Fixed Mw G/Mole; Estimated Vs; Fixed Temp And Fixed Pres. Psia - Siemens SITRANS FUG1010 IP65 NEMA 4X Instruction Manual

Section 4
The Reynolds number is computed as indicated:
Rn = 645 ˜
where: ρ = density at flowing conditions (g/cc)
id = spool inside dia (in)
V = Flow velocity (ips)
f
cP = absolute gas viscosity (centipoise)

4.3.4 FIXED MW g/mole

The flow computer uses the measured gas temperature, sonic velocity and specific heat ratio to com-
pute the average specific gravity of the gas being measure. This feature is useful for identification of the
gas as well as for proper reporting of mass flow in cases where the gas composition varies.
In cases where the gas composition does not vary significantly, a fixed value for molecular weight can be
entered here. A non-zero value for Fixed MW (grams/mole) will override the automatic computation of
specific gravity. Setting Fixed MW back to 0.0 will cause the automatic specific gravity computation to
resume.
4.3.5

ESTIMATED Vs

The [Estimated Vs] menu cell allows the numerical entry for the nominal sound velocity of natural gas.
Consult Controlotron Technical Service Group for gases other than natural gas.
NOTE: Changing the Estimated Vs will require repeating the Transducer Install procedure (refer
to paragraph 4.4).

4.3.6 FIXED TEMP and FIXED PRES. PSIA

The FUG1010GCN flowmeter can accept temperature and pressure input from an external direct sens-
ing instrument. If you do not have external temperature or pressure available, then the meter will auto-
matically use the fixed value(s) as the assumed gas temperature and/or pressure. Keep in mind that for
proper reporting of volume corrected flow, mass flow or specific gravity, the flowmeter must have reli-
able temperature and pressure input. However, if the operating temperature and pressure is very con-
stant, then fixed values may be used where higher accuracy is not required.
NOTE: For meters with on-board RTD temperature capability, the [Fixed Temp] parameter will
not be present. In this case, a fixed value for temperature can be set by spanning the
analog input 4mA setting to the desired temperature value. Providing the analog input
channel is not connected to any current source, the valued returned will be the 4 mA
temperature value. (See paragraph 4.10.3 for details regarding the use of analog in-
puts).
The required units for data entry are determined by the [Preferred Units] menu cell (English or Metric)
selected in the [Meter Facilities] menu. If [Metric] units are selected then the units for temperature and
pressure will be degrees Celsius and BARA (absolute), respectively. For English units, temperature and
pressure will be in degrees Fahrenheit and PSIA.
U ˜ id ˜ V
f
cP
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1010GCNFM-3C