Measuring Range [Ppm]; Detecting Leaks; Feeling Around" The Pipe Using The Selecth2 - Herth+Buss ELPARTS SelectH2 Operating Instructions Manual

Operating Instruction

8.1 Measuring range [ppm]

The high sensitivity of the SelectH2 gas de-
tector makes it possible to detect traces of
gases in the ppm range. For example, 1 ppm
is the quantity of 1cm3 gas in one m3 of air.
The Herth+Buss SelectH2 gas detector uses
this dimension to measure up to 999 ppm.
In the transition to 1000 ppm, the display
switches to the vol% range and changes to
0.1 vol% (see the comparison values in the
following table).
The dimension [ppm]: 1ppm = 1 part per
million
100% = 1,000,000 ppm
10% = 100,000 ppm
1% = 10,000 ppm
0.1% = 1,000 ppm
0.01% = 100 ppm
0.001% = 10 ppm
0.0001% = 1 ppm

8.2 Detecting leaks

As described in 8.3, the quantity of gas lea-
king determines the spread width. However,
as the spread range is unknown, every con-
nection in the accessible parts of the pipe
must be examined carefully. If the device's
sensor head now gets in the "gas cloud" , the
light gas in the sensor head diffuses and has
an effect on the gas-sensitive semiconduc-
tor. Depending on the strength of the gas
concentration, the measuring procedure will
require approx. 2-3 seconds. For the testing
practice, this means:
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Briefly coming close to the screw connection
or the fitting with hemp thread is not enough
to detect small gas leaks.
8.3 "Feeling around" the pipe
using the SelectH2
Slow "feeling around" the connection points
has proven successful in practice. This is the
best way to detect the small bubble of gas
escaping.
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