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The
World Market for Primary Elements
Released
in September 2007
About DP Flow
The DP Flowmeter Market
A complete
statement of the DP flowmeter market should include the following:
- The
value of DP transmitters used to measure flow
- The
value of primary elements used in calculating flow
- For
orifice plate flowmeters, the value of orifice fittings, flanges, and
assemblies that form part of the meter
Once the
value of these devices is taken into account, it should be possible to give
an accurate value for the size of the DP flowmeter market.
The Importance of Primary
Elements
Primary
elements are an important part of the picture, not only because of their
cost, but also because they greatly add to the versatility of DP flow
measurement. There are many
different types of orifice plates, for example, that have different shaped
orifices with different locations. Flow
nozzles are widely used for steam flow measurement.
And Venture tubes are suited for measuring high-speed gas flows,
especially in the larger pipe sizes.
Anyone
who wants to understand DP flow measurement should be aware of the
different types of primary elements available, and should also be aware of
the advantages and disadvantages of each.
The table below gives a summary of the main types of primary
elements, their applications, and their advantages and disadvantages.
Taking a New Look at DP
Flow
DP flow is
important because of its large installed base, its versatility, and because
it is one of the most studied and best understood flow technologies.
DP flowmeters can be used to measure gas, steam, and liquid flows.
They have been around for more than 100 years, and have been studied
by groups such as the American Gas Association and the American Petroleum
Institute. While some DP
flowmeters are being replaced by new-technology meters, customers who
prefer to stay with the tried and true are continuing to order DP
flowmeters. And companies such
as Emerson Rosemount, Honeywell, Foxboro, Siemens, ABB, and others are
continuing to bring out new and improved pressure transmitters.
Coming to
a full appreciation of the true value of the DP flowmeter market will
provide a more realistic understanding of where end-users are spending
their flowmeter dollars. And
it will provide a better understanding of how DP flow stacks up against
competing flowmeter types, both new-technology and traditional technology
flowmeters.
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Flowmeter
Type
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Liquid,
Steam, or Gas
|
Line
Size
|
Advantages
|
Disadvantages
|
Comment
|
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DP-Orifice
Plate
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Liquid,
Steam, Gas
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½
inch and up
|
Low
purchase price;
Easy
to install; Well understood; Industry approvals
|
Limited
rangeability;
Creates
permanent pressure drop;
Uses
square root method to calculate flowrate
|
Most
traditional meter
|
|
DP-Venturi
Tube
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Liquid,
Gas
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2-30
inches
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Cam
be used for both clean and dirty liquids;
|
Can
be difficult to install due to size
|
Larger
sizes for gas
|
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DP-Pitot
Tube
|
Liquid,
Gas
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>
1 inch
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Low
cost;
Very
little pressure drop
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Low
accuracy;
Limited
sampling of flowrate
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Measures
flow only at one point
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DP-Averaging
Pitot Tube
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Liquid,
Gas
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>
1 inch
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Higher
accuracy than single Pitot tube;
Virtually
no pressure drop
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Limited
rangeability;
Not
designed for dirty fluids
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Also
available as Annubar
|
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DP
Flow Nozzle
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Steam
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2-30
inches
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Handles
high velocity fluids well;
Performs
better with dirty fluids better than orifice plate
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High
purchase price;
Not
easily removed for inspection and cleaning
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Widely
used for steam flow measurement
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For
further information on differential pressure, including studies and
articles, see www.FlowDP.com.
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