H
Fall 2014
|
9
feature
ydrogen! Don’t they use it to make bombs?
Yes and no. The hydrogen bomb is made
with a rare hydrogen isotope, Tritium, which
is radioactive and doesn’t occur naturally. In
reality, hydrogen gas is no more dangerous
than other gases we are around all the time,
like natural gas. The explosive limits for
hydrogen in air range from 18.3% to 59%. The
concentration used for leak detection is only
5% with the remaining 95% being nitrogen.
Due to its small molecular structure, hydrogen
can penetrate throughmaterials such as soil and
concrete. This characteristic makes hydrogen
the ideal gas for this detection method.
Metrotech has a PAM-H
2
sensor that can
be used with the HL5000 leak detection
system. The PAM-H
2
, also known as a
tracer gas sniffer, can detect hydrogen at
concentrations as low as 0.7 ppm in air.
The replaceable gas sensor has a life of 2
to 5 years, depending on use.
The Town of Blowing Rock had the perfect
situation for this leak detection system. The
Town has a water leak somewhere around
a busy intersection in downtown. Standard
acoustical leak detection methods have
failed to pinpoint the leak. After obtaining
a cylinder of hydrogen tracer gas, town staff
connected the gas to a water meter upstream
of the suspected leak. The pressure of the
gas was set approximately 10 pounds above
the water pressure on the line. After waiting
a few minutes for the gas to enter the line,
the sniffer was used to search for traces of
hydrogen coming from the leak. No traces of
hydrogen were detected, indicating no leak
on the line. The operation was then moved
to another line in the area. Once again, no
hydrogen was detected along the line.
Unfortunately, the leak was not found
during our first experience with the
hydrogen leak detection system. The Town
was able to eliminate two water lines as
possible sources of the leak. The Town
of Blowing Rock will continue to use the
tracer gas sniffer on additional lines in an
effort to locate the leak.
By Brian Grogan
Using Hydrogen Gas
to Locate Water Leaks
