AGA_US function block parameters

N/A

Determines whether the AGA8 parameters are entered manually or calculated using the detail method. AGA8 parameters include DEN_FLW, DEN_BASE, ZF, ZB, F_PV, and REL_DEN. AGA8_OPT can be either: 

• Calculate AGA-8 parameters using Detail Method - Select this option if the fluid is a natural gas.

• Manually enter the AGA-8 parameters - Select this option for other single-phase, Newtonian fluids under turbulent flow. Manually enter DEN_FLW, DEN_BASE, VISCOSITY, and HTG_VAL (if applicable). Change HTG_VAL, ZF, ZB, F_PV, and REL_DEN to 0.0 when not applicable.

psia (pounds per square inch absolute)

Base pressure. The reference pressure for base density and base volumetric flow.

°F

Base temperature. The reference temperature for base density and base volumetric flow.

N/A

Calculated ratio of orifice bore to pipe inside diameter after temperature correction. Has meaning when METER_TYPE is Differential Pressure.

None

The sum of the mole percents in GAS_COMP. If not between 99.995 and 100.005, results in a runtime ERROR_STATE of Gas composition sum not 100% if AGA8_Opt is Calculate AGA-8 parameters using Detail Method.

MMBTU (million BTUs, decatherm)

The currently active accumulation of energy flow.

Hours

The currently active accumulation of time with flow through the pipe (IN > LOW_CUT (differential pressure) or VOL_FLW_F > 0.0 (turbine)).

MCF (thousand cubic feet)

The currently active accumulation of volumetric flow at base conditions.

lb/ft³ (pounds per cubic foot)

Mass density at base conditions. When AGA8_OPT is Calculate AGA-8 parameters using Detail Method, the value is calculated. Otherwise retains its previous value or the value as entered.

lb/ft³ (pounds per cubic foot)

Mass density at flowing conditions. When AGA8_OPT is Calculate AGA-8 parameters using Detail Method, the value is calculated. Otherwise retains its previous value or the value as entered.

MMBTU/hr (million BTUs per hour)

Instantaneous energy flow.

N/A

Indicates that an error condition is active (0 = no error, 1 = an error condition is active). The error is defined as text in ERROR_STATE.

N/A

The error state of the block. When other than Clear indicates the validity of the calculations is questionable:

• Gas Composition Sum Not 100% — The sum of the mole percents in GAS_COMP does not equal 100.0 and AGA8_OPT is Calculate AGA-8 parameters using Detail Method.

• Invalid Pipe or Orifice Size — Actual beta ratio is less than 0.1 or greater than 0.75, or orifice ID is less than 0.45 inches, or pipe ID is less than 1.9 inches. Applicable when METER_TYPE is Differential Pressure. 

• Reynolds Number Out of Range — Calculated pipe Reynolds number is less than 4000. Applicable when METER_TYPE is Differential Pressure. 

• AGA-8 Algo Not Convergent — The required iterations exceeded ITERATE_LIM8; thus, the AGA8 algorithm did not converge. Applicable when AGA8_OPT is Calculate AGA-8 parameters using Detail Method. 

• AGA-3 Algo Not Convergent — The required iterations exceeded ITERATE_LIM3; thus, the AGA3 algorithm did not converge. .

N/A

Supercompressibility factor. The square root of the ratio of the compressibility factors (base to flowing). When AGA8_OPT is Calculate AGA-8 parameters using Detail Method, the value is calculated. Otherwise retains its previous value or the value as entered.

Mole fractions as percents

An array containing the mole fractions of 21 gas components.

1. Methane

2. Nitrogen

3. Carbon Dioxide

4. Ethane

5. Propane

6. Water

7. Hydrogen Sulfide

8. Hydrogen

9. Carbon Monoxide

10. Oxygen

11. i-Butane

12. n-Butane

13. i-Pentane

14. n-Pentane

15. n-Hexane

16. n-Heptane

17. n-Octane

18. n-Nonane

19. n-Decane

20. Helium

21. Argon

BTU/ft³ (BTUs per cubic foot)

Volumetric heating value. Calculated per ISO6976 from the mole fractions in GAS_COMP, the superior calorific values of the components, and compressibility factors of the components (15/15 data).

inH2O at 68°F (inches of water) [differential pressure], 

ft³/hr (cubic feet per hour) [turbine]

When METER_TYPE is Differential Pressure, IN is the measured differential pressure. When METER_TYPE is Turbine, IN is the volumetric flow from a Pulse Input function block.

N/A

Isentropic exponent of the natural gas or other fluid. Enter the value at expected flowing conditions. The default value is reasonable for natural gases. For an incompressible fluid enter –1.0. Not used when METER_TYPE is Turbine.

N/A

The number of iterations limit for the AGA3 mass flow calculation.

N/A

The number of iterations limit for the AGA8 density and compressibility factor calculations.

MMBTU (million BTUs, decatherm)

The total accumulation of energy flow at the time of the last reset (using TIMER_ACCUM).

Hours

The total accumulation of time with flow through the pipe at the time of the last reset (using TIMER_ACCUM.

MCF (thousand cubic feet)

The total accumulation of base volumetric flow at the time of the last reset (using TIMER_ACCUM).

inH2O at 68 °F

Value of IN (differential pressure) below which flow is assumed to be zero. Not applicable when METER_TYPE is Turbine.

lb/hr (pounds per hour)

Instantaneous mass flow.

N/A

Meter type for flow measurement. The value can be Differential Pressure or Turbine.

inches

Orifice plate bore diameter at reference temperature ORIF_TEMP. Not applicable when METER_TYPE is Turbine.

N/A

Orifice plate material. The value can be Stainless Steel, Monel, or Carbon Steel. Not applicable when METER_TYPE is Turbine.

°F

Reference temperature for the orifice plate. Not applicable when METER_TYPE is Turbine.

Percent

The percentage of the total in CURR_ENERGY where ENGY_FLW had Good status when the value was accumulated.

Percent

The percentage of the total time in CURR_HRS_ON where VOL_FLW_F had Good status when the time was accumulated.

Percent

The percentage of the total in CURR_VOLUME where VOL_FLW_B had Good status when the value was accumulated.

Percent

The percentage of the total in VOL_ACCUM where VOL_FLW_B had Good status when the value was accumulated.

Percent

The percentage of the total in LAST_ENERGY where ENGY_FLW had Good status when the value was accumulated.

Percent

The percentage of the total time in LAST_HRS_ON where VOL_FLW_F had Good status when the time was accumulated.

Percent

The percentage of the total in LAST_VOLUME where VOL_FLW_B had Good status when the value was accumulated.

inches

Pipe internal diameter at reference temperature PIPE_TEMP.

N/A

Pipe material. The value can be Stainless Steel, Monel, or Carbon Steel.

°F

Reference temperature for the pipe ID measurement.

psi (pounds per square inch)

The amount PRES_IN must differ from its value at the time of the previous AGA-8 calculation to trigger another AGA-8 calculation.

psia (pounds per square inch absolute)

Measured static pressure

N/A

Location of the static pressure tap, either Upstream or Downstream of the orifice plate. Not applicable when METER_TYPE is Turbine.

N/A

Calculated Pipe Reynolds number.

N/A

Real gas relative density (specific gravity). When AGA8_OPT is Calculate AGA-8 parameters using Detail Method, the value is calculated. Otherwise retains its previous value or the value as entered.

N/A

Resets VOL_ACCUM when greater than zero. The block then changes RESET_ACCUM back to zero.

N/A

Orifice meter tap type, either Flange Taps, Radius Taps (D-D/2), or Corner Taps.

°F

How much TEMP_IN must change from the last AGA8 calculation temperature in order to trigger another AGA8 calculation.

°F

Measured temperature.

N/A

When 0, allows the accumulation of CURR_VOLUME, CURR_ENERGY, and CURR_HRS_ON. When greater than 0, copies the three CURR_ parameters to the three LAST_ parameters and resets the CURR_ parameters. TIMER_ACCUM is typically wired from a Date Time Event function block.

lb/ft-hr (pounds per foot per hour)

The absolute viscosity of the natural gas or other fluid. Enter the value at expected flowing conditions based on laboratory analysis or other method.

MCF (thousand cubic feet)

Accumulation of volumetric flow at base conditions. It is reset using RESET_ACCUM, which is expected to be performed manually at irregular time intervals. Similar to CURR_VOLUME, which is also an accumulation of base volumetric flow, but CURR_VOLUME is expected to be reset automatically at regular time intervals (using TIMER_ACCUM).

ft³/hr (cubic feet per hour)

Instantaneous volumetric flow at base conditions.

ft³/hr (cubic feet per hour)

Instantaneous volumetric flow at flowing conditions.

N/A

Compressibility factor at base conditions. When AGA8_OPT is Calculate AGA-8 parameters using Detail Method, the value is calculated. Otherwise retains its previous value or the value as entered.

N/A

Compressibility factor at flowing conditions. When AGA8_OPT is Calculate AGA-8 parameters using Detail Method, the value is calculated. Otherwise retains its previous value or the value as entered.