Siemens SIPROCESS GA700, Operating Instructions Manual, Page: 146 / 224

3.7 Reference gas monitoring OXYMAT 7
3.7.1 Notes
NOTICE
Damage to the microflow filters
The microflow filters could be damaged by corrosive components in the sample gas.
Make sure that the microflow filters do not come into contact with the sample gas.
Therefore make sure during operation that there is a continuous supply of reference gas.
Note
Reference gas monitoring
Monitor the reference gas pressure using an internal (optional) or external pressure switch.
Interrupt the sample gas supply if the reference gas pressure is too low, and flush the sample
gas path with inert gas.
3.7.2 Reference gas monitoring with pressure switch
In the case of non-safety-relevant oxygen measurement, a pressure switch for the reference
gas monitoring is sufficient. Monitoring is carried out to check that the reference gas pressure
is at least 1 000 MPa above the sample gas pressure. As long as reference gas is flowing,
sample gas is prevented from diffusing to the microflow sensors and destroying them.
The pressure switch for reference gas monitoring is factory-set to 2 000 hPa (rel.) when
delivered.
Note
Excessive sample gas pressure
Make sure that the maximum permissible sample gas pressure of 1100 bar (abs.) is not
exceeded.
The value when pressure is increasing (response pressure) is always higher than the value
when pressure is decreasing (release pressure). This so-called switching hysteresis of the
pressure switch is approx. 200 hPa.
Description
3.7 Reference gas monitoring OXYMAT 7
Field device
34
Operating Instructions, 05/2015, A5E35640463-02