Envent 330S-Ex, User Manual

Page: 13 / 71

Envent Engineering Ltd. Page 8 Revision 1
Figure 1. H
2
S Analyzer Principle of Operation Diagram
Figure 1 above shows a flow and pressure regulated of a filtered sample gas
passing through the humidifier into the sample chamber. An aperture in the
sample chamber, which differs in sizes depending on the application, allows the
gas to come in contact with the H
2
S sensing tape creating a brown stain.
Flow and pressure are the most important variables when measuring H
2
S and
must be kept at a constant state for the analyzer to measure H
2
S properly.
Pressure should be kept at a constant 15 psig. The lowest pressure found to be
tolerable for proper H
2
S measurement is 0.5 psig. Flow must be kept at a
constant flow of 2 cm (between 100-200 cc/min). A change in flow of +/- 1 cm
affects the reading by 10% of full range.
Analysis Cycles
The analysis of the color rate of change on the H
2
S sensing tape is measured in
analysis cycles. An analysis Cycle lasts up to a maximum of 720 seconds (12
minutes).
Do not change the Maximum Analysis Time, consult Envent Engineering Ltd.
Once an analysis cycle is complete, the motor moves the H
2
S sensing tape
giving the sensor block new tape surface area to start the analysis again. In
normal operation, if the analyzer is being exposed to H
2
S within its range, the