Nitrogen Instead of Compressed Air in Tires

ABOUT AUTHOR
Janakamma K*, Marry Kalyani, Anil Kumar Kavali, Dr. Hindustan Abdul Ahad
Department of ECE, Government Polytechnic College, Anantapur
Balaji College of Pharmacy, Anantapur, AP, India
E-mail: [email protected]

INTRODUCTION
Air is 78% nitrogen, 21% oxygen and the rest is water vapor, CO₂ and small concentrations of noble gases such as neon and argon. We can ignore the other gases. There are several compelling reasons to use pure nitrogen in tires. First is that nitrogen is less likely to migrate through tire rubber than is oxygen, which means that the tire pressures will remain more stable over the long term and less tires heat up. It is bad to have water inside a tire. Water, present as a vapor or even as a liquid in a tire, causes more of a pressure change with temperature swings than dry air does. It also promotes corrosion of the steel or aluminum rim. Filling tires with nitrogen involves filling and purging several times in succession, serially diluting the concentration of oxygen in the tire. This will also remove any water. 
DISCUSSION
Nitrogen tire inflation helps better tire-pressure retention, improved fuel economy and cooler-running tire temperatures.
Better tire-pressure retention:
Over time, a tire will gradually loose pressure. Changes in temperature will accelerate this. The general rule of thumb is a loss of 1 psi for every 10-degree rise or fall in temperature. Nitrogen has a more stable pressure, since it has larger molecules than oxygen that are less likely to seep through the permeable tire walls.
Improved fuel economy: 
The EPA says that under-inflated tires can lower gas mileage by 0.3 percent for every 1 psi drop in pressure of all four tires. The theory is that since nitrogen loses pressure at a slower rate than air and more likely to be at the correct psi and therefore get better fuel economy.
Cooler running temperatures: 
When air is pressurized, the humidity in it condenses to a liquid and collects in the air storage tank at the local gas station. When compressed air is added to the tires, the water comes along for the ride. As the tire heats up during driving, that water changes to a gas, which then expands, increasing tire pressure. Because nitrogen is dry, there is no water in the tire to contribute to pressure fluctuations.
Prevent wheel rot: 
Nitrogen proponents will also point out that water in a tire can lead to wheel rot. Steel wheels have a problem if the paint is damaged.
Conclusion:
With nitrogen, the tire pressures will remain more constant, saving a small amount in fuel and tire-maintenance costs. There will be less moisture inside the tires, meaning less corrosion on the wheels.