Veris Verabar Brochure - Manual (Page 6)

Aerodynamic-Shaped Sensors
Extreme aerodynamic shapes that
permit the stream lines to reattach are
subject to airfoil type lift forces. This
occurs when
the angle of
attack varies
due to sensor
misalignment,
or the direction
of the fluid
varies, as is
common in
industrial piping
with upstream
disturbances.
Result:
The lift forces
can cause an
unpredictable
shift in the low
pressure distribution, producing
inaccurate measurement.
Quality Assurance
Veris manufactures its own leak-proof,
solid one-piece sensor. Our primary
goal is to provide the highest quality
and most accurate sensor in the
industry.
This can result in a significant undetec-
table loss in accuracy.
Verabar is designed to meet or exceed
applicable ANSI and ASME codes.
The Verabar is available to meet B31.1,
B31.3, B31.8, NACE MR-01-75, etc.
Additional QA capabilities include
code welding, hydrostatic and other
non-destructive testing.
Why Average the Velocity
Profile?
Verabar averages the velocity profile
through multi-sensing ports which span
the entire pipe diameter. Other types of
non-averaging insert meters are SINGLE
POINT INSERT METERS (turbine, vortex,
magnetic, sonic, etc.). They assume a
“textbook: turbulent velocity profile, and
use a single “critical” point to infer an
average velocity. In actual industrial appli-
cations, sensors are located downstream
of disturbances, such as elbows or valves,
which produce non-uniform velocity pro-
files. This makes it virtually impossible to
locate a single point that represents the
average velocity.
Result: Inaccuracy ranging from ±10%
to ±20%.
Round Sensors
Round sensors produce unpredictable
accuracy. The original round sensors
were designed for economical fluid
balancing and did
not meet industrial
demands for
accuracy. Round
sensors have
a variable fluid
separation point
that causes an
unstable low
pressure distri-
bution around
the sensor.
Result:
Inaccuracy in
excess of ±5%
and as high
as ±10%.
ISO 9001 Certified
Problems with Other Sensor Shapes
Diamond and T-Shaped Sensors
These sensors produce pulsating, noisy
signals. They improved accuracy by use
of a sharp edge to fix the
fluid’s separation
point. However,
this greatly
amplified the
vortex shedding
forces.
Result:
The sharp
edges generate
extreme vortices,
causing sensor
vibration, pulsa-
tions and a noisy
signal to the point
that transmitter
dampening and
signal averaging
are recommended.
Other manufacturers use a three-piece
sensor design that has no positive
mechanical method of maintaining
a seal between the tubes. Therefore,
temperature, pressure, vibration and
even manufacturing variations can
cause leakage between the chambers.
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Verabar Round T-shaped
sensor sensor sensor
Textbook
profile
Actual profiles
Other
Verabar
Flow
Flow
Flow
Flow
Lift forces
Flow
Flow
Fixed separation
point
Variable separation
point
Control valve
Elbow
Low
Reynolds
Number
Location of average velocity
6315 Monarch Park Place • Niwot, CO 80503 USA • Phone: 303-652-8550 • Fax: 303-652-8552 VB-100 (2/09)
E-Mail: [email protected] • Website: www.veris-inc.com Printed in USA
Verabar…True Performance in Flow Measurement
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