Aga3dens - Cesar Delgado

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ACCOL II Reference Manual
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AGA3Dens
American Gas Association Report No. 3 - Density Module
The AGA3Dens Module computes mass and volume flow rate for fluids
(gases or liquids) in lbs/hour and cubic ft per hour, for orifice plates,
with flange taps ONLY, according to the method explained in the
American Gas Association (AGA) Report #3 of August, 1992, 3rd
Edition (Part 1 and Part 4). This method uses density to perform the
calculations.
Mass flow rate (in pounds per hour at flowing conditions) and Volume
flow rate (in cubic feet per hour at flowing conditions) are calculated.
If base density is supplied, the volume rate at base conditions is also
calculated.
Internal factors used in the calculations can be stored in an ACCOL
signal list for examination.
AGA3Dens
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American Gas Association Report No. 3 - Density Module
❏ Module Equation
The AGA3Dens Module calculates mass flow rate at flowing condi-
tions, per the equation given in the 1992 American Gas Association
(AGA) Report #3, Part 4, Equation 4-46a as follows:
qm = Fmass Cd(FT) Y (2 Rhof hw)
where Fmass = Nc Ev (PI * d
2) / 4
Y = Expansion factor (set to 1.0 for liquids)
 hw = Differential pressure DP.
 Cd(FT)= Coefficient of discharge
 Rhof = Flowing density
Volume flow rate is calculated: qv = qm / Rhof
If base density is supplied, a base volume rate is calculated:
Qb = qm / Rhob
where
Rhob = Base density
NOTE
This equation is for flange tapped orifice plates
ONLY.
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American Gas Association Report No. 3 - Density Module
❏ Module Terminals
DIFF_PRESS Default: None, entry required
Format: Analog signal or constant
Input/Output: Input
is the differential pressure, hw , in inches of water across the orifice
plate. Negative input values are clamped at zero, and zero produces a
zero flow rate.
STAT_PRESS Default: None, entry required
Format: Analog signal or constant
Input/Output: Input
is the upstream or downstream static pressure, specified in psia.
Negative input values are clamped at zero, and zero produces a zero
flow rate. When a downstream pressure is used, the TAP_LOC termi-
nal should be a non-zero value.
TAP_LOC Default: OFF
Format: Logical signal
Input/Output: Input
indicates the pressure tap location for flange taps. When OFF or
unwired, this terminal indicates that the tap location is upstream;
when ON this terminal indicates that the tap location is downstream.
When downstream is specified, the differential pressure is converted
to psi and added to the static pressure to obtain an upstream value for
use in calculations. See 'Module Usage Notes.'
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American Gas Association Report No. 3 - Density Module
ORIF_DIAM Default: None, entry required
Format: Analog signal or constant
Input/Output: Input
is the orifice bore diameter in inches at the reference temperature
value wired to the ORIF_RTEMP terminal. Output of the module will
be zero if the ORIF_DIAM terminal is unwired, or if the value entered
is zero, negative, or larger than 80% of the value on the PIPE_DIAM
terminal.
PIPE_DIAM Default: None, entry required
Format: Analog signal or constant
Input/Output: Input
is the inside diameter of the pipe in inches at the reference tempera-
ture value wired to the PIPE_RTEMP terminal. Output of the module
will be zero if the PIPE_DIAM terminal is unwired, or if the value on
the terminal is zero or negative.
ORIF_COEF Default: 0.00000925
Format: Analog signal or constant
Input/Output: Input
is the orifice coefficient of thermal expansion in inches per inch-degree
Fahrenheit.
PIPE_COEF Default: 0.0000062
Format: Analog signal or constant
Input/Output: Input
is the pipe coefficient of thermal expansion in inches per inch-degree
Fahrenheit.
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American Gas Association Report No. 3 - Density Module
ORIF_RTEMP Default: 68o Fahrenheit
Format: Analog signal or constant
Input/Output: Input
is the reference temperature at which the orifice bore was measured.
PIPE_RTEMP Default: 68o Fahrenheit
Format: Analog signal or constant
Input/Output: Input
is the reference temperature at which the pipe diameter was mea-
sured.
FLOW_TEMP Default: 60o Fahrenheit
Format: Analog signal or constant
Input/Output: Input
is the fluid temperature, Tf , in degrees Fahrenheit.
VISCOSITY Default: 0.010268 centi Poise
Format: Analog signal or constant
Input/Output: Input
is the dynamic viscosity of the fluid at flowing conditions in centi
Poise.
ISEN_COEF Default: 0.0
Format: Analog signal or constant
Input/Output: Input
is the fluid Isentropic exponent. This value is used in the calculation of
the expansion factor, Y. Positive values from 1.0 to 2.0 are used
directly; values outside this range are forced to an internal value of
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American Gas Association Report No. 3 - Density Module
1.3. When the ISEN_COEF terminal is negative or zero, or is unwired,
the internal expansion factor Y is set to 1.0 for liquid flow calculations.
FLOW_DENS Default: 0.0
Format: Analog signal or constant
Input/Output: Input
is the fluid density, in pounds per cubic foot, at flowing conditions. If
this terminal is unwired, or wired and zero, the REL_DENS input is
examined for a relative density value.
BASE_DENS Default: 1.0
Format: Analog signal or constant
Input/Output: Input
is the fluid base density in pounds per cubic foot, at base conditions.
REL_DENS Default: 0.0
Format: Analog signal or constant
Input/Output: Input
is the density of the liquid being metered relative to water. This
terminal is used only when FLOW_DENS is unwired, or wired and
zero, and the ISEN_COEF indicates a liquid. The input value is
multiplied by the density of water to obtain flowing density for calcu-
lations.
TRACK Default: 1.0 or ON
Format: Analog or logical signal
Input/Output: Input
is used to force the module output to zero. When a logical signal is
wired to this terminal, ON enables calculation, and OFF forces the
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American Gas Association Report No. 3 - Density Module
output of the module to zero. If an analog signal is wired to this
terminal, it is used as a differential pressure threshold value or 'cutoff'
level; calculations cease and the output of the module is forced to zero
when the DIFF_PRESS terminal value is less than the TRACK value.
MASS_FLOW Default: None
Format: Analog signal
Input/Output: Output
is the mass flow rate, qm , at flowing conditions in pounds per hour.
VOL_FLOW Default: None
Format: Analog signal
Input/Output: Output
is the volume flow rate, qv , at flowing conditions in cubic feet per
hour.
BASE_FLOW Default: None
Format: Analog signal
Input/Output: Output
is the volume flow rate, Qb , at base conditions in cubic feet per hour.
LIST Default: None
Format: Analog Signal or constant
Input/Output: Input
is the number of a signal list into which the factors used in the equa-
tion are to be moved. Factors are moved to the list in the following
order: CD, E, Y, Fmass , FIP , Reynolds number.
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American Gas Association Report No. 3 - Density Module
❏ Module Usage Notes
Conditions Which Cause Zero Flow Rate to be output by the Module:
The following conditions can force the flow rate output of the
AGA3Dens Module to zero. These are:
a. Negative or zero differential pressure.
b. Negative or zero static pressure.
c. Negative or zero orifice diameter.
d. Negative or zero pipe diameter.
e. Orifice diameter larger than 80% of pipe diameter.
f. Track terminal conditions are satisfied.
g. Negative flowing density.
h. Zero flowing density with relative density <=0.
Bounded Inputs:
The isentropic exponent value used internally will be forced to 1.3 if
the input value is positive but less than 1.0 or larger than 2.0. The
expansion factorY used internally will be forced to 1.0 if the input
value is negative or zero.
Static Pressure Tap Location:
If the static pressure is from a downstream tap, the TAP_LOC should
be non-zero, in which case the differential pressure is converted to
psia and added to the static pressure to obtain an upstream pressure
for internal use.
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American Gas Association Report No. 3 - Density Module
Relative Density Usage:
Relative density can only be used for liquids. The FLOW_DENS
terminal must be unwired, or wired and zero, and the ISEN_COEF
must be unwired, or wired and less than or equal to zero. The value on
the REL_DENS terminal is multiplied by the density of water to
obtain a flowing density for internal calculations. This terminal is
intended for use where a densitometer signal is unavailable but a
relative density (Specific Gravity) is available.
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