Petroleum Engineering Department

Process Engineering A

Laboratory Report #1

Name: Aytan Nabiyeva

Group number: 2(PE18.1)
Experiment Title: Calibration of Pressure Gauges
Date of Experiment: 21 September 2020
Date of Submission: 8 November 2020
Supervisor: Aida Soltanova
Contents
Synopsis......................................................................................................................................................2
İntroduction................................................................................................................................................2
Theory.........................................................................................................................................................4
Experiment details.......................................................................................................................................5
Apparatus and Equipment...........................................................................................................................5
Safety Precautions.......................................................................................................................................7
Procedure....................................................................................................................................................8
Results.........................................................................................................................................................8
Discussion.................................................................................................................................................10
Conclusion................................................................................................................................................12
References.................................................................................................................................................13

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Synopsis
The presented report is planned for embracing detailed, coherent and precise features
directly associated with this laboratory work and outlines the leading specification of the
calibration procedure in the example of pressure measuring apparatus. Besides that, it
is such kind of perception which helps delineate the essence of extremely accurate
calculation in manufacturing platform. The primary target is to get knowledge about
technique of the verifying the deflection in the gadget via Dead-Weight Tester,
additionally, investigating the reason of blunders derived from various causation
(mostly, human and ambient factors). İt can be said that the experiment consists of two
shares: placing and displacing ring weights. Loads with a certain amount of pressure
exerted on the oil by piston are added to the instrument during experimenting. it goes on
several times until all the loads are gone, then, all pressure values obtained are
recorded. After this, it's time to do the opposite, write the values as we leave the
masses. In the last stage, we set up the table in accordance with the data we gained
and sketched the graphs that indicate link between actual and analytic amounts.
Coming to the discussion part of report, it was debated minor acceptable inaccuracies
(min-0.5%, max-4.19%) and its reasons, a few techniques against its manifestation as
well.

İntroduction
To comprehend significantly main calibration principles of manometers by utilizing
special equipment known as Dead Weight Piston Gauge with Bourdon Tube (HM 150
02) is the leading target of lab-work. Here is a good nuance, why dead weight? Why
does it have such a strange name? It is named like that owing to the usage of same
reference masses. Starting with general perception, pressure is a way of describing
precisely how intensely a force is being applied or felt by an object. It is calculated the
magnitude of the force divided by the areas its being applied to. So, this means that the
same force can exert different level of pressure depending on the size of the areas.
Small areas→ large pressure and vice versa large area→ small pressure. Since
reference point is different there are several types of pressure including absolute,
atmospheric, gauge, differential and vacuum. Mechanical pressure measuring gauge
instrument for differential or absolute have been proven millions of times over. The
proper SI unit of pressure is the pascal (Pa) or pounds per square inch psi and the
relationship between units is here:

2
 N
1 Pa=1 2
m
N
1 ¯¿ 10 Pa=10
5 5
2
m
1 atm=1.01325 ¯¿ 101.325 kPa

Let’s take a glance at the history, years ago, more exactly, in 1643 in order to figure out
atmospheric pressure well-known mercury trial was conducted by Italian
scientist Evangelista Torricelli. From that time different types of gadgets which were
referred to variety of working structures, as proof, siphon barometer, piezometer,
aneroid barometer, U-tube manometer, micro-manometer and most used one is
Bourdon pressure gauges (1849/ by Eugene Bourdon) since it differs with high precise,
being long-lived, easy controlling and cost efficiency. Since Dead Weight Piston Gauge
is based on Pascal’s law, it is not difficult to apply this technique to any field, that is why,
it has a great number of application in process industries also other sectors (including
marine, medical, plant industry as well as aerospace).

The predominant objective of experimentation contains the calibration of the Dead

Weight Piston Gauge to investigate if the gadget is working exactly (showing accurate
reaction) or not. All measurement equipment tends to repel punctuality with the passage
of time and use, and if not calibrated, this may cause us some trouble in measurement.
In many industries, to follow regulations regarding with calibration of equipment
periodically is a strict principle. A process plant tries to do this as effectively as possible
by taking the raw material and turning it into finished products. Keeping all critical
process measurements accurate with regular calibrations helps facilities operate more
efficiently and generate more output and money.

Turning to its application and essence of calibration of manometer, it can be said that
words are incapable of describing the importance of the equipment's extremely correct
operation. In fabrication, manometer stands in the 1st place in the most used equipment
list, thereby, the significance of device punctuality is clear. So, the slightest
measurement error can cause unwanted things to happen (for instance, explosions that
killed countless people a sharp drop in productivity or any technical damage to
expensive equipage and so on). İn order to not face these kinds of problems, checking
each apparatus, including manometer is recommended and the equipment that will help
us in this experience is a DWT. Coming to the application of Bourdon Pressure Gauge,
it is utilized in hydraulic systems with low viscosity liquid and gas flow. In addition to its
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wide use in the petroleum industry, Bourdon tube pressure gauges are also made use
of automobile manufacturing (specially, to tell if there is a leak in fuel stations), in the
agricultural industry (pesticide or fertilizer sprayers). As it is evident from this, the results
from the pressure gauge should be as accurate as possible for the process to be more
efficient, therefore it is necessary to calibrate the device in the following cases: before
and after major operations are carried out, after any incident.

Theory
As I mentioned before, the stress which vapour, gas or solid apply to the surface in
perpendicular position is called pressure. Since the second main issue in process
control industry is to calculate the pressure, number of
instruments are currently utilized to do this in more
accurate way and device named Bourdon tube pressure
gauge is one of them.

What is more, HM150 02 apparatus which is implemented

for analysing work-system of manometer calibration
comprises 2 parts namely, Bourdon gauge and Dead-Weight
Figure 1 Bourdon Gauge
piston. When talking about manometers, U-tube one usually
come to mind, on the contrary, HM150 02 has C-shaped tube as in the images.

Turning to the second part, Bourdon gauge is an object which

comprises of piston, cylinder and pipeline. Furthermore, the relation
between pressure and gravitational force also should be take into
account as follows:

F Figure 2 second part of

P= (1) HM150 02
A
where,
P → Pressure applied by object ( ,̄ Pa )

2
A →Cross sectional area of piston (m )

F → gravitational force of object (N )

It can easily be written like below, because of shape of object (ring):

2
π ∙d
A= (2)
4
4
 d → Piston diameter (m)
By considering this,
F=m∙ g(3)
m N
g → gravitational acceleration( , ),
sec kg
2

m →mass of load (kg)

By substituting the second and third equation into the first

4 ∙m ∙ g
P= 2
( 4)
π ∙d

It could be noticed from the final equation that pressure is directly proportional with
mass. That is why the indicator of pressure change when we add ring and remove ring.
(adding mass →increasing pressure and opposite one)

p ascending+ P descending
Paverage = (5)
2

Without any doubts, it is unavoidable to not make any mistake and we need to take into
account these minor but apparent errors. Addition to this, it should be said that there is
an exact limit and it means that it has allowable inaccuracy range of ± 1 % from the final
scale value (2.5 bar) which means, deviation must be 0.025 ¯¿ :

1
∆ P=2.5 ∙ =0.025(6)
100

I would like to spotlight that as test was performed by putting and taking the rings, Paverage
of upper and lower limited pressure should be evaluated in a following way:

Pupper =Ptheoretical −∆ P (7)

Plower =Ptheoretical + ∆ P (8)

Then, absolute (9) and relative (10) error should be computed as here:

ε =|theoretical value−experimental value|(9)

ε
φ %= ∙100 % (10)
theoretical value

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Experiment details
Apparatus and Equipment
The basic experimental device that was employed throughout the lab-operation is
recognized as HM 150 02, fabricated by G.U.N.T company. The comprehensive
introducing and functions of individual parts of calibration device are highlighted as
follows:

2
1

3
5

Figure 3 Layout of the dead-weight piston gauge HM150.02 Figure 4: Top view of device

1. Hydraulic pump with storage tank

2. Transparent scale
3. Bourdon tube pressure gauge
4. Piston manometer
5. A set of weights
6. Base plate

The device also includes sections where the

piston cylinder and loads and manometer
calibration occurs. By the same token, these
two parts are connected by oil-filled pipes to
transmit pressure. At this point, an interesting
question arises, why oil (why no other liquids?).
Answer is straightforward, firstly, the most
available fluid which lets the greasing in motion
of piston and cylinder. Secondly, unlike other
liquids, oil does not cause unwanted foaming Figure 5. Key parts of Bourdon Tube

and evaporation. Let’s get acquainted with the Bourdon pressure gauge which is most
utilized tool in pressure measurement between vacuum pressure and few thousands psi
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in more detailed. The Bourdon Gauge is attached to a transparent dial, whose aim is to
display the inner workings of the gauge. One end of which is connected to the system
(known as rigid) and the other end is free, the device has an elliptical shape and has the
ability to bend up to about 270 degrees (like a C-shape). When pressure is employed,
the pipe tends to become straight, thereby the free end changes marginally and it is
reflected as in the transparent dial.

Safety Precautions
Being aware of a strong set of overall lab safety regulations is crucial factor in order to
prevent laboratory incident & disaster. I want to induce to look at or focus on an
important point that there are general lab rules to be followed in fluid mechanics and
special lab caution regarding to the equipment which was used during testing. A number
of general laboratory safety rules have been known since last year. (To wear safety
goggles wherever necessary, to check electrical wire before starting the experiment, not
to tamper any device without the permission of lab assistant).

 First of all, since the special equipment is intended to use for training aims, to
palpate the mechanism without supervisor is forbidden.
 Secondly, we have ring-shaped objects which are quite heavy, because of
this, it needs to behave more cautiously for not damaging ourselves and
items.
 Next, I can say that large part of the device is made of transparent glass, and
we must be extremely careful not to cut our hands and damage the device.
 There is oil in the system which means that items that can cause a fire
incident should not be used around this equipment.
 As it is obvious from the pictures above, the maximum pressure that can be
applied to this device is 2.5 bar. Therefore, even the extra 0.1 bar pressure
applied to the piston can damage the tube on the manometer.

Procedure
The calibration of pressure gauge experiment is performed in the following sequence, I
make cognizable each step by using below smart diagram:

F ir s t s t e p is t o p r e p a r e t h e d e v ic e f o r c o n d u c ti n g t h e e x p e r im e n t , in o r d e r t o 7
r e a liz e t h is s t a g e t r a n s p o r t c a p s h o u ld b e r e m o v e d f r o m c y lin d e r .
Results
Result part covers information manifested by the variety of calculations that were gained
throughout the trial that is indicated. After all essential data are recorded, it is time to
derive calculation working about applied pressure and insignificant deviation&
inaccuracy from theoretical figures. Once the support mass and load weights, piston
radius are known, the theoretical pressure at each step can be easily evaluated. On the
other hand, we do not need to calculate this via using formula (4), because they have
already given the theoretical values. As I referred above, the minimum and maximum
possible deviation is 0.025 bar (equation6,7,8) The outcome obtained from the
experimentation can be summarized as in the table depicted below:

limit in bar Measured pressure p in bar

mass of
lower average absolute relative
№ load in
theoretical upper limit - increase reduction value error in error %
kg
pressure limit +1% 1% bar
1 0.000 0.000 0.025 -0.025 0.000 0.000 0.000 0.0000
2 0.385 0.334 0.359 0.309 0.330 0.310 0.320 0.0140 4.1916
3 0.578 0.500 0.525 0.475 0.500 0.510 0.505 0.0050 1.0000
4 1.156 1.000 1.025 0.975 1.010 1.020 1.015 0.0150 1.5000
5 1.734 1.500 1.525 1.475 1.517 1.518 1.518 0.0175 1.1667
6 2.312 2.000 2.025 1.975 2.021 2.021 2.021 0.0210 1.0500
7 2.890 2.500 2.525 2.475 2.515 2.510 2.513 0.0125 0.5000

Table 1 gives all required data- theoretical values, experimental inaccuracy (relative and
absolute), allowable deviation and, finally, average figure of pressure. By using the data
given in the table above, we can easily sketch the following graphs –
average&theoretical pressure (1), absolute error&average pressure (2) and last one
relative error &average pressure (3).

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Graph 1. Gauged & theoretical pressure

Gauged pressure vs Theoretical pressure

3.000
2.513
2.500
2.021
Average pressure in bar

2.000
1.518
1.500
1.015
1.000
0.505
0.500 0.320
0.000
0.000
0.000 0.500 1.000 1.500 2.000 2.500 3.000
Theoretical pressure in bar

Graph 2.Absolute error & average pressure

Absolute error Vs average pressure

0.0250
0.0210
0.0200 0.0175
0.0150
0.0140
Absolute error

0.0150 0.0125

0.0100
0.0050
0.0050
0.0000
0.0000
0.000 0.500 1.000 1.500 2.000 2.500 3.000
Average pressure

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Graph 3. Relative error & average pressure

Rela tiv e erro r v s a v era g e p ressu re

4.5000 4.1916
4.0000
3.5000
3.0000
Relative error %

2.5000
2.0000 1.5000
1.5000 1.1667 1.0500
1.0000
1.0000 0.5000
0.5000
0.0000
0.000 0.500 1.000 1.500 2.000 2.500 3.000

Average pressure

Discussion
Commonly, current experimentation was concentrated on analysing pressure calibration
by DWT. İnformation derived from trial was tabulated as well as relationship between
elements of whole system was disclosed by drawing chart via Excel program. In table
(1), all trial parts were illustrated (pressure when putting in and removing weight rings,
average one as well). Right after doing these, with the help of formula (9) and (10)
absolute and relative errors were estimated. Looking at graph (1), it appears to be an
almost smooth line, which leads to almost the identical conclusion of the actual and
theoretical amount, whereas there are middling deviations in graph (2) and (3).

As seen obviously, it is unavoidable to not make any mistake and it is important to take
into account these minor but apparent blunders. All over, the absolute and relative
blunders vary in 0-0.210 and 0%-4.19% interval, respectively. Examining the underlying
causes of the errors, we can see that despite every rotation of the piston when the
weight rings are added, there is static friction between the cylinder and piston seat,
which reduces the pressure and force on fluid. What is more, there is always a small
possibility that small amounts of the accidental admission liquid through a crack that
could affect hydraulic pressure may occur after several uses of a piston seal designed
to hamper liquid leakage from the pipe. Different types of materials are operated to
meet demand with high standard, for instance, stainless steel, beryllium copper,
phosphorus bronze and others. The inevitable truth is that after a while, metal particles
may be weathered, only the right fluid selection can slow the tool's wear rate. The

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Bourdon tube we use is a very sensitive instrument to environmental factors, for
example, temperature, if the temperature is in the range 15 ℃ - 25 ℃, the instrument
will show more accurate results and if otherwise the results may be more than they
should be; the main reason standing behind this distinction is related to spring flexibility.
Furthermore, air blisters and dirt which have a negative effect on the results formed
during the experiment can accumulate on the walls of equipment. One more catalysator
which can result in blunders is hydraulic oil (it leads to alteration in pressure) The next
possible reason might be related to one of the human factors, namely, the eye delusion
sourced from angle of vision in transparent dial.

Once and for all, certainly, there is a way to keep down errors, in an other saying, to
obtain more precise consequence. First of all, we can get more admirable results by
trying a few times. It would also be better to use a loupe when reading the values from
the transparent dial. One of the problems that prevents us from getting more accurate
results is associated with friction, to overcome this issue we need to use more sensitive
materials that can miniaturize friction.

Conclusion
To conclude, the leading mission of this trial -to inspect calibration precept of
manometer was accomplished victoriously. Meticulous knowledge about details of DWT
which has the immense precision degree was mentioned above and it was followed by
info regarding with load supplement. At the same time, the figures for pressure were
noted down and a table was created by combining all information.

When all is said and done, experiment have been performed experiment successfully
and all results are comprehensive, in spite of some minor errors which are less than 5%
and are caused to work improper condition and not have professional equipment. It can
be said that these errors are quite acceptable due to some fact which I mentioned
above.

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References
 Hehn, A.H. (1984). Fluid power troubleshooting. New York: Dekker.
 Van, L. (1963). Weights and measures standards of the United States: a brief
history. Washington: U.S. Government. Printing Office.
 ‌ Little, A.D. and United States. Department of Housing and Urban Development.
Office of Policy Development and Research (1975). Handbook on natural gas
pipeline safety in residential areas served by master meters. Washington, D.C.:
U.S. Department of Housing and Urban Development, Office of Policy
Development and Research, Division of Energy, Building Technology, And
Standards.
 American Society of Mechanical Engineers (1964). Pressure measurement:
Instrument and apparatus. New York: Asme.
 ‌ Herbich, J.B. (1960). Fluid mechanics laboratory manual. Bethlehem, Pa.: Fritz
Engineering Lab., Hydraulics Division.

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 Douslin, D.R., United States. Air Force. Office of Scientific Research and
Bartlesville Petroleum Research Center (U.S (1962). An Inclined-piston dead-
weight pressure gauge. Washington, D.C.: Air Force Office of Scientific
Research, United States Air Force.
 ‌ Mylroi, M.G. and G Calvert (1984). Measurement and instrumentation for
control. London, Uk.: P. Peregrinus On Behalf of The Institution Of Electrical
Engineers.
 IEEE Approved Draft Standard for Ratings and Requirements for AC High
Voltage Circuit Breakers with Rated Maximum Voltage above 1000 V. (2018).
New York, Usa Ieee.

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