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AGA7 American Gas Association Report No.. 7 Module Page AGA7-1 ACCOL II Reference Manual The AGA7 Module calculates the base volume rate (Qb) as described in the American Gas Association Report No. 7, reference catalog No. XQ0508. This module computes the base volume rate by implementing the equations from Section 6, Volumetric Flow Measurement, as well as the equations from Section 7, Mass Flow Measurement. The spe- cific computation method used is selected by the use of module termi- nals. Flow rate of the gas is obtained from a HSCOUNT (High Speed Counter) or LSCOUNT (Low Speed Counter) Module which is typi- cally measured by a turbine flowmeter, positive displacement meter, or vortex shedding meter. ❏ Module Terminals FLOW_SWITCH Default: OFF (Equation A determines base volume flow rate) Format: Logical signal Input/Output: Input if this terminal is OFF, the output flow rate will be in Volume units (Equation A); if this terminal is ON, the output flow rate will be in Mass units (Equation B). Equations A and B are described later, under 'Module Equations'. FLOW_TEMP FLOW_PRESS FLOW_SWITCH DENS_SWITCH RATE BASE_TEMP BASE_PRESS FPV_IN ADJ_PRESS FLOW_DENS BASE_DENS SPEC_GRAV GRAV_TEMP CALIB_FACTR SPAN OUTPUT7 GRAV_PRESS AGA7 ACCOL II Reference Manual Page AGA7-2 AGA7 American Gas Association Report No.. 7 Module ACCOL II Reference Manual Page AGA7-2 AGA7 American Gas Association Report No.. 7 Module DENS_SWITCH Default: OFF (Equation C determines base density) Format: Logical signal Input/Output: Input if this terminal is wired, and OFF, it specifies that a densitometer is supplying both Flowing Density (Df) and Base Density (Db). The Df and Db values are specified by the values on the FLOW_DENS and BASE_DENS terminals. If this terminal is ON, it specifies that a Gravitometer is used, and that the value of D b will be calculated using Equation C, and the values on the SPEC_GRAV, GRAV_TEMP, and GRAV_PRESS termi- nals. The calculated value of D b will then be used in Equation B, along with the FLOW_DENS value. FLOW_TEMP (T f ) Default: 600F Format: Analog signal or constant Input/Output: Input represents the temperature of the flowing gas in degrees F. FLOW_PRESS (Pf) Default: None, entry required when FLOW_SWITCH is OFF Format: Analog signal or constant Input/Output: Input is the static gauge pressure of the flowing gas measured in psig. If Equation A is selected via the FLOW_SWITCH and this terminal is not wired, the OUTPUT will not be updated. DENS_SWITCH Default: OFF (Equation C determines base density) Format: Logical signal Input/Output: Input if this terminal is wired, and OFF, it specifies that a densitometer is supplying both Flowing Density (Df) and Base Density (Db). The Df and Db values are specified by the values on the FLOW_DENS and BASE_DENS terminals. If this terminal is ON, it specifies that a Gravitometer is used, and that the value of D b will be calculated using Equation C, and the values on the SPEC_GRAV, GRAV_TEMP, and GRAV_PRESS termi- nals. The calculated value of D b will then be used in Equation B, along with the FLOW_DENS value. FLOW_TEMP (T f ) Default: 600F Format: Analog signal or constant Input/Output: Input represents the temperature of the flowing gas in degrees F. FLOW_PRESS (Pf) Default: None, entry required when FLOW_SWITCH is OFF Format: Analog signal or constant Input/Output: Input is the static gauge pressure of the flowing gas measured in psig. If Equation A is selected via the FLOW_SWITCH and this terminal is not wired, the OUTPUT will not be updated. AGA7 American Gas Association Report No.. 7 Module Page AGA7-3 ACCOL II Reference Manual RATE (Qf) Default: None, entry required or else OUTPUT is not updated. Format: Analog signal or constant Input/Output: Input is the uncorrected gas flow (either rate or volume in cu.ft./hr.) as measured via the HSCOUNT Module (High Speed Counter) or LSCOUNT Module (Low Speed Counter). BASE_TEMP (Tb) Default: 60 0F Format: Analog signal or constant Input/Output: Input is the contract base temperature in degrees F. BASE_PRESS (P b ) Default: 14.73 Format: Analog signal or constant Input/Output: Input is the contract base pressure (psia). FPV_IN (Fpv) Default: 1.0 Format: Analog signal or constant Input/Output: Input is an output signal from the FPV Module. ADJ_PRESS (Pa) Default: 14.73 Format: Analog signal or constant Input/Output: Input is the atmospheric pressure (that is, the barometric pressure) at the site and is added to the gauge pressure to produce absolute pressure. ACCOL II Reference Manual Page AGA7-4 AGA7 American Gas Association Report No.. 7 Module ACCOL II Reference Manual Page AGA7-4 AGA7 American Gas Association Report No.. 7 Module FLOW_DENS (Df) Default: 0.045923 lb/cu.ft. (based on a specific gravity of 0.6, a tempera- ture of 600F, a pressure of 14.7 psi, and a supercompressibility factor of 1.0.) Format: Analog signal or constant Input/Output: Input is the density of the flowing gas as measured by a densitometer. BASE_DENS (D b ) Default: 0.045923 lb/cu.ft. (based on a specific gravity of 0.6, 600F tem- perature, 14.7 psi pressure, and a supercompressibility factor of 1.0.) Format: Analog signal or constant Input/Output: Input is the contract base density as measured via a densitometer. SPEC_GRAV (SG) Default: 0.6 Format: Analog signal or constant Input/Output: Input is the specific gravity of the gas as measured by a gravitometer. GRAV_TEMP (Tg) Default: 60 0 F Format: Analog signal or constant Input/Output: Input is the temperature at the gravitometer in degrees F. FLOW_DENS (Df) Default: 0.045923 lb/cu.ft. (based on a specific gravity of 0.6, a tempera- ture of 600F, a pressure of 14.7 psi, and a supercompressibility factor of 1.0.) Format: Analog signal or constant Input/Output: Input is the density of the flowing gas as measured by a densitometer. BASE_DENS (D b ) Default: 0.045923 lb/cu.ft. (based on a specific gravity of 0.6, 600F tem- perature, 14.7 psi pressure, and a supercompressibility factor of 1.0.) Format: Analog signal or constant Input/Output: Input is the contract base density as measured via a densitometer. SPEC_GRAV (SG) Default: 0.6 Format: Analog signal or constant Input/Output: Input is the specific gravity of the gas as measured by a gravitometer. GRAV_TEMP (Tg) Default: 60 0 F Format: Analog signal or constant Input/Output: Input is the temperature at the gravitometer in degrees F. AGA7 American Gas Association Report No.. 7 Module Page AGA7-5 ACCOL II Reference Manual GRAV_PRESS (Pg) Default: 14.73 Format: Analog signal or constant Input/Output: Input is the absolute pressure (psia) at the gravitometer. CALIB_FACTR (C) Default: 1.0 Format: Analog signal or constant Input/Output: Input is an optional calibration factor. This factor is used to correct known variations in the measuring equipment. SPAN (K) Default: 1.0 Format: Analog signal or constant Input/Output: Input is a scale factor to adjust the OUTPUT to the desired units. OUTPUT (Qb) Default: None Format: Analog signal Input/Output: Output is the calculated flow rate at base conditions. The units are in MSCFH (thousands of standard cubic feet per hour) unless modified by the SPAN terminal. ACCOL II Reference Manual Page AGA7-6 AGA7 American Gas Association Report No.. 7 Module ACCOL II Reference Manual Page AGA7-6 AGA7 American Gas Association Report No.. 7 Module ❏ Module Equations The following equation, for base volume rate, is taken from Section 6, Volumetric Flow Measurement: Qf Pf + Pa 519.67 Qb = C * K * * * * 1000 Pb Tf + 459.67 (Tb + 459.67) * Fpv 2 Equation A 519.67 where: Qb = Calculated flow rate at base conditions (output in MSCFH) C = Calibration factor K = Span scaling factor Qf = Flow rate at flowing conditions (cubic feet per hour) Pf = Static gauge pressure psig Pa = Atmospheric pressure psia Pb = Base pressure in psia Tf = Flowing temperature indegrees F Tb = Base temperature in degrees F Fpv = Supercompressibility factor The following equation, for base volume rate, is taken from Section 7, Mass Flow Measurement: Qf Df Qb = C * K * * Equation B 1000 Db where all operands are the same as the previous equation except for: Df = Density of flowing gas as measured by a densitometer Db = Base density as measured by a densitometer or calculated by Equation C. ❏ Module Equations The following equation, for base volume rate, is taken from Section 6, Volumetric Flow Measurement: Qf Pf + Pa 519.67 Qb = C * K * * * * 1000 Pb Tf + 459.67 (Tb + 459.67) * Fpv 2 Equation A 519.67 where: Qb = Calculated flow rate at base conditions (output in MSCFH) C = Calibration factor K = Span scaling factor Qf = Flow rate at flowing conditions (cubic feet per hour) Pf = Static gauge pressure psig Pa = Atmospheric pressure psia Pb = Base pressure in psia Tf = Flowing temperature in degrees F Tb = Base temperature in degrees F Fpv = Supercompressibility factor The following equation, for base volume rate, is taken from Section 7, Mass Flow Measurement: Qf Df Qb = C * K * * Equation B 1000 Db where all operands are the same as the previous equation except for: Df = Density of flowing gas as measured by a densitometer Db = Base density as measured by a densitometer or calculated by Equation C. AGA7 American Gas Association Report No.. 7 Module Page AGA7-7 ACCOL II Reference Manual Gravitometer temperature and pressure are used to determine the base density (Db) in the following computation (Equation C): Pg 492 Db = 0.08073 * * * SG * Fpv 2 Equation C 14.7 Tg + 459.67 where: Pg = Absolute pressure (psia) at gravitometer Tg = Temperature (in degrees F) at gravitometer SG = Specific gravity as measured by gravitometer Fpv = Supercompressibility factor at Pg and Tg Return to the Table of Contents Return to the List of Manuals
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