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:Table 6-4 Energy total data points

 

Forward direction

 

Reverse direction

Integer

Fraction

Integer

Fraction

 

 

 

 

PosEnergyPosEnergyFracNegEnergyNegEnergyFrac

 

 

 

 

6.1.13Mass 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 rateMassRate = QFlow ⋅ ρFlow

where

 

 

 

MassRate

=

mass rate (kg/h) (MassRate)

QFlow

=

flow-condition volumetric flow rate (m3/h) (QFlow)

ρ

Flow

=

“in-use” flow-condition gas mass density (kg/m3)

 

 

(RhoMixFlow)

 

 

 

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.

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Mass rate and totals