Purging - Siemens LDS 6 Operating Instructions Manual

Installation Guidelines

3.1.5 Purging

Purging can be divided into purging of optical process interface
and purging of sensors.
Sensor Head Purging
Ambient air contains roughly 1% water vapor. Therefore the sen-
sor heads must be purged with a very dry gas like nitrogen. Since
the resolution of the water vapor application of LDS 6 is better
than 1 ppm the nitrogen should be correspondingly dry.
NOTE
The recommended flow is 10 l/min and the absolute minimum is 6 l/
min. The pressure should be as close to ambient as possible and
should not exceed 1.5 bar absolute. Too low flow rate and/or to
humid purging gas might lead to faulty measurements.
4
2
3
1
Figure 3.18 Gas purging in sensor head
1. Sensor side purging input.
2. Purging bypass tube.
3. Lens.
4. Sensor side purging output check valve.
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CD 6C – Water vapor sensor for LDS 6
A5E00912721-01