3. INTRODUCTON
It is also known as Pipe orifice & Orifice plate. It may be installed in
pipeline with a minimum of trouble and expense. Pipe orifice is a device
used for measuring the rate of flow of a fluid through a pipe.
4. CONSTRUCTION:
It is consider to be a thin plate containing a sharp aperture through which fluid
flows . Normally it is placed between long straight pipes . For present discussion
plate is introduced into pipe and manometer is connected at points A and B.
Diagrammatic representation of orifice
meter
Manometer
5. Working:
When fluid is allowed to pass through the orifice the velocity of the fluid at point B
increases and pressure will be low , as a result at point A pressure will be more .
Bernoulli's equation is applied to point A and point B for experimental conditions.
6. Total energy at point A = Pressure energy + Potential energy + Kinetic energy ,
Bernoulli’s eqn...
The diameter of the liquid stream maximum at point B and lesser than diameter of the orifice .
Hence if a constant is included to correct for difference in liquid velocities at point B and at orifice
it can be written as .
ΔH Difference in pressure head, can be measured by manometer C = constant coefficient of
orifice (friction losses) U0 = velocity of fluid at orifice.
If the diameter of the orifice is 1/5 th of the pipes diameter or less then UA
Is so small compared to so that the earlier equation may be neglected . Then the equation
becomes …
2
U 2
0
0
7. Application:
Orifice plates are most commonly used to measure flow rates in pipes.
when the orifice plate is constructed and installed according to appropriate
standards, the flow rate can easily be determined using published formulae based
on substantial research and published in industry, national and international
standards.
8. CONCLUSION:
Once the orifice plate is designed and installed, the
flow rate can often be indicated with an acceptably
low uncertainty simply by taking the square root of
the differential pressure across the orifice's
pressure and applying an appropriate constant.
Even compressible flows of gases that vary in
pressure and temperature may be measured with
acceptable uncertainty by merely taking the square
roots of the absolute pressure or temperature,
depending on the purpose of the measurement
and the costs of instrumentation.