28
EL3000
CONTINUOUS GAS ANALYZERS | OI/EL3000-EN REV. D
… 4 Preparation for Installation
ZO23
Sample gas
Sample gas inlet conditions
DANGER
Explosion hazard
Explosion hazard when measuring ignitable gas / air or
gas / oxygen mixtures
• The gas analyzer may not be used for the measurement of
ignitable gas / air or gas / oxygen mixtures
ZO23 – sample gas input conditions
Temperature
5 to 50 °C
Inlet pressure
p
e
≤
70 hPa
Flow rate
4 to 20 l/h
• The sample gas flow rate must be kept constant within the
specified range at ±0.2 l/h.
• The sample gas must be taken unpressurized from a bypass.
If the sample gas flow is too low, contamination effects from
the gas lines (leaks, permeability, de-sorption) will lead to
inaccuracies in the measurement result.
If the sample gas flow is too high, asymmetrical cooling of the
sensor may cause measurement errors. This can also cause
quicker aging or damage to the measuring cell.
Note
The temperature, pressure and flow of the sample gas must be
kept constant, to such an extent that the influence of variations
on the measuring accuracy is acceptable, refer to
page 208.
Corrosive gases
The presence of corrosive gases and catalyst poisons, such as
halogens, gases containing sulfur and heavy-metal dust, leads to
quicker aging and / or the destruction of the ZrO
2
cell.
Flammable gases
The analyzer module is suitable for measuring flammable gases
in a non-explosive environment. The concentration of flammable
gases in the sample gas must not exceed 100 ppm.
Associated gas effect
Inert gases (Ar, N
2
) have no effect. Flammable gases (CO, H
2
,
CH
4
) in stoichiometric concentrations to the oxygen content:
conversion O
2
< 20 % of the stoichiometric conversion. If higher
concentrations of flammable gases are present, higher O
2
conversions must be expected.
R
equirements for the sample gas outlet
The outlet pressure must be the same as the atmospheric
pressure.
Test gases
Reference point (electric zero point)
Clean ambient air;
its oxygen concentration is obtained from the dry air value
and the factor for consideration of the water vapor content.
Example:
Water vapor content at 25 °C and 50 % relative humidity =
1.56 Vol.-% H
2
O
Factor 0.98
Oxygen concentration =
20.93 vol. % O
2
× 0.98 = 20.6 Vol.-% O
2
End position
Test gas with oxygen concentration in the smallest
measurement range (for example, 2 ppm O
2
in N
2
).
Note
The pressure conditions at the reference point and the end point
must be identical.
The instructions for checking the reference point and the end
point (see
ZO23 – Checking the reference point and end point
on page 134) must be observed.
Purge gas
If housing purging is selected (for IP65 design only), the purging
may only be carried out using air (not with nitrogen), since the
ambient air is used as a reference gas.
Gas connections
See sections
Gas connections ZO23 (model EL3020)
Gas connections ZO23 (model EL3040)
