final revised mech engg labs - manual 2014

Laboratory Manual

For

MECHANICAL ENGINEERING LABORATORY

ME F215

Prepared by

DEPARTMENT OF MECHANICAL ENGINEERING

EDUCATIONAL DEVELOPMENT DIVISION Birla Institute of Technology & Science, Pilani K.K. Birla Goa Campus

GOA- 403 726 2013-2014

Part I

Mechanics and Dynamics of Solids

1

INDEX

Experiment No. Name of Experiments

Page No.

1. Measurement of tensile strains and modulus of elasticity. 2

2. Measurement of bending moment and deflections in beam. 5

3. Measurement of stiffness of helical springs. 8

4. Measurement of hardness using Rockwell Hardness Testing Machine and Vickers Hardness Testing Machine. 11

5. Estimation and comparison of shock resistance qualities of the materials by conducting Impact Test. 16

6. Study of Gyroscopes 19

7. Study of Dynamic Balancing Machine 21

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EXPERIMENT NO. 1

MEASUREMENT OF TENSILE STRAINS AND MODULUS OF ELASTICITY

NAME_______________________ ID NO _______________________________ SEC. NO. ____________________ BATCH NO___________________________ DATE _______________________ INSTRUCTORS SIGNATURE __________

OBJECTIVE

To measure tensile strain by an extensometer during tension test on a given tensile specimen; and to determine the value of modulus of elasticity.

ACCESSORIES

10000 N (10 Tonne) 'FIE' Hydraulic Universal Testing Machine (UTM); extensometer; Mild steel Test specimen (or specimen of any other material); micrometer (screw gauge); and Vernier Calipers.

THEORY

If a bar or a sheet of steel is pulled at its ends, with the application of force, it is stressed and elongated (strained). Strain may be calculated as the ratio of change in length to the original length. The stress to which the material is subjected, can be calculated by dividing the load with the area of cross section.

If the deformation of the bar is within the elastic limit, there is a linear relationship between stress and strain. A graph between stress and strain, therefore, results in a straight line. The slope of such a straight line is constant and gives the value of modulus of elasticity. Usually the deformation is recoverable on release of load and it is known as elastic deformation

If the deformation of the bar is beyond the elastic limit, there is a nonlinear relationship between stress and strain. A graph between stress and strain, therefore, results in a curved line. The slope of such a straight line is dependent on Local variations of strain with respect to stress. Usually the deformation is not recoverable on release of load and it is known as plastic deformation.

PROCEDURE

1. Study the UTM carefully. Identify different parts of the UTM. (Refer to the user Manual of the UTM). Note down the different measuring instruments available on this machine. Draw a figure of the UTM putting the different labels of each component and attach with your report. (Pencil sketch)

2. Take specimen and inspect it for smoothness. Make a drawing of it.

3. Using a micrometer, determine the diameter of the specimen at five different locations within the gauge length. (Gauge length is that length in which the strain or elongation is expected to be uniform. This enables us to use an extensometer to be fixed within this gauge length). Determine the average of these 5 readings. Find the area of cross section. (Enter the measured values in the observation table of next section)

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4. Firmly grip the upper end of the specimen in the movable crosshead of the testing machine. Grip the lower end of the specimen in the bottom crosshead, after adjusting the required height.

5. Fit the extensometer firmly on the specimen. Switch on the power supplies to the computer and the Microprocessor of the machine. Click on the software of the machine.

6. Enter the values of the variable displayed by the software. Note all the data entered into the computer on your notebook for your reference and study.

7. Run the hydraulic testing machine at the slowest loading rate. Make simultaneous record of the observations of load and extension, at discrete points of load, by freezing the values displayed by the microprocessor. (By freezing these observation points, the test does not stop, but it facilitates recording of the values.)

8. The test is completed now. Unload the specimen and proceed with the calculations. Study your observations in the table below.

OBSERVATIONS

Total length of the test specimen (mm) = Gauge length of specimen (of the extensometer): (L) mm =

Least count of extensometer, mm = (Note it from the console reading of the computer)

Diameter of specimen, (to be measured) mm =

Area of cross section of specimen(calculate)= A in mm2 =

STRESS-STRAIN GRAPH & RESULT: Report the graphs obtained. Show your calculations.

a. Load Vs Displacement, b. Stress Vs Strain

Value of E for given (record the material) specimen is: kN/mm2 ( Gpa)

Obs. No.

Load on specimen (T)

(kN) Stress (T/A) (kN/mm2)

Extensometer Reading (from the console)

(SL)

Strain X 10-5

SL/L

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

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Is the E value in agreement with the accepted value? Yes / No What is the error in the obtained value? Can more accuracy be expected in the Value E? Examine the Uncertainties in the measurements so obtained. Give your analysis?

LEARN MORE:

1. Draw stress-strain diagram for a ductile and a brittle material? 2. Explain plastic deformation occurs in metals with the help of figures? 3. List out few mechanical properties of metals with the help of figures? 4. List out few examples of stress strain behaviour of for ceramics, polymers and composite

materials? 5. Can you characterize mechanical behavior of a material by its stress strain diagram?

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EXPERIMENT NO. 2

MEASUREMENT OF BENDING MOMENT & DEFLECTIONS OF A BEAM


OBJECTIVE:

To measure the deflections of a given beam by dial gauge indicator during bending test; and hence to determine the value of modulus of elasticity of the material and also the bending stresses.

ACCESSORIES:

Beam, dial gauge indicator, Loading frame (Simply supported conditions provided).

THEORY:

For a simply supported beam of span L, carrying a load W at the middle of the span, the maximum bending moment, Mb, is given by MbY/ Iyy. In this formula Y is the distance of the neutral axis for a rectangular beam is at the centre of the beam. From the surface and is equal to half the thickness of the beam. Iyy is the second moment of the area of cross- section of the beam about its neutral axis and is equal to 1/12(Width * thickness3). The maximum stress, on the convex side of the beam, is tensile in nature. The deflection in the beam due to point load applied to beam can be measured with dial gauge indicator. LG

B

LW

L

PROCEDURE

a) Adjust a convenient length L of the simply supported beam by adjusting the distance of the flexible fixture from the fixed fixture.

b) Adjust the Load hanger, such that it should be placed exactly at the LW of the beam, and note down the no load reading (WEIGHT OF THE LOADING PAN) initially.

c) Place a load on the hanger and record the corresponding dial gauge readings. Make such observation for increase of load in discrete steps.

d) Record the dial gauge readings for decrease of load in the same steps as used for increase of load.

AN t

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OBSERVATION:

1. Length of the beam in between two supports (L) =______ m 2. Width of the given beam (b) = ______ m 3. Thickness of the given beam (t) = _____ m 4. Etheoretical documented value for MS specimen/Wood = 210 GPa / 12 GPa 5. No load reading of dial gage indicator = _____

Calculations and Observation table:

Calculation of Bending Stress (b) in N/m2

b = [ Mb y / Iyy ]

Where, Mb = WL/4 for simply supported beam with load acting at the center of beam in N-m. y = Distance from the center of neutral axis to the upper most fiber of specimen in meters Iyy = Area moment of inertia for a given specimen in m4

Calculations of Youngs Modulus (E) in N/m2

For load (W in kg) acting at center (L/2), theoretical deflection equation is given as follows,

Y = WL3/48 E Iyy -----------(1)

Obs. No.

Load (W) in Kg

Dial Gauge reading y in mm at L/4 distance

Bending stress (b )

In N/m2

Expt. Youngs Modulus (Eexp) in

N/m2 1 2 3 4 5 6

Note: 1. Refer Chapter-8 of Mechanics of Solids text book to derive deflection equation

considering simply supported beam condition for a location at L/4 (Since dial gage was fixed at L/4). Accordingly the derived deflection equation as to be rearranged to find Eexp values for a different dial gage readings.

2. Take the E documented value for wooden specimen as 12 GPa and if MS specimen as 210 GPa for your calculations.

3. Further, rearrange the terms having constant values from derived deflection equation and get the equation as follows,

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Eexperiment = K (W/y ) ----------(3)

4. Where, K (CONSTANT) in per meter and (W/y ) is the stiffness in N/m obtained from plotting a best fit graph of Load versus dial gage deflection. The value of E obtained from equation (3) must be used to measure the error involved when compared against the E value obtained from the documented E value for a given specimen.

Conclusions:

Is the E value in agreement with the accepted value? Yes / No What is the error in the obtained value? Can more accuracy be expected in the Value E? Examine the Uncertainties in the measurements so obtained. Give your analysis?

Note: In this experimental set up Different set of readings can be taken by changing 1. The arrangement of both the end fixtures 2. The distance between the end fixtures 3. The material of the test bar

Recommendations:

It is possible to use strain gauge circuit along with strain indicator for measuring the accurate value of strain in the bar specimen. Make a diagram of strain gauge circuit and study the measurement of strains.

Learn More:

1. Derive a deflection equation considering simply supported bean for a location at L/2 and L/3.

2. Observe the plot of stress Vs Strain while loading and unloading the specimen give your comment on the nature of graph in both the condition.

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EXPERIMENT NO. 3

MEASUREMENT OF STIFFNESS FOR HELICAL SPRING


OBJECTIVE

To find the characteristic load behavior of a helical spring or a given machine element and to determine the stiffness of the spring from load versus deflection curve.

ACCESSORIES

Spring Testing Machine, given spring test specimen, micrometer / Vernier calipers

THEORY

A tension (Helical coil) spring is the one, which is subjected to a tensile load, and the resistance is mainly due to its coils and the spring wire. The spring wire is subjected to torsion, when the spring is loaded under tension or compression load.

Closely coiled helical springs subjected to axial pull fall under this category. Such springs are made of rod or wire in the form of a helix described on a right circular cylinder. It is assumed that this type of helical spring is so closely coiled that each turn is practically a plane at right angle to the axis of the helix and the stresses upon the material are almost of pure torsion. The bending couple is negligible in comparison with the torsion couple.

They are used in shock absorbers, railway wagon couplers, spring balances, Bicycle brakes, Vibrators, and many other engineering applications.

PROCEDURE

Study the machine carefully.. The machine can be run on automatic loading mode or hand loading mode using crank lever.

(a) Fix ends of the given spring between upper hook and lower hook of the machine.

(b) By cranking lever, apply the required load, measure the deflection under compression of the given spring using measuring scale.

(c) Using a micrometer, determine the mean diameter of the coil for the spring at least five different locations. Determine the average of these reading.

(d) Using a micrometer, determine the Mean diameter of the wire for the spring at five different locations. Determine the average of these reading, to find the mean diameter.

(e) Draw a graph between load versus deflection, calculate the slope which gives the stiffness of the spring.

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OBSERVATIONS

Total no. of coils: (N) = _________

Mean radius of coil (D) = ________ mm

Diameter of the wire (d) = _______ mm

The axial movement or deflection of the free end of spring is

= 8 (W D3 N)/ Gd4 ;

Spring stiffness (k) = (Gd4/ 8 D3 N) [ can be best determined by slope of W- curve]

Where G is Rigidity modulus of given material of spring

Draw the Load Extension (or Compression) diagram. Determine the slope of the W- curve obtained.

LOAD-DEFLECTION GRAPH & RESULT: Value of Stiffness k for Mild steel spring is: N/mm (as calculated) Stiffness from graph: N/mm

Obs. No. Pressure

applied in ( kPa)

Area of the Piston in

mm Force (N)

Deflection of the free end

Scale reading ()

Deflection of the free end

using theoretical

analysis 1. 2. 3. 4. 5. 6. 7. 8. 9.

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PART B:

LOADING AND UNLOADING OF SHOCK ABSORBER:

The shock absorber is tested on similar lines of spring testing by fixing one end-applying load on the other end. Note the deflections at every stage of loading and unloading the shock absorber. Draw the load versus deflection curve for the shock absorber. Study and interpret the results.

LEARN MORE:

1. Classify springs? 2. Explain the main purpose of spring in engineering applications? 3. When two springs with stiffness k1, k2 are combined in series and parallel, can you derive

the overall stiffness for the series & parallel combinations?

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EXPERIMENT NO. 4

MEASUREMENT OF HARDNESS OF THE GIVEN SAMPLES AND TO CORRELATE THEM WITH THE ULTIMATE

TENSILE STRENGTH OF THE MATERIALS USING VICKERS HARDNESS TESTING MACHINE


OBJECTIVE

To measure the hardness of the given samples and to correlate them with the ultimate tensile strength of the materials using Vickers Hardness Testing Machine.

ACCESSORIES

Power operated Vickers hardness testing machine, Microscope (to measure impressions), Steel ball or diamond indentors and specimens (Mild Steel, Brass, Aluminum, Cast Iron).

THEORY

Hardness is defined as resistance to indentation or resistance to localized plastic deformation. The Vickers test for hardness consists of the application of a hard steel ball or diamond of known diameter under a known load for the specified time period, to the surface of specimen under test. The diameter or diagonal of the resulting impression is measured by means of a microscope.

PROCEDURE

a) The specimen is supported on the hardened steel platen located by a robust steel screw, which is adjusted by means of a hand wheel.

b) An adjusting wheel on the indentor column enables the ball holder to be brought into contact with specimen by judging through the microscope.

c) The load P is applied by means of a single lever mounted on the knife-edges, which carries a hanger for loose weights.

d) An indicator at the front of the machine shows the position of the loading lever and indicates the speed of application of the load P.

e) After the load P is applied with the indentor the diagonal D1 and D2, in mm is measured by Vickers microscope. The mean of the diagonal is calculated.

f) Finally, the VHN of the given specimen is shown on the screen by pressing READ switch.

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OBSERVATIONS

Materials given: _________________

Diagonal D1 = ________ mm and D2 __________ mm of the impression.

Load applied (P): _____ kg

SL No.

Material Load on specimen (P)

Diagonal D1 Diagonal D2

VHN

RESULT AND CORRELATION WITH THE UTS (ULTIMATE STRENGTH)

Hardness number is often used as an indicator of tensile strength of steel. Using graph shown in figure 1. Estimate the tensile strength of steel specimen given to you by applying 3000 kg load and use 10mm standard steel ball for indentation. Compare this figure with tensile test results obtained from your tensile test stress-strain graph.

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PART B

OBJECTIVE

To measure the hardness of the given samples and to correlate them with the ultimate tensile strength of the materials using the Rockwell hardness testing machine.

ACCESSORIES

Direct reading Rockwell hardness testing machine, Diamond cone and steel ball indentors and specimens (Mild Steel, Brass, Aluminum, Cast Iron, Broken HSS bits).

THEORY

The Rockwell test for hardness consists of the application of a hard indentor of known diameter under a known load for the specimen time period, to the surface of specimen under test and the Rockwell hardness of material by measuring the depth of penetration of standard indentors under standard loading conditions, and gives a visible indicator of degree of hardness according to established scales. The dial indicator eliminates the requirement of a microscope for measuring the indentation. The following table gives the standard loads and scales used:

Table 1 Scale

Symbol Indentor Minor Load kg Major Load kg

A Diamond cone 10 50 B Steel ball 10 90 C Diamond cone 10 140

PROCEDURE

a) The specimen is placed on the table and rotating the hand wheel clockwise until contact is made with the indentor raises the table.

b) Continue rotating the hand wheel until the small indicator on the dial indicates the set. c) In the preliminary setting operation as the minor load of 10kg is applied automatically,

the major load P is applied by adjusting back the lever on the right hand side of the machine to its full extent.

d) As soon as the reading of the depth indicator becomes steady the major load is removed automatically and the hardness degree may then be read from the scale A or scale B or scale C as the case may be.

e) The initial load may be removed by rotating the hand wheel anti clockwise and lower the elevating screw to facilitate the removal of the specimen without damaging the indentor.

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OBSERVATIONS

Materials given:

Diameter or angle of indentor: mm

Type of Indentor:

Load applied (P): kg

Reading of scale A or B or C:

Rockwell Hardness:

SL NO.

Material Load on specimen (P) Type of Indentor

Rockwell Hardness A or B or C

RESULT AND CORRELATION WITH THE UTS (ULTIMATE TENSILE STRENGTH) (Please refer to section on hardness and its correlation with strength in the chapter of mechanical properties of materials: Callisters book on Material Science and Engineering) Hardness number is often used as an indicator of tensile strength of steel. Using graph shown in figure estimate the tensile strength of steel specimen given to you. Compare this figure with tensile test results obtained from your tensile test experiment.

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LEARN MORE

1. Why diamond tip is preferred for indentor? 2. Explain the choice of Vickers and Rockwell Harness testing machine is for

measurement? 3. Explain the use of VHN in materials terminology? 4. List out materials in which order the hardness will have for metal, ceramics, polymers,

and composites?

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EXPERIMENT NO. 5

ESTIMATION AND COMPARISON OF SHOCK RESISTANCE QUALITIES OF THE MATERIALS BY CONDUCTING

IMPACT TEST


OBJECTIVES:

To evaluate the energy absorbing characteristics of various materials using the Impact testing Machine by the Charpy and Izod Tests.

EQUIPMENT: Model: Impact testing machine model -IT 30 D.

Description of the control panel: digital control panel and microprocessor based measuring

is used which takes digital pulse input from the rotary encoder and accurately evaluates the

energy absorbed by the test specimen during the test(Charpy/Izod test). It has 4 soft keys to set the machine namely TEST, START, RESET and PRINT Keys and a 4 digit 7.seg display

on the front panel.

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PROCEDURE:

1. Preparation of the Apparatus:

Perform a routine procedure for checking impact machines at the beginning of each day, each shift, or just prior to testing on a machine used intermittently. It is recommended that the results of these routine checks be kept in a log book for the machine for future use. Visually examine the striker and anvils for obvious damage and wear. Check the zero position of the machine.

2. Error measurement:

The pendulum is raised to initial position and locked with safety locking mechanism. The dial is set to zero, and the braking mechanism is checked to ensure that it is deactivated. The supporting bed is checked to ensure that no specimen is mounted. The safety lock is then removed, and the pendulum is released. After the swing is completed, the reading of the dial is noted, and the brake is applied to stop the swinging of the pendulum.

3. Specimen clamping:

Means shall be provided for clamping the specimen in such a position that the face of the specimen is parallel to the striker within 1:1000. The edges of the clamping surfaces shall be sharp angles of 90 61 with radii less than 0.40 mm (0.016 in.). The clamping surfaces shall be smooth with a 2-m (63-in.) finish or better, and shall clamp the specimen firmly at the notch with the clamping force applied in the direction of impact. For rectangular specimens, the clamping surfaces shall be flat and parallel within 0.025mm (0.001 in) The dimensions of the striker and its position relative to the specimen clamps shall be as shown in following figure.

Specimens and Loading Configurations for (a) Charpy V-Notch and (b) Izod Tests (as per ASTM E 23)

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TEST RESULTS:

Impact properties of test materials

Property Initial reading in Joule (1)

Energy absorbed in Joule (2)

Error = (2) (1)

Charpy impact strength

Izod impact strength

CONCLUSIONS:

The relative toughness between the materials selected was determined using the Charpy and Izod impact tests, and the modes of fracture were identified by visual inspection of the specimens after fracture.

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EXPERIMENT NO. 6

STUDY OF GYROSCOPE


OBJECTIVES:

To study the gyroscopic effect using the gyroscope.

EQUIPMENT USED: The gyroscope is a device which is mainly used for measuring the orientation. It works on the principle of conservation of angular momentum. A gyroscope comprises of a rotor disc whose axle is fee to take any orientation. The rotation of the rotor disc can be measured using a non-contact type tachometer. A protractor is fixed at the base to measure the angular displacement of the outer gimbal. A constant torque is provided to the rotor shaft by means of weights suspended at one end of the inner gimbal.

THEORY:

The gyroscope consists of a rotor disc which has to be rotated at a higher speed in order to get sufficient gyroscopic effect. Once the rotor disc starts rotating, the torque on the gyroscope applied perpendicular to its axis of rotation and also perpendicular to its angular momentum causes it to rotate about an axis perpendicular to both the torque and the angular momentum. This effect is known as gyroscopic effect.

PRECAUTION: The apparatus is very delicate. Readings are to be taken in a careful manner in order to get close results.

EXPERIMENTAL PROCEDURE:

1. While holding the shaft on which the rotor disc is fixed, rotate the disc at a speed greater than 200 rpm. At the same instant, start a stop watch.

2. Use a non-contact type tachometer to note down the speed of the rotor disc.

3. Release the inner gimbal and note down the time, the instant it is released.

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4. With split timing, measure the time from the moment the inner gimbal is released till rotation of the outer gimbal stops.

5. Note down the angle of rotation of the outer gimbal.

6. Take 8 to 10 readings by varying the speed of the disc.

CALCULATIONS:

Gyroscopic torque: T = I * * p where, I = Moment of Inertia of the rotor disc I = (MR2/2)-(M R2 /2)

central hole - 4*{( MR2/2)+( M* d2)} outer hole = 0.0058 kg/m2 = angular velocity of the rotor disc = (2N/60) rad/s p = angular velocity of precession p = (d/dt) rad/s

Theoretical torque: T=F*r F=Weight of the mass attached at one end of the inner gimbal (Kg m/s)

TABULATION:

Final speed (rpm)

Mean speed (rpm)

Time (s)

Angle (degree)

Angular velocity of disc (rad/s)

Angular velocity of precession

(rad/s)

Moment of inertia

(kg-m^2)

Experimental gyroscopic

torque (kg-m)

Force applied

(kg)

Perpendicular distance (m)

Theoretical torque (kg-m)

N2

N

dt

d

p

I

T exp

F

R

T th

0.0058

0.0058

RESULT: Thus the study on gyroscopic effect has been done with gyroscope and the readings showing the theoretical and experimental torque has been tabulated.

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EXPERIMENT NO. 7

STUDY OF DYNAMIC BALANCING MACHINE


OBJECTIVES:

1. To study the Dynamic Balancing Machine. 2. Balancing the rotating mass using Dynamic Balancing Machine. 3. To gain insight into the causes of undesirable vibration of rotors and to understand static and

dynamic unbalance conditions of rotors.

THEORY:

There are various rotating components which are required as parts in assembly or independently. Balancing of rotating components is extremely essential in order to avoid Dynamic failure, as centrifugal force acting on shaft is directly proportional to square of angular speed. Balancing of rotating components can be done by dynamic balancing or static balancing.

Production tolerances used in the manufacture of rotors are adjusted as closely as possible without running up the cost of manufacturing prohibitively. In general, it is more economical to produce parts, which are not quite true, and then to subject them to a balancing procedure than to produce such perfect parts that no correction is needed. Typical examples of such machinery are crankshafts, electric armatures, turbo-machinery, printing rollers, centrifuges, flywheels, and gear wheels. Some common causes of irregularity during production are machining error, cumulative assembly tolerances, distortions due to heat treatment, blow holes or inclusions in castings, and material non-homogeneity. Because of these irregularities the actual axis of rotation does not coincide with one of the principal axes of inertia of the body, and variable disturbing forces are produced which result in vibrations. In order to remove these vibrations and establish proper operation, balancing becomes necessary. The forces generated due to an unbalance are proportional to the rotating speed of the rotor squared. Therefore, the balancing of high-speed equipment is especially important. Although there are many possible causes of vibration in rotating equipment, this technique will deal only with that component of vibration, which occurs at running speed (frequency), and is caused by a mass unbalance in the rotor.

The condition of unbalance of a rotating body may be classified as static or dynamic unbalance. In the case of static unbalance, the unbalance appears in a single axial plane. In the case of dynamic unbalance, the unbalance can be in different axial planes. As a result, while in rotation,

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the two unbalanced forces form a couple, which rocks the axis of rotation and causes undesirable vibration of the rotor, mounted in its bearings.

Effect of Unbalance:- The forces of unbalance increase the loads on bearings and stress in the various members, but also produce unpleasant and even dangerous vibrations.

Machine Elements: The machine elements consists of Machine Bed(37) Drive Stand(26) Balancing Stands(4)

Machine Bed (37): - It is made of one piece of cast iron and reinforced underneath by cross ribs for rigidity. On its platform there are two slide rails and center guide. The slide rails serve as bearings for the balancing stand and pass over the whole length of the machine bed.

Drive Stand (26): - It is fabricated body and is placed on the foundation to the left hand end of the bed of the machine by 4 foundation bolts. The driving unit consists of the main driving motor, set of pulleys and belts, which are all housed inside this stand. The phase generating unit, comprising of moving magnet and fixed coil is fitted, at the left side of the driving stand. The driving spindle which runs in ball bearings projects out from the case and carries a graduated disc. Above the graduated disc is an arrow, which indicates the direction of rotation of the spindle. For easy access to the driving motor which is fastened to a plate at the back of the stand, a cover plate is provided with air vent holes for ejection of the generated warm air.

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The driving stand also houses the on/off switch (2) and the two speed rotary switch (1), along with the starter (27) of the motor. The grease system with the brake lever (25) for stopping the rotating specimen is also housed in the driving stand.

Balancing Stands (Left and Right) (4) The balancing stands, also made of cast iron, have a broad base resting over the slide surfaces of the machine bed. The to and fro movement of the two balancing stands No.1 can be controlled by the travel wheels (5) at the bottom of the stands. It contains a work- support, which is rigidly supported by two vertical side plates. It is possible by means of adjusting screws (35) to very height of the roller assembly for true adaptation to the respective shaft diameters of the rotors. The cradle consists of roller plate (34) to hold the balance system. The roller plate can be clamped in any particular position by means of the clamp screws (33). The safety guard (8) is attached to the cradle by means of the hinge (32). The retaining clamp (9) is fastened to the safety guards (8). The safety guard (8) can be fixed in position by means of the hinge screw (31). The roller plate (34) supports a set of rollers (7).A graduated scale is provided on the cradle to adjust the height of the roller bearings according to the diameter of the rotor placed on the balancing stands for balancing. Pressure transducers (11) are fixed on the rear side of the balancing stands and are pre-loaded spring (3) from opposite side. The balancing stands can be fixed at any position of the bed to the machine by means of the T bolts (36)

PRINCIPLE OF BALANCING

Whenever a certain mass is attached to a rotating shaft, it exerts centrifugal force, whose effect is to bend the shaft and to produce vibrations in it. In order to prevent the effect of centrifugal force, another mass is attached to the opposite side of the shaft, at such a position so as to balance the effect of the centrifugal force of the first mass. Therefore the process of providing the second mass in order to counteract the centrifugal force of the first masses called Balancing of Rotating Masses. The Balancing is done in two methods they are:-

I. Balancing of a single rotating mass by a single mass rotating in the same plane. II. Balancing of a single rotating mass by a two masses rotating in the different plane.

The rotor is placed on a work support which is rigidly fixed by side plates. They prevent any moment of rotor while rotating. Rotor rotates around its shaft axis. The centrifugal force resulting from the unbalance is absorbed by the work- support. A pressure transducer senses the centrifugal forces transmitted by the work-support and produces an electrical signal, which is proportional to the rotor unbalance.

The electrical signal is amplified in various stages by electronic circuit and processed through the analogue computer to read the angle of unbalance and the amount of unbalance on two different displays. Unbalance readings of both left and right planes are measured during a single run of rotor.

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PRECAUTIONS:

1. For balancing bodies with high unbalance, the safety guards should be used. The retaining clamps should be fitted with pressure.

2. There operation of drilling out material, welding etc. should not be carried out directly on the machine.

3. Before starting the experiment check that all the bolts should be tight. 4. Machine should be covered when it is in not use.

Different keys and their function:

Data Key: It is a key to enter the data.

Store Key: It is a key to store the data.

Rotor No Key: It is a key to enter the rotor number.

Program PROG: This key is to select the program.

RUN Key: The key starts the execution of the computation program.

Calibration CAL Key: This is active only when the machine is running and is used to calibrate the machine.

Serial No. Key: This key is used to enter the serial No. for the rotor when large No of rotors are to be balanced.

EXPERIMENT ANALYSIS:

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Constant values: A - The distance between left support and left plane in mm B - The distance between the two supports in mm C - The distance between the two planes in mm r1 - Radius of correction in left plane in mm r2 - Radius of correction in right plane in mm tl1 - Tolerance for left plane in gm, mm tl2 - Tolerance for left plane in gm, mm

PROCEDURE:

1. Initial make some unbalance by putting some weight (wt1 in gm) on the rotor of left plane or right plane.

2. Switch on the machine and it displays the current Rotor No. 3. Select the program 1 by pressing the PROG key. 4. Measure the values of constants A, B, C, r1, r2 etc. 5. Enter the data for constants press DATA key, the system displays constant A and its

present value. 6. Enter the value of A and press STORE. The value of A is stored and the system displays B

and its value. 7. Continue the procedure till all the data up to tl2 are entered and stored. After tl2 is stored the

system displays the constants A and its value again. 8. Check the correction mode in + by seeing the display on LED. 9. Run the program by pressing the RUN key. 10. Start the machine by pressing the START button by 2 times. 11. Wait for 1 to 2min so that the machine should stop and take the readings of magnitude (gm)

and direction (deg) for left and right plane. 12. According to the readings displayed apply the magnitude (gm) in a given direction (deg) and

make them balance.

READINGS TABLE

DISTANCE IN mm

INITIAL READING

CORRECTION

FINAL READING

A

B

C

MASS gm

@ANGLE in degree

Mass added gm

@ANGLE in degree

MASS gm

@ANGLE in degree

26

RESULTS

The Dynamic balancing machine was studied and balancing was done on a rotating shaft. Unbalance mass has been calculated and tabulated.

27

Part I

Summary Sheets

28

SUMMARY OF EXPERIMENT NO. 1 MEASUREMENT OF TENSILE STRAINS AND MODULUS OF

ELASTICITY

NAME_______________________ ID NO _______________________________ SEC. NO. ____________________ BATCH NO___________________________ DATE _______________________

OBJECTIVE: To measure tensile strain by an extensometer during tension test on a given tensile specimen; and to determine the value of modulus of elasticity.

OBSERVATIONS

Total length of the test specimen (mm) = Gauge length of specimen (of the extensometer): (L) mm =

Least count of extensometer, mm = (Note it from the console reading of the computer)

Diameter of specimen, (to be measured) mm =

Area of cross section of specimen(calculate)= A mm2 =

STRESS-STRAIN GRAPH & RESULT: Report the graphs obtained. Show your calculations.

c. Load Vs Displacement, d. Stress Vs Strain

Value of E for given (record the material) specimen is: kN/mm2 ( Gpa) Is the E value in agreement with the accepted value? Yes / No

Obs. No.

Load on specimen (T)

(kN) Stress (T/A) (kN/mm2)

Extensometer Reading (from the console)

(SL)

Strain X 10-5

SL/L

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

29

CONCLUSION:

MARKS OBTAINED_____________ INSTRUCTORS SIGNATURE_________________

30

SUMMARY OF EXPERIMENT NO. 2 MEASUREMENT OF BENDING MOMENT & DEFLECTIONS

OF A BEAM


OBJECTIVE: To measure deflections of a given beam by dial gauge indicator during bending test; and hence to determine the value of modulus of elasticity of the material and also the bending stresses

OBSERVATION:

Length of beam between simply supported ends = L = Width of beam = b = Thickness of beam = t = No load reading of dial gauge indicator =

Calculation of stress:

b= Mb y/ Iyy

Where Mb= WL/4, Iyy= bt3/12 (as applicable for rectangular beam), y = t / 2

Bending stress b= W* [1.5L/bt2] kgf/cm2

Where Load multiplier = 1.5L/bt2 1/cm2 :

Obs. No. Load on hanger W (kg) Dial gauge reading (y mm) 1 2 3 4 5 6

LOAD-DEFLECTION Graph:

Plot a graph between load and deflection and measure the slope of load deflection curve. Calculate k / E value from geometry.

Is the E value in agreement with the accepted value? Yes / No What is the error in the obtained value?

31

Can more accuracy be expected in the Value E?

Examine the Uncertainties in the measurements so obtained. Give your analysis?

Value of E for given specimen = ywk.

CONCLUSION:


32

SUMMARY OF EXPERIMENT NO. 3

MEASUREMENT OF STIFFNESS FOR HELICAL SPRING


OBJECTIVE: To find the characteristic load behavior of a helical spring or a given machine element and to determine the stiffness of the spring from load versus deflection curve.

OBSERVATIONS:

Total no. of coils: N

Mean radius of coil, D: mm

Diameter of the wire, d: mm

The axial movement or deflection of the free end of spring is

= 8 (W D3 N)/ Gd4 ;

Spring stiffness = k = (Gd4/ 8 D3 N) [ can be best detaermined by slope of W- curve]

Where G is Rigidity modulus of given material of spring

Obs. No.

Load applied to specimen

(kg) Deflection of the free end Scale

reading ()

Deflection of the free end using

theoretical analysis

1. 2. 3. 4. 5. 6. 7. 8. 9.

Draw the Load Extension (or Compression) diagram. Determine the slope of the W- curve obtained.

33

LOAD-DEFLECTION GRAPH & RESULT:

Value of Stiffness k for Mild steel spring is: N/mm (as calculated) Stiffness from graph: N/mm

CONCLUSION:


34

SUMMARY OF EXPERIMENT NO 4

MEASUREMENT OF HARDNESS OF THE GIVEN SAMPLES AND TO CORRELATE THEM WITH THE ULTIMATE TENSILE

STRENGTH OF THE MATERIALS USING VICKERS HARDNESS TESTING MACHINE


OBJECTIVE: To measure the hardness of the given samples and to correlate them with the ultimate tensile strength of the materials using Vickers Hardness Testing Machine.

OBSERVATIONS

Materials given:

Diagonal D1 and D2 of the impression : mm


SL No.

Material Load on specimen (P)

Diagonal D1 Diagonal D2

VHN

ROCKWELL HARDNESS TESTING

Scale Symbol

Indentor Minor Load kg Major Load kg

A Diamond cone 10 50 B Steel ball 10 90 C Diamond cone 10 140

35

OBSERVATIONS

Materials given:

Diameter or angle of indentor: mm

Type of Indentor:


Reading of scale A or B or C:

Rockwell Hardness:

SL NO.

Material Load on specimen (P) Type of Indentor

Rockwell Hardness A or B or C

CONCLUSION:


36


ESTIMATION AND COMPARISON OF SHOCK RESISTANCE QUALITIES OF THE MATERIALS BY CONDUCTING

IMPACT TEST.


OBJECTIVE: To study the gyroscopic effect using the gyroscope.

OBSERVATION TABLE: Impact properties of test materials

Material

Property

Charpy impact strength

Izod impact strength

CONCLUSIONS:


37


STUDY OF GYROSCOPES


OBJECTIVE: To study the gyroscopic effect using the gyroscope.

CALCULATIONS: Gyroscopic torque: T = I * * p where, I = Moment of Inertia of the rotor disc I = (MR2/2)-(M R2 /2)

central hole - 4*{( MR2/2)+( M* d2)} outer hole = 0.0058 kg/m2 = angular velocity of the rotor disc = (2N/60) rad/s p = angular velocity of precession p = (d/dt) rad/s

READINGS:

Final speed (rpm)

Mean speed (rpm)

Time (s)

Angle (degree)

Angular velocity of disc (rad/s)

Angular velocity of precession

(rad/s)

Moment of inertia

(kg-m^2)

Experimental gyroscopic

torque (kg-m)

Force applied

(kg)

Perpendicular distance (m)

Theoretical torque (kg-m)

N2

N

dt

d

p

I

T exp

F

R

T th

0.0058

0.0058

CONCLUSIONS:


38


STUDY OF DYNAMIC BALANCING MACHINE


OBJECTIVES:

1. To study the Dynamic Balancing Machine. 2. Balancing the rotating mass using Dynamic Balancing Machine. 3. To gain insight into the causes of undesirable vibration of rotors and to understand static and

dynamic unbalance conditions of rotors.

READINGS:

DISTANCE IN mm

INITIAL READING

CORRECTION

FINAL READING

A

B

C

MASS gm

@ANGLE in degree

Mass added gm

@ANGLE in degree

MASS gm

@ANGLE in degree

CONCLUSIONS


39

Part II

Hydraulics and Fluid Mechanics

40

INDEX

Experiment No. Name of Experiments

Page No.

1. Verification of Bernoullis theorem. 41

2. Study of flow measurement 47

3. Study of temperature measuring devices 59

4. Study of pressure measurement 64

5. Study of Reynolds apparatus. 69

6. Study of viscometers 73

7. Study of Pressure Losses in Pipe and Pipe Fittings 79

8. Study of Impact of jets and Free and Forced Vortices 82

41

EXPERIMENT NO. 1

VERIFICATION OF BERNOULLIS THEOREM

NAME_______________________ ID NO _______________________________

SEC. NO. ____________________ BATCH NO___________________________

DATE _______________________ INSTRUCTORS SIGNATURE __________

OBJECTIVES

The goal of this experiment is to understand and experimentally verify Bernoullis equation for incompressible fluid flow

The objectives of this experiment are:

1. To record the pressure head, flow rate and pressure differential 2. To calculate velocity (from measured flow rate) and pressure 3. To analyze the relationship between pressure and velocity 4. To plot the total energy line versus distance

APPARATUS

The experimental set-up for verifying Bernoullis theorem is self-contained recirculating unit. The set-up accompanies the sump tank, constant head tank, centrifugal pump for water lifting, measuring tank etc. A control valve and by-pass valve is provided to regulate the flow of water in constant head tank. A conduit, made of Perspex, of varying cross section provided, which is having converging and diverging section. Piezometer tubes are fitted on this test section at regular intervals. The inlet of the conduit is connected to constant head tank. At the outlet of conduit, a valve is provided to regulate the flow of water through the test section. After achieving steady state, discharge through test section can be measured with the help of measuring tank and stopwatch.

UTILITIES REQUIRED

1. Water supply 2. Electrical supply: single phase, 220 Volts, 50 Hz, 5 Amp with earth connection.

THEORY

The Bernoullis theorem states that when there is a continuous connection between particles of flowing mass of fluid, the total energy at any section of flow will remain the same provided there

42

is no reduction or addition of energy at any point. Thus for a steady, inviscid, incompressible flow, the same can be expressed in mathematical form as follows:

=++ zuP 21 2 constant along a streamline (1)

where

P = pressure of fluid, Pa u = velocity of fluid, m/s = density of fluid, kg/ m3 = specific weight (N/m3) Z = elevation (m)

Basic assumptions used in the derivation are:

1. Viscous effects are assumed negligible 2. The flow is assumed to be steady 3. The flow is assumed to be incompressible 4. The equation is appropriate only along a streamline

An alternative but equivalent form of the Bernoulli equation is obtained by dividing each term by the specific weight, g = to obtain

zg

uP++

2

21

= constant along streamline (2)

Each of the terms in this equation has the units of energy per weight or length (m) and represents a certain type of head.

The elevation term z is called elevation head

The pressure term, P

, is called the pressure head and represents height of a column of

the fluid that is needed to produce the pressure P.

The velocity term, g

u

2

2

, is the velocity head and represents vertical distance needed for a

fluid to fall freely if it is to reach velocity u from rest.

The Bernoullis equation thus states that the sum of the pressure head, the velocity head, and the elevation head is constant along a streamline.

Thus if 2 points along a streamline is considered then the Bernoullis equation can be written as follows:

43

2

22

2

21

21

1

1

21

21

zg

uPz

uPE ++=++=

(3)

where

E = total energy per unit weight or total head available at any point along a streamline P1 = pressure of fluid at point 1 on the stream line under consideration P2 = pressure of fluid at point 2 on the streamline under consideration u1 = velocity of fluid at point 1 on the stream line under consideration u2 = velocity of fluid at point 2 on the stream line under consideration = density of fluid g = acceleration due to gravity

1P

= pressure energy per unit weight of fluid or pressure head at point 1 on the stream line under

consideration

2P

= pressure energy per unit weight of fluid or pressure head at point 2 on the stream line under

consideration

gu

2

21

= kinetic energy per unit weight or kinetic head at point 1 on the stream line under

consideration

gu

2

22

= kinetic energy per unit weight or kinetic head at point 2 on the stream line under

consideration

Z1 = Potential energy per unit weight or potential head at point 1 on the stream line under consideration Z2 = Potential energy per unit weight or potential head at point 2 on the stream line under consideration

44

SKETCH OF APPARATUS

PROCEDURE

1. Close the drain valves provided. 2. Fill the sump tank with clean water. 3. Close the valve given at the end of test section. 4. Open by-pass valve given on the water supply line to overhead tank. 5. Ensure that all ON/OFF switches given on the panel are at OFF position. 6. Now switch on the main power supply (220 V AC, 50 Hz). 7. Switch on the pump ensuring supply of water back to the sump tank through the already open

by-pass valve 8. Slowly open the valve connecting the sump and over head tank closing the by-pass valve at

the same time. These ensure that water is directed to the overhead tank for filling. 9. Once the overhead tank is filled to the desired level, regulate flow of water through main test

section with the help of given gate valve at the end of the test section. The water in this case flows back into the sump tank

10. Measure flowrate using measuring tank and stopwatch. When measuring flowrate, ensure that the water is directed to the measuring tank before measurement.

11. Repeat the experiment for different flow rates.

Closing Procedure

1. When experiment is over, switch off pump. 2. Switch off power supply to panel.

PRECAUTIONS

1. Ensure that the sump tank is filled with water before start-up. 2. Keep periodic watch on the pump ensuring it runs smooth without getting hot. 3. Do not run the pump at low voltages. (Less than 180 V).

45

4. Never at any time fully close the Delivery line and By-pass line Valve simultaneously. OBSERVATIONS

Known data

Cross sectional areas at peizometric points

Peizometric point

Distance from Reference point. in m

Cross- sectional area at test points in m2

1. 0.03 6.1707 x 10-4 2. 0.07 5.0074 x 10-4 3. 0.11 4.1620 x 10-4 4. 0.15 3.3329 x 10-4 5. 0.19 2.7172 x 10-4

Peizometric point

Distance from Reference point. in m

Cross- sectional area at test points in m2

6. 0.23 3.3006 x 10-4 7. 0.27 4.2273 x 10-4 8. 0.31 5.1794 x 10-4 9. 0.35 6.4063 x 10-4

g = acceleration due to gravity = 9.81 m/s2; A = area of measuring tank = 0.1 m2

Data Acquisition

Run. No.

Height of water

collected in

measuring tank in cm

Time of collection

in seconds

Peizometric column height.

1 2 3 4 5 6 7 8 9

46

CALCULATIONS

Run No. =

Discharge or volumetric flowrate (Q) in m3/s =

(s) collection of time)(m tank measuring of area c/s (m) tank measuringin collected water ofheight 2

Velocity of flow (u) in m/s = volumetric flowrate / cross sectional area at test point

DATA REDUCTION

Tube no. 1 2 3 4 5 6 7 8 9 V (m/s) P/ g = h

(m) u2/2g (m)

Z (m) E

EXPECTED RESULTS

1. Do calculations and tabulate results as shown above for different runs, i.e. different flowrates.

2. Plot a graph and observe the variation of total energy (y axis) across the peizometric points, i.e. Plot the energy grade line with peizometric distance for each run.

3. Interpret the result obtained and present conclusions for the same. 4. Understand and explain the significance of the hydraulic grade line.

REFERENCES

1. McCabe, W. L.; Smith, J. C. and Harriott, P. Unit Operations of Chemical Engineering 2. Fox and Mcdonald, Introduction to fluid mechanics

STUDY OF

NAME_______________________ ID NO _____________________

SEC.NO. ____________________ BATCH NO_____________________

DATE _______________________ INSTRUCTORS SIGNATURE_____

OBJECTIVES

The goal of this experiment is to measure flow of fluid using different measuring devices.

The objectives of these experiments are

1) To measure water flow using and water meter

2) To calculate point velocity in a fluid using pitot tube3) To calculate the calculate coefficient of discharge of venturimeter and orificemeter4) To calculate accuracy of rotameter

APPARATUS

The experimental setup consists of flow measuring devices like venturimeter, orificemeter, pitot tube, rotameter, and water meter as shown in the figure below:

47

EXPERIMENT No. 2

STUDY OF FLOW MEASUREMENT

NAME_______________________ ID NO _____________________

SEC.NO. ____________________ BATCH NO_____________________



The objectives of these experiments are

To measure water flow using different apparatus like venturimeter, orificemeter, rotameter,

To calculate point velocity in a fluid using pitot tube To calculate the calculate coefficient of discharge of venturimeter and orificemeterTo calculate accuracy of rotameter and water meter

The experimental setup consists of flow measuring devices like venturimeter, orificemeter, pitot tube, rotameter, and water meter as shown in the figure below:

FLOW MEASUREMENT

NAME_______________________ ID NO _____________________

SEC.NO. ____________________ BATCH NO_____________________



different apparatus like venturimeter, orificemeter, rotameter,

To calculate the calculate coefficient of discharge of venturimeter and orificemeter

The experimental setup consists of flow measuring devices like venturimeter, orificemeter, pitot

48

The setup consists of the above mentioned devices, a supply tank for storing and supplying water, a pump for closed loop circulation of water, acrylic tank with graduations for measuring discharge of water and differential pressure measuring tubes fixed on a stand alone structure.

UTILITIES

a. Water supply b. Electric power supply 230V, 50Hz, 5 Amps single phase supply

GENERAL START-UP PROCEDURE

1) Remove the supply tank and fill it with distilled water. Place the supply tank at its location. Ensure that the measuring tank drainpipe is inside the supply tank.

2) Ensure that the vent valve on the rubber bulb is fully closed. Keep the flow regulating valve (V1) 50% and valve (V2) 100% open and switch on the pump.

3) Check the working of rotameter by manipulating flow-regulating valve (V1). 4) Set the flow rate to 60 lph. Press rubber bulb 2-3 times to lower down the water levels in the

manometer tubes. Gently tap the manometer tubes to remove air entrapped. 5) Loosen the vent valve on the rubber bulb slightly. The water will rise in manometer tubes.

Set the water level at mid scale of the manometer. Ensure that all air bubbles are removed by varying the flow rate from minimum to maximum range. (The average level in the manometer can be raised by slightly venting out the air from vent valve of the air bulb or it can be lowered by pumping air by rubber bulb).

THEORY AND EXPERIMENTAL PROCEDURE FOR VENTURIMETER, ORIFICEMETER, PITOTTUBE, ROTAMETER AND WATERMETER

a) Venturimeter

Theory

The venturi is particularly adapted to installation in pipelines not having long, unobstructed runs. The flow of fluid through the venturi tube establishes the pressure differential, which can then be measured and related to the flow rate. Because of the gradual reduction in the area of flow there is no vena contracta and the flow area is a minimum at the throat so that the coefficient of contraction is unity. The meter is equally suitable for compressible and incompressible fluids. Following figure shows general construction details.

49

Experimental Procedure

1) Start the set up as explained under general start-up procedure section. 2) Adjust rotameter flow rates in steps of 50 lph from 60 to 600 lph and wait for few minutes

till the steady state is reached. 3) Note the pressure difference across the venturi meter. 4) Close the outlet valve at the measuring tank. 5) Measure the time required for collecting 1.5 lit of water in measuring tank by stopwatch. 6) Drain the measuring tank by opening the drain valve (immediately).

b) Orificemeter

Theory

The orifice meter consists of a thin circular metal plate with circular sharp edge hole in it. The concentric orifice is by far the most widely used. As the fluid passes through the orifice, it contracts in area. The minimum flow area is called vena contracta. Different types of taps are used for orifice mete. The flow of fluid through the orifice meter establishes the pressure differential across the orifice plate, which can then be measured and related to the flow rate.


1) Start the set up as explained under general start-up procedure section. 2) Adjust rotameter flow rates in steps of 50 lph from 60 to 600 lph and wait for few minutes till

the steady state is reached. 3) Note the pressure difference across the orifice meter. 4) Close the outlet valve at the measuring tank. 5) Measure the time required for collecting 1.5 lit of water in measuring tank by stopwatch. 6) Drain the measuring tank by opening the drain valve (immediately).

c) Pitot tube

Theory

The Pitot tube is primarily a device for measuring fluid velocity. It is combination of a total head tube and a static tube. It consists simply of a tube supported in the pipe with the impact opening

50

arranged to point directly towards the incoming fluid. This is called the impact opening and is used to measure the stagnation pressure. The static pressure is measured through the ordinary pressure tap. The difference between impact pressure and static pressure represents velocity head.


1) Start the set up as explained under general start-up procedure section. 2) Adjust rotameter flow rates in steps of 50 lph from 60 to 600 lph and wait for few minutes till

the steady state is reached. 3) Note the pressure difference between impact pressure and static pressure. 4) Close the outlet valve at the measuring tank. 5) Measure the time required for collecting 1.5 lit of water in measuring tank by stopwatch. 6) Drain the measuring tank by opening the drain valve (immediately).

d) Rotameter

Theory

Rotameter is a variable area meter. In the variable area meter, the drop in pressure is constant and the flow rate is a function of the area of the constriction. A rotameter consists of a tapered tube with the smallest diameter at the bottom. The tube contains a freely moving float, which rests on a stop at the base of the tube. When the fluid is flowing, the float rises until its weight is balanced by the up thrust of the fluid, its position then indicating the rate of flow. The area for flow is the annulus formed between the float and the wall of the tube. (The figure below shows schematic details of rotameter tube and float. Use top edge of the float to note rotameter reading)

51


1) Start the set up as explained under starting of equipment sub heading. 2) Adjust rotameter flow rates in steps of 50 Lph from 60 to 600 Lph and wait for few minutes

till the steady state is reached. 3) Close the outlet valve at the measuring tank. 4) Measure the time required for collecting 1.5 liters of water in measuring tank by stop watch. 5) Drain the measuring tank by opening drain valve (immediately).

e) Water meter

Theory

Water meters are used for measuring cumulative water flow. The meter contains a rotating vanes housed in side a cylindrical body. The flow of water through the meter results in the positive displacement of vanes. The water enters in to slotted casing forcing the vanes to rotate about vertical axis. The cumulative flow of water is obtained by gearing rotational motion of the vanes to a counter. (The figure below shows internal construction of water meter. Black digits show cumulative flow in Kiloliters. Next two digits in red color show reading in further decimals of kiloliters. The small round dial in red shows reading in liter. The wiper blades can be used for cleaning the cover window from inside.)


1) Ensure clean water in supply tank and switch on the pump.2) Ensure that the outlet valve at the measuring tank is open.3) Adjust Rotameter flow rate to say 300 lph and

reached. 4) Note reading of water meter and start the stop watch.5) Note the water meter reading after some time interval say 15 minutes.

OBSERVATIONS

a) Venturimeter

Known data

Inlet pipe diameter (D) Throat diameter (d) Acceleration due to gravity Quantity of water measured (Q) Density of water () Viscosity of water ()

52


Ensure clean water in supply tank and switch on the pump. Ensure that the outlet valve at the measuring tank is open. Adjust Rotameter flow rate to say 300 lph and wait for few minutes till the steady state is

Note reading of water meter and start the stop watch. Note the water meter reading after some time interval say 15 minutes.

= 0.0185 m = 0.010 m

Acceleration due to gravity = 9.81 m/s2 Quantity of water measured (Q) = 1.5x 10-3 m-3

= 998 kg/m3 = 1.00x10-3 kg/m.s

wait for few minutes till the steady state is

Note the water meter reading after some time interval say 15 minutes.

53

Data acquisition

S.No Rotameter

reading (lph)

Time (t) required for 1.5 litres

Pressure difference

across venturi in

(m) 1 60 2 100 3 150 4 200 5 250

b) Orificemeter

Known data

Inlet pipe diameter (D) = 0.0185 m Orifice diameter (d) = 0.0122 m Acceleration due to gravity = 9.81 m/s2 Quantity of water measured (Q) = 1.5x 10-3 m-3 Density of water () = 998 kg/m3 Viscosity of water () = 1.00x10-3 kg/m.s

Data acquisition

S. No Rotameter

reading (Lph)

Time required for 1.5 lit.

(sec) t

Pressure difference

across orifice

(m) 1 60 2 100 3 150 4 200 5 250

c) Pitot tube

Known data

Inlet pipe diameter (D) = 0.0185 m Acceleration due to gravity = 9.81 m/s2 Quantity of water measured (Q) = 1.5x 10-3m-3 Density of water () = 998 kg/m3 Viscosity of water () = 1.00x10-3 kg/m.s

54

Data acquisition

S.no Rotameter

reading (lph)

Time required for 1.5

litres (sec)

Pressure difference

across pitot tube

(m) 1 60 2 100 3 150 4 200 5 250

d) Rotameter

Data acquisition

S.no Rotameter reading in lph

Time required for 1.5 liters. in sec

1 60 2 100 3 150 4 200

e) Watermeter

Data acquisition

S.no Rotameter reading in lph Initial

Watermeter reading in liters

Final Watermeter reading liters

1 60 2 100 3 150 4 200 5 250

CALCULATIONS

a) Venturimeter Inlet area of the venturimeter (a1) = 2

4xD

pi m

2

Throat area of the venturimeter (a2) = 24xdpi

m2

55

Venturimeter constant (K) = gaa

xaa2

22

21

21

Actual discharge (Qa) = tV

m3/s

Theoretical discharge (QT)= HK m3/s

Coefficient of discharge (Cd) =T

a

QQ

=

discharge lTheoriticadischarge Actual

Velocity of pipe (u)= Qa/a1

Reynolds number =

Du

DuRe ========

Data reduction

S.no Rotameter

reading (Lph)

Time required for 1.5 lit.

(sec) t

Actual discharge

(Lph)

Pressure diff.across

Venturi (m) H

Theoritical discharge

(Lph) Coeff.of

discharge Reynolds number

1 60 2 100 3 150 4 200 5 250

Required results

1. Determine Coefficient of discharge of Venturimeter. 2. Draw Graph for coefficient of discharge versus Reynolds number. 3. Draw Graph for actual discharge versus theoretical discharge.

b) Orifice meter

Inlet area of the orifice meter (a1) = 24xD

pi m

2

Area of the orifice (a2) = 24xdpi

m2

Actual discharge (Qa)= tV

m3/s

Theoretical discharge (QT)= xgxHaa

a 22

22

1

2

m3/s

56

Coefficient of discharge (Cd)=T

a

QQ

Velocity of pipe (u)= Qa/a1

Reynolds No.=

Du

DuRe ========

Data reduction

S.no Rotameter

reading (lph)

Time required for 1.5

liters (sec)

Actual discharge

(lph)


Venturi (m) H


(lph) Coeff.of


1 60 2 100 3 150 4 200 5 250

Required results

1. Determine Coefficient of discharge of Orificemeter. 2. Draw Graph for coefficient of discharge versus Reynolds number. 3. Draw Graph for actual discharge versus theoretical discharge.

c) Pitot tube Inlet area of the Pitot tube (a1) = 2

4xD

pi m

2

Actual discharge (Qa)= tV

m3/s

Theoretical fluid velocity (V)= xgxH2 m/s

Theoretical discharge (QT)= A x Vm3/s

Coefficient of discharge (Cd)=T

a

QQ

Velocity of pipe (u)= Qa/A Reynolds No.=

DuRe =

57

Data reduction

Sr.No Rotameter

reading (lph)

Time required for 1.5 liters (sec)

Actual discharge

(lph)


Venturi (m) H


(lph) Coeff.of


1 60 2 100 3 150 4 200 5 250

Required results

1. Determine Coefficient of discharge of Pitot tube. 2. Draw Graph for coefficient of discharge versus Reynolds number. 3. Draw Graph for actual discharge versus theoretical discharge.

d) Rotameter Actual discharge =

rliter wate for1.5 required Time1.5x3600

Error = Rotameter reading- actual discharge

Accuracy=Rotameter of flow Full100Error x

Data reduction

S.no Rotameter

reading (Lph)

Time required for 1.5 lit. (sec) t

Actual discharge

(Lph) Error (Lph)

Accuracy %

1 60 2 100 3 150 4 200

Required results

1) Determine Accuracy of Rotameter in %. 2) Draw Graph for actual discharge versus rotameter reading. 3) Draw Graph for accuracy versus rotameter reading.

58

e) Watermeter

Water quantity by water meter= Final water meter reading Initial water meter reading Error= Water quantity by water meter-Water quantity by Rotameter

Accuracy =quantity water Indicated

100Error x

Data reduction

S.no

Rotameter

reading (lph) F

Initial Watermeter reading Liters, A

Final Watermeter

reading Liters, B

Water quantity by

Watermeter, lit (B-A)

Water quantity

by Rotameter

(Liters) F*t/60

Error (Liters)

Accuracy %

1 60 2 100 3 150 4 200 5 250

Required results

1. Determine accuracy of Watermeter in %.

2. Draw Graph for actual discharge versus watermeter reading

LEARN MORE:

1. Other flow measuring devices. 2. Why rotameter tube is tapered? 3. Why vena contracta forms at distance after crossing orifice?

4. Which is the best flow-measuring device out of five available in the lab? 5. Different applications of flow measuring devices.

REFERENCES

McCabe, W. L., Smith, J. C. and Harriott, P. Unit Operations of Chemical Engineering

59

EXPERIMENT No. 3

STUDY OF TEMPERATURE MEASURING DEVICES


OBJECTIVES

The goal of this experiment is to study various temperature measuring devices, their characteristics and time constants. Different temperature measuring devices are:

A) Resistance Temperature Detector (RTD) B) Thermistor C) Thermocouple D) Liquid filled thermometer E) Bimetallic Thermometer

APPARATUS

The temperature-measuring set-up consists of temperature sensors such as mercury in glass thermometer, bimetallic dial Thermometer, RTD, thermistor and thermocouple. It has a hot water bath, ice bath, multimeter and 4.1/2 digit milivoltmeter and a temperature indicator. It also has bare elements of RTD, thermistor, and thermocouple to visualize actual elements. Using the Multimeter it is possible to check the output of RTD, thermistor and thermocouple. The RTD type temperature sensor shows resistance in , the Thermistor type sensor shows resistance in K and thermocouple type sensor gives out put in milivolts.

UTILITIES

1. Electric supply: single phase, 220V AC

THEORY

Resistance Temperature Detector (RTD)

A resistance temperature detector (RTD) is a transducer. The metallic resistance of RTD increases with the temperature. This increase is nearly linear. Metals used in these devices vary from platinum, which is very repeatable, quite sensitive and very expensive, to nickel, which is not quite as repeatable, more sensitive and less expensive. An RTD is simply a length of wire whose resistance is to be monitored as a function of temperature. The construction is in general such that the wire is wound in form of a coil to achieve small size and improve thermal

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conductivity to decrease response time. In many cases, the coil is protected from the environment by a sheath or protecting tube that certainly increases response time but may be necessary in hostile environments.

Thermistors

Thermistors are semiconductors made from carbon, germanium, silicon and mixtures of certain metallic oxides that show high temperature coefficients. The resistance temperature relationship of a thermistor is negative and highly nonlinear. Thermistors are usually designated in accordance with their resistance at 25C. The commonly used ratings are from 1 Kohms to 470 Kohms.

Thermocouples

A thermocouple consists of two dissimilar metals, joined together at one end, which produce a small unique voltage at a given temperature. This voltage is measured and interprets for temperature measurement. Thermocouple gives an economic means of measuring temperature. It is capable of measuring over wide temperature ranges. Thermocouples are easy to install and are available in many forms, from probes to bare wires or foil. The thermocouple is essentially a differential rather than an absolute temperature measuring device, one junction must be at a known temperature to find the temperature of the other junction.

Liquid Filled Thermometers

Liquid filled thermometers operate on the principle of liquid expansion with increase of temperature. The glass thermometer was the first closed thermal expansion system. Liquid filled thermometers are intermediate in cost and performance between the simplest measuring devices like bimetallic thermometers and the more complex electrical measuring elements. Mercury or some other liquid (alcohol, pentane) fills the glass bulb and extends in to the capillary bore of the stem.

Bimetallic Temperature Sensors

Bimetallic devices take advantage of the difference in rate of thermal expansion between different metals. Strips of two metals are bonded together. When heated, one side will expand more than the other, and the resulting bending is translated into a temperature reading by mechanical linkage to a pointer.

EXPERIMENTAL PROCEDURE

Use of Multimeter and milli-voltmeter

1. For measuring the response of RTD and Thermistor, take the out put to multimeter and adjust the multimeter for reading the resistance

2. For reading the response of the thermocouple, the milivoltmeter provided can be connected to the thermocouple output in addition to using the multimeter..

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For finding out the time constant of the temperature measuring device (as per instructor)

1. Heat the water in electric kettle, to some fixed temperature (say 90 oC) and maintain the temperature constant.

2. Adjust the timing of the beep near to a pre-decided value. 3. Dip the particular temperature sensor in the electric kettle and note the response of the sensor

at each beep. 4. Plot the time vs response curve for each temperature sensor. 5. Find out the time constant, i.e. the time taken for the sensors to reach 63.2 % of the total

change indicated. 6. Classify the sensors in terms of the responsiveness based on the results of the experiment

For plotting the characteristics of different sensors and calibration

1. Take some crushed ice in the thermos and dip the resistance sensor to be studied along with a thermometer.

2. Allow time for steady state to reach and then note down the temperature of the bath and the reading shown by a particular temperature sensor in appropriate units.

3. Remove some ice and add some water and thus slightly increase in the temperature of the water. Note corresponding sensor reading.

4. Repeat step 3 till room temperature is reached noting sensor reading (for each temperature rise).

5. Now shift the sensor probe and the thermometer to the electric kettle. Switch on the heater. 6. Increase the temperature in steps and allow steady state to reach at each step before recording

the reading of the particular sensor. 7. Plot the temperature vs resistance curve for the sensor. 8. For thermocouple, keep one probe always dipped in ice bath and follow same steps from 1-6

mentioned above and plot temperature vs milivolts curve. 9. Now these curves can give the value of temperature for a particular value of resistance or

voltage and gives us a calibration of a particular temperature sensor.

PRECAUTIONS

1. Take care while handling hot water so that it does not spill on you 2. Thermometers should be handled with care to avoid any kind of breakage 3. Never switch on the heater when no water is there in the electric kettle.

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OBSERVATIONS

Time Response of various Temperature Sensors

Beep interval in seconds (T):

Reading No.(beep)

Time in seconds

Observed Temp.

(Thermometer reading)

C

Observed Temp. (Bi-

metallic thermometer

reading) C

Observed Resistance

(RTD reading)

Observed Resistance

(Thermistor reading) k

Observed Voltage

(Thermocouple reading) milivolts

0 (Initial) 0

1

2

3

4

5

6

7

Up to Steady State

Observation table of RTD

Approx. temperature at readings to be taken.

C Thermometer reading

C Resistance of RTD

0 10 20 30 40 50 60 70 80

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Observation table of Thermistor



C Resistance of Thermistor

k

0 10 20 30 40 50 60 70 80

Observation table of Thermocouple



C Output of Thermocouple

(milivolts) 0 10 20 30 40 50 60 70 80

EXPECTED RESULTS

1. Determine the time constant for various temperature-measuring instruments studied. 2. Understand the variation of resistance with temperature for RTD and thermistor. 3. Plot necessary graphs as instructed.

TO LEARN MORE

1. Find out the various applications for each of the temperature sensors 2. Identify various sources of errors in measurement of temperature and also find out possible

remedies for the same.

REFERENCES

1. McCabe, W. L.; Smith, J. C. and Harriott, P. Unit Operations of Chemical Engineering

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EXPERIMENT NO. 4

PRESSURE MEASUREMENT

NAME_______________________ ID NO _____________________

SEC.NO. ____________________ BATCH NO_____________________


OBJECTIVES

The goal of this experiment is to understand the concept of pressure and the various instruments used for measuring the same.

The objectives of this experiment are:

1. To understand pressure, atmospheric pressure, barometric pressure, standard pressure and vacuum

2. To understand the difference between absolute and gauge pressures 3. To study the working principle of various pressure measuring devices like Bourdon

gauge, diaphragm gauge, U-tube and inclined manometers, etc. 4. To convert gauge pressure into absolute pressure 5. To calculate pressure from the density and height of a column of fluid 6. To understand the concept of pressure gauge calibration

APPARATUS

Pressure test bench consisting of different pressure measuring devices (for measuring pressure above and below atmospheric pressure)

UTILITIES

1. Air compressor with appropriate 3 phase electric supply for the same 2. Oil for hydraulic comparator 3. Vacuum pump with appropriate single phase supply

THEORY

Pressure is defined as the normal force per unit area. The SI unit of pressure is Pa or N/m2. The pressure at the bottom of a static (non-moving column of fluid is given by

oPghAFP +==

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where

P = the pressure at the bottom of the column of fluid F = force A = area = fluid density g = acceleration due to gravity h = height of fluid column Po = pressure at the top of the column of fluid

Pressure like temperature can be expressed by either absolute or relative scales. Whether relative or absolute pressure is measured in a pressure-measuring device depends on the nature of the instrument used to make the measurements. Gauge pressure is pressure measured relative to atmospheric pressure while absolute pressure is pressure measured relative to absolute zero or complete vacuum.

The pressure of air that surrounds us all the time is referred to as atmospheric pressure. Atmospheric pressure is measured using a barometer and is also referred to as barometric pressure. The atmospheric pressure must never be confused with standard atmospheric pressure. The standard atmosphere is defined as the pressure in a standard gravitational field (g = 9.80665 m/s2) and is equivalent to 1 atmosphere or 760 mm of mercury or other equivalent value, whereas atmospheric pressure must be obtained from a barometer each time it is needed. The value of standard atmospheric pressure in SI units is 101325 Pa (1 Pa = 1 N/m2).

Pressures are measured using pressure-measuring devices like manometers, pressure gauges, pressure transducers etc. These devices can be used to measure pressures above and below atmospheric, the latter referred to as negative pressure or vacuum. The values of gauge pressures obtained from pressure measuring devices can be converted into absolute pressure using the relation

Absolute pressure = Atmospheric pressure + gauge pressure (for pressures above atmospheric)

Absolute pressure = Atmospheric pressure - gauge pressure (for pressures below atmospheric)

Several instruments are available for measuring pressure. In the case of a U-tube manometer, a state of hydrostatic balance is reached wherein the manometric fluid is stabilized and the pressure exerted at the bottom of the U-tube in the part of the tube open to the atmosphere or vacuum exactly balances the pressure at the bottom of the U-tube in the part of tube connected to the system whose pressure is to be measured. Another type of common measuring device is the visual Bourdon gauge which normally (but not always) reads zero pressure when open to the atmosphere. The pressure-sensing device in the Bourdon gauge is a thin metal tube with an elliptical cross section head at one end that has been bent into an arc. As the pressure increases at the open end of the tube, it tries to straighten out and the movement of the tube is converted into a dial movement by gears and levers. Similarly a diaphragm gauge is used for measuring pressure of corrosive fluids.

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EXPERIMENTAL PROCEDURE

Pressures above atmospheric: In this case emphasis is placed on understanding the working principle of various instruments for measuring pressures above atmospheric pressure using a pneumatic system. The pressure unit 2 (shown in figure below) has been provided with two numbers gauge connection station and one micro adjuster cylinder to raise or lower pressure as required while maintaining the same above atmospheric. The micro adjustor cylinder is capable of generating adequate pressure for pressure gauges, manometers (if needed without help of any external source)

Bourdon gauge

1. Start the air compressor. 2. Using the pressure regulator and valves (operate and release valves) provided for the

pneumatic comparator, control flow of air to the Bourdon gauge and read different values of pressure from the gauge dial. Use the operate valve to allow air into the gauge (to increase pressure). The release valve can be used to lower pressure reading on the gauge.

3. Use the micro adjustor if needed to get the exact reading on the gauge. 4. Visually observe the working principle of the gauge.

U tube manometer

1. Isolate the compressor befor

final revised mech engg labs - manual 2014

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