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ACCOL II Reference Manual Page AGA3Term-1 AGA3TERM American Gas Association Report No. 3 - Terms Module The AGA3TERM Module1 is identical to the AGA3 module in that it performs the gas flow calculations for Orifice meters specified by the American Gas Association, Report No.3 (AGA-3) ANSI/API 2530, 1985 edition and produces an output flow rate in thousands of cubic feet per hour (MSCFH). This module differs from the AGA3 module as follows. 1. The actual AGA-3 factors used in internal calculations can be moved to a list for verification or comparison. 2. Input terminals allow you to substitute factors as needed. 3. The POINT terminal (construction code) can be changed on-line without disturbing module execution. Module Terminals DIFF_PRESS (hw) is the differential pressure across an orifice in inches/water at 60o F. Default: None, entry required Format: Analog signal, constant Input/Output: Input PIPE_DIAM ORIF_CONST POINT ORIF_DIAM OUTPUT TRACK T3 INPUT_n LIST ADJ _PRESS DIFF_ PRESS STAT_ PRESS FLOW_TEMP SPEC_GRAV FPV BASE _TEMP BASE _PRESS 1. This module was previously referred to by the names 'AGA3T,' or 'AGAT3.' AGA3TERM ACCOL II Reference Manual Page AGA3Term-2 AGA3TERM American Gas Association Report No. 3 - Terms Module STAT_PRESS (Pf) is the static pressure of the flowing gas in psig. ADJ_PRESS is the average barometric pressure in psia. ORIF_DIAM is the orifice diameter in inches. This value can be changed online. All affected parameters will be automatically re-calculated. PIPE_DIAM is the inside diameter of the pipe in inches. This value can be changed online. All affected parameters will be automatically re-calculated. ORIF_CONST (K = Fa Fm Fl) is a Combined Orifice Constant K. This terminal is typically the Fa Default: None, entry required Format: Analog signal, constant Input/Output: Input Default: 14.73 psia Format: Analog signal, constant Input/Output: Input Default: None; entry is mandatory Format: Analog signal, constant Input\Output: Input Default: None; entry is mandatory Format: Analog signal, constant Input/Output: Input Default: 1.0 Format: Analog signal Input/Output Input ACCOL II Reference Manual Page AGA3Term-3 AGA3TERM American Gas Association Report No. 3 - Terms Module value for Orifice Thermal Expansion unless other corrections are required. BASE_PRESS (Pb) is the base or contract pressure of the gas in psia. BASE_TEMP (T b ) is the required (contract) base temperature of the flowing gas in degrees Fahrenheit. FLOW_TEMP (Tf) is the flowing temperature of the gas in degrees F. FPV_IN (Fpv) is the supercomcompressibility factor of the gas. POINT is the pressure tap construction code. This entry applies to the pipe tap and flange tap construction described in Basic Orifice Factor Default: 14.73 psia Format: Analog signal, constant Input/Output: Input Default: 600F Format: Analog signal, constant Input/Output: Input Default: 600F Format: Analog signal, constant Input/Output: Input Default: 1 Format: Analog signal, constant Input/Output: Input Default: 1 Format: Analog signal or constant Input/Output: Input ACCOL II Reference Manual Page AGA3Term-4 AGA3TERM American Gas Association Report No. 3 - Terms Module under the 'AGA3' section of this manual. Unlike the AGA3 Module, the POINT terminal in the AGA3TERM Module can be changed while the unit is on-line without first manually inhibiting module execution. The module will recalculate any affected internal values. SPEC_GRAV (G) is the specific gravity of the flowing gas. TRACK is used to force the gas flow output to zero under certain measurement conditions. The TRACK signal may be an analog or logical variable. If it is an analog value, it will be compared to the value of the differential pressure (DIFF_PRESS). As long as the differential pressure exceeds the TRACK value, the computed flow rate will be furnished to the OUTPUT terminal. Should the differential pressure fall below the TRACK value, the OUTPUT will be set to zero. In this way, the TRACK signal acts as a cutoff limit. If the TRACK signal is a logical variable, the ON state will allow the flow rate output to be furnished to the OUTPUT terminal. If the TRACK signal is in an OFF state, the module output will be set to zero percent of scale. Default: 0.6 Format: Analog signal, constant Input/Output: Input Default: None, entry is optional Format: Analog or logical signal Input/Output: Input ACCOL II Reference Manual Page AGA3Term-5 AGA3TERM American Gas Association Report No. 3 - Terms Module OUTPUT (Qh) is the corrected gas flow rate at base conditions in MSCFH. NOTE: In firmware prior to AK.00, the OUTPUT would be set to 0.0 when the numeric ratio of DIFF_PRESS (h w ) to STAT_PRESS (P f ) exceeded 4 to 1, e.g. DIFF_PRESS = 101 inches and STAT_PRESS = 25 psig. This was done because the h w /P f ratio in tables 6, 7, 10, and 11 of the 1978 AGA3 report did not contain ratios higher than 4.0. In firmware revision AK.00 (and newer) the OUTPUT is set to 0.0 if the ratio of h w to Pf exceeds 20 to 1. LIST is the number of a signal list which contains the factors used in the AGA-3 equation. Factors are moved to the list in the following order: C', Fb, Fr, Y, Fpb, Ftb, Ftf, Fg, Fpv, K, Ext. INPUT_n contain factors of the AGA-3 equation which will be substituted for the calculated ones. When INPUT is positive (including zero), it will be substituted in the equation and the internal factor will not be used. Negative INPUTs are ignored and the internal factor is used. If the C' factor is wired and is zero or positive, no internal factors are calculated at all. If any Default: None Format: Analog signal (in thousands of standard cubic feet per hour) Input/Output: Output Default: None Format: Analog signal Input/Output: Input Default: None Format: Analog signal Input/Output: Input ACCOL II Reference Manual Page AGA3Term-6 AGA3TERM American Gas Association Report No. 3 - Terms Module INPUT is incorrectly wired with a logical signal, the value used will be 1.0 for signal ON, 0.0 for signal OFF. There is no Fpv or Fa input because these terminals are already provided. The output list specified on the LIST terminal will always contain the factor used in calculations whether it comes from an input terminal or is calculated by the module. When the C' factor is supplied externally, the list will contain zero values for all other factors except the Exten- sion. INPUT_1 C' - Orifice Flow Constant in CFH INPUT_2 F b - Basic Orifice Factor INPUT_3 Fr - Reynolds Number Factor INPUT_4 Y - Expansion Factor INPUT_5 Fpb - Pressure Base Factor INPUT_6 F tb - Temperature Base Factor INPUT_7 Ftf - Flowing Temperature Factor INPUT_8 F g - Specific Gravity Factor. INPUT_9 Ext - Square-root of the product of Differential Pressure and Static Pressure. Equations Flow calculations done by the AGA3TERM Module are explained under the 'AGA3' section. Return to the Table of Contents Return to the List of Manuals
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