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Positive displacement (PD) flowmeters are the workhorses of
today’s flowmeter world. They perform many important flow measurements that
many people take for granted. Most notably, they are widely used for water and
gas billing in residential, commercial, and industrial applications. Despite
competition from new-technology meters, positive displacement meters are holding
their own, especially in the oil and gas market.
Flow Research has published a new study, The World
Market for Positive Displacement Flowmeters, 3rd Edition. This is
the first study devoted exclusively to PD meters since our last full positive
displacement study in 2012. Our research, published in December 2021, will
determine how well PD meters are holding their own in today’s competitive
environment.
Flow
Research forecasts that PD revenues and units sold worldwide will stay
relatively steady through 2024. China is expected to show the highest growth due to its
economy, including increased activity in downstream oil and gas. In
general, PD meters are widely used to measure the flow of
hydrocarbon products at custody transfer points both upstream and downstream of
refineries.
How PD meters work
PD flowmeters
operate by repeatedly filling and emptying compartments of known volume with the
liquid or gas from the flowstream. Flowrate is calculated based on the number of
times these compartments are filled and emptied. The main types of PD flowmeters
used for gas applications are diaphragm and rotary. These types of meters differ
according to the way they trap the liquid into compartments with different
shapes.
 The
main PD flowmeter types are:
• Oval gear
• Rotary
• Helical gear
• Nutating disc
• Oscillating piston
• Diaphragm
• Spur gear
Diaphragm meters have several diaphragms that capture the fluid as it passes
through the meter. Differential pressure across the meter causes one diaphragm
to expand and one to contract. A rotating crank mechanism helps produce a smooth
flow of gas through the meter. This mechanism is connected via gearing to the
index, which registers the amount of fluid that passes through the meter.
Diaphragm meters are used for gas applications.
Rotary flowmeters have one or more rotors that are used to trap the fluid. With
each rotation of the rotors, a specific amount of fluid is captured. Flowrate is
proportional to the rotational velocity of the rotors. Rotary meters are used
for gas applications.
Thomas Glover of England invented the first diaphragm meter in 1843. Glover’s
meter was made in response to difficulties with liquid sealed drum meters, which
were created in the early 1800s. This meter had diaphragms of sheepskin and with
sheet metal enclosures. Today diaphragm meters are made from cast aluminum and
have diaphragms of synthetic rubber-on-cloth.
Why the PD
market is still growing
The large,
saturated PD market makes revenue growth challenging. However, at the same time,
the PD market overall benefits from the strength of a large installed base, high
accuracy, and its strength in the utilities market.
Even though
PD meters face stiff competition from new-technology meters in some segments,
they still remain the best solution for certain applications. PD meters excel
where many other flowmeters have difficulties: low flow rates and high viscosity
liquids.
Positive displacement flowmeters remain one of the most widely used types of
flowmeters for measuring the flow of water, gas, and petroleum liquids. They
remain a solid choice for many applications in today’s modern process control
environment.
Large
installed base
One major growth factor for positive displacement flowmeters is the large
installed base of positive displacement flowmeters worldwide. Because they were
introduced more than 100 years before new-technology meters, PD flowmeters have
had much more time to penetrate the markets in Europe, North America, and Asia.
Installed base is a relevant growth factor because often when ordering
flowmeters, especially for replacement purposes, users tend to replace like with
like. The investment in a flowmeter technology is more than just the cost of the
meter itself. It also includes the time and money invested in training people
how to install and use the meter. In addition, some companies stock spare parts
or even spare meters for replacement purposes. As a result, when companies
consider switching from one flowmeter technology to another, there is more than
just the purchase price to consider. We predict that the large installed base of
positive displacement flowmeters worldwide will continue to be a source of
orders for new and replacement meters in the future.
High accuracy a major factor
Accuracy and reliability continue to be the strongest driving forces behind the
flowmeter market -- and positive displacement meters are highly accurate because
they actually separate the fluid into compartments and count the number of times
this is done. There is no need for the inferential method that occurs with
meters that correlate flow with velocity, or use the differential pressure
method to measure flow. PD meters are widely used for billing applications
because they are both accurate and reliable. Both the degree of accuracy and
reliability vary with the manufacturer and the type of PD meter.
Utility applications dominate
 While
new-technology flowmeters are making inroads into traditional meters in many
areas and applications, this is less true for positive displacement flowmeters
for gas applications. Close to 80 percent of revenues from PD meters for gas
flow measurement derive from utility applications, where PD meters are highly
entrenched. This includes PD meters for commercial and industrial
applications, where utility companies use them to measure the amount of gas
consumed by restaurants, office buildings, and other establishments. While there
has been a shift from diaphragm to rotary PD meters for these applications,
these applications have seen no strong shift away from PD meters. Turbine meters
are used for high speed flow utility applications, however.
The use of PD diaphragm and rotary meters for gas applications is somewhat like
the use of nutating disc and piston PD meters for utility and billing
applications in the water industry. PD meters, along with single-jet and
multi-jet turbines are still the dominant meter for utility measurement of water
flows, especially in residential and smaller commercial applications. However,
some new-technology flowmeters such as magnetic and Coriolis are beginning to
gain approvals from industry associations for use in utility measurement of
water. It is likely, then, that new-technology meters will eventually be used on
a more widespread basis for utility gas measurement.
Thomas
Glover of England invented the first diaphragm meter in 1843. Glover’s meter
was made in response to difficulties with liquid sealed drum meters, which were
created in the early 1800s. This meter had diaphragms of sheepskin and with
sheet metal enclosures. Today diaphragm meters are made from cast aluminum and
have diaphragms of synthetic rubber-on-cloth.
Articles
About Positive Displacement Flowmeters
The
World Market for Positive Displacement Flowmeters, 2nd Edition
Published in
2012
The
World Market for Positive Displacement Flowmeters
Published in 2002
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