FACULTY OF CHEMICAL ENGINEERING FACULTY OF CHEMICAL ENGINEERING UNIVERSITI TEKNOLOGI MALAYSIAUNIVERSITI TEKNOLOGI MALAYSIA

FLUID MECHANICS LABORATORYFLUID MECHANICS LABORATORY

TITLE OF EXPERIMENT TITLE OF EXPERIMENT

CALIBRATION OF BOURDON TUBE PRESSURE GAUGECALIBRATION OF BOURDON TUBE PRESSURE GAUGE (EXPERIMENT 5) (EXPERIMENT 5)

Name Name

Matrix No.Matrix No.

Group / SectionGroup / Section

SupervisorSupervisor

Date of Experiment Date of Experiment

Date of SubmissionDate of Submission

Marks obtained (%)Marks obtained (%)

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Objective

The objective of this experiment is to perform pressure calibration on a Bourdon tube

pressure gage using a dead weight tester.

INTRODUCTION

The pressure intensity at any point in static or moving fluid can be measured using various types of pressure measuring instrument. One of these devices is the Bourdon tube pressure gage. Bourdon-tube pressure gages are most widely used now-a-days because of their reliability, compactness, low cost and ease of use. It consists of a curved tube of elliptical cross-section bent into a circular arc as shown in Fig. 1. When pressure is applied to the tube, it tends to straighten out, and the deflection of the end of the tube is communicated through a system of levers to a recording pointer. This gauge is widely used for steam and compressed gases. The pressure indicated is the difference between the system pressure and to the external (ambient) pressure, and is usually referred to as the gauge pressure

Fig. 1: Schematic of a bourdon-tube pressure gage

As the Bourdon tube pressure gage is used extensively, the stiffness of the internal components change from factory setup and therefore calibration is necessary to give correct pressure readings. Calibration means checking the pressure gage readings against a very accurate device. One of the calibration devices that is available in our lab is the so-called “Dead Weight Tester”

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Apparatus

This dead weight pressure gauge calibrator consists of a precision machined piston and

cylinder assembly mounted on levelling screws. A Bourdon gauge is supplied for

calibration. The weights supplied are added to the upper end of the piston rod which is

rotated to minimise friction effects. The gauge is thus subject to known pressures which

may be compared with the gauge readings and an error curve drawn.

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Experimental Procedures

1. Fill up a cylinder and a connecting hose with water

2. Insert the piston into the cylinder and remove as much air bubble as possible from

cylinder and hose

3. Load weights on the piston in an increment of 0.5 kg so as to cover the Bourdon-

tube pressure range from zero to maximum pressure on the scale

4. Read the indicated Bourdon-tube pressure gauge reading. Prior to taking a reading

for each weight rotate the piston to minimize friction effect on the reading.

5. After the maximum pressure reading is obtained, unload weights from the piston

by the same increment and repeat step 4.

6. Obtain the calibration curve by plotting the True Pressure against the Bourdon-tube

pressure gauge reading.

Data analysis

Mass of the piston : 1 kg

Cross sectional area of the piston: ______________ m2

Mass of the piston x (9.81 x 10-3)

True Pressure exerted by piston = ------------------------------------------------ kN/m2

Cross sectional area of piston

Total mass (weight + piston) x (9.81 x 10-3)

True pressure exerted by total mass = ----------------------------------------------------kN/m2

Cross sectional area of piston

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EXPERIMENTAL DATA

Mass(kg)

True pressure(kN/m2)

Calibrated pressure (Bourdon gauge) (kN/m2)

Percentage of error

(1) (2) (3) (4) (5) (6) (7)Mass

Added(kg)

Total mass (kg)

Pressure exerted by total mass

Increasing order of weight

Decreasing order of weight

Increasing order of weight

Decreasing order of weight

0 1 (piston)

5

Laboratory report

1. Show sample calculations

2. Plot a graph of bourdon pressure (calibrated ) for increasing and decreasing

orders of weight versus true pressure. Extend the graphs and check if they

intercept a point of origin. Comment on the difference in the graph profiles and

explain the possible reason for the graphs (if so) not intercepting the origin

point.

3. Plot a graph of percentage of error versus true pressure. Compare and comment

on the difference in the percentage of error with respect to true pressure and

briefly discuss factors contributing to such error.

4. Propose recommendation to improve the results

5. Briefly discuss safety measures taken during the experiment

6. Conclusions

7. References

WATER PUMP

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