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Aga3term - Cesar Delgado

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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.
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