Experiment No. (2).pdf

1. 1
Experiment Name
Dead weight for Calibration
Pressure Gauges
Petroleum Engineering Department
Faculty of Engineering
Koya University
Prepared by:
1-Kaiwan B. HamaSalih 2-Rebin F. Hussien
Supervised by:
Dr. Jaffar A. Ali Mr. Nawrasi
Fluid Mechanics Lab
Lab Report

2. 2
Summary
The aim of this experiment was to calibrate a Bourdon type of pressure gauge and to establish
the calibration curve of Bourdon Gauge. At first, we open the overflow valve and remove the
transport-cap. And we degrade (decrease) the level of hydraulic oil until it touches the surface
of the container (if it’s necessary you can also topping up the level of hydraulic oil). After that
we insert the piston, we check the zero point of bourdon gauge, by proceed the followings:
1. We pressed the piston out of the cylinder using hand wheel.
2. Then we removed the piston and weight support.
3. And we adjust the oil level in the open cylinder until the cylinder is filled up to the
edge.
The gauge pressure being tested should now indicate zero,
as it is only subject to ambient pressure.

3. 3
And after the zero point of Bourdon gauge has been checked, the weight support is re-inserted
into the cylinder of the pressure gauge unit. The piston is then slowly lowered by unscrewing
the counterbalance cylinder until it is freely suspended. And in order to avoid static friction,
set the weight support in gentle rotation. The mass of the support is 385 g. Taking into account
the piston diameter of 12 mm, it is now possible to read the increase in pressure from Bourdon
gauge. Finally, we take different measuring data’s and we achieved 0.3 bar by placing a weight
with a mass of 0.385 kg on the support. After that the display of 0.5 bar is achieved by placing
a weight with a mass of 193 g on the support. The other weights weigh 578 g, which is
equivalent to a pressure increase of 0.5 bar each time.

4. 4
Table of Content
Subject Pages
Introduction……………………………………......……………………………. 5
Aim/Objective of Experiment…….........……………………………………… 6
Table of Reading.…………………...………………………………………. 7
Sample of Calculation....…………...………………………………………. 7-9
Table of Calculation………………...………………………………………. 10
Result………………………………………………………………………… 10
Discussion (Kaiwan B. HamaSalih) ....……………………………………… 11-13
Discussion (Rebin F. Hussien) ....…………………………………………… 14
Conclusion………………………....………………………………………… 15
Reference………………………....………………………………………… 16

5. 5
Introduction
Asst. lect. Nagham Rajaa, Asst. lect. Tebe Tariq (No date) Instrument calibration is one of the
primary processes used to maintain instrument accuracy [1]. Asst. lect. Nagham Rajaa, Asst.
lect. Tebe Tariq (No date) It is the process of configuring an instrument to provide results
within an acceptable range [1]. Asst. lect. Nagham Rajaa, Asst. lect. Tebe Tariq (No date)
Known weights have been applied on a Dead Weight Calibrator to apply pressure to a fluid for
checking the accuracy of readings from a pressure gauge [1]. Asst. lect. Nagham Rajaa, Asst.
lect. Tebe Tariq (No date) Various types of pressure measuring instrument have been used to
measure the pressure intensity at any point in static or moving fluid [1]. Asst. lect. Nagham
Rajaa, Asst. lect. Tebe Tariq (No date) One of these devices is the Bourdon tube pressure
gauge. Bourdon-tube pressure gauges are most widely used now-a-days because of their
reliability, compactness, low cost and ease of use [1]. Asst. lect. Nagham Rajaa, Asst. lect.
Tebe Tariq (No date) It consists of a curved tube (Figure 1) of elliptical cross-section bent into
a circular arc [1]. Asst. lect. Nagham Rajaa, Asst. lect. Tebe Tariq (No date) 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 [1]. Asst. lect. Nagham Rajaa,
Asst. lect. Tebe Tariq (No date) This gauge is widely used for steam and compressed gases [1].
Asst. lect. Nagham Rajaa, Asst. lect. Tebe Tariq (No date) 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 [1].

6. 6
Aim/Objective of Experiment
To calibrate a Bourdon type pressure gauge and to establish the calibration curve of
Bourdon Gauge.
Also determine the gauge errors.

7. 7
Experimental Work:
Table of Readings
No. Mass (gm) Pressure (bar)
1 385 0.335
2 385+193 0.5
3 577+578 1.01
4 578+577+577 1.52
5 578+577+577+577 2.03
Sample of Calculation
𝐹 = 𝑚. 𝑔
Pact.=
𝐹
𝐴
1 bar = 105
pa
Where:
A: cross-sectional area of the piston.
d: piston diameter (d=12 mm).
F: Force.
Pact.: Actual pressure.
m: Mass of load unit.
g: Gravity constant.

8. 8
Sample of Calculation
Pact.=
𝐹
𝐴
𝐹 = 𝑚. 𝑔 𝐴 = 𝜋𝑟2
r=
𝑑
2
d=12 mm
𝐴 = 𝜋 (
12 × 10−3
2
)
2
𝐴 = 0.000113 m2
1. For (m1=0.385 kg)
F= 0.385 kg× 9.81
𝑚
𝑠2
= 3.77685 N
Pact.=
𝐹
𝐴
= 3.77685
0.000113
= 3× 104
Pa
Note: 1 bar= 105
pa
3× 104
Pa ×
1 𝑏𝑎𝑟
105 𝑃𝑎
= 0.3 bar
2. For (m2= 0.578 kg)
F= 0.578 gm× 9.81
𝑚
𝑠2
= 5.67 N
Pact.=
𝐹
𝐴
= 5.67
0.000113
= 5× 104
Pa
5× 104
Pa ×
1 𝑏𝑎𝑟
105 𝑃𝑎
= 0.5 bar
3. For (m3= 1.155 kg)
F= 1.155 kg× 9.81
𝑚
𝑠2
= 11.33055 N
Pact.=
𝐹
𝐴
= 11.33055
0.000113
= 1× 105
Pa
1× 105
Pa ×
1 𝑏𝑎𝑟
105 𝑃𝑎
= 1 bar

9. 9
4. For (m4= 1.732 kg)
F=1.732 kg× 9.81
𝑚
𝑠2
= 16.99092 N
Pact.=
𝐹
𝐴
= 16.99092
0.000113
=1.5× 105
Pa
1.5× 105
Pa ×
1 𝑏𝑎𝑟
105 𝑃𝑎
= 1.5 bar
5. For (m5= 2.309 kg)
F=2.309 kg× 9.81
𝑚
𝑠2
= 22.65129 N
Pact.=
𝐹
𝐴
= 22.65129
0.000113
= 2× 105
Pa
2× 105
Pa ×
1 𝑏𝑎𝑟
105 𝑃𝑎
= 2 bar

10. 10
Table of Calculation
No. Pm (bar) Pact. (bar)
1 0.335 0.3
2 0.5 0.5
3 1.01 1
4 1.52 1.5
5 2.03 2
Results:
 We knew how to calibrating the bourdon gauge.
 We knew how to define the errors and how to fix it if it was possible.

11. 11
Discussion-Kaiwan B. HamaSalih
1. Define the calibrating curve and explain the purpose of it?
The calibration curve is the graphical analysis to the relation between two numbers and how
they are changing by change of another number like we have pm and pact. In this experiment.
The relationship is often a straight line. Calibration curves are used to understand the relation
between pm and pact..
2. Draw the calibrating curve between pm & pact. And then discuss it.
For the calibration curve we used the data that we get in the test, so in the test we used
the weight to determine the Pm after that we used the equation to find the Pact, after
finishing all tests a we started to draw the curve by using this information’s, we know that
in curve we have Y line and X line so we used Pm as a X, and Pact as a Y, after using all
data’s and put it in their place we draw the curve, now we can see the curve shows that the
upward of the pressure.
0
0.5
1
1.5
2
2.5
0 0.5 1 1.5 2 2.5
pact.
pm
Calibration curve between pm and pact.

12. 12
3. What is the reason that we use the hydraulic oil in our experiment instate of using
other kind of fluids?
Because, when a device is used in a process containing hydraulic media, it is generally more
appropriate to calibrate with it hydraulic fluid. If it is calibrated with air or nitrogen, it must
be thoroughly cleaned to prevent contamination of the pressure calibrator being used.
4. What does it mean if the gauge reads a higher value?
If a pressure gauge reads a higher value during calibration than the actual pressure
applied, it typically means that the gauge is over-reading or indicating a pressure higher
than it should. This can be a concern because an inaccurate pressure gauge can lead to
various issues, including safety hazards and incorrect process control. Several factors
could cause a pressure gauge to read a higher value during calibration:
1. Calibration Error: The calibration process itself may have been performed incorrectly,
leading to an inaccurate adjustment of the gauge.
2. Damage or Wear: Physical damage, wear and tear, or internal component issues in the
pressure gauge can affect its accuracy. A damaged or worn spring or diaphragm, for
example, can cause the gauge to read high.
3. Temperature Effects: Pressure gauges are often calibrated at specific temperatures. If
the calibration and the actual usage temperatures differ significantly, it can affect the
gauge's accuracy.
4.Environmental Factors: Environmental conditions, such as humidity, altitude, or
atmospheric pressure, can influence the gauge's performance.

13. 13
5. What are the possible sources of errors in this experiment?
There are some possible ways to have errors in this experiment like the gauge itself, maybe
it’s not working as it could be or maybe it's not zeroed or maybe the weight corroded in some
ways and that will not provide the actual Measure, and also the gravity is one of the sources
because we all know that the gravity isn't the same in everywhere like if we do that test up on
the mountain we see that the results be different than the results in somewhere else because
the gravity is lower there, and also if we have an electronic device maybe there be errors too
and this errors maybe we have it because of the problem in the software or the data reading in
that device.
6. Does its necessary to do calibration for our gauges?
Yes, they should be calibrated to ensure safety and efficiency.
7. How often should a pressure gauge be calibrated?
Calibrate a pressure gauge at least once a year.
8. Is the relative height between the calibrator and the gauge important in
calibration?
Yes, it is and the height of gauge that is being calibrated and the height of the calibration
equipment should be considered before beginning the calibration process. This is important
because the height difference can cause error due to the hydrostatic pressure of the pressure
media. In case it’s impossible to set the equipment and the gauge at the same height, than the
effect of height difference should be calculated and noted during calibration.

14. 14
Discussion-Rebin F. Hussien
1. Define the calibrating curve and explain the purpose of it?
A calibration curve is way to identify the concentration of an unknown substance. These
curves use data points of known substances at varying concentrations, and researchers or
developers can use these curves to find where an unknown substance.
2. Draw the calibrating curve between pm & pact. And then discuss it.
In the curve we showed the P actual as Y axis and P maximum as X axis so the curve is linear
between the both of P actual and P maximum as a result the line on the curve will be increase
as a straight line.
3. Does its necessary to do calibration for our gauges?
For best performance, gauges should be calibrated at regular intervals. How often depends
on the application and industry.
4. How often should a pressure gauge be calibrated?
The recommended calibration intervals for most pressure gauges are every12 months or
annually, but in some cases, it may be necessary to check the calibration more frequent.
0
0.5
1
1.5
2
2.5
0 0.5 1 1.5 2 2.5
pact.
pm
Calibration curve between pm and pact.

15. 15
Conclusion:
Pressure Gauge is a device which is used to measure pressure in a system. The pressure
measured by a pressure gauge is always above the atmospheric pressure. Hence, absolute-
pressure of the system is obtained by adding atmospheric pressure to the pressure measured by
gauge pressure. To different kinds of error may normally be expected in a gauge of this type.
First, there is the possibility of hysteresis due to friction and backlash, so that the gauge will
tend to read lower values then the pressure is increasing than when decreasing. Secondly, there
is the graduation error due to the scale being marked off incorrectly. So, while calibrating a
pressure gauge, firstly, one must check that pressure gauge loading is set to zero. If not, then
calculate the zero error and then add it to the final reading to obtain the accurate result. From
the data table, we can notice that pressure being tested, increases linearly with the increase in
applied load. We can also notice that variation between up pressure and down pressure is 0.5
(bar) which is very less. Which says that pressure gauge is working well. The accuracies of
dead-weight tester are limited due to: (1) the friction between the cylinder and the piston, (2)
the uncertainty in the area of piston, (3) the buoyancy error and (4) gravity error.

16. 16
Reference:
1. Asst. Lect. Nagham Rajaa, Asst. Lect. Tebe Tariq (No date), Calibration of a Bourdon
pressure gauge, Available at https://uomustansiriyah.edu.iq, Accessed at 20/10/2023.