Koya UniversityFaculty of Engineering

School of Chemical & Petroleum EngineeringChemical Engineering department

MECHANICAL FLUID

EXPERIMENT NUMBER SIX

Dead-weight piston gauge

Instructor: Mr. Ali & Miss. HawzheenAuthor Name: Aree Salah Tahir

Experiment Contacted on: 26/Nov/2013Report Submitted on: 3/Dec /2013

Group:A

The aim of this experiment:

The objective of this experiment is to calibrate the Bourdon gauge, which is used to measure gauge

pressure .

Introduction:

Dead Weight Pressure Gauge are used for calibrating and standardizing pressure gauges Dead Weight Pressure Gauge Testers are so designed and manufactured that extremely small variations and very small pressure scan be measured with great accuracy. The standardizing pressure is developed by loading with standardized weights a vertically arranged ram which works in a cylinder filled with oil. This cylinder is connected to an oil reservoir through an isolating valve (which transfers the pressure to the gauge). A priming pump, a pressure pump, pressure gauge adaptors etc. are also connected to the cylinder. A set of standardized weights, forth testing range of the tester, is supplied with each instrument. A set of adaptors for different sizes of pressure gauge threads is also provided along with a set of spanners needle puller and a screw driver.

Theory:

Pressure sensor calibration

Variation in a pressure sensor reading may be calibrated, using known pressures, to give a gauge reading in engineering units. As has been seen in exercise A, the dead-weight calibrator produces a known reference pressure by applying a mass to a

column of fluid. The pressure produced is where Fa=mg

Fa is the force applied to the liquid in the calibrator cylinder.

M is the total mass (including that of the piston)

g is the acceleration due to gravity

Pact .= FA

A=π r2A is the area of piston.

The device for calibrating pressure gauges essentially consist of two units:

1 .The pressure gauge unit, this is where the device needs to be calibrated and loads are measured with

units from bourdon gauge .

2 .The load unit, this is the part where standard weight are loaded and measured in the pressure gauge unit, the higher the weights the more pressure it reads, the

pressure is transferred via oil filled line .

The layout unit:

The following sectional drawing shows load unit and pressure gauge unit are connected as youcansee, bothunitsare 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 element. 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. Load and pressure measurement unit are connected to each other via a pipe, when the piston is loaded the pressure in the system rises and acts against the spring on the manometer.

Performing the experiment:

-Open the overflow valve

-Remove the transport-cap

-If necessary topping up the hydraulic oil

-inserting the piston

To check the zero point of the 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.

-Assemble Bourdon’s pressure gauge with dead weight tester

-Apply pressure in terms of weights on table and measure the value of it on pressure gauge

-Repeat the procedure for ascending and descending weights on table and corresponding

Apparatus :

weights

bourdon gauge

weight support

base plate

Discussion:

Define the calibrating curve and explain the purpose of it .

A calibration curve is the graphic or mathematic relationship between the readings obtained in a process and the theoretical value in a calibration. The relationship is often established as 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.

Draw the calibration curve between the Pm and Pact. Then discuss it.

Calibration equation:

Y=mX+b

m= y 2− y 1x 2−x1

m=1.004

Y=1.00 4 X+B

We have some types of bourdon tube to find pressure1.C-tube2.spiral3.twisted4.helical