5 Key features
5.2 P-T-Z Measurement
Honeywell 2024
74
5.2.2.2 Fixed Gas temperature
The EC350 can be configured to function as a fixed temperature device by setting item 111 to fixed
temperature. In that mode, the temperature value configured in item 1162–Fixed temperature value
(instead of the live temperature at item 26) is used for temperature correction.
5.2.3 Supercompressibility
Gases actually behave in a manner slightly different from what the ideal gas laws indicate. This deviation
depends on the molecular composition of the gas as well as the pressure and temperature. Natural gas,
for instance, compresses by a greater amount than that computed by Boyle’s law and hence the term
“supercompressibility” is used for this deviation. It is small at very low pressure, but becomes substantial
as the pressure increases.
5.2.3.1 Supercompressibility Factor
Gases actually behave in a manner slightly different from what the ideal gas laws indicate. This deviation
depends on the molecular composition of the gas as well as the pressure and temperature. Natural gas,
for instance, compresses by a greater amount than that computed by Boyle’s law and hence the term
“supercompressibility” is used for this deviation. It is small at very low pressure, but becomes substantial
as the pressure increases. The EC350 automatically applies the supercompressibility factor and therefore
the equation for total volume correction that EC350 applies to metered volume is expressed as:
Vb = Vm * Fp * Ft * (Fpv)²
Where:
l
Vb (item 0) = volume corrected to base conditions
l
Vm (item 2) = volume from the meter (at measured conditions)
l
Fp (item 44) = pressure factor
l
Ft (item 45) = temperature factor
l
Fpv (item 47) = supercompressibility factor per NX-19 or AGA-8 standard (derived for orifice
meters)
l
(Fpv)2 (item 116) = supercompressibility factor used for diaphragm, rotary, and turbine meters
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