20
8024252/AE00/V1-0/2020-07| SICK
O P E R A T I N G I N S T R U C T I O N S | ZIRKOR200 Ex-D
Subject to change without notice
4
LAYOUT AND FUNCTION
4.2
Measuring principle
The ZIRKOR200 Ex-D oxygen measuring system consists of an in-situ probe, which is
installed on the duct with the gas to be analyzed, and a control unit for voltage and gas
supply as well as for signal processing. An oxygen sensor regulated to 800 °C which
functions according to the zirconium oxide principle is fitted on the probe tip. An mV signal
is measured between the reference gas side of the sensor (inside, instrument air 20.95%
O
2
) and the measuring gas side, which depends logarithmically on the relation of the
oxygen partial pressures of both sides. The mV signal is converted to the oxygen partial
pressure in the sample gas using the Nernst equation, which determines the O
2
concentration in the sample gas.
4.3
Scope of application
The ZIRKOR200 Ex-D DustEx oxygen measuring system is suitable for measuring oxygen
(O
2
) in flue gases.
4.4
Potential hazards
4.5
Process interruption
The oxygen measuring system must remain in operation even when the process is
interrupted or the system is temporarily switched off (e.g. at night or on weekends).
Frequent cooling and heating of the measuring probe leads to a thermal load on hot
measuring probe components (heater, thermoelement and O
2
sensor) and shortens their
service life. SICK shall not be liable for any resulting damage.
NOTICE:
The system must not be used to determine the oxygen content of combustible gases
because the measuring accuracy cannot be guaranteed when combustible gases occur.
NOTICE:
Device damage with regular O
2
concentrations below 0.5%. Under normal process
conditions, the minimum concentration of O
2
in the flue gas should not be less than
0.5%.
▸
The cell protection circuit option is recommended when the O
2
concentration
regularly falls below 0.5%. Called LL
2
(LongLife
2
), so that the O
2
sensor is
permanently protected.
WARNING: Danger of burns on hot components which are in the process gas
The temperature of the probe filter head and all parts in the process gas is 150 °C to
800 °C (302 °F to 1472 °F) during operation. Directly touching hot parts for
disassembly or maintenance causes serious burns!
▸
Use heat protection gloves when removing the probe.
▸
Switch the electronics supply voltage off before removing the probe.
▸
Place the probe in a safe, protected area after removal and wait until the probe
temperature has cooled down to the ambient temperature.
