CiDRA GVF-100 Gas Volume Fraction Monitoring System - Manual (Page 76)

Copyright © 2006 CiDRA Corporation Page 10-2
20639-01 Rev 03
•
Pressure
This input is an important parameter for accurate GVF measurement.
If the process pressure is constant, input the normal process operating
pressure into the transmitter in units of PSIg, Barg or kPag.
For applications where the process pressure varies, it is
recommended that a correction for pressure be performed in the
process control system. Alternatively, a pressure transmitter can be
input to the SONARtrac
TM transmitter as described in Pressure Sel
below.
If a plant control system is used to correct for pressure, the correction
at the control system is made as follows:
GVF
act
= GVF
meas
* [(P
proc
+ P
atm
)/( P
trans
+ P
atm
)]
where: GVF
act
= the GVF corrected for pressure
GVF
meas
= the GVF reported by the transmitter
P
atm
= 14.696 if at sea level, correct for elevation if necessary (psia)
P
proc
= the pressure from the pressure transducer (psig)
P
trans
= the pressure input to the transmitter (psig)
If a pressure transmitter is connected to the SONARtrac TM transmitter,
the calculation above is performed by the SONARtrac TM unit and no
pressure correction should be made in the process control system.
•
Temperature
Used to input the approximate process / fluid temperature (in ºC or ºF)
expected. A pressure transmitter can be input to the SONARtrac
TM
transmitter as described in Temperature Sel below.
This input has minimal affect on GVF calculation.
•
Pressure Sel
Used to select if the pressure values for calculating GVF will be fixed
(that is, assumed to be steady state and use the values input earlier
during GVF set up), or if the values will be based on a pressure
transducer. If the values are based on a pressure transducer, user
must configure the sensor inputs in the ‘Input Config’ menu.
•
Temperature Sel
Used to select if the temperature values for calculating GVF will be
fixed (that is, assumed to be steady state and use the values input
earlier during GVF set up), or if the values will be based on a
temperature transducer. If the values are based on a temperature
transducer, user must configure the sensor inputs in the ‘Input
Config
’ menu.