Vortex meters are among
the most versatile of meters, in that they can measure liquid, gas, and steam flows with relative
ease. They are, however, more intrusive than ultrasonic and magnetic flowmeters, since they rely on the presence of a bluff body in the
flowstream to generate vortices. Even so, they are significantly less intrusive than DP or turbine
meters, and also cause less pressure drop. Pressure drop from vortex meters
is minimal since most shedder bars are relatively small in size.
One important development in recent years has been the introduction of reducer vortex meters.
Reducer meters have a smaller line size than the pipe they are placed in,
enabling them to measure lower flows. Most incorporate a single line size reduction,
al though some incorporate two line- size reductions.
since vortex flowmeters were introduced in 1969 include anti-vibration software and electronics, multivariable flowmeters,
reduced bore meters, and plastic flowmeters, and much more.
Today there is a wide diversity of choices for customers to make
when specifying or purchasing vortex flowmeters.
at a reasonable price
Even though vortex meters are not as accurate as Coriolis meters, many vortex meters offer
accuracy readings of better than one percent, depending on fluid and application.
They offer a price advantage over other new-technology flowmeters and a wide range of
Steam flow measurement is an excellent application for vortex flowmeters given the typical price
point in a competitive segment. Vortex flowmeters can handle the high pressures and
temperatures that typically accompany steam flow measurement. Endusers looking for an alternative to DP flow measurement may wish to consider using vortex
flowmeters for measuring steam flow.
about New Technology Flowmeters:
flowmeters operate on a principle called the von Karman effect. This principle concerns the behavior of fluids when an obstacle is
placed in the path of flow. Under
the right conditions, the presence of the obstacle generates a series of
alternative vortices called the von Karman street. This phenomenon occurs in liquid, gas, and steam, and has been
observed in many diverse contexts including cloud layers passing an island
and whitewater rapids.
flowmeters, the obstacle takes the form of an object with a broad, flat
front called a bluff body. The bluff body is mounted at right angles to the flowstream. Flow velocity is proportional to the frequency of the vortices.
Flowrate is calculated by multiplying the area of the pipe times the
velocity of the flow.
order to compute the flowrate, vortex flowmeters count the number of
vortices generated by the bluff body. They use a variety of techniques for sensing the presence of a
vortex. The majority of vortex
flowmeters use a piezoelectric sensor; however, some use a capacitive
sensor and others use an ultrasonic sensor to detect vortices.
Some inline meters, such as
multipath ultrasonic meters, make multiple measurements and create a
calculated average to determine flowrate.
Insertion vortex meters make
a point measurement and then compute the flow through the whole pipe based
on flow profile considerations. The formula used to make this calculation
is based on extensive testing and can be improved with time and
flowmeters have become increasingly popular since Sierra Instruments
introduced them in 1997. A
number of suppliers have brought out their own multivariable vortex
flowmeters, including ABB (Goettingen, Germany), abzil (Tokyo,
Japan), Krohne (Duisburg, Germany), and Endress+Hauser (Reinach,
fowmeters house an RTD temperature sensor and a pressure
transducer. By using
information from these sensors, together with detection of vortices
generated, the flowmeter can output volumetric flow, temperature, pressure,
fluid density, and mass flow. Multivariable
flowmeters measure more than one process variable, and typically use this
information to compute mass flow. This makes the flowmeter measurement more accurate in
changing temperature and pressure conditions.
Even though multivariable flowmeters are somewhat more expensive
than their single-variable counterparts, they enable users to obtain
significantly more information about the process than single-variable
volumetric meters. This
additional information can result in increased efficiencies that more than
make up for the additional cost of the multivariable flowmeter.
Vortex flowmeters are available in
flanged, wafer, and insertion styles, and the right choice depends on multiple
considerations: required accuracy and repeatability, line size, fluid type, and the desired
supplier or distributor.
Flanged and wafer (inline) styles offer
greater accuracy than insertion meters, but are not practical in large line
sizes -- vortex meters top out in the 16 range. (The sweet spot in terms of size for vortex flowmeters is from 1 to 4.)Insertion vortex flowmeters offer a viable option to companies that want to
measure flow in large pipes, especially pipes with an internal diameter greater than 12.
Insertion meters are sometimes
used to measure flow in pipes that cannot be shut down. Because insertion meters can be hot tapped, the meters
can be swapped out or parts can be replaced without shutting down the line.
Inline meters do not have this advantage unless a bypass line is installed,
and even so the line has to be shut down to install the bypass line.This gives
insertion vortex meters additional flexibility over inline meters.
Insertion vortex meters cannot achieve the same accuracy as some inline
meters because they make a single-point measurement inside the pipe.
While flanged vortex
meters are somewhat more expensive than wafer-style meters, they are more secure and
provide less opportunity for leakage than wafer-style meters. The longer bolts
that are used to secure wafer-style meters have a tendency to expand, creating a possibility
of leakage. This could create a safety hazard, potentially resulting in fugitive emissions and lost product. It
is easier to install flanged vortex meters correctly than wafer-style vortex meters.
Companies that are downsizing may have fewer skilled engineering staff to perform these installations.
further information on vortex meters, including detailed market reports,
please see www.flowvortex.com.