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Average weighted flow velocity using chord proportions
Section 4: Flow measurement
3410 Series Gas Ultrasonic Meters Operations Manual
January 2018
3-9000-777 Rev E
In the event of a chord failure with at least one operating chord, the meter’s average weighted
flow velocity is estimated as shown in
Equation 4-7
.
Equation 4-7 Estimating average flow velocity using proportion values
where
For each non-failed chord, the interpolated proportion value used in
Equation 4-7
is calculated
as follows:
•
if the chord’s velocity is surrounded by non-default (average velocity, average proportion)
data pairs, then the interpolated proportion is the linear interpolation between the two
data pairs
•
if the chord’s velocity has a non-default (average velocity, average proportion) data pair
on one side of it but not the other, then the interpolated proportion is the data pair
average proportion
•
if there are only default (average velocity, average proportion) data pairs, then the
interpolated proportion is the corresponding bin’s default average proportion value.
=
estimated average weighted flow velocity (m/s)
(AvgWtdFlowVel)
=
(non-failed) chord velocity (m/s) (FlowVelA ... FlowVelD)
=
(non-failed) chord interpolated proportion value
(dimensionless)
VAvgWtd
est
Vchord
Non Failed
–
Chord s
( )
InterpPropchord
Non Failed
–
Chord s
( )
----------------------------------------------------------------------------
=
VAvgWtd
est
Vchord
InterpPropchord
