by Maryam Hussain
What is natural gas?
Natural gas is a mixture of
gaseous hydrocarbons. Natural gas is composed mainly of methane, ethane,
propane, and butane which all are highly flammable. Natural gas is primarily
employed as a clean heating fuel in industry, commercial installations, and
households.
Inflammability and toxicity of
natural gas?
When natural gas comes out of the
ground at its source, it has neither color nor smell. Companies that
supply gas to consumers add the very noticeable odor of rotten eggs to
gas so that a leak is easy to detect because of its odor only.
If you should ever smell a strong
odor of natural gas, do not use any devices that might make a spark.
Light switches, phones, and even turning on a flashlight could ignite the gas
and cause an explosion. Leave your home immediately and take anyone else in the
house with you, including pets.
Natural gas is lighter than
air, non-toxic, and contains no poisonous ingredients. Breathing natural
gas is harmful in the atmosphere when there is an adequate supply of
oxygen.
If pressurized gas leak fires are
extinguished, but the leakage is not stopped, the vapors can again be reignited
and produce an explosive blast. Fire of natural gas falls in class C.
Such fires can be extinguished using foam or dry powder in conjunction with
water to cool any containers involved or nearby.
The uncontrolled flow of some
material through a boundary may be called leakage.
The usual leakage points of
gas:
The usual leakage points of gas
may be the gaskets, seals of joints or shafts, flanged joints, drain points,
points where the flexible tube is lagged on the metallic nozzle as a junction,
ruptured diaphragm of the gas pressure reducer, stuck open safety relief valve
on the gas supply line, stuck open ball valve, stuck open burner main flame
valve, stuck open burner pilot valve, holes due to corrosion, etc.
Technology help for leaked gas
detection:
If the house is in an open area,
then small leakages from the house may be dispersed by the wind. If the house
is in a building, or there are houses in the periphery then the dispersal of
natural gas may be slow and may pose a hazard of vapor cloud explosion.
The movement of vapor clouds or
gas clouds in the air is due to turbulence, gravity spreading, and mixing. In
the case of natural gas, this movement occurs due to turbulence and mixing, and
gravity spreading is neglected because natural gas (mainly methane is lighter
than air).
Gas clouds now have one or more
of the following characteristics:
The highest
natural gas concentration is at the point of leakage and inside the pipe.
The shape of the
gas cloud is dependent on wind direction, wind speed, and wind temperature.
Outdoor natural
gas clouds dissipate faster and hence have lower natural gas
concentrations.
Large natural gas leaks can be
detected by pressure sensors on gas providers’ systems. Medium and larger
natural gas leaks are easier to detect due to the size of the gas cloud
than smaller leaks. The most dangerous and limiting situations arise from small
leaks for which the importance of inflammable leaked gas detection cannot be
overestimated.
Optimum location of leaked
natural gas detectors:
The optimum way to locate a gas
detector is where the frequency or chances are more. To detect natural gas
leakage, that is lighter than air (CH4), detectors should be mounted at
ceilings and preferably use a collecting cone.
The leakage of natural gas
poses a smaller toxic hazard because of its nature.
The effect of a large fire
hazard can be greatly mitigated if people take the right action:
The occurrence of an inflammable
natural leakage event is not limited to a specific time i.e. it may occur
whether it is day or noon or evening or night. The occurrence of domestic
natural gas leakage may also occur whether the resident is awake or asleep.
Therefore, the remedial action by the resident of the house, i-e the isolation
and evacuation or at least one of these, should be as early as possible.
To execute quick remedial actions,
the location of the isolation valve and knowledge of a safe exit route is
essential for the resident. The evacuation from the scene of leakage
is based on the memory of evacuation routes. But what about the visibility of
safe passages? So we modify the previous statement that “the evacuation from
the scene of leakage is based on memory to evacuation routes and availability
of visibility of route. To have visibility of the route during loss of light
(night or power failure mode), guiding fluorescent tapes, may already be
installed on the evacuation routes.
It is recognized that the total
failure of domestic pipelines supplying gas to consumers is very rare. Better
estimates are available of fewer failures of pipelines and sufficient time is
available for emergency action such as the closure of isolation valves,
provided the detection is early.
So after coming out of the house,
close the main isolation valve of the gas supply line because it is usually
located out of your house’s covered area, and call the gas supply company.
Call rescue providers and
firefighters:
In Pakistan,16 is
designated as a fire emergency number while 15/1122 can be used to redirect to
any service.112 from any GSM handset will forward to the local emergency
number.
In Saudi Arabia,998 is designated
as a fire emergency number. In the United Arab Emirates,997 is
designated as a fire emergency number.
The usually used emergency
number in European countries is 112 (following Directive
2002/22/EC – Universal Service Directive) and is also standard on GSM mobile
phones.
Therefore, the emergency call
number 112 is used in Latvia, Liechtenstein, Lithuania, Luxembourg,
Republic of Macedonia, Malta, Netherlands, Norway, Poland, Portugal, Romania,
Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Ukraine, Austria,
Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, and Italy in addition to
their other emergency numbers.
Closing remarks:
To prevent the leakage of natural gas, both the gas supply company and gas usage consumer should follow the national code of conduct regarding monitoring the health of the gas supply system and consumer appliances.
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