Siemens SIPROCESS GA700, Operating Instructions Manual, Page: 182 / 224

8.3 OXYMAT 7
WARNING
Incorrect reference gas
Explosion hazard when used in the hazardous area.
Use nitrogen exclusively as the reference gas for combustible media in the hazardous area.
Also ensure that the reference gas pressure is at least 2.2 bar (3.2 bar abs.).
8.3.1 Reference gas
Only used nitrogen as the reference gas.
Make sure that the reference gas pressure is 2000 hPa +/- 150 hPa above the sample gas
pressure.
8.3.2 Zero point error
Accompanying gases (interfering gases) cause a zero point deviation that is positive with
paramagnetic gases and negative with diamagnetic gases. The extent of this offset per 100
vol. % accompanying gas, expressed in vol. % O
2
absolute, is listed in the following table. The
values in the tables refer to nitrogen at 60 °C and 1 000 hPa absolute to IEC 1207/3.
Table 8-1 Zero point error of organic gases
Accompanying gas (concentration 100 vol. %) Zero point deviation in
vol. % O
2
absolute
Ethane C
2
H
6
-0.49
Ethene (ethylene) C
2
H
4
-0.22
Ethine (acetylene) C
2
H
2
-0.29
1.2 butadiene C
4
H
6
-0.65
1.3 butadiene C
4
H
6
-0.49
n-butane C
4
H
10
-1.26
Isobutane C
4
H
10
-1.30
1-butene C
4
H
8
-0.96
Isobutene C
4
H
8
-1.06
Dichlorodifluoromethane (R12) CCl
2
F
2
-1.32
Ethanoic acid CH
3
COOH -0.64
n-heptane C
7
H
16
-2.40
n-hexane C
6
H
14
-2.02
Cyclo-hexane C
6
H
12
-1.84
Methane CH
4
-0.18
Methanol CH
3
OH -0.31
Commissioning
8.3 OXYMAT 7
Field device
70
Operating Instructions, 05/2015, A5E35640463-02