ABB EasyLine EL3000 Operating Instruction page 30

30 EL3000 CONTINUOUS GAS ANALYZERS | OI/EL3000-EN REV. D
... 4 Preparation for Installation
... ZO23
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 ambient
air.
The sample gas pressure must be reduced at the sampling point.
An evaporating pressure regulator must be provided for
sampling from liquid gas lines.
Sample gas feed
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 on the gas analyzer is intended for a
pipe with a 3 mm outside diameter.
The connectors should be made 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 diameter 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 draws gas flow 8 l/h. An excess of approx.
20 l/h remains. If several ZO23 analyzer modules are supplied
with gas in parallel (redundant measurement), the flow must be
set so large that the bypass has an excess 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 bypass 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.