2. Presentation Outline
What is Differential pressure
Differential Pressure Flow Meter Technology
Elements of a Differential Pressure Flow Meter
Operating principle of a DP flowmeters
Differential Pressure Measurement Equation
Differential Pressure Meter Characteristics
Types of Differential Pressure Flowmeters
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3. What is Differential pressure ?
“Differential pressure is
defined as the difference of
pressure measurements
between two points in a
system”
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4. Differential Pressure Flow Meter
Technology
Differential pressure flowmeters, also
known as DP flowmeters, works
according to Bernoulli's Law.
Bernoulli's Law states “Energy can't be
created nor destroyed”.
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5. Bernoulli's Principle In Fluid Dynamics
In fluid dynamics, Bernoulli's principle
states that an increase in the speed of
a fluid occurs simultaneously with the
decrease in pressure or a decrease in
the fluid’s potential energy.
Daniel Bernoulli
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6. Elements of a Differential Pressure Flow
Meter
A differential pressure flow meter (DP flow meter) combines
three essential elements:
The primary element is something inside the pipe that creates
a change in pressure.
The second element is a structure connecting the primary
element and the pressure created by it to the transmitter. This
covers impulse lines, tubing, valves, and other mechanical
bits.
The transmitter reads the pressure change and converts it to
numbers we can read.
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7. Operating principle of a DP flowmeters
Differential pressure flowmeters introduce a
constriction in the pipe that creates a pressure
drop across the flowmeter. When the flow
increases, more pressure drop is created.
Impulse piping routes the upstream and
downstream pressures of the flowmeter to the
transmitter that measures the differential
pressure to determine the fluid flow. This
technology accounts for about 21% of the world
market for flowmeters.
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10. Differential Pressure Meter Characteristics
There is a square root
relationship between flowrate
and differential pressure
The Density of the fluid must be
taking into account for both
volumetric flow and mass flow
measurement
Measurement is dependent on
Beta Ratio
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11. Types of Differential Pressure Flowmeters
Flat metal plate with an opening in the
plate, installed perpendicular to the
flowing stream in a circular pipe.
Restriction causes an increase in velocity
and decrease in pressure.
A differential pressure transmitter is used
to measure pressure between the orifice
and the pipe flow stream.
Orifice differential pressure flowmeters
can be constructed to measure gas, liquid
or steam.
Orifice plates are primary flow elements
which measure flow as a function of
differential pressure
Orifice Flowmeters
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13. Venturi Flowmeters
A restriction with a relatively long
passage having a smooth entry and
exit.
A venturi produces less permanent
pressure loss than an orifice but is
more expensive.
They are often used in dirty
streams because there is no build-
up of the foreign material.
Venturi flow meters can be
constructed to be either gas
flowmeters or liquid flow meters. 13
15. Nozzle Flowmeters
smooth entry and sharp exit.
Permanent pressure loss is on the
same level as an orifice, with the
added ability to handle dirty and
abrasive fluids.
A differential pressure
transmitter is used to measure
pressure between the nozzle and
the pipe
flow stream. This type of
differential pressure flowmeter
technology can be constructed to
measure either gas or liquids.
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