of 15

# Pressure Measurements | Comprehensive search

You'll find a wonderful explanation of the following topics:- Sensing Elements ,Bellows ,Bourdon tube,Impact of Operating Environment ,Diaphragm,Differen,capacitance,tial Pressure Transmitters,strain gauge
Published on: Mar 4, 2016
Published in: Engineering
Source: www.slideshare.net

#### Transcripts - Pressure Measurements | Comprehensive search

• 1. PRESSURE MEASUREMENT PRESENTED BY: MOHANAD FAEK NOORI
• 2. PRESSURE MEASUREMENT Pressure is the action of one force against another over, a surface. The pressure P of a force F distributed over an area A is defined as: [ P = F/A ] Units of pressure: standard: N/m2 (Pa-Pascal), Kpa (Kilo Pascal) 1Bar=100kpa
• 3. Pressure Measurement Divided into four categories :- 1.Absolute pressure – pressure at a point in a fluid relative to a vacuum (absolute zero of pressure) 2.Gauge Pressure – pressure relative to local atmospheric pressure. 3.Differential Pressure – difference between two unknown pressures, either of which is atmospheric pressure. 4.Atmospheric pressure : Sea level standard atmospheric pressure is 101.325Kpa but it changes with altitude of earth.1 atmosphere [technical] is equal to 98.0665Kpa Relationship between absolute and gauge pressures Pabs=Pgauge+Patm
• 4. SENSING ELEMENTS The main types of sensing elements are •Bourdon tubes •diaphragms •bellows The basic pressure sensing element can be configured as a C-shaped Bourdon tube (A); a helical Bourdon tube (B); flat diaphragm (C); a convoluted diaphragm (D); a capsule (E); or a set of bellows (F).
• 5. BELLOWS • bellows sensor is an axially flexible, cylindrical enclosure with folded sides. When pressure is applied through an opening, the closed end extends axially. • Bellows elements can measure absolute pressure, gauge pressure, vacuum, or differential pressure.
• 6. BOURDON TUBE • 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. • bourdon are often used in harsh environments and high pressures, but can also be used for very low pressures; the response time however, is slower than the bellows or diaphragm. C-type bourdon psi Range as low as 0 - 15 psi up to 0-1500 Helical bourdon Range as low as 0 - 200 psi up to 0 – 6000 psi Spiral bourdon Range as low as 0-10 psi up to 0-100,000 psi.
• 7. Diaphragm • A diaphragm is a circular-shaped convoluted membrane that is attached to the pressure fixture around the circumference . The pressure medium is on one side and the indication medium is on the other. • Diaphragms provide fast acting and accurate pressure indication. However, the movement or stroke is not as large as the bellows .
• 8. Diaphragm • There are two different devices that are referred to as capsule. • The first is shown in figure . The pressure is applied to the inside of the capsule and if it is fixed only at the air inlet it can expand like a balloon. This arrangement is not much different from the diaphragm except that it expands both ways. • The capsule consists of two circular shaped, convoluted membranes (usually stainless steel) sealed tight around the circumference. The pressure acts on the inside of the capsule and the generated stroke movement is shown by the direction of the arrow. • The second type of capsule is like the one shown in the differential pressure transmitter (DP transmitter). The capsule in the bottom is constructed with two diaphragms forming an outer case and the interspace is filled with viscous oil. Pressure is applied to both side of the diaphragm and it will deflect towards the lower pressure.