The document describes an experiment to calibrate a Bourdon pressure gauge using a dead-weight pressure gauge calibration system. The system applies pressure via weighted pistons which act on hydraulic oil, allowing a test gauge to be calibrated by comparing its readings to known pressure levels. Procedures are outlined for checking the zero point and then taking readings at incremental pressure levels by adding weights to the system. Sources of potential error are discussed. Calibration curves are examined to verify the accuracy of the test gauge by comparing actual pressure values to measured readings.

1. Faculty of Engineering Petroleum
Engineering Department
Fluid Mechanics Laboratory, 2nd stage
Experiment Name: Dead –Weight pressure gauge
Prepared by: Muhammed Fuad Rashid
Ahmad Jalal Hassan
Muhammad Hassan Aziz
Safwan Tofiq Ameen
Group: A
Supervised by: Mr. Dara & Mr. Awara
Date of Submit: 30/09/2019
©2019

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Aim of the experiment
Calibrating the Bourdon gauge

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Introduction
Dead-Weight pressure Gauge is used for checking and adjusting pressure gauges. The pressure
is applied via weights which are placed on a weight support. The latter has a piston which acts
on hydraulic oil in a pipe system, so that a pressure gauge which is also connected to the system
should indicate certain pressures.
The device contains a Bourdon gauge with a transparent dial. The display mechanism and the
various adjustment opportunities are therefore clearly identifiable.
Hydraulic oil is used to transfer pressure.

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Tools used in Experiment
1. Base Plate
2. Bourdon gauge
3. Weight support
4. Weight
5. Overflow
6. Drain plug
7. Hydraulic valve
The description unit
The device for calibrating pressure gauges
essentially consists of two units:
1. The pressure gauge unit
This is where the pressure gauge to be calibrated is screwed in. For experimental purposes, the
unit comes supplied with a Bourdon gauge already screwed in.
2. The load unit
The load unit consists of several weights and a cylinder with a piston. An increase in the load
results in an increase in pressure. The load unit is
connected to the pressure gauge unit via an oil-filled line, enabling the Bourdon gauge to
display the increase in pressure.

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The layout unit :
The following sectional drawing shows how the
load unit and pressure gauge unit are connected.
As you can see, both units are connected by means
of a pipeline. When the support is loaded
with weights, the oil pressure in the system
increases. The seal between the piston and the
cylinder is metallic, with no other sealing elements.
The fit has been very carefully designed to ensure
that the piston operates almost entirely without
friction, and with minimal oil leakage. The weights
are designed in such a way that pressure increments
of 0.5 bar are possible. Place the small weight on the
weight support first.
A guide pin is provided for this purpose. The other
weights would lie askew on the plunger, and would
corrupt the measurements due to different levels of
friction. The unit is also equipped with a drain valve in
order to drain the oil. In addition, an overflow is
incorporated, so that any leaked oil can be siphoned off.
The overflow can be emptied via a tap.

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Procedure
- Open the overflow valve
- Remove the transport-cap
- If necessary topping up the hydraulic oil
- Inserting the piston
-To check the zero point of Bourdon gauge, proceed
as follows:
* Press the piston out of the cylinder
using the hand wheel.
* Remove the piston and weight support.
*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.

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-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.
-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.
-Other pressures occurring when the weight on the support is increased can be calculated in
exactly the same way. 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.

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Discussion:
1- Define the calibrating curve and explain the purpose of it.
2- Draw the calibrating curve between Pm & Pact. then discuss it.
Answers by Muhammed Fuad
1-A Calibration curve is a general method for determining the
concentration of a substance in an unknown sample by comparing
the unknown to a set of standard samples of known concentration.
A calibration curve is one approach to the problem of instrument
calibration; other approaches may mix the standard into the
unknown.
2- if we look at the diagram we’ll see the readings are almost
equal and there’s a few differences between P actual and P
measurement. I think it’s just because some physical errors like
pipe friction or probably we haven’t done the readings properly or
while we read the numbers on the gauge , the gauge wasn’t on the
eye level or maybe the tools that we used in measuring are out of
order and need to be calibrated, and the deice was analog ad every
analog process are due to some errors , it’s not like digital devices.

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3. Prove that Pact =m*86.814 KN/m2
F= mg
Pact = Pact =m
Pact =m Pact=m*86814 N/m2
Pact =m*86.814 KN/m2
Answers by Safwan Tofiq Ameen
Pact =

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1.The graphic or mathematic relationship between the
readings obtained in an analytic process.
The relationship is often a straight line rather than a curve.
The purpose of the calibration curve is used to determine the
accuracy of the instrument and to ensure that readings from an
instrument are consistent with other instruments.
2.
3. what are possible sources errors in this experiment?
A/ 1- The calibrator (calibration devise) that using for this
experiment may be used for many years and the gauge has some
error for example when we do this experiment the gauge pressure
start in 0.02 instead 0.00.
2- The calibrator device is not digital therefore it has some error.
Answers by Ahmad Jalal Hassan
1.Calibration curve is referring to the way of adjusting and
evaluating its precision and accuracy of the equipment’s

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measuring, the calibration curve of the instruments for example in
the lab tests, tend to dissipate or reduce bias (error) in the reading
of the instrument in a range of a serious values of instruments
reading and theoretical values.
2. according to the calibrating curve there’s a very small and
precision and bias in this diagram between instruments reading
which is Pm and Pact which theoretically found, this error is due to
some reasons: I. the reading of the pressure gauge is not properly
and in the right way (which mustn’t be read in a slope)
II. error in measuring the weights that will lead to a bigger
pressure or smaller.
3 Why do pressure gauges fail?
The studies have shown that vibration is the main cause of
pressure gauge fails in the manufacturing facilities. Vibration has
the bad impact on gauge accuracy.it is hard to accurately read the
pointer on a dial when a gauge is vibrating, which finally the
instrument reads wrong value.
Answers by Muhammad Hassan Aziz
1.at analytical chemistry, a calibration curve is a general
method for determining the concentration for a substance at
an unknown sample with comparing the unknown to the set of
the standard samples of known concentration.
2.The values of readings and calculating are nearly the same,
but there is a struggle between the two values that caused by
some practical and instruments performance like friction in
the parts of the instrument which will lead to error in the
reading values.

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3. How often should a pressure gauge be calibrated?
Accuracy verification prior to installation is suggested as a gauge is
not staying calibrated indefinitely. After installation, it is to be
recommended to do the pressure gauge calibration process at least
once in a year. This applies on all gauges in all industries, no matter
the application is.

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References:
1. www.scribd.com
2. Fluid Mechanics, SI Version (WSE) by Fox and McDonald
3. A text book of Fluid Mechanics and Hydraulic Mechanics by R K Bansal
www.science.gov