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204 Mass rate and totals
Section 6: Meter operation Reference, Installation, and Operations Manual
June 2013 3-9000-743 Rev S
The energy rate validity is indicated by the EnergyRateValidity data point TRUE(1) indicates
valid). The energy rate is valid if the base-condition volumetric flow rate is valid (indicated by
QBaseValidity where TRUE(1) indicates valid) and if the in-use gas properties are valid
(indicated by AreGasPropertiesInvalidInUse where FALSE(0) indicates valid).
The energy rate is accumulated into the corresponding direction energy total regardless of the
energy rate validity.
The forward and reverse direction energy 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, an energy total of 12345.750 MJ is stored as 12345 MJ for the integer portion and
0.750 MJ as the fractional portion. Note that while the energy rate can be positive (indicating
forward flow) or negative (indicating reverse flow), the energy totals are always positive values.
The non-volatile energy total data points are as listed in the table below:
6.1.13 Mass rate and totals
The Daniel Mark III Ultrasonic Gas 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 6.1.15), the gas
composition is available (either fixed or optionally read from a GC, see Section 6.1.16), and the
AGA8 calculations are performed (internally by the meter or externally with the results written
to the meter, see Section 6.1.17).
The mass rate is calculated as shown in Equation 6-22.
Equation 6-22 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.
Table 6-4 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