Mujahid

Pressure(Bourden Tube) gauge Objective: To study the working of dead weight pressure gauge

Apparatus: 1 Hydro dynamic bench 2 Dead weight pressure gauge 3 Bourden tube pressure gauge 1 Plunger 1 Weight

Theory: Many pressure-measuring instruments are called gauges. However, this section will be restricted to two mechanical instruments that contain elastic elements that respond to pressures found in fluid power systems

Bourdon tube Gauge: It is a pressure indicator, it works with a "C" shaped tube oval in cross section that tries to straighten under pressure. When the tube tries to straighten it pulls on a connecting arm which turns a needle that is against a card that states the pressure. A Bourdon gauge uses a coiled tube, which, as it expands due to pressure increase causes a rotation of an arm connected to the tube. The pressure sensing element is a closed coiled tube connected to the chamber or pipe in which pressure is to be sensed. As the gauge pressure increases the tube will tend to uncoil, while a reduced gauge pressure will cause the tube to coil more tightly. This motion is transferred through a linkage to a gear train connected to an

indicating needle. The needle is presented in front of a card face inscribed with the pressure indications associated with particular needle deflections. In a barometer, the Bourdon tube is sealed at both ends and the absolute pressure of the ambient atmosphere is sensed. Differential Bourdon gauges use two Bourdon tubes and a mechanical linkage that compares the readings. The transparent cover face of the pictured combination pressure and vacuum gauge has been removed and the mechanism removed from the case. This particular gauge is a combination vacuum and pressure gauge used for automotive diagnosis:

Dead weight pressure gauge: this is consists of a piston and cylinder of known area, which is connected to a fluid through tube.By changing the weight we measure the different pressure on dead weight gauge this pressure is indicated by the pointer.

Procedure: ➢ First of all set the apparatus by setting dead weight pressure gauge,calibration apparatus and bourden tube. ➢ Assemble Bourdon’s pressure gauge with plunger and weights.

➢ Then take water and put into the tube. ➢ Air trapped between the plunger and water will pass out in form of bubbles. ➢ Then wait till the gauge show certain reading on it. ➢ After noting the first reading, start loading the plunger and keep on

noting the reading.

➢ Repeat the procedure for ascending and descending weights on the

plunger and corresponding measurement on Bourdon pressure gauge…. ➢ The pressure on the fluid, in the pipe, is calculated from the relation, Pressure =weight /Area of the plunger

1 Observations: S R NO

Area of the Weight on plunger plunger (m^2)

(N)

Pressure on dead weight gauge

Pressur e on bourden tube gauge (bar)

(bar)

1

2.45*10^-4

14.715

.6006

.6

2

2.45*10^-4

29.43

1.2012

1.2

3

2.45*10^-4

34.335

1.40145

1.4

4

2.45*10^-4

39.24

1.6016

1.6

5

2.45*10^-4

44.145

1.8018

1.8