36
Mass rate and totals
Section 4: Flow measurement
3410 Series Gas Ultrasonic Meters Operations Manual
January 2018
3-9000-777 Rev E
The non-volatile energy total data points are as listed in the table below:
4.5.10
Mass rate and totals
The Daniel 3410 Series Gas Ultrasonic Flow Meter meter calculates the mass rate and mass totals
(forward and reverse). These calculations requires that the flow-condition pressure and
temperature are available (either fixed or optional analog inputs,
see Section 5.11.1
), the gas
composition is available (either fixed or optionally read from a GC,
see Section 5.11.2
), and the
AGA8 calculations are performed (internally by the meter or externally with the results written
to the meter,
see Section 5.11
).
The mass rate is calculated as shown in
Equation 4-17
.
Equation 4-17 Mass rate
where
The sign of the mass rate indicates the flow direction: a positive value indicates flow in the
forward direction, a negative value indicates flow in the reverse direction.
The mass rate validity is indicated by the
MassRateValidity
data point (TRUE(1) indicates valid).
The mass rate is valid if the flow-condition volumetric flow rate is valid (indicated by
QFlowValidity
where TRUE(1) indicates valid) and if the AGA8 flow-condition calculation is valid
(indicated by
AGA8FlowCalcValidity
where TRUE(1) indicates valid).
The mass rate is accumulated into the corresponding direction mass total regardless of the mass
rate validity.
The forward and reverse direction mass totals are each stored in non-volatile memory as a data
pair: a 64-bit unsigned integer portion and a 32-bit floating point fractional portion. For
example, a mass total of 12345.750 kg is stored as 12345 kg for the integer portion and
0.750 kg as the fractional portion. Note that while the mass rate can be positive (indicating
forward flow) or negative (indicating reverse flow), the mass totals are always positive values.
Table 4-4 Energy total data points
Forward direction
Reverse direction
Integer
Fraction
Integer
Fraction
PosEnergy
PosEnergyFrac
NegEnergy
NegEnergyFrac
=
mass rate (kg/h) (
MassRate
)
=
flow-condition volumetric flow rate (m
3
/h) (
QFlow
)
=
“in-use” flow-condition gas mass density (kg/m
3
) (
RhoMixFlow
)
MassRate
Q
Flow
ρ
Flow
×
=
MassRate
Q
Flow
ρ
Flow
