Introduction; Applications; Terms And Dimensions - Herth+Buss ELPARTS 95980002 Notice D'emploi

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Operating manual
SelectH selective gas detector
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1

Introduction

1.1

Applications

The Herth+Buss SelectH gas detector is a selective and sensitive
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hydrogen gas detector. Indication on the display ranges from
0 ppm to the lower explosion limit of the gas.
The range is stored in the micro-processor and can be
requested through selective sensors. The gas detector is
equipped with a suction pump, a GGS 1000 and GGS 6000.
1.2

Terms and dimensions

ppm
ppm stands for parts per million = number of parts per million other
parts – a customary value for smallest quantities in gas detection
technology. 1 ppm is the quantity of 1 cm
1 ppm = 0.0001 Vol.%, which means 0.1% gas = 1000 ppm.
Lower explosion limit
At certain mixing values with air (air oxygen), which differ from one
gas to another, combustible gases reach a point where explosion
like ignition takes place when a source of ignition acts on the gas.
With hydrogen, this so-called lower explosion limit (sometimes
also called lower ignition limit) is 4.0 Vol.% depending on the
composition. In other words, relatively small amounts suffice to
achieve an ignitable mixture.
The graph illustrates this using a room as an example. As the
room gradually fills with gas, the value of 4.0% is quickly reached.
The range from 0% gas to the lower explosion limit is divided into
% of the lower explosion limit. 4.0% hydrogen in air corresponds to
100% of the lower explosion limit.
The gas detector Hydrogen-Power indicates by acoustic signal that
the value is approaching this lower explosion limit.
of gas in 1 m of air.
3 3
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UEG: lower explosion limit
<
OEG: upper explosion limit
<
Safety instructions
Even if a concentration that is below the lower explosion limit is
measured with the device at a certain position in the room – e.g.
at usual working height – a higher concentration that is within the
potentially explosive range can be present in other parts of the room
or building.
Gas detection method
The gas detection method using forming gas 5/95 (5% hydrogen in
nitrogen) was developed for locating the tiniest of leaks that cannot
be
detected by acoustic methods. The selection of hydrogen gas for indi-
cation means there is no interference through other gases such as
methane or sludge gas. Please contact Herth+Buss for a detailed
description of the method, including practical examples if required.