thisisnotso perfectif youare livingonan apartment or duplex because it will
surely disturb your neighbors. It is a major downside for people who don’t have excess area to run loud
equipmentlike aircompressor.If youare planningtogetan air compressor,make sure that you have an extra lot
or area where you can place the equipment and make it run.
Each type of air compressor comes with different sizes. They say that a huge air compressor can provide a
higher level of power. If you don’t have enough excess area for the compressor, this will be a major drawback
mostespeciallyif youneeded too much energy. However, there are small sizes of air compressor but it doesn’t
provide high level energy compared to huge air compressors.
Compressed air is used for many purposes, including:
 Pneumatics, the use of pressurized gases to do work
o Air tools
 Vehicle propulsion (compressed air vehicle)
 Energy storage (compressed air energy storage)
 Air brakes, including:
o railway braking systems
o road vehicle braking systems
 Refrigeration
 Air-start systems in engines
 Cleaning dust and small debris in tiny spaces
 Painting
 Inflating tiers of vehicles
Q7. Vapour compression refrigeration system
The most importantof all the refrigerationsystemisthe vapourcompressionrefrigerationsystem with the view point of
commercial and domestic utility. This system is the most practical form of refrigeration
Principle
In this system Freon-12 or freon-22 is used as refrigerant. This refrigerant is capable of readily evaporation and
condensation without leaving the plant during the evaporation state it absorbs heat from heated body. This absorbed
heatis usedas latentheatfor converting it from liquid to vapour state. In the condensation or cooling process it rejects
the heat to the external body. Thus it produces a cooling effect in the working fluid.

Description
Vapour compression refrigeration system consists of the following parts.
Compressor:The purpose of the compressoristo raise the temperature and pressure of the input refrigerant which has
low pressure and low temperature.
Discharge line:A discharge line isused for delivering the high pressure, high temperature vapour from the discharge of
the compressor to the condenser.
Condenser: The temperature of the hot refrigerant is reduced using a coolant with the help of condenser.
Receiver tank: Receiver tank is used to provide storage for a condensed liquid so that a constant supply of liquid is
available to the evaporator as required.
Liquid line: A liquid line transmits the liquid refrigerant from the receiver tank to the refrigerant flow control.
Expansion valve: The proper amount of refrigerant liquid to the evaporator is controlled by the expansion valve.
Evaporator: An evaporator provides a cooling effect to the refrigerated space. The liquid refrigerant absorbs heat from
the refrigerated surface and gets converted into refrigerant vapour.
Suction line:The lowpressure vapourfromthe evaporatoris transferred to the suction inlet of the compressor with the
help of suction line.
Working principle
A simple vapour compression system follows the following chain,
Compression – condensation – expansion – vaporization
The vapour at low temperature and low pressure enters the compressor where it is compressed which makes the
temperature and pressure to increase considerably. From the compressor the vapour enters the condenser where it is
condensed to a very high pressure liquid and it is collected in a receiver tank. From the receiver tank, the refrigerant
slowly passes through the expansion valve, where it is throttled down to a lower pressure. Finally it reaches the
evaporator where it extracts heat from the surrounding where it is being refrigerated and vaporizes to low pressure
vapour.Thus the surroundingiscooled.Fromthe evaporatorthe low pressure refrigerantvapour enters the compressor.
This process is repeated as a cycle.
Advantages of vapour compression refrigeration system
· Running cost of this system is low
· For a fixed capacity of refrigeration, it is compact in size.
· This is employed for a large range of temperatures.
· The size of the evaporator is small.
· This system is available in variety of sizes.
Disadvantages of vapour compression refrigeration system
· Cost of the refrigerant is high.

· Refrigerant leakage is a problem.
· Initial cost is high.
· Energy consumption in the form of electricity is high.
Q8. What are the advantages of AC and DC power supply in welding?
1. A.C. welding machine is cheaper, small in size, light in weight and simple to operate.
2. Maintenance of A.C. welding machine is easier and more economical, because there is no moving parts in it.
3. Heat generated is equal at both the poles, so it does not require changing of polarity.
4. A.C. welding machine is not suitable for welding all metals particularly non-ferrous metals and alloys.
5. Bare electrode cannot be used. Only specially designed coated electrodes can be used.
6. A.C. welding machine is not suitable for welding of sheet metals due to difficulty in starting the arc.
7. The problem of arc-blow can be easily controlled.
8. Voltage drop in A.C. is less, hence, can be used at a large distances from the power supply.
9. It can only be used when A.C. power supply is available.
10. Less electric energy consumption per kg of metal deposited (3 to 4 kWh.).
11. A.C. Welding machine has high efficiency (0.8 to 0.85).
12. A.C. Welding machine has lower operating cost.
13. A.C. Welding machine has an disadvantage of using low power factor at the welding station, (0.3 to 0.4).
D.C arc welding
1. D.C. welding machine is two to three times costlier, larger in size, heavier in weight and is more complicated.
2. Maintenance cost is higher because of many moving parts in it.
3. Heat generated is different at the work and the electrode by changing the polarity.
4. D.C. welding machine is suitable for welding all types of metals by changing the polarity.
5. Both coated and bare electrode can be used in D.C. welding machine.
6. It is used for all sorts of work as starting of the arc is easier comparatively.
7. Arc-blow is severe and difficulty to control.
8. Voltage drop is relatively higher, it can be used only at a short distance from the power supply.
9. It can be used anywhere with engine driven D.C. generator or by rectified A.C. supply.
10. Higher electric energy consumption per kg of metal deposited (6 to 10 kWh).

11. Efficiency of D.C. Welding machine is low only 0.3 to 0.6.
12. It has higher operating cost.
13. The motor in a D.C. Welding has an advantage of high power factor of 0.6 to 0.7
Q9. Friction Clutch
A clutchis a device usedtotransmitthe rotary motion of one shaft to another when desired. The axes of the two shafts
are coincident.
In frictionclutches,the connectionof the engine shaft to the gear box shaft is affected by friction betwee n two or more
rotatingconcentricsurfaces.The surfacescan be pressedfirmlyagainstone another when engaged and the clutch tends
to rotate as a single unit.
1.Single plate clutch(Disc clutch)
A discclutch consistsof a clutchplate attachedto a splinedhubwhich is free to slide axially on splines cut on the driven
shaft. The clutch plate is made of steel and has a ring of friction lining on each side. The engine shaft supports a rigidly
fixed flywheel.
A spring-loaded pressure plate presses the clutch plate firmly against the flywheel when the clutch is engaged. When
disengaged, the springs press against a cover attached to the flywheel. Thus, both the flywheel and the
pressure plate rotate withthe inputshaft.The movementof the clutchpedal istransferredto the pressure plate through
a thrust bearing.
Figure showsthe pressure plate pulledbackbythe release leversandthe frictionliningsonthe clutch plate are no longer
in contact with the pressure plate or the flywheel. The flywheel rotates without driving the clutch plate and thus, the
driven shaft.

Whenthe foot istakenoff the clutch pedal,the pressure onthe thrustbearingisreleased.Asaresult,the springsbecome
free to move the pressure plate to bring it in contact with the clutch plate. The clutch plate slides on the
splined hub and is tightly gripped between the pressure plate and the flywheel.
The friction between the linings on the clutch plate, and the flywheel on one side and the pressure plate on the other,
cause the clutchplate andhence,the drivenshaft to rotate. In case the resisting torque on the driven shaft exceeds the
torque at the clutch, clutch slip will occur.
Single Plate Clutch Advantages
1. This clutch respond very fast.
2. It generates low heat, so non need of cooling medium.
Single Plate Clutch Disadvantages
1. Torque transmitting capacity is very less.
2. This is old type of clutch.
3. Not used in small vehicles
2. Multiple Clutch
In a multi-plateclutch,the numberof frictional linings and the metal plates is increased which increases the capacity of
the clutch to transmit torque. Figure shows a simplified diagram of a multi-plate clutch.
The frictionringsare splinedontheiroutercircumferenceandengage with corresponding splines on the flywheel. They
are free toslide axially.The frictionmaterial thus,rotateswiththe flywheel and the engine shaft. The number of friction
rings depends upon the torque to be transmitted.
The drivenshaftalsosupportsdiscson the splineswhichrotate withthe driven shaftandcan slide axially.If the actuating
force on the pedal is removed, a spring presses the discs into contact with the friction rings and the
torque istransmittedbetweenthe engine shaftandthe drivenshaft.If n isthe total numberof plates both on the driving
and the driven members, the number of active surfaces will be n – 1.
3. Cone clutch
In a cone clutch the contact surfaces are in the form of cones. In the engaged position, the friction surfaces of the two
cones A and B are in complete contact due to spring pressure that keeps one cone pressed against the
other all the time. When the clutch is engaged, the torque is transmitted from the driving shaft to the driven shaft
throughthe flywheelandthe friction cones.Fordisengagingthe clutch, the cone B is pulled back through a lever system
against the force of the spring.

4. Centrifugal clutch
Centrifugal clutchesare beingincreasinglyusedinautomobiles and machines. A centrifugal clutch has a driving member
consisting of four sliding blocks (Fig. 8.16). These blocks are kept in position by means of flat springs provided for the
purpose. As the speed of the shaft increases, the centrifugal force on the shoes increases. When the centrifugal force
exceeds the resisting force of the springs, the shoes move forward and press against the inside of the rim and thus,
torque istransmittedtothe rim.In thisway,the clutchisengagedonlywhenthe motor gains sufficient speed to take up
the load in an effective manner. The outer surfaces of the shoes are lined with some friction material
Q10. Couplings
A couplingisa device usedtoconnecttwoshaftstogetherattheirendsforthe purpose of transmittingpower. Couplings
do notnormallyallowdisconnection of shafts during operation, however there are torque limiting couplings which can
slip or disconnect when some torque limit is exceeded.
The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of
misalignment or end movement or both. By careful selection, installation and maintenance of couplings, substantial
savings can be made in reduced maintenance costs and downtime.
Uses
Shaft couplings are used in machinery for several purposes. The most common of which are the following.
 To transfer power from one end to another end.(ex: motor transfer power to pump through coupling) Primary
function.
 To provide forthe connectionof shaftsof units that are manufactured separately such as a motor and generator
and to provide for disconnection for repairs or alterations.
 To provide for misalignment of the shafts or to introduce mechanical flexibility.
 To reduce the transmission of shock loads from one shaft to another.
 To introduce protection against overloads.
 To alter the vibration characteristics of rotating units.
 To connect driving and the driven part
 slips when overload occurs

Types
Clampedorcompressionrigidcouplingscome intwopartsand fittogetheraroundthe shaftsto forma sleeve. They offer
more flexibilitythansleevedmodels,andcanbe usedon shaftsthatare fixedinplace.Theygenerallyare large enough so
that screws can pass all the way through the coupling and into the second half to ensure a secure hold. Flanged rigid
couplings are designed for heavy loads or industrial equipment. They consist of short sleeves surrounded by a
perpendicular flange. One coupling is placed on each shaft so the two flanges line up face to face. A series of screws or
boltscan thenbe installedinthe flangestoholdthemtogether.Because of theirsize and durability, flanged units can be
used to bring shafts into alignment before they are joined together. Rigid couplings are used when precise shaft
alignment is required; shaft misalignment will affect the coupling's performance as well as its life. Examples:
Sleeve or Muff coupling
A sleeve couplingconsistsof apipe whose bore isfinishedtothe requiredtolerance basedonthe shaftsize.Based on the
usage of the coupling a keyway is made in the bore in order to transmit the torque by means of the key. Two threaded
holes are provided in order to lock the coupling in position.
Sleeve couplingsare alsoknownas Box Couplings.Inthiscase shaft ends are coupled together and abutted against each
other which are enveloped by muff or sleeve. A gib head sunk keys hold the two shafts and sleeve together. in other
words,thisisthe simplesttype of the coupling.Itismade from the cast iron and very simple to design and manufacture.
It consistsof a hollowpipe whose innerdiameterissame as diameterof the shafts.The hollow pipeisfittedovera two or
more endsof the shaftswiththe helpof the tapersunkkey.A keyand sleeve are useful totransmitpowerfromone shaft
to another shaft.
Clamp or Split-muff coupling
In thiscoupling,the muff orsleeve ismade intotwohalvespartsof the castiron andtheyare joinedtogetherbymeansof
mildsteel studsorbolts.The advantages of this coupling is that assembling or disassembling of the coupling is possible
without changing the position of the shaft. This coupling is used for heavy power transmission at moderate speed.
Tapered shaft lock
A taperedlock is a formof keyless shaftlockingdevice thatdoes not require any material to be removed from the shaft.
The basic ideaissimilartoa clamp couplingbutthe momentof rotationiscloserto the centerof the shaft. An alternative
couplingdevice tothe traditional parallelkey,the taperedlockremovesthe possibility of play due to worn keyways. It is
more robust than using a key because maintenance only requires one tool and the self-centering balanced rotation
means it lasts longer than a keyed joint would, but the downside is that it costs more.[

Flexible
Flexible couplings are usually used to transmit torque from one shaft to another when the two shafts are slightly
misaligned. They can accommodate varying degrees of misalignment up to 3° and some parallel misalignment. In
addition,theycanalsobe usedfor vibrationdampingornoise reduction.Inrotatingshaftapplications a flexible coupling
can protect the driving and driven shaft components (such as bearings) from the harmful effects of conditions such as
misaligned shafts, vibration, shock loads, and thermal expansion of the shafts or other components.
Q11. Difference between Centrifugal Pump and Reciprocating Pump:
S. No. Centrifugal pump Reciprocating pump
1. It is one of the rotary pumps which used
kinetic energy of impeller.
It is a positive displacement type pump
which is forced by piston.
2. It continuously discharges the fluid. It does not discharge the fluid
continuously.
3. In centrifugal pump the flow rate decreases
which increasing the pressure.
The pressure does not affect flow rate in
reciprocating pumps.
4. It is used for pumping high viscous fluid. It is used for pump low viscous fluid.
5. In this pumps discharge is inversely
promotional to the viscosity of fluid.
In reciprocating pump viscosity of fluid
does not affect the discharge rate.
6. Efficiency of these pumps are low compare to
reciprocating pump.
Efficiency is high.
7. Centrifugal pump have problem of priming. It does not have any problem of priming.
8. It uses impellers to transfer energy to fluid. It uses piston cylinder device to transfer
energy to fluid.
9. They are lighter than reciprocating pumps. These are heavier compare to centrifugal
pump.
10. It gives higher discharge at low heads. These gives higher heads at low discharge.
11. It is less costly. These are costly.
12. These pumps required less maintenance. These required higher maintenance.
13. Centrifugal pumps are easy to install. These
required less floor space.
These pumps are difficult to install. These
required more floor area.
14. It is mostly used for domestic purpose and
where higher discharge at low head required.
These are mostly used in industries and
high viscous fluid pumped at a high head.
Q12. Centrifugal pump is a hydraulic machine which converts mechanical energy into hydraulic energy (i.e. pressure
energy) by the use of centrifugal force acting on the fluid.
Working Principle
It works on the principle of forced vortex flow. The forced vortex flow means when a certain mass of fluid or liquid is
allowed to rotate by an external torque than there is a rise in pressure head of the rotating liquid takes place. This rise in
pressure head is used to deliver water from one location to another. It is centrifugal force acting on the fluid that makes it to
flow within the casing.

Construction
1. Impeller
2. Casing
3. Suction pipe with a foot valve and strainer
4. Delivery pipe
Let’s discuss about each one of them one by one
1. Impeller
It is the rotating part of the pump. The impeller is mounted on a shaft and the shaft of impeller is again connected with the
shaft of an electric motor. It is rotated by the motor and consists of series of backward curved blades.
2. Casing
It is an air tight passage which surrounds the impeller. The design of the casing is done in such a way that it is capable of
converting the kinetic energy of the water discharging from the outlet of the impeller into pressure energy before it leaves
the casing and enters into the delivery pipe.
Commonly three types of casing are used in centrifugal pump and these are
(i). Volute Casing: It is a spiral type of casing in which the area of flow increases gradually. The increase in area of flow
decreases the velocity and increases the pressure of the liquid that flows through the casing. The volute casing is shown in
figure above:
(ii). Vortex Casing: In vortex casing, a circular chamber is introduced in between the impeller and casing. This is done in
order to prevent the loss of energy due to formation of eddies. The efficiency of the vortex casing is more than that of the
volute casing.
(iii). Casing with Guide Blades: In this casing, the impeller is surrounded by series of guide blades.

3. Suction Pipe with Foot Valve and Strainer
A pipe whose one end is connected with the inlet of the impeller and the other end is dipped into the sump of water is
called suction pipe. The suction pipe consists of a foot valve and strainer at its lower end. The foot valve is a one way valve
that opens in the upward direction. The strainer is used to filter the unwanted particle present in the water to prevent the
centrifugal pump from blockage.
4. Delivery Pipe
It is a pipe whose one end is connected to the outlet of the pump and other end is connected to the required height where
water is to be delivered.
Working
 As the electric motor starts rotating, it also rotates the impeller. The rotation of the impeller creates suction at the
suction pipe. Due to suction created the water from the sump starts coming to the casing through the eye of the
impeller.
 From the eye of the impeller, due to the centrifugal force acting on the water,the water starts moving radially
outward and towards the outer of casing.
 Since the impeller is rotating at high velocity it also rotates the water around it in the casing. The area of the casing
increasing gradually in the direction of rotation, so the velocity of the water keeps on decreasing and the pressure
increases,at the outlet of the pump, the pressure is maximum.
 Now form the outlet of the pump, the water goes to its desired location through delivery pipe.
Advantages ofcentrifugal pump
 As there is no drive sealso there is no leakage in pump
 It can pump hazardous liquids
 There are very less frictional losses
 There in almost no noise
 Pump has almost have 100 efficiency
 Centrifugal pump have minimum wear with respect to others
 There is a gap between pump chamber and motor, so there is no heat transfer between them
 Because of the gap between pump chamber and motor, water cannot enter into motor
 Centrifugal pump use magnetic coupling which breakup on high load eliminating the risk of damaging the motor
Disadvantages ofcentrifugal pump
 Because of the magnetic resistance there is some energy losses
 Unexpected heavy load may cause the coupling to slip
 ferrous particles in liquid are problematic when you are using magnetic drive. This is because particle collect at
impeller and cause the stoppage of pump after some time
Application
The centrifugal pump is used in almost every field to raise the liquid from low level to high level. They are mostly used at
home for filling water tanks,almost in every industry such as chemical, automobile, marine, manufacturing, for irrigation
etc.
What is priming and why it is necessary?
It is process in which the suction pipe, casing and delivery pipe upto the delivery valve is filled completely with liquid to be
raised from outside source before starting the motor. Priming is done to remove the air from the pump.

If air is not removed from the pump than a small negative pressure is created at the suction pipe and it cannot suck the
water from the water sump. So it is advised to fill the pump with water before starting it.
Q13 . Reciprocating pump
Advantages of reciprocating pump
 High efficiency
 No priming needed

 Can deliver water at high pressure
 Can work in wide pressure range
 Continuous rate of discharge
Disadvantages of reciprocating pump
 More parts mean high initial cost
 High maintenance cost
 No uniform torque
 Low discharging capacity
 Pulsating flow
 Difficult to pump viscous fluid
 High wear in parts
Q14. CASTING
There are many types of casting which works differently but all these processes involves following steps.
 First metal is melted in a suitable furnace.
 Now molten metal poured into a predefine cavity.
 The molten metal allows to solidify at desire cooling rate.
 Removal of cast part from mould and clean it for further processes like machining, surface finishing polishing etc.
Casting Terminology:
Flask:
The moulding flask is used to hold the sand mould. The sand mould has desire cavity of object which to be casted. The
sand is rammed into the flask to create sand mould in which metal is poured to get desire shape. It is created into minimum
two pieces which allows removal of pattern easily.
Cope:
The upper part of moulding flask is known as cope.
Drag:
The lower part of moulding flask is known as drag.

Cheeks:
When the moulding flask made into more than two parts, the intermediate parts are known as cheeks. These are used in
complex casting.
Pattern:
Pattern is replica of object to be created. It is made by either wood, wax or other suitable material. It is placed into
moulding flask and sand rammed over it which forms an object cavity into sand.
Pouring Basin:
It is a funnel shape cavity at the top of the mould. The metal is poured into pouring basin from where it is supplied at
different parts of mould.
Runner:
Runner is a horizontal passage of molten metal. It connects sprue to getting system. Normally it is situated at lower half of
mould.
Riser:
Riser is used as reservoir of molten metal when pouring of molten metal has stopped. When the cavity is filled by molten
metal, the pouring is stopped which allows solidifying object. During solidification, volumetric shrinkage takes place which
reduces the desire size and shape of object. The riser is provided into the mould which supplies the molten metal to remove
effect of volumetric shrinkage during solidification. These are further divided into top riser, blind riser, side riser etc.
Sprue:
It is a passage which connects pouring basin to the runner. It controls the flow of molten metal from pouring basin. It is
tapered in shape.
Ingate :
It is the entry point through which molten metal enters into the actual mould cavity.
Core:
Core is used to cast hollow cavity. It is also a sand structure and placed at right place into mould cavity where hollow part
is to be created. The metal poured into mould cavity does not fill the part at which core is placed thus form a hollow cavity.
Chaplets:
These are supporting components of core. These used to support and hold the core into mould cavity. These protect the
core from various forces encounter in casting.
Chills:
Chills are generally solid metal pieces which are placed into cavity to increase cooling rate. Mainly it is used to create
direction solidification of molten metal. They have high thermal conductivity.
Vents:
These are small passages made in mould which allow to escape the gases during solidification.
Advantages and Disadvantages:
Advantages:
Casting has following advantages over other manufacturing process.
 It can create any complex structure economically.
 The size of object doesn’t matter for casting.
 The casting objects have high compressive strength.
 All structure made by casting has wide range of properties.
 This can create an accurate object.
 All material can be cast.
 It creates isotropic structure.

 It is cheapest among all manufacturing processes.
 Composite component can be easily made by casting.
Disadvantages:
Along these advantages, casting has following disadvantages.
 It gives poor surface finish and mostly requires surface finish operation.
 Casting defects involves in this process.
 It gives low fatigue strength compare to forging.
 It is not economical for mass production.
Q15. Modesof heat transfer
Heat isa form of energywhich transfersbetweenbodieswhichare keptunderthermal interactions.Whenatemperature
difference occursbetweentwobodiesorabodywithitssurroundings,heattransferoccurs.
Heat transferoccursin three modes.Three modesof heattransferare describedbelow.
1. Conduction
2. Convection and
3. Radiation
Conduction:
In Conduction,heattransfertakesplace due toa temperature difference inabodyor betweenbodiesinthermal contact,
withoutmixingof mass. The rate of heat transferthroughconductionisgovernedbythe Fourier’slaw of heatconduction.
Duringconduction there will be nomovmentof the moleculestakesplace.
Q = -kA(dT/dx)
Where,‘Q’isthe heatflowrate by conduction
‘K’is the thermal conductivityof bodymaterial
‘A’is the cross-sectional areanormal todirectionof heatflow and
‘dT/dx’isthe temperature gradientof the section.
Convection:
In convection,heatistransferredtoamovingfluidatthe surface overwhichitflowsbycombinedmoleculardiffusionand
bulkflow.Convectioninvolvesconductionandfluidflow.The rate of convective heattransferisgovernedbythe
Newton’slawof cooling.
Q = hA(Ts-T∞)
Where ‘Ts‘is the surface temperature
‘T∞‘ isthe outside temperature
‘h’is the coefficientof convection.
Radiation:
In radiation,heatistransferredinthe formof radiantenergyorwave motionfromone bodyto anotherbody.Nomedium
for radiationtooccur. The rate of heatradiationthatcan be emittedbyasurface at a thermodynamictemperatureis
basedon Stefan-Boltzmann law.
Q = σ.T4
Where ‘T’ isthe absolute temperature of surface
Q16. Bernoulli's Theorem.
According to this theorem the total energy (pressure energy, potential energy and kinetic energy) per unit
volume or mass of an incompressible and non-viscous fluid in steady
flow through a pipe remains constant throughout the flow, provided
there is no source or sink of the fluid along the length of the pipe.
Mathematically for unit volume of liquid flowing through a pipe.
 2
2
1
vghP  constant
To prove it consider a liquid flowing steadily through a tube of non-
uniform area of cross-section as shown in fig. If 1P and 2P are the pressures
A1
h1
P2
v2
P1
B
C
A2
h2v1

at the two ends of the tube respectively, work done in pushing the volume V of incompressible fluid from point B to C
through the tube will be VPPVPVPW )( 2121  ......(i)
This work is used by the fluid in two ways.
(i) In changing the potential energy of mass m (in the volume V ) from mgh1 to mgh2,
i.e., )( 12 hhmgU  ......(ii)
(ii) In changing the kinetic energy from 2
1
2
1
mv to 2
2
2
1
mv , i.e., )(
2
1 2
1
2
2 vvmK  ......(iii)
Now as the fluid is non-viscous, by conservation of mechanical energy
KUW 
i.e., )(
2
1
)()( 2
1
2
21221 vvmhhmgVPP 
or )(
2
1
)( 2
1
2
21221 vvhhgPP   [As Vm / ]
or 2
222
2
111
2
1
2
1
vghPvghP  
or  2
2
1
vghP  constant
This equation is the so called Bernoulli's equation and represents conservation of mechanical energy in
case of moving fluids.
(i) Bernoulli's theorem for unit mass of liquid flowing through a pipe can also be written as:
 2
2
1
vgh
P

constant
(ii) Dividing above equation by g we get
g
v
h
g
P
2
2


= constant
Here
g
P

is calledpressure head, h is called gravitational head and
g
v
2
2
is called velocity head. From this equation
Bernoulli's theorem can be stated as.
In streamline flowof anideal liquid,the sumof pressure head, gravitational head and velocity head of every cross
section of the liquid is constant.
Q17. Venturimeter : It is a device based on Bernoulli's theorem used for measuring the rate of flow of liquid
through pipes.
It consistsof twoidentical coaxial tubes A and C connected by a narrow co-axial tube B. Two vertical tubes D and E
are mounted on the tubes A and B to measure the pressure of the following liquid.
When the liquid flows in the tube ABC, the velocity of flow in part B will be larger than in the tube A or C. So the
pressure inpart B will be lessthanthatintube A or C. By measuringthe pressure difference between A and B, the rate of
flow of the liquid in the tube can be calculated.
Let 21 ,aa area of cross section of tube A and B respectively
21, vv Velocity of flow of liquid through A and B respectively
21, PP Liquid pressure at A and B respectively
 ghPP  21 ......(i)
[  = density of flowing liquid]
From Bernoulli's theorem for horizontal flow of liquid
2
22
2
11
2
1
2
1
vPvP  
C
E
B
D
A
v1
v2
a2a1
h

)(
2
1 2
1
2
221 vvPP   ......(ii)
From (i) and (ii) )(
2
1 2
1
2
2 vvgh   = 





 2
1
2
2
2
2
2
1
a
V
a
V
 [As 2211 vavaV  ]
 2
2
2
1
2
2
2
12 2
aa
hgaa
V

 or 2
2
2
1
21
2
aa
hg
aaV


Q18. Constructionofpitottube
It isbasicallyafluidvelocitymeasuringinstrumentthatcanalso be usedfor flow measurement of liquidsandgases.It
consistsof twohollowtubesthatsense pressure atdifferentplaceswithinthe pipe.Thishollow tubescan be mounted
separatelyinapipe or installingtogetherinone casingas a single device.One tube measuresthe stagnationorimpact
pressure andanothertube measuresonlystaticpressure usuallyatthe wall of the pipe.
Working principle of Pitottube
When a solid body is kept centrally,and stationery in a pipeline with flowingfluid, the velocity of the fluid starts
reducing (at the same time the pressure fluid increases due to the conversion of kinetic energy into pressure
energy) due to the presence of the body. At directly in front of the solid body, the velocity becomes zero. This point
is knownas the stagnation point.
The fluid flow can be measured by measuring the differences between the pressure at the normal flow line (static
pressure) and the stagnation point (stagnation pressure).
- Pitottube velocity equation
The equationof velocityisderivedbyapplying Bernoulli’sprinciple;the final equationisgivenbelow
Velocity,
g = accelerationdue togravity
Actual velocity,
Cv = Coefficientof pitottube
Applications of pitot tube
The pitottube is usedinutilitystreamswhere highaccuracyisnotnecessary.Itisusedin the air duct andpipe system.It
isusedin aircraft to measure airflowvelocity.Theyare usedformappingflow profileinachannel or duct

Q19. WELDING
Weldingis a materialsjoiningprocesswhichproducescoalescence of materialsbyheatingthemtosuitable
temperatureswithorwithoutthe applicationof pressure orbythe applicationof pressure alone,andwithorwithout
the use of fillermaterial.
Weldingis usedformakingpermanentjoints.Itisusedinthe manufacture of automobile bodies,aircraftframes,
railwaywagons,machine frames,structural works,tanks,furniture,boilers,generalrepairworkandshipbuilding.
Classificationofweldingprocesses:
(i).Arc welding
1. Carbonarc
2. Metal arc
3. Metal inertgas
4. Tungsteninertgas
5. Plasmaarc
6. Submergedarc
7. Electro-slag
(ii). GasWelding
1. Oxy-acetylene
2. Air-acetylene
3. Oxy-hydrogen
(iii). Resistance Welding
1. Butt
2. Spot
3. Seam
4. Projection
5. Percussion
(iv) Thermit Welding
(v) SolidState Welding
1. Friction
2. Ultrasonic
3. Diffusion
4. Explosive
(vi) NewerWelding
1. Electron-beam
2. Laser

(vii) RelatedProcess
1. Oxy-acetylenecutting
2. Arc cutting
3. Hard facing
4. Brazing
5. Soldering
Arc welding methods
1. Metal arc welding
It isa processof joiningtwo metal piecesbymeltingthe edgesbyanelectricarc.The electricarc isproduced
betweentwoconductors.The electrode isone conductorandthe workpiece isanotherconductor.The electrode andthe
workpiece are broughtnearerwithsmall airgap. (3mm app.)
Whencurrentis passedan electricarcis producedbetweenthe electrode andthe workpiece.The workpiece
and the electrode are meltedbythe arc.Both moltenpiece of metal becomeone.Temperature of arcisabout 4000°c
Electrodesusedinarc weldingare coatedwithaflux.Thisflux producesagaseousshieldaroundthe moltenmetal.It
preventsthe reactionof the moltenmetal withoxygenandnitrogeninthe atmosphere.The fluxremovesthe impurities
fromthe moltenmetal andforma slag.Thisslag getsdepositedoverthe weldmetal.Thisprotectsthe weldseamfrom
rapidcooling.Fig.1showsarc weldingprocess.
Equipments:(ReferFig2)
 A weldinggenerator(D.C.) orTransformer(A.C.)
 Two cables- one forworkand one forelectrode
 Electrode holder
 Electrode
 Protective shield
 Gloves
 Wire brush
 Chippinghammer
 Goggles

Fig. 1 Arc Welding
Fig 2 ElectricArc WeldingEquipments
Advantages
 Most efficientwaytojoinmetals
 Lowest-costjoiningmethod
 Affordslighterweightthroughbetter utilization of materials
 Joinsall commercial metals
 Providesdesignflexibility

Limitations
1. Manuallyapplied,therefore highlaborcost.
2. Needhighenergycausingdanger
3. Notconvenientfordisassembly.
4. Defectsare hard to detectat joints.
Comparisonof A.C. and D.C. arc welding
Alternating Current (from Transformer) Direct Current (from Generator)
1 More efficiency Less efficiency
2 Power consumption less Power consumption more
3 Cost of equipment is less Cost of equipment is more
4 Higher voltage – hence not safe Low voltage – safer operation
5 Not suitable for welding non ferrous metals suitable for both ferrous non ferrous metals
6 Not preferred for welding thin sections preferred for welding thin sections
7 Any terminal can be connected to the work or
electrode
Positive terminal connected to the work
Negative terminal connected to the electrode
GAS WELDING
Oxy-Acetylene welding
In gas welding,agasflame isusedtomeltthe edgesof metalstobe joined.The flame isproducedatthe tip of
weldingtorch.OxygenandAcetyleneare the gasesusedtoproduce the weldingflame.The flame will onlymeltthe
metal.A flux isusedduringweltingtopreventoxidationsandtoremove impurities.Metals2mmto50mm thickare
weldedbygaswelding.The temperature of oxyacetylene flameisabout3200°c. Fig3 showsGas weldingequipments.
Gas WeldingEquipment
1. Gas Cylinders
Pressure
Oxygen– 125 kg/cm2
Acetylene –16 kg/cm2
2. Regulators

Workingpressure of oxygen1kg/cm2
Workingpressure of acetylene 0.15kg/cm2
Workingpressure variesdependsuponthe thicknessof the workpieceswelded.
3. Pressure Gauges
4. Hoses
5. Weldingtorch
6. Checkvalve
7. Non returnvalve
Fig- 4 Gas WeldingEquipment
TYPES OF FLAMES
• Whenacetylene isburnedinair,itproducesa yellow sootyflame,whichisnotenoughforweldingapplications

• Oxygenisturnedon,flame immediatelychangesintoalongwhite innerarea(Feather) surroundedbya
transparentblue envelopeiscalled Carburizingflame (30000c)
• Thisflamesare usedforhardeningthe surfaces
• Additionof littlemore oxygengive abrightwhitishcone surroundedbythe transparentblue envelope iscalled
Neutral flame (Ithas a balance of fuel gasand oxygen)
• Most commonlyusedflame because ithastemperature about32000c
• Usedfor weldingsteels,aluminium,copperandcastiron
• If more oxygenisadded,the cone becomesdarkerandmore pointed,whilethe envelope becomesshorterand
more fierce iscalled Oxidizingflame
• Has the highesttemperature about34000c
• Usedfor weldingbrassandbrazingoperation
Fig4 showsthe typesof flames.
Fig 5 Types of Gas Flames

Advantages
1. Equipmenthasversatile
2. Same equipmentcanbe usedforoxyacetylene cuttingandbrazingbyvaryingthe torchsize
3. Heat can controlledeasily
Disadvantages
1. Slowerprocess
2. Riskisinvolvedinhandlinggascylinders
Q20 TURNING
Turning is a form of machining, a material removal process, which is used to create rotational parts by cutting away
unwanted material. The turning process requires a turning machine or lathe, workpiece, fixture, and cutting tool. The
workpiece isapiece of pre-shapedmaterial thatissecuredtothe fixture,whichitself is attached to the turning machine,
and allowed to rotate at high speeds.
Operations in turning
Turning is not a single process but class of many and different operations performed on a lathe.
Turning of cylindrical surfaces
The lathe can be used to reduce the diameter of a part to a desired dimension. The resulting machined surface is
cylindrical.
Turning of flat surfaces
A lathe can be used to create a smooth, flat face very accurately perpendicular to the axis of a cylindrical
part. Tool is fed radially or axially to create a flat machined surface.

Threading
Different possibilities are available to produce a thread on a lathe. Threads are cut using lathes by
advancingthe cuttingtool at a feedexactlyequaltothe thread pitch. The single-point cutting tool cuts in a helical band,
whichisactuallya thread.The procedure callsfor correct settings of the machine, and also that the helix be restarted at
the same location each time if multiple passes are required to cut the entire depth of thread. The tool point must be
ground so that it has the same profile as the thread to be cut.
Form turning
Cutting tool has a shape that is imparted to the workpiece by plunging the tool into the workpiece.
In form turning, cutting tool is complex and expensive but feed is linear and does not require special
machine tools or devices.

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