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miniELCOR
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4.3 Compressibility calculation
4.3.1 PTZ, TZ conversion
The compressibility factor is calculated from the composition of the gas listed in
the parameters, using one of the following methods implemented in the device: AGA
NX-19-mod, SGERG-88, AGA8-G1, AGA8-G2 or AGA8-92DC.
Calculation of the compressible factor is performed in each measuring period. In
the SGERG-88 and AGA8-G1 methods the value of the heat of combustion is
entered for the combustion temperature 25°C / gas temperature 0°C. The service SW
contains a built-in calculator for the conversion of the heat of combustion at different
temperatures.
Due to the required accuracy of the device, the use of the individual methods of
calculation of compressibility is limited by the pressure and temperature ranges
pursuant to the following table:
Pressure
measuring range
Method
AGA NX-19
mod
SGERG-88 AGA8-G1
AGA8-G2
AGA8-92DC
80 ÷ 520 kPa -25 ÷ +60 °C -25 ÷ +60 °C -25 ÷ +60 °C -25 ÷ +60 °C
200 ÷ 1000 kPa N/A -25 ÷ +60 °C -25 ÷ +60 °C -25 ÷ +60 °C
400 ÷ 2000 kPa N/A -25 ÷ +60 °C -25 ÷ +60 °C -25 ÷ +60 °C
700 ÷ 3500 kPa N/A -10 ÷ +60 °C -10 ÷ +60 °C -25 ÷ +60 °C
1400 ÷ 7000 kPa N/A -10 ÷ +60 °C -10 ÷ +60 °C -25 ÷ +60 °C
80 ÷ 1000 kPa N/A -25 ÷ +60 °C -25 ÷ +60 °C -25 ÷ +60 °C
400 ÷ 7000 kPa N/A -10 ÷ +60 °C -10 ÷ +60 °C -25 ÷ +60 °C
Table 1 Limitation of standard validity range of compressibility calculation
Note:
At device there is applied compressibily calculation method GOST NX-19 which
is not approved by Č MI certificate.
Usage of method GOST NX-19 is limited only for temperature range from -23°C
to +60°C.
Default compressibility
For the set method during each calculation, it is checked whether the measured
pressure and temperature value are in the valid interval of the pertinent method. If
some of the values are outside the valid interval, the so called default compressibility
is used for the conversion. The value of the default compressibility must be entered
by the user during device configuration.
4.3.2 PT, T conversion
The device also allows the setting of the ratio of compressibility factors (K) as a
fixed constant. The range of the entered constant is not limited.