measurements lab manual,mechanical engineering,mg university

MECHANICAL MEASUREMENTS LAB

DEPARTMENT OF

MECHANICAL ENGINEERING

SIXTH SEMESTER ICE

MECHANICAL MEASREMENTS LABLAB MANUAL

S N M INSTITUTE OF MANAGEMENT AND TECHNOLOGYMALIANKARA P O, MOOTHAKUNNAM, ERNAKULAM-683 516

Dept. of Mechanical 1 SNMIMT


EXPERIMENT NO. 1

CALIBRATION OF GIVEN VERNIER CALIPER

AIM

1. To study the working principle of vernier calipers and slip gauges.2. To calibrate the given vernier caliper using slip gauges as the standard

APPARATUS REQUIRED

Vernier calipers and slip gauges.

PRINCIPLE

The vernier calipers consist of two scales, one fixed and the other moving. The fixed scale (main scale) is calibrated on the L shaped frame and carries a fixed jaw. The movable scale called the vernier the vernier scale slides over the main scale and carries a movable jaw. The movable as well as the fixed jaws carry the measuring tips.

When the two jaws are close, the zero of the vernier scale coincides with the zero of the main scale. If they do not coincide, there is zero – error. For precise setting of the movable jaw an adjustment screw is provided. Also an arrangement is provided to lock the sliding scale on to the fixed main scale.

LEAST COUNT OF THE VERNIER CALIPERS

Least count is the difference between the value of the main scale division and the vernier scale division.

The least count of the vernier instrument is given by,

LC = Value of smallest division on main scale – Value of smallest division on vernier scale



Value of smallest division on main scale = 1mm

50 divisions on the vernier scale coincides with 49 divisions on the main scale.

Thus value of smallest division on vernier scale = 4950

LC = 1 - 4950 = 0.02 mm

PROCEDURE

Before using the instrument it should be checked for zero error. Then take the reading in millimeters on the main scale to the left of the zero on the sliding scale. Then count the number of divisions on the vernier scale from zero to a line which exactly coincides with a line on the main scale. The total reading = main scale reading + the number of divisions exactly coincides with a division on the main scale X Least Count.

Parts of Vernier caliper:

1. Outside jaws: Used to measure external diameter or width of an object.2. Inside jaws: Used to measure internal diameter of an object.3. Depth Probe: Used to measure depth of an object or a hole.4. Main scale: Gives measurements of up to one decimal place (in cm).5. Vernier scale: Gives measurements of up to two decimal place (in cm).

SLIP GAUGES

Slip gauges are universally accepted end standard of length in industry. Slip gauges are rectangular blocks of high grade steel with exceptionally close tolerance. These blocks are suitably hardened out to ensure maximum resistance to wear. They are then stabilized by heating and cooling successively in stages so that hardening stresses are removed. After being hardened they are carefully finished by high grade lapping to a high degree of finish, flatness and accuracy. For successful use of slip gauges, their working faces are made truly flat and parallel. Any two slips when perfectly clean may wrung together. The dimensions are permanently marked on one of the measuring faces of gauge blocks.

Wringing of slip gauges

The success of precision measurement by slip gauges depends on the phenomenon of wringing. The slip gauges are wrung by hand through a combined sliding and twisting motion. The gap between two wrung slips is only of the order of 0.00635 microns which is negligible.

Procedure for Wringing

Before using, the slip gauges are cleaned by using a lint free cloth, chamois leather or a cleaning tissue.

One slip gauge is then oscillated slightly over the other gauge with a high pressure.



One gauge is then placed at 90 to the other by using light pressure and then it is rotated until the blocks one brought in one line.

When the two gauges are wrung in this manner is exactly the sum of their individual dimensions.

The wrung gauge can be handled as a unit without the need for clamping all the pieces together.

Selection of Slip Gauges for required dimension

Always start with the last decimal place and deduct this from the required dimension. Select the next smallest figure in the same way, find the reminder, and continue this until the required dimension should be selected. After selecting the minimum number of slip gauges in this manner, clean them by using lint – free cloth, or a cleaning tissue to remove dirt, oil, dust etc. now, begin wringing with the largest sizes first. While using avoid touching the measuring surfaces with figures and handle them as little as possible place one gauge over the other at right angles, and with light pressure twist it through until the block are brought in one line. When the largest gauges have been assembled, follow with others in order of decreasing size until the required combination is build up.

OBSERVATION & TABULAR COLUMN

Zero Error = …………….. mm

Sl. No.Slip Gauge Readings

( X )

Length of slip gauges measured using Vernier Caliper X2 XY Error

MSR VSR TR ( Y )

CALCULATION

Total Reading = MSR + (VSR x LC)

From table,

∑ X2 = …………………

∑ X = …………………..

∑ Y = …………………..

∑ XY =…………………



Equation of the curve, Y = A + Bx

A- Y axis intercept of calibration curveB- Slope of the calibration curve

Solution is obtained by the following equations

An + B∑ X = ∑ Y

A ∑X + B ∑ X2 = ∑ XY

Where n = no: of input variables

By solving the equations by substituting the necessary values, we can obtain the calibration equation. The slope of the calibration curve represents the sensitivity of the instrument. The slope of the calibration curve represents the sensitivity of the instrument.

RESULT

The measurements are taken using the given vernier calipers with the slip gauges as the standard reference. The calibration curve for the vernier caliper is also plotted using the obtained results.

INFERANCE



EXPERIMENT NO. 2

CALIBRATION OF GIVEN OUTSIDE MICROMETER

AIM

To study the working principle of outside micrometer and to calibrate the given outside micrometer using slip gauge as standard.

APPARATUS REQUIRED

Outside micrometer and slip gauge.

PRINCIPLE

A micrometer sometimes known as a micrometer screw gauge is a device used widely in mechanical engineering and machining for precisely measuring, along with other metrological instrument such as calipers and vernier calipers. The accuracy of micrometer derives from the accuracy of the thread form of the screw that is at its heart.

The basic operating principles of a micrometer as follows.

1. The amount of rotation of an accurately made screw can be directly and precisely correlated to a cer6tain amount of axial movement through the constant known as the screw’s lead. A screw’s lead is the distance it moves forward axially with one complete turn (360°).

2. With in appropriate lead and major diameter of the screw, a given amount of axial movement will be amplified in the resulting circumferential movement.

For example if the lead of a screw is 1 min. but the major diameter (here, outer diameter) is 10 mm, then the circumference of the screw is 10π, cr about 31.4 mm. Therefore movement of axial movement of 1mm is amplified to a circumferential movement of 31.4 mm. This amplification allows a small difference in the sizes of two similar measured objects to correlate to a larger difference in the position of a micrometer’s thimble.



The main parts of an outside micrometer are

1. U shaped steel frame: It holds all the micrometer parts together. The gap of the frame permits the maximum diameter or length of the job to be measured.

2. Anvil and Spindle: The micrometer has fixed anvil protruding 3 mm from the left hand side of the frame. The diameter of the anvil is the same as that of the spindle. Another movable anvil is provided on the front of the spindle. The anvils are accurately ground and lapped with its measuring faces flat and parallel to the spindle these are also available with tungsten carbide faces. The spindle is the movable measuring face with anvil on the front side. The spindle engages with the nut. It should run freely and smoothly throughout the length of its travel, there should be no backlash between the spindle screw and the nut, there should be no backlash between the spindle screw and the nut there should be full engagement of nut and screw when micrometer is at its full reading.

3. Lock nut: A lock nut is provided on the micrometer spindle to lock it when the micrometer is at its correct reading. The design of the locknut is such that it effectively locks the spindle without altering the distance between the measuring faces. It thus retains the spindle in perfect alignment.

4. Sleeve or barrel: The sleeve is accurately divided and clearly marked in .5 mm division along its length which serves as a main scale. It is chrome plated and adjustable for zero setting.

5. Thimble: The thimble can be moved over the barrel. It has 50 equal divisions around its circumference. Each division having a value of .01 mm.

6. Ratchet: The ratchet is provided at the end of the thimble. It is used to assure accurate measurement and to prevent too much pressure being applied to the micrometer. When the spindle reaches near the work surface to be measured the operator uses the ratchet screw to tighten the thimble. The ratchet automatically slips when the correct pressure is applied and prevents the application of too much pressure.

LEAST COUNT OF THE VERNIER CALIPERS

Least count is the minimum distance which can be measured accurately by an instrument.

Given micrometer has screw of 0.5 mm pitch, with thimble graduated in 50 divisions to provide a direct reading of pitch.

LC = pitch of the spindle screw / number of divisions on the spindle

LC = 0.5050

= 0.01 mm



PROCEDURE

Select the micrometer with a desired range depending upon the size of the work piece to be measured. The next step is to check the zero error. It is checked by contacting the faces of the fixed anvil and the spindle. The zero on the thimble should coincide with the zero on the reference line on the barrel. If this does not happen and then zero error is present in the micrometer which must be taken into account while taking the readings.

The barrel has graduations in intervals of 1 mm above the reference line. There are also graduations below the reference line at the middle of successive upper graduations, so as to read 0.5 mm.

For measuring particular dimension, hold the work between the faces of the anvil and spindle and then move the spindle by rotating the thimble until the anvil and spindle touches the work surface. Make fine adjustment with ratchet. Now take the reading on the main scale taking into account the divisions below the reference line.

Take the thimble reading which coincides with the reference line on the sleeve. Total reading = main scale reading + Least Count X reading on the thimble.


Zero Error = …………….. mm

Sl. No.Slip Gauge Readings

( X )

Length of slip gauges measured using micrometer

X2 XY ErrorBarrel reading

Thimble reading

TR ( Y )

CALCULATION

From table,

∑ X2 = …………………

∑ X = …………………..

∑ Y = …………………..

∑ XY =…………………






An + B∑ X = ∑ Y

A ∑X + B ∑ X2 = ∑ XY



RESULT

The measurements are taken using the given outside micrometer with the slip gauges as the standard reference. The calibration curve for the outside micrometer is also plotted using the obtained results.

INFERANCE



EXPERIMENT NO. 3

CALIBRATION OF GIVEN BEVEL PROTRACTOR

AIM

To study the working principle of the instrument and calibrate it using angle gauge.

APPARATUS REQUIRED

Bevel protractor, Surface plate and angle gauge.

THEORY

Bevel protractor is designed for precision lay out and measurement of angles in degrees. It is provided with a vernier scale for fine measurement. It consists of a base plate attached to main body and an adjustable blade is attached to a circular plate containing vernier scale. The main scale graduated in degrees is provided on the main body. The adjustable blade is capable of rotating freely about the centre of the main scale engraved on the body of the instrument and can be locked in any position by tightening the blade clamp nut. The base of the base plate is made flat so that it could be laid flat upon the work and any angle can be measured.

LEAST COUNT OF BEVEL PROTRACTOR

Main scale is graduated in degrees of arc. The vernier scale has 12 divisions on each side of the centre zero. These are marked 0 – 60 minutes of arc, so that each division equals to 1/12th of 60. That is 5 minutes of arc. These 12 divisions occupy the same space as 23 of main scale. Each

division of vernier is equal to 1/12th of 23 or 11112

.



PROCEDURE

Study the bevel protractor and identify its main parts. Introduce the adjustable blade on the slot of the body and clamp it with the help of knob in

convenient position. Place the working edge of the stock on the surface of the job and rotate the turret holding the

blade so that the working edge of the blade coincides with another surface of the job. Fix turret and read the angle. Measure the angle of sample pieces with protractor and record the reading.


Sl. No.

Angle Gauge

Readings( X )

Angle measured using bevel Protractor

X2 XY Error

MSR VSRTR

( Y )

CALCULATION

Total Reading = MSR + (VSR x LC)

From table,

∑ X2 = …………………

∑ X = …………………..

∑ Y = …………………..

∑ XY =…………………




An + B∑ X = ∑ Y

A ∑X + B ∑ X2 = ∑ XY





RESULT

Measurements are taken using the given bevel protractor with angle gauges as standard reference. The calibration curve for bevel protractor is also plotted using the obtained results.

INFERENCE



EXPERIMENT NO. 4

CALIBRATION OF VENTURIMETER

AIM

1. To Determine the Coefficient of discharge Cd of the given venturimeter for different rates of flow.

2. To calibrate the venturimeter

3. To plot the following graphs (a) Cd Vs HHg , (b) ln Qa Vs ln HHg , (c) Qa Vs HHg

SPECIFICATION

Pipe diameter =

Throat Diameter =

Specific gravity of manometric liquid =

THEORY

When water flows through a venturimeter, a pressure difference is created between inlet pipe and throat of venturimeter. This pressure difference is called venture head, expressed in terms of flowing liquid. By applying continuity equation and Bernoulli’s equation between these two sections, as expression for discharge can be obtained in terms of venture head, which is found to be a theoretical discharge. Actual discharge can be found with the help of a measuring tank. Rate of actual to theoretical discharge is called Coefficient of Discharge (Cd).

Hence Qa is equal to Cd X Qth = KHn

Taking logarithm, log K + n log H



Now conducting series of tests under various flow rates the constants K & n can be evaluated.

Now assuming a range of manometer level differences, corresponding Qa = KHHg. Plotting a curve

Qa Vs HHg (Calibration Curve), discharge through venturimeter can be found out for any flow.

PROCEDURE

Mark sure that no air bubble remains in the limbs of venturimeter and pipe of experimental setup and allow water flow through the venturimeter to the maximum level in order to find

the maximum possible head difference HHg. Divide the value into seven equal divisions in order to fix the steps in the pressure difference for the seven steps of readings.

Adjust the inlet valve to get the required pressure difference in the manometer and note the

level difference HHg in manometer. Note the time to collect water for a rise of x cm in the collecting tank. Repeat the experiment for different manometer reading by adjusting inlet valve. Take at least

7 sets of readings.

GRAPHICAL METHOD OF FINDING CALIBRATION CONSTANTS

Coefficient of discharge, Cd = Qa

Q t

Qa=Cd Qt=Cd a1 a2 √2 gh

√a12−a2

2 = Cd a1 a2√2g H Hg X 12.6

√a12−a2

2

Qa = KHn

Taking logarithms, log Qa = log K + n log H



Which is similar to equation of straight line y = a + bx. Curve of log Qa Vs log K is plotted. Y intercept of curve represents log K. Antilog of y intercept gives values of K. to find n ( slope of

curve), ratio of ∆ y∆ x

is taken.

CONSTRUCTION OF CALIBRATION CHART

A series of values of venturihead (in cm of HHg ) at equal intervals in the possible range of

measurement is considered. Using the values obtained for K & n, the discharge Qa is found out by the relationship

Qa = KH Hgn

A curve of Qa is plotted against HHg which represents the calibration curve.

Analytical method of determining calibration constants.

The line of best fit is represented by

log Qa = log K + n log H

i.e, y = a + bx………………. (1)

a = y intercepts, b = slope of line of best fit.

The normal equation is represented as Σy = Na + b Σx……… (2) Where N = number of readings

Σ xy = a Σ x + b Σx2 ……………… (3)

Solving the equations we get values of K & n.


Inlet diameter of pipe, D =

Throat diameter of venturimeter, d =

Area of collecting tank =

Sl. No

Manometer readingsHHg = H2 – H1

Time for x cm rise of water, t

(sec)

Venturimeter head (H) HHg x 12.6 of water

Qa

cm3 / sQth

cm3 / sCd

log Qa

log HHg

H1 H2 HHg

CALIBRATION CHART



Sl. No.HHg

(cm of Hg)Qa

(m3/ sec)

CALCULATION

Area of inlet pipe, a1 = π4

D2


d2

Manometric reading HHg = H2 – H1 of Hg

Venturihead, H = 12.6 HHg of water.

Qa = Aht

Qth = a1 a2 √2 gh

√a12−a2

2 m of water,

Cd = Qa

Qth

RESULT

A calibration chart for given venturimeter is plotted. The curve can be used for determining discharge corresponding to any venturimeter head.

Coefficient of discharge through venturimeter =

INFERENCE



EXPERIMENT NO. 5

CALIBRATION OF RECTANGULAR NOTCH

AIM

To determine the coefficient of discharge of given rectangular notch and plot the graph

1. Qa Vs h2. Cd Vs h3. Log Qa Vs log h (cm)

APPARATUS REQUIRED

Rectangular Notch experiments set up measuring tank and stop watch

THEORY

Qact=A ht

m3/sec

A=Area of measuring tank

h=height of liquid raised (20cm)

t=Time taken to collect the water to rise 20cm in sec.

The theoretical discharge through the rectangular notch is given by the equation

Qtheoretic=23

L√2 g H32

L=Length of the rectangular notch (8.4 X 10-2m)

G=Acceleration due to gravity

H=Hook gauge reading in m

Coefficient of discharge Cd=Qact/Qthe



PROCEDURE

1. Fill the channel with water until the water tends to overflow. Take the hook gauge reading as sill level of notch

2. Increase the flow rate of water and take the hook gauge reading. Note down as final reading.

3. Close the outlet valve of measuring tank and start stopwatch simultaneously. Take the time required till tank is 20cm.

4. Repeat 2&3 steps for varying flow rate and tabulate the reading.5. from the time taken to rise 20cm the actual discharge can be found.6. From the hook gauge reading the theoretical discharge can be found.7. From the reading following graph are plotted

1. Qa Vs h2. Cd Vs h3. Log Qa Vs log h

TABULAR COLUMN

Sl.No

Hook Reading Guage

H= final-initial Time for 20 cm rise

Qact x 10-3 Qthe x 10-3 Cd

initial final

Area of measuring tank = 0.4 x 04=0.16 m2

Qact=A ht

Qtheoretic=23

L√2 g H32

L=8.4 X 10-2m

Log Qa log H

RESULT

Calibrated the given rectangular notch and plotted the following graph

INFERENCE



EXPERIMENT NO. 6

STUDY AND MEASUREMENT USING VERNIER HEIGHT GAUGE

AIM

To make a study on vernier height gauge and to measure heights of various steps of given specimen using vernier height gauge.

APPARATUS REQUIRED

Vernier height gauge, Specimen and surface plate.

THEORY

Vernier height gauge is similar to vernier caliper, but in this instrument the graduated bar is held in a vertical position and it is used in conjunction with a surface plate.

A vernier height gauge consists of

(a) A finely ground and lapped base. The base is massive and robust in construction to ensure rigidity and stability.

(b) A vertical graduated beam or column supported on the massive base.(c) Attached to the beam is a sliding vernier head carrying vernier scale and a clamping screw.



(d) An auxiliary head which is also attached to the beam above the sliding vernier head. It has fine adjusting and clamping screw.

(e) Measuring jaw or a scriber attached to the front of sliding vernier.

Least count of Vernier Height Gauge

Least count is the difference between the value of main scale division and the vernier scale division.

LC = Value of smallest division on main scale – Value of smallest division on vernier scale

= 1 - 4950 = 0.02 mm

PROCEDURE

Firstly the measuring jaw is checked for zero error. The zero of main scale and vernier scale should coincide when measuring arm rest on surface plate. LC is also calculated.

Now the stepped specimen is placed in a vertical position on the surface plate. Slide the blade up and place its tip on the first step. Clamp the slider there using the screw. Note down MSR and VSR. Multiply VSD with LC and add it with MSD. Zero error is present should be added or subtracted from the reading to get net height. Raise the slider to the next step and proceed as before. At least 3 readings must be taken for each step and their mean should be found out.


Zero error = ………………..mm

Steps Name MSR VSRTotal Height

MSR + (VSR x LC)Net Height

CALCULATION

Total Height = MSR + (VSR x LC)

Net Height = Total Height ± Zero Error

RESULT

The study is carried out on vernier height gauge. Different heights of stepped specimen were calculated using vernier height gauge.

INFERENCE



EXPERIMENT NO. 7

STUDY AND MEASUREMENT USING SINE BAR & SLIP GAUGE

AIM

To make a study on sine bar and to determine the angle of tape of given specimen.

APPARATUS REQUIRED

Sine bar, Slip gauge set, Dial gauge, and Specimen.

SPECIFICATION

Dial Gauge, LC = 0.01

Range = 0 – 10 mm

Length of sine bar (l) = 300 mm

THEORY

Sine bar is a precision instrument used along with slip gauge for the measurement of angles. It is used to measure the angles very accurately and to locate the work to a given angle within very close limits. Sine bar are made from high carbon, high chromium, corrosion resistant steel, suitably hardened, precision ground and stabilized. It consists of a steel bar and two rollers. Rollers are of accurate and equal diameters and are attached to ends of steel bar. The axis of two cylinders are mutually parallel to each other’s and also parallel to upper surface of bar.

PROCEDURE

Find angle approximately with help of Bevel protractor. Set up the sine bar at that angle with slip gauge combination. Component to be checked is placed over the surface of the sine bar and clamp it to an angle

plot.



Set the dial gauge at one end of the work piece and along the upper surface of the component. Check the variation of parallelism of upper surface with surface plate. Adjust the slip gauge combination until upper surface of the component is truly parallel to the

surface plate.

Angle of component, = Sin-1( hl )


Sl. No.Slip gauge Combination

( h)Dial Reading

DifferenceInitial Final

1

2

3

CALCULATION

Taper of work piece, = Sin-1( hl )

Where, h = Slip gauge combination reading

l = Length of sine bar

RESULT

Taper of work piece = ……………………..

INFERENCE

EXPERIMENT NO. 8



CALIBRATION OF ORIFICEMETER

AIM

1. To Determine the Coefficient of discharge Cd of the given orificemeter for different rates of flow.

2. To calibrate the orificemeter

3. To plot the following graphs (a) Cd Vs HHg , (b) log Qa Vs log HHg , (c) Qa Vs HHg

SPECIFICATION

Pipe diameter = 20 mm

Orifice Diameter = 10 mm

Specific gravity of manometric liquid = 13.6

THEORY

When water flows through an orificemeter, a pressure difference is created at venacontrate of orificemeter. This pressure difference is called orifice head, expressed in terms of flowing liquid. By applying continuity equation and Bernoulli’s equation between these two sections, as expression for discharge can be obtained in terms of orifice head, which is found to be a theoretical discharge. Actual discharge can be found with the help of a measuring tank. Rate of actual to theoretical discharge is called Coefficient of Discharge (Cd).

Hence Qa is equal to Cd X Qth = KHn

Taking logarithm, ln K + n ln H



Now conducting series of tests under various flow rates the constants K & n can be evaluated.

Now assuming a range of manometer level differences, corresponding Qa = KHHg. Plotting a curve

Qa Vs HHg (Calibration Curve), discharge through orificemeter can be found out for any flow.

PROCEDURE

Mark sure that no air bubble remains in the limbs of orificemeter and pipe of experimental setup and allow water flow through the orificemeter to the maximum level in order to find the

maximum possible head difference HHg. Divide the value into seven equal divisions in order to fix the steps in the pressure difference for the seven steps of readings.

Adjust the inlet valve to get the required pressure difference in the manometer and note the

level difference HHg in manometer. Note the time to collect water for a rise of x cm in the collecting tank. Repeat the experiment for different manometer reading by adjusting inlet valve. Take at least

7 sets of readings.

GRAPHICAL METHOD OF FINDING CALIBRATION CONSTANTS

Coefficient of discharge, Cd = Qa

Q t

Qa=Cd Qt=Cd a1 a0 √2 gh

√a12−a0

2 = Cd a1 a0 √2 g HHg X 12.6

√a12−a0

2

Qa = KHn

Taking logarithms, log Qa = log K + n log H



Which is similar to equation of straight line y = a + bx. Curve of log Qa Vs log K is plotted. Y intercept of curve represents log K. Antilog of y intercept gives values of K. to find n ( slope of

curve), ratio of ∆ y∆ x

is taken.

CONSTRUCTION OF CALIBRATION CHART

A series of values of venturihead (in cm of HHg ) at equal intervals in the possible range of

measurement is considered. Using the values obtained for K & n, the discharge Qa is found out by the relationship

Qa = KH Hgn

A curve of Qa is plotted against HHg which represents the calibration curve.

Analytical method of determining calibration constants.

The line of best fit is represented by

log Qa = log K + n log H

i.e, y = a + bx………………. (1)

a = y intercepts, b = slope of line of best fit.

The normal equation is represented as Σy = Na + b Σx……… (2) Where N = number of readings

Σ xy = a Σ x + b Σx2 ……………… (3)

Solving the equations we get values of K & n.


Inlet diameter of pipe, D =

Orifice diameter, d =

Area of collecting tank =

Specific gravity of water, S1 =

Specific gravity of mercury, S2 =

Sl. No

Manometer readings

HHg = H2 – H1

Time for x cm rise of water, t

(sec)

Orificemeter head (H) HHg

x 12.6 of water

Qa

cm3 / sQth

cm3 / sCd

log Qa

log HHg

H1 H2 HHg



CALIBRATION CHART

Sl. No.HHg

(cm of Hg)Qa

(m3/ sec)

CALCULATION


D2

Area of throat, a2 = π4

d2

Manometric reading HHg = H2 – H1 of Hg

Orificehead, H = 12.6 HHg of water.

Qa = Aht

Qth = a1 a0 √2 gh

√a12−a0

2 m of water,

Cd = Qa

Qth

RESULT

A calibration chart for given orificemeter is plotted. The curve can be used for determining discharge corresponding to any orificemeter head.

Coefficient of discharge through orificemeter =

INFERENCE



EXPERIMENT NO. 9

CALIBRATION OF TRIANGULAR NOTCH

AIM

To determine the coefficient of discharge of the given triangular notch and plot the graph

1. Qac Vs H2. Cd Vs H

APPARATUS REQUIRED

Triangular notch experimental setup, measuring tank and stop watch.

THEORY

Actual discharge, Qac = Aht m3/ sec

A – area of measuring tank in m2

h – level of water in the tank in mm

t – time taken to collect the water at a height in sec

The threshold discharge through the triangular notch is calculated using the realation,

Qtheo = 8

15tan(θ/2¿)√2 g¿ H 5 /2 m3/ sec

Where, - angle of triangular notch

g – gravitational constant

H – head over the notch in m of water

Cd = Qact

Qtheo



PROCEDURE

Allow the water to fill in the notch till it tends to over flow and take the sill level reading H1 using hook gauge provided.

Increase the discharge of the notch at the maximum possible level and take the hook gauge reading H2. The maximum head over the notch H = H2 - H1.

Adjust the discharge so that we may get the first set of reading. Note the hook gauge reading H2.

Allow the water to collect in the collecting tank and note the time required for a rise of ‘h’ meter of water in the measuring tank.

Repeat the experiment for different heads by adjusting heads by adjusting discharge.


Sill level reading, h1 = ……………cm

= …………

Area of tank, A = …………….

Sl No.

Hook gauge

reading h2

(cm)

Head over notch

H = h2 – h1

Time taken for 20cm

rise of water in sec

Qact X 10-4

(m3/sec)Qthe X 10-4

(m3/sec)Cd

CALCULATION

Hook gauge reading, h2 =

Head over the notch, H = h2 – h1



Actual discharge, Qac = Aht

Qtheo = 8

15tan(θ/2¿)√2 g¿ H 5 /2

Cd = Qact

Qtheo

RESULT

Coefficient of discharge of triangular notch determined and graphs are plotted.

1. Qac Vs H2. Cd Vs H

INFERENCE


measurements lab manual,mechanical engineering,mg university

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