70
AO2000
CONTINUOUS GAS ANALYZERS | OI/AO2000-EN REV. B
Gas sampling
The nominal diameter of the line from the sampling point to the first
switch-over valve should be 4 mm.
A bypass can be positioned upstream of the first switch-over valve, in order
to obtain a faster analysis. With a nominal diameter of 4 mm, the bypass
should be longer than 3 m, in order to prevent back diffusion from the am-
bient air.
The sample gas pressure must be reduced at the sampling point. An evapo-
rating pressure regulator must be provided for sampling from liquid gas
lines.
Sample gas supply line
The sample gas supply line must consist of stainless steel tubing, be as
short as possible and have as few transitions as possible.
The diameter of tube from the beginning of the first switch-over valve
should be 3 mm on the outside and 2 mm on the inside. The sample gas
connection to the gas analyzer is specified for a tube with an outside diam-
eter of 3 mm. The connections should be executed as Swagelok® fittings.
The ZO23 oxygen trace analyzer module may not be connected in series with
other ZO23 analyzer modules or other gas analyzers.
Gas outlet line
The gas outlet line can be executed as a flexible tube. With a nominal diame-
ter of 4 mm, its length should be more than 3 m, in order to prevent back
diffusion from the ambient air.
Bypass
The gas analyzer is connected to a gas flow in the bypass at a constant flow
rate (approx. 30 l/h). The needle valve is installed upstream of the branch to
the gas analyzer and the bypass flowmeter downstream of the branch to the
gas analyzer.
The gas analyzer takes 8 l/h from the gas flow. A surplus of approx. 20 l/h
remains. If several ZO23 analyzer modules are supplied with gas in parallel
(redundant measurement), the flow rate must be set, so that the bypass has
a surplus of 20 l/h.
With a nominal diameter of 4 mm, the bypass from the outlet of the gas
analyzer should be longer than 3 m, in order to prevent back diffusion from
the ambient air.
On account of possible leaks, the flowmeters are always placed in the by-
pass feed path downstream of the branch to the gas analyzer, respectively,
downstream of the gas analyzer; they may on no account be installed in the
sample gas supply line upstream of the sample cell.
Waste gas
The sample gas and the bypass must be conducted into the atmosphere or
into an unpressurized waste gas collecting system at an adequate distance
from the gas analyzer. Long line runs and pressure variations must be
avoided.
For metrological and technical safety reasons, sample gas and bypass may
not be discharged into the atmosphere in the vicinity of the gas analyzer,
since the ambient air serves as reference air and also to exclude suffocation
through a lack of oxygen. It must be ensured that the waste gas only reaches
respiratory air when adequately diluted.
