Gas Sample Conditioning System - H
2
S in Natural Gas
4–4 H
2
S in Natural Gas
However, regular checks of the specified values via the pressure gauges and
flow meters on the system is recommended.
Servicing the Scrubber
The H
2
S scrubber contains material that gradually loses its scrubbing ability
with use. The lifetime of the material depends on how much H
2
S flows through
the system (gas composition) and how often (switching frequency). Thus,
scrubber lifetime is very application specific. However, under normal operating
conditions (~10 ppm H
2
S) the scrubber is expected to last approximately 12
months.
Upon exhaustion, the scrubber indicator, shown in Figure 4–3, changes color
from turquoise to dark grey, as shown in Figure 4–4. Alternatively, regular
validation of the system with an appropriate gas standard will indicate when
the scrubber needs to be replaced. The system will issue a scrubber alarm
every 6 months as a reminder to check the scrubber and scrubber indicator.
When specifying gas standards, make sure the background gas is
that specified or, if not specified, a mix that closely resembles the
contents of the process stream and have the gas standard
certified to better than the specified precision of the analyzer, if
possible.
SCRUBBER
SCRUBBER
INDICATOR
FLOW
Figure 4–3 Scrubber and scrubber indicator.
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