Commercial vehicles
constitute 1.1% of total vehicular population in Delhi, but account for 90% of
total vehicular pollution.
THE
GOVERNMENT MUST TAKE STRINGENT MEASURES TO CONTROL POLLUTION BY DIESEL
COMMERCIAL VEHICLES
Fossil fuel-based vehicles
using petrol and diesel emit various air pollutants like CO (carbon monoxide), HC (unburned hydrocarbons), NOx (nitrogen oxides),
SOx (Sulphates) and PM (particulate matter). These pollutants in auto exhaust
are responsible for major diseases and are extremely harmful for humans. In Delhi
for instance, one out of every third child is currently suffering from Asthma
and related respiratory diseases.
A study conducted by
IIT Delhi in 2007 established that even though CNG operated buses are present
in Delhi since the year 2000, pollution due to diesel commercial vehicles is
a major source of air Pollution in the city. Although commercial vehicles
constitute only 1.1% of the total vehicular population in Delhi, they account
for 90% of the total vehicular pollution in the city. People of Delhi will distinctly remember the day when all diesel
based buses were sent off the road and CNG buses were introduced, one could
start seeing the blue sky over Delhi. This highlights the effect of diesel
vehicles on the air pollution in cities.
This is not only the
case with developing country like India; the similar situation prevails in
developed countries like USA, Japan, Europe and our close neighbour China. Pollution
is the cause of concern especially for urban areas in India.
Hence, tight control
over the emission of diesel commercial vehicles is absolutely essential all
over the country to protect the health of humans, especially in urban areas
where there is heavy traffic. Through strict emission norms and effective
implementation all across the country, we can achieve growth of both health and
wealth of India. Stainless steels play a very useful role in the mitigation of
pollution from diesel/petrol powered vehicles.
Impact
of pollution
Diseases caused due
to vehicular pollution include Asthma, Alzheimer, Strokes, Pulmonary diseases and
irritation in eyes etc., depending upon the exposure to air pollution. This
effectively shortens the life span of living beings. The effect is much greater
in urban areas because of higher vehicular population. A survey has revealed
that over 900 million people in India are affected by air pollution. The number
of premature deaths through harmful emission keeps on increasing. Deterioration
of health is the major and visible result of air pollutants which has been released
by vehicular exhaust.
Given below are the
health impacts of air pollution caused by vehicles:
1. Oxides
of nitrogen (NOx): This
gas can make children susceptible to respiratory diseases in winters.
2. Carbon monoxide (CO): It combines with haemoglobin to lessen the amount of oxygen that enters our blood through the lungs. The binding with other haemoglobin in proteins causes changes in the function of the affected organs such as the brain and the cardiovascular system, and also the developing foetus. It can impair our concentration, slow our reflexes, and make us confused and sleepy.
3. Sulphur dioxide (SO2) : SO2 in the air is caused due to combustion of fossil fuels. It can oxidize and form sulphuric acid mist. SO2 in the air leads to diseases of the lungs and other lung disorders such as wheezing and shortness of breath. Long-term effects are more difficult to ascertain as SO2 is often combined with that of SPM.
Suspended Particulate
Matter (SPM): Suspended matter consists of dust, fumes, mist and smoke. The
main chemical components of SPM that is of major concern is lead, others being
nickel, arsenic, and those present in diesel exhaust. These particles when
breathed in, lodge in our lung tissues and cause lung damage and respiratory
problems
Moreover, increased
nitrogen loading in water bodies, particularly coastal estuaries, upsets the
chemical balance of nutrients used by aquatic plants and animals. Additional
nitrogen accelerates “eutrophication,” which leads to oxygen depletion and
reduces fish and shellfish populations. NOx emission in the air is one of the
largest sources of nitrogen pollution in water bodies.
It is important
to understand that the above pollutions are not only affecting the health of
human beings, but all forms of life on the planet earth.
Key Factor for Air
Pollution – Commercial Vehicles
Boom in industrial
and agricultural output in India, alongwith the favourable policies of government
towards farmers and factors such as migration of population towards urban
centres for education, jobs, medical facilities and entrepreneurial
opportunities contribute to high density of population in urban centres. To supply
food, vegetables, dairy products, clothing and other day-to-day needs of urban
centres with high population, we need more and more diesel commercial vehicles.
This is a necessary evil, which is necessary to feed India.
In order to reduce harmful emission of
gases from vehicles, including carbon dioxide, the governments all over the
world have been taking steps for cleaning the environment. India has also
issued the Clean Air Act which is popularly known as Bharat Stage, which is in line with EURO norms.
In India, it
was in 1991, that the first set of emission norms came into picture for petrol
vehicles and the same was imposed on diesel vehicles in 1992. In 1995, the next
regulation was extended to four metro cities (Delhi, Calcutta, Mumbai and
Chennai). According to this, it was mandatory to fit catalytic converters in
new petrol passenger cars sold. This step was so needed at that time as “Lead”
the highly toxic pollutant, was required to be taken out of petrol. Unleaded fuel was introduced first in metro
cities and then in other 42 major cities.
One part of
the emission is Particulate Matter (PM) emit by diesel vehicles only, which
causes serious damage to human beings. PM is considered as main source of
pollution. In 1996, regulation was made that there should be cold start
emission test for diesel vehicles below 3.5 ton GVW (Gross Vehicle Weight).
In 2010,
Bharat Stage IV (BSIV) was adopted only in 13 major cities in India, but the
implementation is still not proper.
We are
leaving a legacy of pollution for future generations. This needs to change
keeping in mind both the current requirement and also the future requirements.
Polluting gases and harmful emissions are required to be curbed by effective
emission norms in India. This could be done by uniform emission norms
throughout the country.
Comparison of materials for exhaust systems
As customers,
we are concerned about the quality of the vehicle while purchasing a personal
vehicle or diesel commercial vehicle. In case of personal vehicles, we look
into the aesthetic value, the mileage, the ergonomics, brand value and cost. In
diesel commercial vehicles, the customer looks for products which have lower
maintenance cost, higher load carrying capacity and best mileage. In the market,
exhaust systems with pipes of mild steel, mild steel coated with aluminium and
stainless steel are the choices.
Since the service
life of the exhaust system has not been defined in the Bharat Emission norms,
in order to reduce their selling price, manufacturers use lowest cost materials
like mild steel or aluminised steel for their exhaust system and provide only
one year warranty. Their perception is that stainless steel exhaust system is
too “costly”. However, when the operational, maintenance and replacement costs
to the customer over the service life of the vehicle, say 8 years, stainless
steel systems prove to be the least cost option to the user (See Table II).
Table
I
|
FACTORS MATERIAL
|
Mild Steel
|
Aluminised Steel
|
Stainless Steel
|
|
Initial Cost
|
Cheap
|
Cost twice of MS
|
Costs 5 times of MS
|
|
High Temperature
Resistance
|
Low Resistance
|
Can perform till 500O C.
|
Can perform at higher temperature.
|
|
Maintenance Cost
|
High
|
High
|
Low
|
|
Service Life
|
1 year
|
1 year
|
8 – 10 years (depending on the conditions)
|
|
Replacements over 8 years
|
7
|
7
|
None
|
|
Resistance to
corrosion at working temperature
|
Starts Immediately
|
Can resist till the layer is intact but layer starts depleting
at working temperature
|
8 – 10 years of workability
|
|
Life Cycle cost
|
High
|
High
|
Low
|
|
Mileage
|
Low
|
Low
|
High
|
First and
foremost, stainless steels can withstand high operating temperatures of the
exhaust system without corrosion over the life of the vehicle. This means (a)
the high operating temperatures of the exhausts will maximize the burning of
the fuel and will lead to lesser emission of PM and other harmful gases; (b)
There will be increased fuel efficiency (read: mileage) (c) There will be no
need to change the exhaust system during the life of the vehicle; (d)
Maintenance costs will be minimal and NO replacements; (e) Because of high
corrosion resistance, thin gauges are used, reducing the weight of the vehicle
and further enhancing fuel efficiency. In other words, higher initial outlay on
stainless steel systems gives life-long benefits and helps keep our environment
clean. (f) At the end of service life all the stainless steel in the exhaust
train is 100% recycled whereas in the case of mild steel and aluminised steel
there is a significant loss of material due to corrosion in service.
The other two
options i.e. mild steel and aluminised steel, though appear to be “costing
less” initially, are life-long trouble, probably seven replacements and a
constant threat to the environment through leakage of exhaust when in a state
of repair (both air and noise pollution), and a big source of pollution when
not replaced. When you choose stainless
steel, you are minimizing the cost and saving the environment. The choice is yours!
An exhaust
system comprises of following components: an exhaust manifold, front pipe,
flexible pipe, catalytical convertor, centre pipe, main muffler, and tail end
pipe.
DIFFERENT
PARTS OF EXHAUST SYSTEM
Exhaust
system has differential temperature at its two ends. At the head end it has the
highest temperature (900 degree centigrade) but at the tail end it has
relatively low temperature (100 – 400 degree centigrade). The material for
these parts should be chosen carefully so that it possesses these temperature
characteristics to meet the aim. Different grades of stainless steel have the
necessary properties to make a successful exhaust system with better fuel
efficiency, excellent oxidation resistance, good formability and weldability
with a better aesthetic feel.
Exhaust Train Components:
Manifolds: should have the property to bear high temperature
near 900 degree centigrade, good oxidation resistance, thermal fatigue life and
good workability because of its structure. So the best supporting material in
the case of Manifolds is 304, 316 or 321 stainless steel.
Front Pipe and Flexible Tube: should be able to withstand a
temperature of 600 – 800 degree centigrade. Good oxidation resistance is must
in this part also. Grades of stainless steel that are best fit in these parts
of Exhaust system are: 409L, 436L.
Catalytic Convertor: this includes shell and catalyst
carriers. This part of exhaust system should have the highest temperature
strength, approximately 1000 - 1200 degrees centigrade. Also, it should have the
high thermal shock resistance as this is the part which is very near to engine.
Workability and resistance to chloride attack in coastal areas is a must for this
part because of its working. Smart Catalytic convertor can be made up of these
grades of stainless steel: 409L, 439, and 441.
Center pipe: this
has relatively low temperature (600 degree centigrade) but the material used to
make this should have more corrosion resistance. 409L, 439
grades Stainless Steel are the best fit as a countermeasure
against the corrosion of the inner and outer surfaces.
Main Muffler and Tail End Pipe: this part has to face the exhaust
gas condensation which forms a very high moist atmosphere inside the muffler. The
Tail End Pipe should have its own feature other than oxidation resistance. This
should have good exterior as this part is visible. Thus, ferritic stainless
steel like
409, 436, and
430 are used for this part.
Conclusion
In view of what has been clarified in the
body of this article, we request the authorities to consider the following
suggestions: (a) Strictly implement BSIV norms for diesel commercial vehicles
across the country without exception; (b) Make use of stainless steel exhaust
systems mandatory both from the point of view of mitigating pollution and to
minimize the cost to the nation in doing so.
Finally, it may be noted that various grades
of stainless steel for use in different sections of the exhaust system are
available indigenously.
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