M & I

Group # 2 Section: C

Members Registration #WAQAS GUL BSME01113066

RASHID MUNIR BSME01113015

PRESSURE GAUGES

PRESSURE

P = F/A

PRESSURE GAUGE

Instruments Used To Measure Pressure Is

Called Pressure Gauges.

Types of pressure gauges

Bourdon Tube Pressure Gauge

Diaphragm Pressure Gauge

Bellow Differential Pressure Gauge

BOURDON TUBE PRESSURE GAUGE

Bourdon Tube Pressure Gauge

The Bourdon pressure gauge uses the principle that a flattened tube tends to straighten or regain its circular form in cross-section when pressurized.

Working Principle Of Bourdon Tube Pressure Gauge

When an elastic transducer is subjected to a pressure, it defects. This deflection is proportional to the applied pressure

when Calibrated.

Description of Bourdon tube Pressure Gauge

The cross-section of the bourdon tube is elliptical. The bourdon tube is in a bent form to look like a circular arc. To the free end of the bourdon tube is attached an adjustable link, which is intern connected to a sector and pinion. To the shaft of the pinion is connected a pointer which sweeps over a pressure calibrated scale.

Parts of Bourdon tube Pressure Gauge

Pinion Sector Scale Borden Tube Spring Segment Lever Socket

RASHID MUNIRBSME 01113015


The pressure to be measured is connected to the fixed open end of the bourdon tube. The applied pressure acts on the inner walls of the bourdon tube. Due to the applied pressure, the bourdon tube tends to change in cross section from elliptical to circular. This tends to straighten the bourdon tube causing a displacement of the free end of the bourdon tube.


This displacement of the free closed end of the bourdon tube is proportional to the applied pressure. As the free end of the bourdon tube is connected to a link section pinion arrangement, the displacement is amplified and converted to a rotary motion of the pinion.

As the pinion rotates, it makes the pointer to assume a new position on a pressure calibrated scale to indicate the applied pressure directly. As the pressure in the case containing the bourdon tube is usually atmospheric, the pointer indicates gauge pressure.

Applications of Bourdon Tube pressure gauge

They are used to measure medium to very high pressures.

Advantages of Bourdon tube pressure gauge

These Bourdon tube pressure gauges give accurate results.

Bourdon tube cost low. Bourdon tube are simple in construction. They can be modified to give electrical outputs. They are safe even for high pressure

measurement. Accuracy is high especially at high pressures.

Limitations of bourdon tube pressure gauge

They respond slowly to changes in pressure.

They are subjected to hysteresis. They are sensitive to shocks and

vibrations. Amplification is a must as the

displacement of the free end of the bourdon tube is low.

It cannot be used for precision measurement.

WAQAS GULBSME 01113066

DIAPHRAGM PRESSURE GAUGE

Diaphragm Pressure Gauge

Diaphragm pressure gauge is composed of a conventional pressure measuring instruments, a connector and a diaphragm seal. This combination enables a general purpose pressure gauge to measure media of strong corrosion, high temperature, high viscosity, containing suspended matter or crystallizing.

Working Principle Of diaphragm Pressure Gauge

The diaphragm pressure gauge uses a mechanical principle to transfer the pressure form the diaphragm to the movement. It is suitable for all gaseous and liquid media, as well as for viscous media and suspended solids.

Parts of diaphragm Pressure Gauge

Spring Tube Pressure Instrument Sealing Liquid Isolation Diaphragm

Description of diaphragm Pressure

Gauge Pressure is applied to a flexible thin

stainless steel transmitter diaphragm clamped between the lower flanges. Deflection of this lower diaphragm transmits the pressure up the liquid filled coiled tube to the “working” diaphragm clamped between the upper flanges. Movement of the working diaphragm is indicated by the gauge pointer via a mechanism in the normal way.


Gauge The working diaphragm and gauge

mechanism are situated far enough away from the hot fluid for the reading not to be affected by fluid temperatures up to 300°C


Gauge The diaphragm has a flexible membrane

with two sides. On one side is an enclosed capsule containing air or some other fluid at a predetermined pressure. The other side can be left open to the air or screwed in to whatever system the gauge is meant to measure. The diaphragm also attaches to some sort of meter, which shows how high the pressure is.

Applications of diaphragm pressure gauge

They are used to measure medium to very high pressures.

Pharmaceutical, Chemical, Petrochemical, Oil & Gas, Refinery, Paper & Pulp, Sugar, Breweries, Food & Beverages, Cement Industries, etc

TAUSWER NIAZ BSME 01113065

Advantages diaphragm pressure gauge

Good Overload performance. Linear Measurement Suitable for absolute and differential

pressure Small size and moderate cast Suitable for viscous and serous material

disadvantages diaphragm pressure gauge

Poor impact and Vibration Resistance Difficult to maintain Small Measurement Range.

BELLOW DIFFERENTIAL

PRESSURE GAUGE

Bellow Differential Pressure Gauge

Bellows gauge contains an elastic element that is a convoluted unit that expands and contracts axially with changes in pressure. The pressure to be measured can be applied to the outside or inside of the bellows.

Description of Bellow Differential Pressure Gauge

A bellows gauge contains an elastic element that is a convoluted unit that expands and contracts axially with changes in pressure. The pressure to be measured can be applied to the outside or inside of the bellows. However, in practice, most bellows measuring devices have the pressure applied to the outside of the bellows.

Parts of Bellows Differential Pressure Gauge

Scale Sector Connecting Link Bellows Spring Case Pressure Connection

HAROON AFZAL BSME 01113017

Working of Bellows Differential Pressure Gauge

When differential pressure is applied to the high and low pressure connections, the high pressure bellows contracts, forcing fluid through the center plate into the low pressure bellows which expands. The resulting linear motion of the low pressure bellows is converted to a 6° rotary motion of the output shaft through temperature compensating linkage. Over-range protection up to the pressure rating of the housing is provided by two fluid shut off valves located on this linkage. The output shaft is part of a low friction, “O” ring sealed shaft and bearing assembly which carries the rotary motion to the external area of the bellows unit and into the instrument case.

Application of Bellows Differential Pressure Gauge

They are used to measure Low to Medium pressures.

Differential measurement pressure. Flow and level measurement

Advantages of Bellows Differential Pressure Gauge

Its Used to measure absolute and Differential pressure.

Its used to measure low and medium pressuer range.

disadvantages of Bellows Differential Pressure Gauge

Its not used to measure high value pressure.

DIFFERENCES

Aneroid Gauges

Aneroid gauges are based on a metallic pressure sensing element that flexes elastically under the effect of a pressure difference across the element. "Aneroid" means "without fluid," and the term originally distinguished these gauges from the hydrostatic gauges.

Difference Between B.D.P.G And Diaphragm gauge

Diaphragm gauge

B.D.Pressure Gauge

Uses Deflection of flexible membrane.

Amount Of deflection is repeatable so use callibration.

Amount of deflection depends on pressure diff. between two faces.

Uses sealed chambers

Sealed chambers as reference pressure and driven by external pressure.

Difference Between Burdon And Diaphragm gaugeDiaphragm Gauge Burdon Gauge

Uses Deflection of flexible membrane.

Amount Of deflection is repeatable so use callibration.

Amount of deflection depends on pressure diff. between two faces.

A flattened tube tends to straighten

Although this change in cross-section may be hardly noticeable

M & I

Engineering

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