Purging - Siemens LDS 6 Operating Instructions Manual

In-situ laser gas analyzer

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3.5

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 sensor 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.

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.

Figure 3-18

1. Sensor side purging input.

2. Purging bypass tube.

3. Lens.

4. Sensor side purging output check valve.

Sensor CD 6C Operating Instructions

Operating Instructions, 12/2007, A5E00912721-02

Gas purging in sensor head

Installation Guidelines

3.5 Purging

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