Elgas DATCOM, Operating Instructions Manual

Page: 141 / 228

8
Metrological Features
139
using one of the following methods implemented in the device: AGA NX-19-mod, SGERG-88,
AGA8-G1, AGA8-G2, GOST 13390.2, GOST 13390.3 or AGA8-DETAIL. Other quantities also
enter into the calculation, especially the reference values of pressure Pb and temperature Tb and
the current values of pressure p and temperature t of the gas.
The analysis of the chemical composition of the gas is carried out by chromatographs whose
output is also the physical properties of the gas calculated according to ISO 6976 but with the
conditions preferred for billing purposes:
- relative density
d at temperature t
b
and pressure p
b
= 101.325 kPa,
- the heat of combustion H
s
at t
1
/t
b
and pressures p
1
= p
b
= 101.325 kPa.
That is why a calculator is built into the service SW to calculate the physical properties of gas to
the condition required by the methods for calculating the compressibility factor:
- relative density
d at temperature t
b
= 0°C and pressure p
b
= 101.325 kPa,
- the heat of combustion H
s
(applied to methods SGERG-88 and AGA8-G1) at a burning
temperature of t
1
= 25°C and a pressure p
1
= 101.325 kPa / gas temperature t
b
= 0°C and a gas
pressure p
b
= 101.325 kPa.
Note: in literatures is abbreviated as H
s
(25/0)
Calculation of the compressibility factor K = Z/Z
b
is performed by each measuring period.
Due to the required accuracy of the device, the use of compressibility calculation methods is
limited in terms of pressure and temperature ranges as shown in the following tables Table 20
and Table 21:
Pressure
Measurement
Range
Method
AGA NX-19
mod
SGERG-88
AGA8-G1
AGA8-G2
AGA8-DETAIL
80 ÷ 520 kPa
-25 ÷ +70°C -25 ÷ +70°C,
optional
-40 ÷ +70°C
-25 ÷ +70°C,
optional
-40 ÷ +70°C
-25 ÷ +70°C, optional
-40 ÷ +70°C
80 ÷ 1000 kPa N/A -25 ÷ +70°C -25 ÷ +70°C -25 ÷ +70°C, optional
-40 ÷ +70°C
80 ÷ 2000 kPa
N/A -25 ÷ +70°C -25 ÷ +70°C -25 ÷ +70°C, optional
-40 ÷ +70°C
200 ÷ 1000 kPa N/A -25 ÷ +70°C -25 ÷ +70°C -25 ÷ +70°C, optional
-40 ÷ +70°C
400 ÷ 2000 kPa N/A -25 ÷ +70°C -25 ÷ +70°C -25 ÷ +70°C, optional
-40 ÷ +70°C
400 ÷ 7000 kPa N/A -10÷ +70°C -10÷ +70°C -25 ÷ +70°C, optional
-40 ÷ +70°C
700 ÷ 3500 kPa
N/A -10 ÷ +70°C -10 ÷ +70°C -25 ÷ +70°C, optional
-40 ÷ +70°C
1400 ÷ 7000 kPa N/A -10 ÷ +70°C -10 ÷ +70°C -25 ÷ +70°C, optional
-40 ÷ +70°C
2500 ÷ 13000 kPa N/A -10 ÷ +70°C -10 ÷ +70°C -25 ÷ +70°C, optional
-40 ÷ +70°C
Table 20 Limitation of standard applicability given by limitation in compressibility calculation
(AGA, SGERG)