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Compared to looking for gas leaks, finding a needle in a responsive and sensitive, the area is
haystack is a doddle. Gas detection often involves tiny heated to a very high temperature.
amounts of gas, lurking behind parked vehicles or under Flame ionization detection (FID) is
pavements. James Eadie, Key Account Manager for Utilities based on the detection of ions
formed during combustion of gas
(UK & Ireland) at INFICON, explains the methods available in a hydrogen flame.
for finding these gas traces and the technology helping to Infrared (IR) sensors use infrared light
preserve our streets passing through a tube with gas. The gas
will absorb some of the energy of the
infrared beam. The loss of light intensity
as detection has come a long means less inconvenience for the indicates the concentration of gas.
way since the days coal miners general public. With a smaller operation
used canaries in the tunnels to overall, services can be restored to Competing technologies
detect the presence of harmful customers quickly. Cost savings can be All these methods have their drawbacks
G gases – if the canary stopped passed back to customers. and their benefits. In the case of IR, the
singing (or worse, died) it was time to But finding natural gas is not drawback used to be cost, although this
clear the tunnel. straightforward, as it mainly consists of has come down considerably in recent
Today, gas utilities have a slightly methane, which also occurs naturally years and the technology has become
different challenge as they work to in the environment. To distinguish affordable for widespread use. The
detect the presence of gas above natural gas from other sources of main benefits are high sensitivity, rapid
ground to see whether any has escaped methane, such as decomposing organic startup, quick reaction and recovery, near
from their pipelines. Out in the open, matter, the detection equipment needs instant gas analysis and ease of handling.
instruments far more sensitive than to identify another component, ethane, The semiconductor sensor is highly
canaries are required. which only occurs in natural gas. sensitive, but its main drawback is
The main objective, however, that it reacts to all combustible gases.
remains the same – to avoid dangerous Using modern equipment, There is no way of knowing whether a
concentrations of gas. But even if operatives can find gas leaks reading relates to a leaking gas pipe, a
explosions are rare, escaping gas is nearby sewer, or uncombusted fuel in
still problematic. If the leaking gas with relative ease. The operator the exhaust fumes of a passing vehicle.
gathers in one place, urgent attention needs to find the suspected Also, the instrument is not suitable for
will eventually be required. Provided leak, pinpoint the location on measuring high concentrations as it
the gas leak can be located before reaches its maximum signal at just a
any hazardous accumulation builds a map and verify the presence few per cent of methane. In addition,
up, the repairs can be planned and of gas – preferably all with the the sensor takes a long time to recover
carried out in an orderly fashion. same tool, rather than one after an alarm to start measuring
Escaping natural gas also represents piece of equipment for each job. accurately again. Nevertheless, this
lost revenue. In addition, it is harmful measuring method continues to be very
to the environment, as it is a potent popular, as it is the least costly of the
greenhouse gas. The percentage of ethane in natural gas three technologies.
Using modern equipment, operatives varies with the origins of the gas. North The main disadvantage of FID is that
can find gas leaks with relative ease. The Sea gas, for instance, usually contains it is very cumbersome, as it requires
operator needs to find the suspected 6-8 per cent ethane. Other the operator to
leak, pinpoint the location on a map and sources can contain less carry a hydrogen
verify the presence of gas – preferably all than one per cent. cylinder for the
with the same tool, rather than one piece combustion,
of equipment for each job. Detecting gas plus a spare
Once a suspected gas leak has been Several methods to detect one on the
detected, the operator normally drills a gas have been developed back.
series of bar holes in a pre-determined over the years. Over
pattern around the site, to decide the time, the technology
location with the highest concentration has become less costly
of gas. This will indicate the spot to and easier to use.
start digging to make the repair. Today, there are mainly
At this point, the network operator three technologies
will want to be reasonably certain that in operation for
the location has been surveyed with detecting gas in
some degree of accuracy. Digging in the low concentrations: AN IR DETECTOR OFFERS
wrong place is a very costly business semiconductors, flame HIGH SENSITIVITY,
RAPID REACTION, NEAR
and causes disruption. ionization and infrared INSTANT GAS ANALYSIS
AND EASE OF HANDLING
detectors.
Finding and fixing leaks A semiconductor
Rapid detection and remediation of gas sensor changes its
leaks gives several advantages. Accurate resistance depending
detection means less damage to road on the concentration
surfaces, as it leads operators straight of gas present. To
to the faulty pipework. Less excavation make the sensor

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