Mechanical engineering is the discipline thatapplies the principles of engineering, physics,and materials science for the design,analysis, manufacturing, and maintenanceof mechanical systems. It is the branch ofengineering that involves the design,production, and operation of machinery.

Material Science is the study of relationshipbetween structure and properties ofengineering materials.The reason for structurein materials is manufacturing process likemachining, casting.

Petro-chemicals and RefineriesHeating,Ventilating and Air ConditioningEngine, TransmissionsPower plantsDesigningFluid mechanicsManufacturingMaterial scienceStress analysisCAD and CAMMeasurement and MetrologyMaintenance-Preventive,Breakdown and time based.

Measurement may be defined as branch ofengineering that deals with measuring devicesthat are used to determine various parameters ofa system or a process.

Measuring instruments are useful in processindustries like textile plants, for measuring andcontrolling variables like pressure, temperature,viscosity and flow rate etc.

There are three types of element present ingeneral measuring instrument which are:-

1. Initial sensing element

2. Signal conditioning element

3. Data Presentation element

Initial Sensing Element

Data Presentation

Element

Variable Manipulation

Element

Variable Transformation

Element

Data Transmission

Element

Input

Observedreading

Data Storage Element

Block Diagram to represent the measuring instrument

This instrument is used to measure fluid pressure. As pressureincreases, the tube tries to regain its circular form causingmovement of pointer through gears.

U TUBE MANOMETER

DIGITAL MANOMETER

It is used to measure levelof liquid in big containers,As the level of liquid invessel increases beyond acertain limit, thediaphragm ( flat convextype) bends and themotion is transferredthrough rod and levermechanism to the leverwhich connects thepointer, Here it is digitaldisplay.

RPM is measured by a device called tachometer.Torque & power transmitted by a shaft is measured byDynamometer.

ROPE BRAKE DYNAMOMETER

MECHANICAL TACHOMETER

TEMPERATURE MEASUREMENT

Temperature devices can be of following types:

• Liquid Expansion device like liquid filled andmercury filled thermometer.

• Bimetallic thermometer

• Electrical sensors like thermocouple andthermistor

• Pyrometers which can be radiation(700-2000oC)and optical pyrometer(850-1200oC).It is used formeasuring very high temperature without anyphysical contact with the hot body.

Bimetallic thermometer

VIBRATION MEASUREMENT

Vibration refers to repeated cyclic oscillations of asystem.It may be due to misalignment of matingparts,unbalanced rotating parts or some externalunbalanced force or from design, installation etc.Excessive vibrations in machines can lead toaccumulation of stress, fatigue and ultimatelyfailure of parts. It can also induced dimensionalerrors in the component being machined. Sovibration analysis is important for Thermal PowerPlants, Refineries plant, petrochemical plants.

OUR OBJECTIVES IS:-

• To increase equipment protection.

• To improve safety for personnel.

• To improve maintenance procedures.

• To detect problems early.

• To avoid catastrophic failures.

• To extend equipment life.

• To enhance operations.

Therefore we try to prevent vibration.

Some equipments which we need to analyze are:

• Boiler feed pumps,• Circulating water pumps,• Condensate extraction pumps,• Induced draft fans (ID fan),• Force draft fans (FD fan),• Raw water pumps,• Cooling water pumps,• Pipe vibrations,• Journal Bearings• Gears• Compressors etc.

Note: As automation is donein plants so now adays sound andvibration softwaresare used formeasurement and forpiping specialsoftwares like Pulsim,CAESAR etc are used.

VENTURIMETER

A venturimeter is essentially ashort pipe consisting of twoconical parts with a shortportion of uniform cross-sectionin between. This short portionhas the minimum area and is

known as the throat. Thevelocity increases in thedirection of flow according tothe principle of continuity,while the pressure decreasesaccording to Bernoulli’stheorem.

VENTURIMETER IN PIPELINE

ORIFICEMETER

An orificemeter provides a simpler and cheaperarrangement for the measurement of flow through apipe. An orificemeter is essentially a thin circular platewith a sharp edged concentric circular hole in it.

METROLOGY It is the science of measurement, precision and accuracy. To

summarize, it is a quantitative analysis of a specimen interms of length, angle or say linear, angular measurements.

Accuracy: It is degree of closeness of measured value to thetrue value.

Precision:It is degree of repetitiveness or say closeness ofmeasured value with respect to the previous or consecutivevalues.

LINEAR MEASRUEMENT

It involves measurement of length, thickness and diameter,height etc.

1. Vernier Callipers- Used for measuring external dia,internaldia and thickness.It works on principle that when two scalesor divisions slightly different is size are used, the differencebetween them can be utilized to enhance the accuracy.

2. Micrometer- Its working mechanism is based on principle of screwand nut,we know that when a screw is turned through the nut by onerotation, it advances through one pitch distance.Thus one rotation ofscrew corresponds to linear displacement of one pitch length.Usedfor measuring diameter of shafts , thickness of parts etc.

In Material science we talk about 3 levels of structure:

Macro Structure( < 100x): External geometricalcharacteristics of a material that can be observed bynaked eye. For Eg- length, width,grooves,notches etc.

Micro Structure( ≥ 100x): Internal structuralcharacteristics of a material which can be observedunder microscope at high magnifications of order ≥

100x.For eg- grains,grain boundaries, phases etc.

Crystal Structure: Exhibit three dimensional long rangeperiodicity of arrangement of atoms,or ions ormolecules in the internal structure depending on whichwe have metals, ceramics and polymers respectively.

Dendritic structure form in casting

We can change microstructure of materials by:

Heat treatment process

Addition of alloying element

Cold working and hot working

Varying cooling rate

Forming process like Forging, Rolling etc.

Note: Forming processes are particular manufacturing processes which make use of suitable stresses (like compression, tension, shear or combined stresses) to cause plastic deformation of the materials to produce required shapes.

WHAT IS HEAT TREATMENTHeat treatment is a general term referring to a cycle

of heating and cooling which alters the internalstructure of a metal and thereby changes itsproperties.

Metal and alloys are heat treated for a number ofpurposes:-

1. To Increase their hardness and strength

2. To improved ductility

3. To soften them for subsequent operations (cutting)

4. Stress relieving

5. Eliminate the effects of cold work

Elasticity:-

Elasticity is the tendency of solid materials to return to their original shape after being deformed.

Plasticity:-

Plasticity is the property by which a metal retains its deformation permanently, when the external force applied on it is releas

Ductility:-

Ductility is the property by which a metal can be drawn into thin wires. It is determined by percentage elongation and is measured in terms of percentage reduction in area of a metal

Brittleness:-

• Brittleness:

• Tendency of a material to fracture or fail upon the application of a relatively small amount of force.

Creep:

• When a metal is subjected to a constant force at high temperature below its yield point, for a prolonged period of time, it undergoes a permanent deformation.

Hardness:-

Hardness is the ability of a material to resist scratch, penetration.

Fatigue:-

Fatigue is the of material weakening or breakdown of material subjected to stress, especially a repeated series of stresses.

STIFFNESS

The ability of a material to resist elastic deformation is stiffness.

Toughness:

Toughness is the ability of a metal to resist fracture.(impact toughness testing machine) Meaning to say that the ability to absorb energy uptofracture point.

STRESS -STRAIN CURVE

HEAT TREATMENT PROCESSES

ANNEALING

• Residual stresses remove and ductility is restored.

• Strength and hardness decreases and high machinabilitydue to controlled furnace cooling

NORMALIZING

• Faster cooling rate results in fine grains.

• Strength and hardness will be more.

HARDENING

• The main purpose of hardening tool steel is to develop high hardness.

• Heating steel upto 1100oC followed by sudden quenching in water.

• Problem is surface cracking can occur as stresses not relieved

Tempering

• Relieves internal stresses of hardened steel and make them stable and Improves toughness of hardened steel.

• Also improves wear resistance. Gears, shafts and bearings .

ALLOY ELEMENT AND ITS EFFECTSAlloying Element Its Effect

Chromium Increases corrosion resistance

Cobalt Increases toughness

Sulphur Increases machinability

Silicon & Phosphorus Increases hardenability

Nickel Increases toughness

Titanium Increases strength

Vanadium Increases strength

Molybdenum Increases creep resistance

Zirconium increases strength and limits grains size.

Manganese improves hardenability, ductility and wear resistance.

THERMODYNAMICS

• Thermodynamics is a branch of science which dealswith the energy interaction of the system with respectto surroundings and its effect on the properties ofsystem.The properties may be temperature , pressure,enthalpy ,specific heat thermal conductivity etc.

ZEROTH LAW OF THERMODYNAMICS:-

Given by RH Fowler

• Heat is considered as low grade energy and work is consideredas high grade energy.

• The complete conversion of low grade energy into high gradeenergy is impossible but the high grade energy is completelyconverted into low grade energy.

• Heat engine is a device used to convert one form of energyinto another useful form.

KELVIN PLANK’S STATEMENT: It is impossible to construct adevice which operates in a cycle producing work continuouslywhile interacting with single thermal reservoir.It providesconcept of work producing device.

CLAUSIUS STATEMENT: It is impossible to construct a devicewhich operates in a cycle amd transfers heat from lowtemperature reservoir to high temperature reservoir withoutconsuming any other form of energy.It provides concept ofwork absorbing devices

THE SECOND LAW OF THERMODYNAMICS

The Second Law of Thermodynamics:-

HEAT ENGINE EXAMPLE

• Heat engine is a system that converts heat orthermal energy to mechanical energy, whichcan then be used to do mechanical work.

HEAT PUMP• Pump, as part of a central heating and cooling

system, uses the outside air to both heat a home in winter and cool it in summer. :-

ISOTHERMAL PROCESS

An isothermal process in which the temperature remains constant: ΔT = 0.

ADIABATIC PROCESS

An adiabatic process is one thatoccurs without transfer of heatbetween a thermodynamicsystem and its surroundings. Inan adiabatic process, energy istransferred only as work. .i.e noheat interaction takes placewith the system.

ISENTROPIC PROCESSAn isentropic process is anidealized thermodynamicprocess that is adiabatic andin which the work transfers ofthe system are frictionless;there is no transfer of heat orof matter and the process isreversible. During anisentropic process there areno dissipative effects and thesystem neither absorbs norgives off heat. For this reasonthe isentropic process issometimes called thereversible adiabatic process.

HEAT EXCHANGER

An equipment thatpermits efficienttransfer of heat from ahot fluid to a cold fluidwithout any or withdirect contact of fluids.

On the direction of theliquids flow it is threetypes :-

a). parallel-flow

b).cross-flow,c).countercurrent.

COUNTERCURRENT HEAT EXCHANGERS

In counter current heatexchangers, the fluid pathsflow in oppositedirections.The counterflowarrangement isthermodynamicallysuperior to any other flowarrangement.It is most efficient flowarrangement, producingthe highest temperaturechange in each fluidcompared to any othertwo fluid flowarrangements for a givenoverall heat transfercoeficient.

Cross-flow Heat exchanger:-

• Shell and tube heat exchanger is used for distillation columns, boilers, evaporators and other heavy-duty high temperature and pressure chemical processes. A shell and tube exchanger can handle very high temperature even at 1000 degrees Celsius. The cost of shell and tube heat exchanger is more expensive than other types and it may need large space. Due to its simple operations, shell and tube type is easy to control and operate.

STEAM

• Steam is the vapour or gaseous phase of water.

• It is produced by heating of water and carrieslarge quantities of heat within itself.

• Hence, it could be used as a working substancefor heat engines and steam turbines

• Quality of steam or dryness fraction is used toquantify the amount of water within steam. Ifsteam contains 10% water by mass, it's said to be90% dry, or have a dryness fraction of 0.9.

BOILERS MOUNTINGS AND ACCESSORIES• There are different fittings and devices that are necessary for

operations and safety of a boiler. These devices are mountedon boiler shell.

• Accessories can be Economizer , Air preheater , Superheater.

• According to IBR following mountings should be fitted toboilers:

1. Two safety valves

2. Two water level indicators

3. A pressure gauge

4. A steam stop valve

5. A feed check valve

6. A blow off cock

7. An attachment for inspector’s test gauge

8. A man hole

CASTING

casting

CASTING PROCESS

• Manufacturing of a machine part by melting (heating a metalor alloy above its melting point ) and pouring the liquidmetal/alloy in a cavity approximately of same shape and sizeas the machine part is called casting process. After the liquidmetal cools and solidifies, it acquires the shape and size of thecavity and resembles the required finished product. Theplace, where castings are made is called foundry.

• The casting procedure:• Preparation of a pattern,• Preparation of a mould with the help of the pattern,• Melting of metal or alloy in a furnace,• Pouring of molten metal into mould cavity,• Breaking the mould to retrieve the casting,• Cleaning the casting and cutting off risers, runners etc., (this

operation is called ‘fettling’),• Inspection of casting.

TWO CATEGORIES OF CASTING PROCESSES

1. Expendable mould processes - Mould is sacrificed to remove part

– Advantage: more complex shapes possible

– Disadvantage: production rates often limited by time to makemould rather than casting itself

2. Permanent mould processes -mould is made of metal and can beused to make many castings. Parts include gears, wheels, pipefittings, fuel injection housings, and automotive engine pistons

• Advantage: higher production rates

• Disadvantage: Part geometry is limited with this process as themold needs to open and close. Because of the high tooling costinvolved, a high production volume is needed in order to make thisprocess and economically viable manufacturing option.

• The higher the pouring temperature of the molten metal, theshorter the life of the mould.

Two forms of mold: (a) open mould, simply a container in the shape ofthe desired part; and (b) closed mould, in which the mould geometryis more complex and requires a gating system (passageway) leadinginto the cavity

DIE CASTING

STEPS IN DIE CASTING 1. Close and lock the two halves of a die. 2. Inject the molten metal under pressure into the die. 3. Maintain the pressure until metal solidifies. 4. Open die halves. 5. Eject the casting along with runner, riser etc. 6. The above cycle is repeated.

METAL FORMING PROCESS

• Forming processes are particular manufacturingprocesses which make use of suitable stresses (likecompression, tension, shear or combined stresses) tocause plastic deformation of the materials to producerequired shapes.

• During forming processes no material is removed, i.e.they are deformed and displaced

• Some examples of forming processes are:

1. Forging

2. Extrusion

3. Rolling

4. Sheet metal working

FORGING

• Forging is a manufacturing process involving the shapingof metal using compressive forces. The blows aredelivered with a hammer (often a power hammer) or adie.Forged parts are widely used in mechanismsand machines wherever a component requireshigh strength.Forgings usually require further processing(such as machining) to achieve a finished part.

Open die forging of rolled ring

Forging can produce a piece that is stronger than anequivalent cast or machined part. As the metal is shaped duringthe forging process, its internal grain deforms to follow thegeneral shape of the part. As a result, the grain is continuousthroughout the part, giving rise to a piece with improvedstrength characteristics.

Rolling

• Rolling is the most extensively used metal forming process.

• The material to be rolled is drawn by means of friction into the tworevolving roll gap.

• The compressive forces applied by the rolls reduce the thickness ofthe material or changes its cross sectional area.

• The geometry of the product depend on the contour of the rollgap.

• Roll materials are cast iron, cast steel and forged steel because ofhigh strength and wear resistance requirements.

• Hot rolls are generally rough so that they can bite the work, andcold rolls are ground and polished for good work.

• In rolling the crystals get elongated in the rolling direction. In coldrolling,crystal more or less retain the elongated shape but in hotrolling ,they start reforming after coming out from the deformationzone

Seamless Pipe manufacturing. Steel ingot is heated and pierced

EXTRUSION

One type ofsheet metaloperation( Bending)

MACHINING

• Machining is a process in which a piece of raw materialis cut into a desired final shape and size by a controlledmaterial-removal process.

• Machining is the most important of the manufacturingprocesses. Machining can be defined as the process ofremoving material from a workpiece in the form of chips.The term metal cutting is used when the material ismetallic. Most machining has very low set-up costcompared to forming, molding, and casting processes.However, machining is much more expensive for highvolumes. Machining is necessary where tight toleranceson dimensions and finishes are required.

DRILLING OPERATIONS:

In a drilling machine holesmay be drilled quickly andat low cost. The hole isgenerated by the rotatingedge of a cutting tool

known as the drill whichexerts large force on thework clamped on the table.

The cutting motion isprovided by rotating thedrill.Here the drill used hastwo cutting edges called lips

A milling machine is a machine tool that removes metal as the workis fed against a rotating multi point cutter. The cutter rotates at ahigh speed and because of the multiple cutting edges it removesthe metal at a very fast rate. Some of the tasks that can run a millingmachine are: drilling, cutting, planing, keyway, slot cutting andshaping edges etc.

Milling operations:-

LATHE MACHINE

A Lathe, machine toolthat performs turningoperations in whichunwanted materialisremoved from aworkpiece rotatedagainst a cutting tool.

MACHINING OPERATIONS TURNING OPERATIONS-

Turning operationsare operations thatrotate theworkpiece as theprimary method ofmoving metalagainst the cuttingtool. Lathes are theprincipal machinetool used in turning

WELDING

It is the process of joining similar dissimilar metals with / without

application of heat, with / without application of pressure and with /

without addition of filler material.

WELDABILITY: It is the capacity of being welded into inseparable

joints having specified properties such as definite weld strength,

proper structure etc. Weldability depends on : (1) Melting point (2)

Thermal conductivity (3) Thermal expansion (4) Surface condition (5)

Change in Micro structure etc.

WELDING CLASSIFICATION

The Welding characteristics may be controlled / corrected

by proper shielding atmosphere, proper fluxing material,

proper filler material, proper welding procedure, proper

heat treatment before and after deposition.

Types of Welds & Welded joints:

• The different types of joints are Lap, Butt, Corner,etc.

• Butt Joints require edge preparation like V, U, Bevel.

• V –Joints are easier to make but amount of metal

to be filled increases with thickness. Hence other

preparations are preferred for higher thicknesses.

• Double preparation is done for still higher thicknesses.

GAS WELDING

It is a process of generating the heat required for melting the joint by means of

an electric arc. This is most widely used than Gas welding because of the ease

of use and high production rates. Selection of power source is mainly

dependent on type welding process. The open circuit voltage normally ranges

between 70-90 V and short circuit current ranges between 600-1000A in any

welding transformer. Welding voltages and welding currents are lower as

compared to open circuit voltage of the power source.

ARC WELDING

ELECTRODES:

The electrodes used can be consumable (same base material) (or) Non-

consumable (Tungsten, Carbon or Graphite). The consumable electrode

can be either coated (stick electrode) or uncoated (bare electrode). The

coatings serve a No. of purposes.

1.To facilitate establishment and maintenance of arc

2. To produce shield gas around arc & weld pool

3. To provide formation of slag to reduce rapid cooling.

4.To introduce alloying elements not contained in core wire.

TUNGSTEN INERT GAS WELDING

This process was invented forwelding Al as Al forms an oxidelayer immediately on exposingto atmosphere. DCEP was usedin welding Al as it causes peelingof oxide layer (Cathodecleaning process).

This process is being

widely used for thin

sheets for precision

welding in nuclear, air

craft, space craft,

chemical industries.

RESISTENCE WELDING

WELDING DEFECTS

• Elasticity

• Plasticity

• Ductility and Brittleness

• Malleability

• Toughness

• Hardness

• Creep and Fatigue

Symbol Meaning SI units/value

A Area M2

BTU British Thermal Unit 1 BTU = 1055 J

CP Specific heat at

constant pressure

J/kgK

CV Specific heat at

constant volume

J/kgK

C Sound speed m/s

COP Coefficient Of

Performance

---

D Diameter m (meters)

E Energy J (Joules)

E Elastic modulus N/m2

E Internal energy per

unit mass

J/kg

Symbol Meaning SI unit/ Value

Q Heat transfer rate W (Watts)

R Electrical resistance Ohms

Re Reynolds number ---

R Radius Meter

S Entropy J/K

T Temperature K

T Tension (in a rope or cable)N

U Internal energy J

V Volume M3

V Voltage Volts

V Velocity m/s

Symbol Meaning SI unit

Kinematic viscosity = µ/ m2/s

Poisson’s ratio ---

Density Kg/m3

Normal stress N/m2

Shear stress N/m2

m Mass flow rate kg/s

h Convective heat transfer

Coefficient

W/m2K

I Moment of inertia M4

M Moment of force N m (Newtons x meters)

k Thermal conductivity W/mK

P Pressure N/m2

PROPERTIES OF FLUIDS

• Matter exists in two states- the solid state and the fluid state.This classification of matter is based on the spacing between different molecules of matter as well as on the behaviour of matter when subjected to stresses. Because molecules in solid state are spaced very closely, solids possess compactness and rigidity of form. The molecules in fluid can move more freely within the fluid mass.

PROPERTIES OF FLUIDS:-

• THE PROPERTIES OF FLUIDS ARE:-

• 1 VISCOSITY

• 2. Density

• 3. Specific weight

• 4. Specific gravity

• 5. compressiblity

1. VISCOSITY :-

• It describes the internal friction of a moving fluid.

• A fluid with large viscosity resists motion because its molecular makeup gives it a lot of internal friction.

• A fluid with low viscosity flows easily because its molecular makeup results in very little friction when it is in motion.

VISCOSITY :-• It describes the internal

friction of a moving fluid.

• A fluid with large viscosity resists motion because its molecular makeup gives it a lot of internal friction.

• A fluid with low viscosity flows easily because its molecular makeup results in very little friction when it is in motion.

• APPLICATION OF VISCOSITY:-

• Transparent and storing facilities for fluids ie, pipes, tanks

• Designing of the sewer line or any other pipe flow viscosity play an important role in finding out its flow behaviour.

• Drilling for oil and gas requires sensitive viscosity.

• To maintain the performance of machine and automobiles by determining thickness of lubricating oil or motor oil.

VISCOSITY

2. Density:--The density of a fluid is its mass per unit volume.

DT:-• destructive testing (DT) includes methods

where your material is broken down in order to determine mechanical properties, such as stress ,strength, toughness and hardness.

toughness and hardness:-

NDT:-The use of noninvasivetechniques to determine the integrity of a material, component or structure

NDT(nondestructive testing):-

Visual method:-

NDT(nondestructive testing):-

Mannual TAPE testing method:-Ultrasonic method Tape testing method:- :-

NDT(nondestructive testing):-

Laser testing method :- X-ray type testing method :-

NDT(nondestructive testing):-

Liquid pentration method :- Thermography:-