Gas Leak detectors, often called sniffers, are a class of instruments specially designed to find small leaks in enclosed gas systems.
The use of pressurized gases in pipelines and vessels is very common in
industrial or commercial settings. Pipes carry LPG or natural gas to
any number of refrigerant gases to cooling systems; and caustic or
toxic gases to and from the production floor as an ingredient or
byproduct of an
Long, complex piping runs with an assortment of valves, adapters and
fittings provide a multitude of places leaks can develop. When those
leaks do develop,
they can lead to decreased performance or the failure of equipment and
the release of dangerous gases.
The need for leak detectors is well established. Refrigerant leaks are
the number one cause of poor HVAC cooling performance. Leaks in natural
gas or LPG
lines can create immediate fire/explosion hazards for workers and
facilities. Many gases used in commercial or industrial processes have
been identified as
harmful to the environment and are therefore highly regulated and leaks
can result in heavy fines. Having and knowing how to effectively use a
is an important role for plant technicians.
Using a Gas Leak Detector
There was a time before gas leak detectors came into the market that finding a leak involved a lot of detective work. If the leak was large enough a technician could perhaps hear it, provided background noise didn’t drown out the sound. Sometimes pressure gauges would identify a leak and shut-offs could be used to isolate the area of the leak. Sometimes technicians, armed with spray bottles filled with soap and water, had to work their way down a pipe looking for bubbles to announce the location of the leak.
While all these methods are still used today, none of them provide the
reliable means to identify and locate gas leaks in a closed pipeline.
Though leak detectors are closely related to personal gas detectors,
they are designed to do different things. Personal gas detectors
identify the presence
of a gas in the environment while leak detectors are used to check for
leaks and identify their source.
Aside from the sensor, gas leak detectors are generally equipped with features allowing them to easier pinpoint leaking pipelines. Flexible probes, for example, permit operators to closely trace pipeline routes checking for leaks along the way. These probes often extend several inches from the meter making it easier to extend into hard-to-reach areas.
Most gas leak detectors also include sensitivity adjustment. When gas leak detectors find evidence of an escaped gas and alarm is triggered. Many detectors do not include a display to show concentration readings. To find the location of the leak once the alarm has sounded involves lowering the sensitivity of the instrument and directing it until the alarm sounds again. This indicates increasingly high areas of concentration and point the direction towards the leak.
Having the right gas leak detector and checking its operation technique could mean the difference between finding a leak and missing it.
Leak Detector Technology
Since detecting gases leaking from closed systems is fundamentally
different from identifying the presence of gases in the environment,
leak detectors use
different sensing technology than gas detectors.
Though there are some new technologies for detecting leaking gas, most
leak detectors use one of the following sensing technologies:
Heated diode gas leak detectors operate on the principle that a small electrical current is produced when halogenated gases—commonly used as refrigerants—come into contact with a heated ceramic diode. That current, in turn, triggers an alarm.
Heated diode sensors are very sensitive. They are capable of finding
leaks as small as 0.1 ounce per year with the refrigerant R-134a. Also,
because they only
react with halogenated gases, are less prone to false alarms caused by
the presence of other gases.
Heated diode sensors are susceptible to contamination via moisture and
oils. They have a short service life, typically just 2-3 years though
replacement sensors are inexpensive.
Solid state sensors use a metal oxide (often tin oxide or aluminum
oxide) formed into a bead-type sensor. A heating element is used to keep
the sensor at an
optimal temperature for the gas to be detected.
Since solid state sensors identify leaks by sensing changes in
conductivity, a pair of biased electrodes are embedded into the sensor
to measure the
conductivity change. When the sensor comes in contact with gas escaping
from a leak, that gas is adsorbed onto the sensor surface, changing the
of the sensor material. When the gas disappears, the sensor returns to
its original condition.
What makes solid state sensors especially good for finding gas leaks is
the strong signal they produce, which increases in the presence of high
concentrations. This makes it easier to “point” the detector towards
the area of highest concentration– the leak.
Solid state sensors are very versatile. They detect both low and high
concentrations of gas and can be customized to detect many different
gases by varying
the sensor’s materials, construction and operating temperature.
The primary strength of solid state sensors is their long life
expectancy. In clean conditions, the sensor can last up to 10 years,
than other sensor types. This is a big advantage for an instrument that
is used only intermittently (unless you have a lot of gas leaks!).
Solid state sensors are, however, more susceptible to interference from
background gases than other sensor types. In applications where
are present, solid state sensors can trigger false alarms. Sometimes,
these background gases can be filtered out minimizing their adverse
Ultrasonic leak detectors operate on a very different principle than
other leak detectors. Whereas solid state and heated diode sensors look
of specific gases seeping from leaks, ultrasonic leak detectors
identify the sound waves emitted when gas escapes through a leak.
When gas escapes a pressurized line, it generates a sound in the range
of 25 kHz to 10 MHz, well above the frequencies the human ear is
sensitive to but
in a range easily identifiable to ultrasonic sensors. When the detector
senses ultrasonic frequencies they are isolated from normal background
and converted to a frequency audible to humans.
Since ultrasonic gas detectors search for the sounds of leaks rather
than escaping gases, they are able to detect leaks of any gas type.
Though they are
unable to measure gas concentration, the device is able to determine
the leak rate of an escaping gas because the ultrasonic sound level
depends on the
gas pressure and size of the leak.
Ultrasonic gas detectors work in just about any environment but they
are especially useful for remote sensing in outdoor environments where
quickly dissipate before reaching solid state or heated diode sensors
which require contact with the gas escaping from a leak to identify the
If you have any questions regarding gas leak detectors or would like purchase one please don’t hesitate to contact us.